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<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title></title><link rel="stylesheet" type="text/css" href="ref-style.css" /><meta name="generator" content="DocBook XSL Stylesheets V1.76.1" /></head><body><div xml:lang="en" class="book" lang="en"><div class="titlepage"><div><div><h1 class="title"><a id="ref-manual"></a></h1></div><div><div class="authorgroup">
            <div class="author"><h3 class="author"><span class="firstname">Richard</span> <span class="surname">Purdie</span></h3><div class="affiliation">
                    <span class="orgname">Linux Foundation<br /></span>
                </div><code class="email">&lt;<a class="email" href="mailto:richard.purdie@linuxfoundation.org">richard.purdie@linuxfoundation.org</a>&gt;</code></div>

        </div></div><div><p class="copyright">Copyright © 2010-2013 Linux Foundation</p></div><div><div class="legalnotice" title="Legal Notice"><a id="idm153280"></a>
      <p>
        Permission is granted to copy, distribute and/or modify this document under
        the terms of the <a class="ulink" href="http://creativecommons.org/licenses/by-sa/2.0/uk/" target="_top">Creative Commons Attribution-Share Alike 2.0 UK: England &amp; Wales</a> as published by Creative Commons.
      </p>
      <div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
          Due to production processes, there could be differences between the Yocto Project
          documentation bundled in the release tarball and the
          <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/ref-manual/ref-manual.html" target="_top">Yocto Project Reference Manual</a> on
          the <a class="ulink" href="http://www.yoctoproject.org" target="_top">Yocto Project</a> website.
          For the latest version of this manual, see the manual on the website.
      </div>
    </div></div><div><div class="revhistory"><table border="1" width="100%" summary="Revision history"><tr><th align="left" valign="top" colspan="2"><strong>Revision History</strong></th></tr>
            <tr><td align="left">Revision 4.0+git</td><td align="left">24 November 2010</td></tr><tr><td align="left" colspan="2">Released with the Yocto Project 0.9 Release</td></tr>
            <tr><td align="left">Revision 1.0</td><td align="left">6 April 2011</td></tr><tr><td align="left" colspan="2">Released with the Yocto Project 1.0 Release.</td></tr>
            <tr><td align="left">Revision 1.0.1</td><td align="left">23 May 2011</td></tr><tr><td align="left" colspan="2">Released with the Yocto Project 1.0.1 Release.</td></tr>
            <tr><td align="left">Revision 1.1</td><td align="left">6 October 2011</td></tr><tr><td align="left" colspan="2">Released with the Yocto Project 1.1 Release.</td></tr>
            <tr><td align="left">Revision 1.2</td><td align="left">April 2012</td></tr><tr><td align="left" colspan="2">Released with the Yocto Project 1.2 Release.</td></tr>
            <tr><td align="left">Revision 1.3</td><td align="left">October 2012</td></tr><tr><td align="left" colspan="2">Released with the Yocto Project 1.3 Release.</td></tr>
            <tr><td align="left">Revision 1.4</td><td align="left">Sometime in 2013</td></tr><tr><td align="left" colspan="2">Released with the Yocto Project 1.4 Release.</td></tr>
        </table></div></div></div><hr /></div><div class="toc"><p><strong>Table of Contents</strong></p><dl><dt><span class="chapter"><a href="#intro">1. Introduction</a></span></dt><dd><dl><dt><span class="section"><a href="#intro-welcome">1.1. Introduction</a></span></dt><dt><span class="section"><a href="#intro-manualoverview">1.2. Documentation Overview</a></span></dt><dt><span class="section"><a href="#intro-requirements">1.3. System Requirements</a></span></dt><dd><dl><dt><span class="section"><a href="#detailed-supported-distros">1.3.1. Supported Linux Distributions</a></span></dt><dt><span class="section"><a href="#required-packages-for-the-host-development-system">1.3.2. Required Packages for the Host Development System</a></span></dt></dl></dd><dt><span class="section"><a href="#intro-getit">1.4. Obtaining the Yocto Project</a></span></dt><dt><span class="section"><a href="#intro-getit-dev">1.5. Development Checkouts</a></span></dt></dl></dd><dt><span class="chapter"><a href="#usingpoky">2. Using the Yocto Project</a></span></dt><dd><dl><dt><span class="section"><a href="#usingpoky-build">2.1. Running a Build</a></span></dt><dd><dl><dt><span class="section"><a href="#build-overview">2.1.1. Build Overview</a></span></dt><dt><span class="section"><a href="#building-an-image-using-gpl-components">2.1.2. Building an Image Using GPL Components</a></span></dt></dl></dd><dt><span class="section"><a href="#usingpoky-install">2.2. Installing and Using the Result</a></span></dt><dt><span class="section"><a href="#usingpoky-debugging">2.3. Debugging Build Failures</a></span></dt><dd><dl><dt><span class="section"><a href="#usingpoky-debugging-taskfailures">2.3.1. Task Failures</a></span></dt><dt><span class="section"><a href="#usingpoky-debugging-taskrunning">2.3.2. Running Specific Tasks</a></span></dt><dt><span class="section"><a href="#usingpoky-debugging-dependencies">2.3.3. Dependency Graphs</a></span></dt><dt><span class="section"><a href="#usingpoky-debugging-bitbake">2.3.4. General BitBake Problems</a></span></dt><dt><span class="section"><a href="#usingpoky-debugging-buildfile">2.3.5. Building with No Dependencies</a></span></dt><dt><span class="section"><a href="#usingpoky-debugging-variables">2.3.6. Variables</a></span></dt><dt><span class="section"><a href="#recipe-logging-mechanisms">2.3.7. Recipe Logging Mechanisms</a></span></dt><dt><span class="section"><a href="#usingpoky-debugging-others">2.3.8. Other Tips</a></span></dt></dl></dd><dt><span class="section"><a href="#maintaining-build-output-quality">2.4. Maintaining Build Output Quality</a></span></dt><dd><dl><dt><span class="section"><a href="#enabling-and-disabling-build-history">2.4.1. Enabling and Disabling Build History</a></span></dt><dt><span class="section"><a href="#understanding-what-the-build-history-contains">2.4.2. Understanding What the Build History Contains</a></span></dt></dl></dd></dl></dd><dt><span class="chapter"><a href="#technical-details">3. Technical Details</a></span></dt><dd><dl><dt><span class="section"><a href="#usingpoky-components">3.1. Yocto Project Components</a></span></dt><dd><dl><dt><span class="section"><a href="#usingpoky-components-bitbake">3.1.1. BitBake</a></span></dt><dt><span class="section"><a href="#usingpoky-components-metadata">3.1.2. Metadata (Recipes)</a></span></dt><dt><span class="section"><a href="#usingpoky-components-classes">3.1.3. Classes</a></span></dt><dt><span class="section"><a href="#usingpoky-components-configuration">3.1.4. Configuration</a></span></dt></dl></dd><dt><span class="section"><a href="#shared-state-cache">3.2. Shared State Cache</a></span></dt><dd><dl><dt><span class="section"><a href="#overall-architecture">3.2.1. Overall Architecture</a></span></dt><dt><span class="section"><a href="#checksums">3.2.2. Checksums (Signatures)</a></span></dt><dt><span class="section"><a href="#shared-state">3.2.3. Shared State</a></span></dt><dt><span class="section"><a href="#tips-and-tricks">3.2.4. Tips and Tricks</a></span></dt></dl></dd><dt><span class="section"><a href="#x32">3.3. x32</a></span></dt><dd><dl><dt><span class="section"><a href="#support">3.3.1. Support</a></span></dt><dt><span class="section"><a href="#future-development-and-limitations">3.3.2. Future Development and Limitations</a></span></dt><dt><span class="section"><a href="#using-x32-right-now">3.3.3. Using x32 Right Now</a></span></dt></dl></dd><dt><span class="section"><a href="#licenses">3.4. Licenses</a></span></dt><dd><dl><dt><span class="section"><a href="#usingpoky-configuring-LIC_FILES_CHKSUM">3.4.1. Tracking License Changes</a></span></dt><dt><span class="section"><a href="#enabling-commercially-licensed-recipes">3.4.2. Enabling Commercially Licensed Recipes</a></span></dt></dl></dd></dl></dd><dt><span class="chapter"><a href="#migration">4. Migrating to a Newer Yocto Project Release</a></span></dt><dd><dl><dt><span class="section"><a href="#moving-to-the-yocto-project-1.3-release">4.1. Moving to the Yocto Project 1.3 Release</a></span></dt><dd><dl><dt><span class="section"><a href="#1.3-local-configuration">4.1.1. Local Configuration</a></span></dt><dt><span class="section"><a href="#1.3-recipes">4.1.2. Recipes</a></span></dt></dl></dd></dl></dd><dt><span class="chapter"><a href="#ref-structure">5. Source Directory Structure</a></span></dt><dd><dl><dt><span class="section"><a href="#structure-core">5.1. Top level core components</a></span></dt><dd><dl><dt><span class="section"><a href="#structure-core-bitbake">5.1.1. <code class="filename">bitbake/</code></a></span></dt><dt><span class="section"><a href="#structure-core-build">5.1.2. <code class="filename">build/</code></a></span></dt><dt><span class="section"><a href="#handbook">5.1.3. <code class="filename">documentation</code></a></span></dt><dt><span class="section"><a href="#structure-core-meta">5.1.4. <code class="filename">meta/</code></a></span></dt><dt><span class="section"><a href="#structure-core-meta-yocto">5.1.5. <code class="filename">meta-yocto/</code></a></span></dt><dt><span class="section"><a href="#structure-core-meta-yocto-bsp">5.1.6. <code class="filename">meta-yocto-bsp/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-hob">5.1.7. <code class="filename">meta-hob/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-skeleton">5.1.8. <code class="filename">meta-skeleton/</code></a></span></dt><dt><span class="section"><a href="#structure-core-scripts">5.1.9. <code class="filename">scripts/</code></a></span></dt><dt><span class="section"><a href="#structure-core-script">5.1.10. <code class="filename">oe-init-build-env</code></a></span></dt><dt><span class="section"><a href="#structure-basic-top-level">5.1.11. <code class="filename">LICENSE, README, and README.hardware</code></a></span></dt></dl></dd><dt><span class="section"><a href="#structure-build">5.2. The Build Directory - <code class="filename">build/</code></a></span></dt><dd><dl><dt><span class="section"><a href="#structure-build-pseudodone">5.2.1. <code class="filename">build/pseudodone</code></a></span></dt><dt><span class="section"><a href="#structure-build-conf-local.conf">5.2.2. <code class="filename">build/conf/local.conf</code></a></span></dt><dt><span class="section"><a href="#structure-build-conf-bblayers.conf">5.2.3. <code class="filename">build/conf/bblayers.conf</code></a></span></dt><dt><span class="section"><a href="#structure-build-conf-sanity_info">5.2.4. <code class="filename">build/conf/sanity_info</code></a></span></dt><dt><span class="section"><a href="#structure-build-downloads">5.2.5. <code class="filename">build/downloads/</code></a></span></dt><dt><span class="section"><a href="#structure-build-sstate-cache">5.2.6. <code class="filename">build/sstate-cache/</code></a></span></dt><dt><span class="section"><a href="#structure-build-tmp">5.2.7. <code class="filename">build/tmp/</code></a></span></dt><dt><span class="section"><a href="#structure-build-tmp-buildstats">5.2.8. <code class="filename">build/tmp/buildstats/</code></a></span></dt><dt><span class="section"><a href="#structure-build-tmp-cache">5.2.9. <code class="filename">build/tmp/cache/</code></a></span></dt><dt><span class="section"><a href="#structure-build-tmp-deploy">5.2.10. <code class="filename">build/tmp/deploy/</code></a></span></dt><dt><span class="section"><a href="#structure-build-tmp-deploy-deb">5.2.11. <code class="filename">build/tmp/deploy/deb/</code></a></span></dt><dt><span class="section"><a href="#structure-build-tmp-deploy-rpm">5.2.12. <code class="filename">build/tmp/deploy/rpm/</code></a></span></dt><dt><span class="section"><a href="#structure-build-tmp-deploy-licenses">5.2.13. <code class="filename">build/tmp/deploy/licenses/</code></a></span></dt><dt><span class="section"><a href="#structure-build-tmp-deploy-images">5.2.14. <code class="filename">build/tmp/deploy/images/</code></a></span></dt><dt><span class="section"><a href="#structure-build-tmp-deploy-ipk">5.2.15. <code class="filename">build/tmp/deploy/ipk/</code></a></span></dt><dt><span class="section"><a href="#structure-build-tmp-sysroots">5.2.16. <code class="filename">build/tmp/sysroots/</code></a></span></dt><dt><span class="section"><a href="#structure-build-tmp-stamps">5.2.17. <code class="filename">build/tmp/stamps/</code></a></span></dt><dt><span class="section"><a href="#structure-build-tmp-log">5.2.18. <code class="filename">build/tmp/log/</code></a></span></dt><dt><span class="section"><a href="#structure-build-tmp-pkgdata">5.2.19. <code class="filename">build/tmp/pkgdata/</code></a></span></dt><dt><span class="section"><a href="#structure-build-tmp-work">5.2.20. <code class="filename">build/tmp/work/</code></a></span></dt></dl></dd><dt><span class="section"><a href="#structure-meta">5.3. The Metadata - <code class="filename">meta/</code></a></span></dt><dd><dl><dt><span class="section"><a href="#structure-meta-classes">5.3.1. <code class="filename">meta/classes/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-conf">5.3.2. <code class="filename">meta/conf/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-conf-machine">5.3.3. <code class="filename">meta/conf/machine/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-conf-distro">5.3.4. <code class="filename">meta/conf/distro/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-recipes-bsp">5.3.5. <code class="filename">meta/recipes-bsp/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-recipes-connectivity">5.3.6. <code class="filename">meta/recipes-connectivity/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-recipes-core">5.3.7. <code class="filename">meta/recipes-core/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-recipes-devtools">5.3.8. <code class="filename">meta/recipes-devtools/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-recipes-extended">5.3.9. <code class="filename">meta/recipes-extended/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-recipes-gnome">5.3.10. <code class="filename">meta/recipes-gnome/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-recipes-graphics">5.3.11. <code class="filename">meta/recipes-graphics/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-recipes-kernel">5.3.12. <code class="filename">meta/recipes-kernel/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-recipes-multimedia">5.3.13. <code class="filename">meta/recipes-multimedia/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-recipes-qt">5.3.14. <code class="filename">meta/recipes-qt/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-recipes-rt">5.3.15. <code class="filename">meta/recipes-rt/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-recipes-sato">5.3.16. <code class="filename">meta/recipes-sato/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-recipes-support">5.3.17. <code class="filename">meta/recipes-support/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-site">5.3.18. <code class="filename">meta/site/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-recipes-txt">5.3.19. <code class="filename">meta/recipes.txt</code></a></span></dt></dl></dd></dl></dd><dt><span class="chapter"><a href="#ref-bitbake">6. BitBake</a></span></dt><dd><dl><dt><span class="section"><a href="#ref-bitbake-parsing">6.1. Parsing</a></span></dt><dt><span class="section"><a href="#ref-bitbake-providers">6.2. Preferences and Providers</a></span></dt><dt><span class="section"><a href="#ref-bitbake-dependencies">6.3. Dependencies</a></span></dt><dt><span class="section"><a href="#ref-bitbake-tasklist">6.4. The Task List</a></span></dt><dt><span class="section"><a href="#ref-bitbake-runtask">6.5. Running a Task</a></span></dt><dt><span class="section"><a href="#ref-bitbake-commandline">6.6. BitBake Command Line</a></span></dt><dt><span class="section"><a href="#ref-bitbake-fetchers">6.7. Fetchers</a></span></dt></dl></dd><dt><span class="chapter"><a href="#ref-classes">7. Classes</a></span></dt><dd><dl><dt><span class="section"><a href="#ref-classes-base">7.1. The base class - <code class="filename">base.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-autotools">7.2. Autotooled Packages - <code class="filename">autotools.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-update-alternatives">7.3. Alternatives - <code class="filename">update-alternatives.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-update-rc.d">7.4. Initscripts - <code class="filename">update-rc.d.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-binconfig">7.5. Binary config scripts - <code class="filename">binconfig.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-debian">7.6. Debian renaming - <code class="filename">debian.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-pkgconfig">7.7. Pkg-config - <code class="filename">pkgconfig.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-src-distribute">7.8. Distribution of sources - <code class="filename">src_distribute_local.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-perl">7.9. Perl modules - <code class="filename">cpan.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-distutils">7.10. Python extensions - <code class="filename">distutils.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-devshell">7.11. Developer Shell - <code class="filename">devshell.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-packagegroup">7.12. Package Groups - <code class="filename">packagegroup.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-package">7.13. Packaging - <code class="filename">package*.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-kernel">7.14. Building kernels - <code class="filename">kernel.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-image">7.15. Creating images - <code class="filename">image.bbclass</code> and <code class="filename">rootfs*.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-sanity">7.16. Host System sanity checks - <code class="filename">sanity.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-insane">7.17. Generated output quality assurance checks - <code class="filename">insane.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-siteinfo">7.18. Autotools configuration data cache - <code class="filename">siteinfo.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-useradd">7.19. Adding Users - <code class="filename">useradd.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-externalsrc">7.20. Using External Source - <code class="filename">externalsrc.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-others">7.21. Other Classes</a></span></dt></dl></dd><dt><span class="chapter"><a href="#ref-images">8. Images</a></span></dt><dt><span class="chapter"><a href="#ref-features">9. Reference: Features</a></span></dt><dd><dl><dt><span class="section"><a href="#ref-features-distro">9.1. Distro</a></span></dt><dt><span class="section"><a href="#ref-features-machine">9.2. Machine</a></span></dt><dt><span class="section"><a href="#ref-features-image">9.3. Images</a></span></dt><dt><span class="section"><a href="#ref-features-backfill">9.4. Feature Backfilling</a></span></dt></dl></dd><dt><span class="chapter"><a href="#ref-variables-glos">10. Variables Glossary</a></span></dt><dd><dl><dt><span class="glossary"><a href="#ref-variables-glossary">Glossary</a></span></dt></dl></dd><dt><span class="chapter"><a href="#ref-varlocality">11. Variable Context</a></span></dt><dd><dl><dt><span class="section"><a href="#ref-varlocality-configuration">11.1. Configuration</a></span></dt><dd><dl><dt><span class="section"><a href="#ref-varlocality-config-distro">11.1.1. Distribution (Distro)</a></span></dt><dt><span class="section"><a href="#ref-varlocality-config-machine">11.1.2. Machine</a></span></dt><dt><span class="section"><a href="#ref-varlocality-config-local">11.1.3. Local</a></span></dt></dl></dd><dt><span class="section"><a href="#ref-varlocality-recipes">11.2. Recipes</a></span></dt><dd><dl><dt><span class="section"><a href="#ref-varlocality-recipe-required">11.2.1. Required</a></span></dt><dt><span class="section"><a href="#ref-varlocality-recipe-dependencies">11.2.2. Dependencies</a></span></dt><dt><span class="section"><a href="#ref-varlocality-recipe-paths">11.2.3. Paths</a></span></dt><dt><span class="section"><a href="#ref-varlocality-recipe-build">11.2.4. Extra Build Information</a></span></dt></dl></dd></dl></dd><dt><span class="chapter"><a href="#faq">12. FAQ</a></span></dt><dt><span class="chapter"><a href="#resources">13. Contributing to the Yocto Project</a></span></dt><dd><dl><dt><span class="section"><a href="#resources-intro">13.1. Introduction</a></span></dt><dt><span class="section"><a href="#resources-bugtracker">13.2. Tracking Bugs</a></span></dt><dt><span class="section"><a href="#resources-mailinglist">13.3. Mailing lists</a></span></dt><dt><span class="section"><a href="#resources-irc">13.4. Internet Relay Chat (IRC)</a></span></dt><dt><span class="section"><a href="#resources-links">13.5. Links</a></span></dt><dt><span class="section"><a href="#resources-contributions">13.6. Contributions</a></span></dt></dl></dd></dl></div>
    

    <div class="chapter" title="Chapter 1. Introduction"><div class="titlepage"><div><div><h2 class="title"><a id="intro"></a>Chapter 1. Introduction</h2></div></div></div><div class="toc"><p><strong>Table of Contents</strong></p><dl><dt><span class="section"><a href="#intro-welcome">1.1. Introduction</a></span></dt><dt><span class="section"><a href="#intro-manualoverview">1.2. Documentation Overview</a></span></dt><dt><span class="section"><a href="#intro-requirements">1.3. System Requirements</a></span></dt><dd><dl><dt><span class="section"><a href="#detailed-supported-distros">1.3.1. Supported Linux Distributions</a></span></dt><dt><span class="section"><a href="#required-packages-for-the-host-development-system">1.3.2. Required Packages for the Host Development System</a></span></dt></dl></dd><dt><span class="section"><a href="#intro-getit">1.4. Obtaining the Yocto Project</a></span></dt><dt><span class="section"><a href="#intro-getit-dev">1.5. Development Checkouts</a></span></dt></dl></div><div class="section" title="1.1. Introduction"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="intro-welcome"></a>1.1. Introduction</h2></div></div></div><p>
        This manual provides reference information for the current release of the Yocto Project.
        The Yocto Project is an open-source collaboration project focused on embedded Linux
        developers.
        Amongst other things, the Yocto Project uses the OpenEmbedded build system, which
        is based on the Poky project, to construct complete Linux images.
        You can find complete introductory and getting started information on the Yocto Project
        by reading the
        <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/yocto-project-qs/yocto-project-qs.html" target="_top">Yocto Project Quick Start</a>.
        For task-based information using the Yocto Project, see the
        <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html" target="_top">Yocto Project Development Manual</a>.
        You can also find lots of information on the Yocto Project on the
        <a class="ulink" href="http://www.yoctoproject.org" target="_top">Yocto Project website</a>.
    </p></div><div class="section" title="1.2. Documentation Overview"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="intro-manualoverview"></a>1.2. Documentation Overview</h2></div></div></div><p>
        This reference manual consists of the following:
        </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em>
                <a class="link" href="#usingpoky" title="Chapter 2. Using the Yocto Project">Using the Yocto Project</a>:</em></span> This chapter
                provides an overview of the components that make up the Yocto Project
                followed by information about debugging images created in the Yocto Project.
                </p></li><li class="listitem"><p><span class="emphasis"><em>
                <a class="link" href="#technical-details" title="Chapter 3. Technical Details">Technical Details</a>:</em></span>
                This chapter describes fundamental Yocto Project components as well as an explanation
                behind how the Yocto Project uses shared state (sstate) cache to speed build time.
                </p></li><li class="listitem"><p><span class="emphasis"><em>
                <a class="link" href="#ref-structure" title="Chapter 5. Source Directory Structure">Directory Structure</a>:</em></span>
                This chapter describes the
                <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#source-directory" target="_top">source directory</a> created
                either by unpacking a released Yocto Project tarball on your host development system,
                or by cloning the upstream
                <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#poky" target="_top">Poky</a> Git repository.
                </p></li><li class="listitem"><p><span class="emphasis"><em>
                <a class="link" href="#ref-bitbake" title="Chapter 6. BitBake">BitBake</a>:</em></span>
                This chapter provides an overview of the BitBake tool and its role within
                the Yocto Project.</p></li><li class="listitem"><p><span class="emphasis"><em>
                <a class="link" href="#ref-classes" title="Chapter 7. Classes">Classes</a>:</em></span>
                This chapter describes the classes used in the Yocto Project.</p></li><li class="listitem"><p><span class="emphasis"><em>
                <a class="link" href="#ref-images" title="Chapter 8. Images">Images</a>:</em></span>
                This chapter describes the standard images that the Yocto Project supports.
                </p></li><li class="listitem"><p><span class="emphasis"><em>
                <a class="link" href="#ref-features" title="Chapter 9. Reference: Features">Features</a>:</em></span>
                This chapter describes mechanisms for creating distribution, machine, and image
                features during the build process using the OpenEmbedded build system.</p></li><li class="listitem"><p><span class="emphasis"><em>
                <a class="link" href="#ref-variables-glos" title="Chapter 10. Variables Glossary">Variables Glossary</a>:</em></span>
                This chapter presents most variables used by the OpenEmbedded build system, which
                using BitBake.
                Entries describe the function of the variable and how to apply them.
                </p></li><li class="listitem"><p><span class="emphasis"><em>
                <a class="link" href="#ref-varlocality" title="Chapter 11. Variable Context">Variable Context</a>:</em></span>
                This chapter provides variable locality or context.</p></li><li class="listitem"><p><span class="emphasis"><em>
                <a class="link" href="#faq" title="Chapter 12. FAQ">FAQ</a>:</em></span>
                This chapter provides answers for commonly asked questions in the Yocto Project
                development environment.</p></li><li class="listitem"><p><span class="emphasis"><em>
                <a class="link" href="#resources" title="Chapter 13. Contributing to the Yocto Project">Contributing to the Yocto Project</a>:</em></span>
                This chapter provides guidance on how you can contribute back to the Yocto
                Project.</p></li></ul></div><p>
    </p></div><div class="section" title="1.3. System Requirements"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="intro-requirements"></a>1.3. System Requirements</h2></div></div></div><p>
        For general Yocto Project system requirements, see the
        "<a class="ulink" href="http://www.yoctoproject.org/docs/1.4/yocto-project-qs/yocto-project-qs.html#yp-resources" target="_top">What You Need and How You Get It</a>" section
        in the Yocto Project Quick Start.
        The remainder of this section provides details on system requirements
        not covered in the Yocto Project Quick Start.
    </p><div class="section" title="1.3.1. Supported Linux Distributions"><div class="titlepage"><div><div><h3 class="title"><a id="detailed-supported-distros"></a>1.3.1. Supported Linux Distributions</h3></div></div></div><p>
            Currently, the Yocto Project is supported on the following distributions:
            </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>Ubuntu 10.04.4 LTS</p></li><li class="listitem"><p>Ubuntu 11.10</p></li><li class="listitem"><p>Ubuntu 12.04.1 LTS</p></li><li class="listitem"><p>Ubuntu 12.04.1 LTS</p></li><li class="listitem"><p>Ubuntu 12.10</p></li><li class="listitem"><p>Fedora release 16 (Verne)</p></li><li class="listitem"><p>Fedora release 17 (Beefy Miracle)</p></li><li class="listitem"><p>Fedora release 18 (Spherical Cow)</p></li><li class="listitem"><p>CentOS release 5.6 (Final)</p></li><li class="listitem"><p>CentOS release 5.7 (Final)</p></li><li class="listitem"><p>CentOS release 5.8 (Final)</p></li><li class="listitem"><p>CentOS release 6.3 (Final)</p></li><li class="listitem"><p>Debian GNU/Linux 6.0.6 (squeeze)</p></li><li class="listitem"><p>openSUSE 11.4</p></li><li class="listitem"><p>openSUSE 12.1</p></li><li class="listitem"><p>openSUSE 12.2</p></li></ul></div><p>
        </p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
            For additional information on distributions that support the
            Yocto Project, see the
            <a class="ulink" href="https://wiki.yoctoproject.org/wiki/Distribution_Support" target="_top">Distribution Support</a> wiki page.
        </div></div><div class="section" title="1.3.2. Required Packages for the Host Development System"><div class="titlepage"><div><div><h3 class="title"><a id="required-packages-for-the-host-development-system"></a>1.3.2. Required Packages for the Host Development System</h3></div></div></div><p>
            The list of packages you need on the host development system can
            be large when covering all build scenarios using the Yocto Project.
            This section provides required packages by Linux distribution and
            further categorized by function.
        </p><div class="section" title="1.3.2.1. Ubuntu"><div class="titlepage"><div><div><h4 class="title"><a id="ubuntu-packages"></a>1.3.2.1. Ubuntu</h4></div></div></div><p>
                The following list shows the required packages by function
                given a supported Ubuntu Linux distribution:
                </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em>Essentials:</em></span>
                        Packages needed to build an image on a headless
                        system:
                        </p><pre class="literallayout">
     $ sudo apt-get install gawk wget git-core diffstat unzip texinfo \
     build-essential chrpath
                        </pre></li><li class="listitem"><p><span class="emphasis"><em>Graphical Extras:</em></span>
                        Packages recommended if the host system has graphics support:
                        </p><pre class="literallayout">
     $ sudo apt-get install libsdl1.2-dev xterm
                        </pre></li><li class="listitem"><p><span class="emphasis"><em>Documentation:</em></span>
                        Packages needed if you are going to build out the
                        Yocto Project documentation manuals:
                        </p><pre class="literallayout">
     $ sudo apt-get install make xsltproc docbook-utils fop
                        </pre></li><li class="listitem"><p><span class="emphasis"><em>ADT Installer Extras:</em></span>
                        Packages needed if you are going to be using the
                        <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/adt-manual/adt-manual.html#using-the-adt-installer" target="_top">Application Development Toolkit (ADT) Installer</a>:
                        </p><pre class="literallayout">
     $ sudo apt-get install autoconf automake libtool libglib2.0-dev
                        </pre></li></ul></div><p>
            </p></div><div class="section" title="1.3.2.2. Fedora Packages"><div class="titlepage"><div><div><h4 class="title"><a id="fedora-packages"></a>1.3.2.2. Fedora Packages</h4></div></div></div><p>
                The following list shows the required packages by function
                given a supported Fedora Linux distribution:
                </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em>Essentials:</em></span>
                        Packages needed to build an image for a headless
                        system:
                        </p><pre class="literallayout">
     $ sudo yum install gawk make wget tar bzip2 gzip python unzip perl patch \
     diffutils diffstat git cpp gcc gcc-c++ eglibc-devel texinfo chrpath \
     ccache
                        </pre></li><li class="listitem"><p><span class="emphasis"><em>Graphical Extras:</em></span>
                        Packages recommended if the host system has graphics support:
                        </p><pre class="literallayout">
     $ sudo yum install SDL-devel xterm
                        </pre></li><li class="listitem"><p><span class="emphasis"><em>Documentation:</em></span>
                        Packages needed if you are going to build out the
                        Yocto Project documentation manuals:
                        </p><pre class="literallayout">
     $ sudo yum install make docbook-style-dsssl docbook-style-xsl \
     docbook-dtds docbook-utils fop libxslt
                        </pre></li><li class="listitem"><p><span class="emphasis"><em>ADT Installer Extras:</em></span>
                        Packages needed if you are going to be using the
                        <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/adt-manual/adt-manual.html#using-the-adt-installer" target="_top">Application Development Toolkit (ADT) Installer</a>:
                        </p><pre class="literallayout">
     $ sudo yum install autoconf automake libtool glib2-devel
                        </pre></li></ul></div><p>
            </p></div><div class="section" title="1.3.2.3. OpenSUSE Packages"><div class="titlepage"><div><div><h4 class="title"><a id="opensuse-packages"></a>1.3.2.3. OpenSUSE Packages</h4></div></div></div><p>
                The following list shows the required packages by function
                given a supported OpenSUSE Linux distribution:
                </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em>Essentials:</em></span>
                        Packages needed to build an image for a headless
                        system:
                        </p><pre class="literallayout">
     $ sudo zypper install python gcc gcc-c++ git chrpath make wget python-xml \
     diffstat texinfo python-curses
                        </pre></li><li class="listitem"><p><span class="emphasis"><em>Graphical Extras:</em></span>
                        Packages recommended if the host system has graphics support:
                        </p><pre class="literallayout">
     $ sudo zypper install libSDL-devel xterm
                        </pre></li><li class="listitem"><p><span class="emphasis"><em>Documentation:</em></span>
                        Packages needed if you are going to build out the
                        Yocto Project documentation manuals:
                        </p><pre class="literallayout">
     $ sudo zypper install make fop xsltproc
                        </pre></li><li class="listitem"><p><span class="emphasis"><em>ADT Installer Extras:</em></span>
                        Packages needed if you are going to be using the
                        <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/adt-manual/adt-manual.html#using-the-adt-installer" target="_top">Application Development Toolkit (ADT) Installer</a>:
                        </p><pre class="literallayout">
     $ sudo zypper install autoconf automake libtool glib2-devel
                        </pre></li></ul></div><p>
            </p></div><div class="section" title="1.3.2.4. CentOS Packages"><div class="titlepage"><div><div><h4 class="title"><a id="centos-packages"></a>1.3.2.4. CentOS Packages</h4></div></div></div><p>
                The following list shows the required packages by function
                given a supported CentOS Linux distribution:
                </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em>Essentials:</em></span>
                        Packages needed to build an image for a headless
                        system:
                        </p><pre class="literallayout">
     $ sudo yum -y install gawk make wget tar bzip2 gzip python unzip perl patch \
     diffutils diffstat git cpp gcc gcc-c++ glibc-devel texinfo chrpath
                        </pre></li><li class="listitem"><p><span class="emphasis"><em>Graphical Extras:</em></span>
                        Packages recommended if the host system has graphics support:
                        </p><pre class="literallayout">
     $ sudo yum -y install SDL-devel xterm
                        </pre></li><li class="listitem"><p><span class="emphasis"><em>Documentation:</em></span>
                        Packages needed if you are going to build out the
                        Yocto Project documentation manuals:
                        </p><pre class="literallayout">
     $ sudo yum -y install make docbook-style-dsssl docbook-style-xsl \
     docbook-dtds docbook-utils fop libxslt
                        </pre></li><li class="listitem"><p><span class="emphasis"><em>ADT Installer Extras:</em></span>
                        Packages needed if you are going to be using the
                        <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/adt-manual/adt-manual.html#using-the-adt-installer" target="_top">Application Development Toolkit (ADT) Installer</a>:
                        </p><pre class="literallayout">
     $ sudo yum -y install autoconf automake libtool glib2-devel
                        </pre></li></ul></div><p>
                </p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>Depending on the CentOS version you are using, other requirements
                    and dependencies might exist.
                    For details, you should look at the CentOS sections on the
                    <a class="ulink" href="https://wiki.yoctoproject.org/wiki/Poky/GettingStarted/Dependencies" target="_top">Poky/GettingStarted/Dependencies</a>
                    wiki page.</div><p>
            </p></div></div></div><div class="section" title="1.4. Obtaining the Yocto Project"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="intro-getit"></a>1.4. Obtaining the Yocto Project</h2></div></div></div><p>
        The Yocto Project development team makes the Yocto Project available through a number
        of methods:
        </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em>Releases:</em></span> Stable, tested releases are available through
                <a class="ulink" href="http://downloads.yoctoproject.org/releases/yocto/" target="_top">http://downloads.yoctoproject.org/releases/yocto/</a>.</p></li><li class="listitem"><p><span class="emphasis"><em>Nightly Builds:</em></span> These releases are available at
                <a class="ulink" href="http://autobuilder.yoctoproject.org/nightly" target="_top">http://autobuilder.yoctoproject.org/nightly</a>.
                These builds include Yocto Project releases, meta-toolchain tarball installation scripts, and
                experimental builds.</p></li><li class="listitem"><p><span class="emphasis"><em>Yocto Project Website:</em></span> You can find releases
                of the Yocto Project and supported BSPs at the
                <a class="ulink" href="http://www.yoctoproject.org" target="_top">Yocto Project website</a>.
                Along with these downloads, you can find lots of other information at this site.
                </p></li></ul></div><p>
    </p></div><div class="section" title="1.5. Development Checkouts"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="intro-getit-dev"></a>1.5. Development Checkouts</h2></div></div></div><p>
        Development using the Yocto Project requires a local
        <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#source-directory" target="_top">Source Directory</a>.
        You can set up the source directory by downloading a Yocto Project release tarball and unpacking it,
        or by cloning a copy of the upstream
        <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#poky" target="_top">Poky</a> Git repository.
        For information on both these methods, see the
        "<a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#getting-setup" target="_top">Getting Setup</a>"
        section in the Yocto Project Development Manual.
    </p></div></div>

    <div class="chapter" title="Chapter 2. Using the Yocto Project"><div class="titlepage"><div><div><h2 class="title"><a id="usingpoky"></a>Chapter 2. Using the Yocto Project</h2></div></div></div><div class="toc"><p><strong>Table of Contents</strong></p><dl><dt><span class="section"><a href="#usingpoky-build">2.1. Running a Build</a></span></dt><dd><dl><dt><span class="section"><a href="#build-overview">2.1.1. Build Overview</a></span></dt><dt><span class="section"><a href="#building-an-image-using-gpl-components">2.1.2. Building an Image Using GPL Components</a></span></dt></dl></dd><dt><span class="section"><a href="#usingpoky-install">2.2. Installing and Using the Result</a></span></dt><dt><span class="section"><a href="#usingpoky-debugging">2.3. Debugging Build Failures</a></span></dt><dd><dl><dt><span class="section"><a href="#usingpoky-debugging-taskfailures">2.3.1. Task Failures</a></span></dt><dt><span class="section"><a href="#usingpoky-debugging-taskrunning">2.3.2. Running Specific Tasks</a></span></dt><dt><span class="section"><a href="#usingpoky-debugging-dependencies">2.3.3. Dependency Graphs</a></span></dt><dt><span class="section"><a href="#usingpoky-debugging-bitbake">2.3.4. General BitBake Problems</a></span></dt><dt><span class="section"><a href="#usingpoky-debugging-buildfile">2.3.5. Building with No Dependencies</a></span></dt><dt><span class="section"><a href="#usingpoky-debugging-variables">2.3.6. Variables</a></span></dt><dt><span class="section"><a href="#recipe-logging-mechanisms">2.3.7. Recipe Logging Mechanisms</a></span></dt><dt><span class="section"><a href="#usingpoky-debugging-others">2.3.8. Other Tips</a></span></dt></dl></dd><dt><span class="section"><a href="#maintaining-build-output-quality">2.4. Maintaining Build Output Quality</a></span></dt><dd><dl><dt><span class="section"><a href="#enabling-and-disabling-build-history">2.4.1. Enabling and Disabling Build History</a></span></dt><dt><span class="section"><a href="#understanding-what-the-build-history-contains">2.4.2. Understanding What the Build History Contains</a></span></dt></dl></dd></dl></div><p>
        This chapter describes common usage for the Yocto Project.
        The information is introductory in nature as other manuals in the Yocto Project
        documentation set provide more details on how to use the Yocto Project.
    </p><div class="section" title="2.1. Running a Build"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="usingpoky-build"></a>2.1. Running a Build</h2></div></div></div><p>
        This section provides a summary of the build process and provides information
        for less obvious aspects of the build process.
        For general information on how to build an image using the OpenEmbedded build
        system, see the
        "<a class="ulink" href="http://www.yoctoproject.org/docs/1.4/yocto-project-qs/yocto-project-qs.html#building-image" target="_top">Building an Image</a>"
        section of the Yocto Project Quick Start.
    </p><div class="section" title="2.1.1. Build Overview"><div class="titlepage"><div><div><h3 class="title"><a id="build-overview"></a>2.1.1. Build Overview</h3></div></div></div><p>
            The first thing you need to do is set up the OpenEmbedded build environment by sourcing
            the <a class="link" href="#structure-core-script" title="5.1.10. oe-init-build-env">environment setup script</a> as follows:
            </p><pre class="literallayout">
     $ source oe-init-build-env [build_dir]
            </pre><p>
        </p><p>
            The <code class="filename">build_dir</code> is optional and specifies the directory the
            OpenEmbedded build system uses for the build -
            the <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#build-directory" target="_top">Build Directory</a>.
            If you do not specify a Build Directory it defaults to <code class="filename">build</code>
            in your current working directory.
            A common practice is to use a different Build Directory for different targets.
            For example, <code class="filename">~/build/x86</code> for a <code class="filename">qemux86</code>
            target, and <code class="filename">~/build/arm</code> for a <code class="filename">qemuarm</code> target.
            See <a class="link" href="#structure-core-script" title="5.1.10. oe-init-build-env">oe-init-build-env</a>
            for more information on this script.
        </p><p>
            Once the build environment is set up, you can build a target using:
            </p><pre class="literallayout">
     $ bitbake &lt;target&gt;
            </pre><p>
        </p><p>
            The <code class="filename">target</code> is the name of the recipe you want to build.
            Common targets are the images in <code class="filename">meta/recipes-core/images</code>,
            <code class="filename">/meta/recipes-sato/images</code>, etc. all found in the
            <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#source-directory" target="_top">Source Directory</a>.
            Or, the target can be the name of a recipe for a specific piece of software such as
            <span class="application">busybox</span>.
            For more details about the images the OpenEmbedded build system supports, see the
            "<a class="link" href="#ref-images" title="Chapter 8. Images">Images</a>" chapter.
        </p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
            Building an image without GNU General Public License Version 3 (GPLv3) components
            is only supported for minimal and base images.
            See the "<a class="link" href="#ref-images" title="Chapter 8. Images">Images</a>" chapter for more information.
        </div></div><div class="section" title="2.1.2. Building an Image Using GPL Components"><div class="titlepage"><div><div><h3 class="title"><a id="building-an-image-using-gpl-components"></a>2.1.2. Building an Image Using GPL Components</h3></div></div></div><p>
            When building an image using GPL components, you need to maintain your original
            settings and not switch back and forth applying different versions of the GNU
            General Public License.
            If you rebuild using different versions of GPL, dependency errors might occur
            due to some components not being rebuilt.
        </p></div></div><div class="section" title="2.2. Installing and Using the Result"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="usingpoky-install"></a>2.2. Installing and Using the Result</h2></div></div></div><p>
        Once an image has been built, it often needs to be installed.
        The images and kernels built by the OpenEmbedded build system are placed in the
        <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#build-directory" target="_top">Build Directory</a> in
        <code class="filename">tmp/deploy/images</code>.
        For information on how to run pre-built images such as <code class="filename">qemux86</code>
        and <code class="filename">qemuarm</code>, see the
        "<a class="ulink" href="http://www.yoctoproject.org/docs/1.4/yocto-project-qs/yocto-project-qs.html#using-pre-built" target="_top">Using Pre-Built Binaries and QEMU</a>"
        section in the Yocto Project Quick Start.
        For information about how to install these images, see the documentation for your
        particular board/machine.
    </p></div><div class="section" title="2.3. Debugging Build Failures"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="usingpoky-debugging"></a>2.3. Debugging Build Failures</h2></div></div></div><p>
        The exact method for debugging build failures depends on the nature of the
        problem and on the system's area from which the bug originates.
        Standard debugging practices such as comparison against the last
        known working version with examination of the changes and the re-application of steps
        to identify the one causing the problem are
        valid for the Yocto Project just as they are for any other system.
        Even though it is impossible to detail every possible potential failure,
        this section provides some general tips to aid in debugging.
    </p><div class="section" title="2.3.1. Task Failures"><div class="titlepage"><div><div><h3 class="title"><a id="usingpoky-debugging-taskfailures"></a>2.3.1. Task Failures</h3></div></div></div><p>The log file for shell tasks is available in
            <code class="filename">${WORKDIR}/temp/log.do_taskname.pid</code>.
            For example, the <code class="filename">compile</code> task for the QEMU minimal image for the x86
            machine (<code class="filename">qemux86</code>) might be
            <code class="filename">tmp/work/qemux86-poky-linux/core-image-minimal/1.0-r0/temp/log.do_compile.20830</code>.
            To see what BitBake runs to generate that log, look at the corresponding
            <code class="filename">run.do_taskname.pid</code> file located in the same directory.
        </p><p>
            Presently, the output from Python tasks is sent directly to the console.
        </p></div><div class="section" title="2.3.2. Running Specific Tasks"><div class="titlepage"><div><div><h3 class="title"><a id="usingpoky-debugging-taskrunning"></a>2.3.2. Running Specific Tasks</h3></div></div></div><p>
            Any given package consists of a set of tasks.
            The standard BitBake behavior in most cases is: <code class="filename">fetch</code>,
            <code class="filename">unpack</code>,
            <code class="filename">patch</code>, <code class="filename">configure</code>,
            <code class="filename">compile</code>, <code class="filename">install</code>, <code class="filename">package</code>,
            <code class="filename">package_write</code>, and <code class="filename">build</code>.
            The default task is <code class="filename">build</code> and any tasks on which it depends
            build first.
            Some tasks exist, such as <code class="filename">devshell</code>, that are not part of the
            default build chain.
            If you wish to run a task that is not part of the default build chain, you can use the
            <code class="filename">-c</code> option in BitBake as follows:
            </p><pre class="literallayout">
     $ bitbake matchbox-desktop -c devshell
            </pre><p>
        </p><p>
            If you wish to rerun a task, use the <code class="filename">-f</code> force option.
            For example, the following sequence forces recompilation after changing files in the
            working directory.
            </p><pre class="literallayout">
     $ bitbake matchbox-desktop
               .
               .
        [make some changes to the source code in the working directory]
               .
               .
     $ bitbake matchbox-desktop -c compile -f
     $ bitbake matchbox-desktop
            </pre><p>
        </p><p>
            This sequence first builds <code class="filename">matchbox-desktop</code> and then recompiles it.
            The last command reruns all tasks (basically the packaging tasks) after the compile.
            BitBake recognizes that the <code class="filename">compile</code> task was rerun and therefore
            understands that the other tasks also need to be run again.
        </p><p>
            You can view a list of tasks in a given package by running the
            <code class="filename">listtasks</code> task as follows:
            </p><pre class="literallayout">
     $ bitbake matchbox-desktop -c listtasks
            </pre><p>
            The results are in the file <code class="filename">${WORKDIR}/temp/log.do_listtasks</code>.
        </p></div><div class="section" title="2.3.3. Dependency Graphs"><div class="titlepage"><div><div><h3 class="title"><a id="usingpoky-debugging-dependencies"></a>2.3.3. Dependency Graphs</h3></div></div></div><p>
            Sometimes it can be hard to see why BitBake wants to build some other packages before a given
            package you have specified.
            The <code class="filename">bitbake -g targetname</code> command creates the
            <code class="filename">depends.dot</code>, <code class="filename">package-depends.dot</code>,
            and <code class="filename">task-depends.dot</code> files in the current directory.
            These files show the package and task dependencies and are useful for debugging problems.
            You can use the <code class="filename">bitbake -g -u depexp targetname</code> command to
            display the results in a more human-readable form.
        </p></div><div class="section" title="2.3.4. General BitBake Problems"><div class="titlepage"><div><div><h3 class="title"><a id="usingpoky-debugging-bitbake"></a>2.3.4. General BitBake Problems</h3></div></div></div><p>
            You can see debug output from BitBake by using the <code class="filename">-D</code> option.
            The debug output gives more information about what BitBake
            is doing and the reason behind it.
            Each <code class="filename">-D</code> option you use increases the logging level.
            The most common usage is <code class="filename">-DDD</code>.
        </p><p>
            The output from <code class="filename">bitbake -DDD -v targetname</code> can reveal why
            BitBake chose a certain version of a package or why BitBake
            picked a certain provider.
            This command could also help you in a situation where you think BitBake did something
            unexpected.
        </p></div><div class="section" title="2.3.5. Building with No Dependencies"><div class="titlepage"><div><div><h3 class="title"><a id="usingpoky-debugging-buildfile"></a>2.3.5. Building with No Dependencies</h3></div></div></div><p>
            If you really want to build a specific <code class="filename">.bb</code> file, you can use
            the command form <code class="filename">bitbake -b &lt;somepath/somefile.bb&gt;</code>.
            This command form does not check for dependencies so you should use it
            only when you know its dependencies already exist.
            You can also specify fragments of the filename.
            In this case, BitBake checks for a unique match.
        </p></div><div class="section" title="2.3.6. Variables"><div class="titlepage"><div><div><h3 class="title"><a id="usingpoky-debugging-variables"></a>2.3.6. Variables</h3></div></div></div><p>
            The <code class="filename">-e</code> option dumps the resulting environment for
            either the configuration (no package specified) or for a
            specific package when specified; or <code class="filename">-b recipename</code>
            to show the environment from parsing a single recipe file only.
        </p></div><div class="section" title="2.3.7. Recipe Logging Mechanisms"><div class="titlepage"><div><div><h3 class="title"><a id="recipe-logging-mechanisms"></a>2.3.7. Recipe Logging Mechanisms</h3></div></div></div><p>
            Best practices exist while writing recipes that both log build progress and
            act on build conditions such as warnings and errors.
            Both Python and Bash language bindings exist for the logging mechanism:
            </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em>Python:</em></span> For Python functions, BitBake
                    supports several loglevels: <code class="filename">bb.fatal</code>,
                    <code class="filename">bb.error</code>, <code class="filename">bb.warn</code>,
                    <code class="filename">bb.note</code>, <code class="filename">bb.plain</code>,
                    and <code class="filename">bb.debug</code>.</p></li><li class="listitem"><p><span class="emphasis"><em>Bash:</em></span> For Bash functions, the same set
                    of loglevels exist and are accessed with a similar syntax:
                    <code class="filename">bbfatal</code>, <code class="filename">bberror</code>,
                    <code class="filename">bbwarn</code>, <code class="filename">bbnote</code>,
                    <code class="filename">bbplain</code>, and <code class="filename">bbdebug</code>.</p></li></ul></div><p>
        </p><p>
            For guidance on how logging is handled in both Python and Bash recipes, see the
            <code class="filename">logging.bbclass</code> file in the
            <code class="filename">meta/classes</code> folder of the
            <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#source-directory" target="_top">Source Directory</a>.
        </p><div class="section" title="2.3.7.1. Logging With Python"><div class="titlepage"><div><div><h4 class="title"><a id="logging-with-python"></a>2.3.7.1. Logging With Python</h4></div></div></div><p>
                When creating recipes using Python and inserting code that handles build logs
                keep in mind the goal is to have informative logs while keeping the console as
                "silent" as possible.
                Also, if you want status messages in the log use the "debug" loglevel.
            </p><p>
                Following is an example written in Python.
                The code handles logging for a function that determines the number of tasks
                needed to be run:
                </p><pre class="literallayout">
     python do_listtasks() {
         bb.debug(2, "Starting to figure out the task list")
         if noteworthy_condition:
             bb.note("There are 47 tasks to run")
         bb.debug(2, "Got to point xyz")
         if warning_trigger:
             bb.warn("Detected warning_trigger, this might be a problem later.")
         if recoverable_error:
             bb.error("Hit recoverable_error, you really need to fix this!")
         if fatal_error:
             bb.fatal("fatal_error detected, unable to print the task list")
         bb.plain("The tasks present are abc")
         bb.debug(2, "Finished figuring out the tasklist")
     }
                </pre><p>
            </p></div><div class="section" title="2.3.7.2. Logging With Bash"><div class="titlepage"><div><div><h4 class="title"><a id="logging-with-bash"></a>2.3.7.2. Logging With Bash</h4></div></div></div><p>
                When creating recipes using Bash and inserting code that handles build
                logs you have the same goals - informative with minimal console output.
                The syntax you use for recipes written in Bash is similar to that of
                recipes written in Python described in the previous section.
            </p><p>
                Following is an example written in Bash.
                The code logs the progress of the <code class="filename">do_my_function</code> function.
                </p><pre class="literallayout">
     do_my_function() {
         bbdebug 2 "Running do_my_function"
         if [ exceptional_condition ]; then
             bbnote "Hit exceptional_condition"
         fi
         bbdebug 2  "Got to point xyz"
         if [ warning_trigger ]; then
             bbwarn "Detected warning_trigger, this might cause a problem later."
         fi
         if [ recoverable_error ]; then
             bberror "Hit recoverable_error, correcting"
         fi
         if [ fatal_error ]; then
             bbfatal "fatal_error detected"
         fi
         bbdebug 2 "Completed do_my_function"
     }
                </pre><p>
            </p></div></div><div class="section" title="2.3.8. Other Tips"><div class="titlepage"><div><div><h3 class="title"><a id="usingpoky-debugging-others"></a>2.3.8. Other Tips</h3></div></div></div><p>
            Here are some other tips that you might find useful:
            </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>When adding new packages, it is worth watching for
                    undesirable items making their way into compiler command lines.
                    For example, you do not want references to local system files like
                    <code class="filename">/usr/lib/</code> or <code class="filename">/usr/include/</code>.
                    </p></li><li class="listitem"><p>If you want to remove the psplash boot splashscreen,
                    add <code class="filename">psplash=false</code> to  the kernel command line.
                    Doing so prevents psplash from loading and thus allows you to see the console.
                    It is also possible to switch out of the splashscreen by
                    switching the virtual console (e.g. Fn+Left or Fn+Right on a Zaurus).
                    </p></li></ul></div><p>
        </p></div></div><div class="section" title="2.4. Maintaining Build Output Quality"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="maintaining-build-output-quality"></a>2.4. Maintaining Build Output Quality</h2></div></div></div><p>
        A build's quality can be influenced by many things.
        For example, if you upgrade a recipe to use a new version of an upstream software
        package or you experiment with some new configuration options, subtle changes
        can occur that you might not detect until later.
        Consider the case where your recipe is using a newer version of an upstream package.
        In this case, a new version of a piece of software might introduce an optional
        dependency on another library, which is auto-detected.
        If that library has already been built when the software is building,
        then the software will link to the built library and that library will be pulled
        into your image along with the new software even if you did not want the
        library.
    </p><p>
        The <code class="filename">buildhistory</code> class exists to help you maintain
        the quality of your build output.
        You can use the class to highlight unexpected and possibly unwanted
        changes in the build output.
        When you enable build history it records information about the contents of
        each package and image and then commits that information to a local Git
        repository where you can examine the information.
    </p><p>
        The remainder of this section describes the following:
        </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>How you can enable and disable
               build history</p></li><li class="listitem"><p>How to understand what the build history contains
               </p></li><li class="listitem"><p>How to limit the information used for build history
               </p></li><li class="listitem"><p>How to examine the build history from both a
               command-line and web interface</p></li></ul></div><p>
    </p><div class="section" title="2.4.1. Enabling and Disabling Build History"><div class="titlepage"><div><div><h3 class="title"><a id="enabling-and-disabling-build-history"></a>2.4.1. Enabling and Disabling Build History</h3></div></div></div><p>
            Build history is disabled by default.
            To enable it, add the following statements to the end of your
            <code class="filename">conf/local.conf</code> file found in the
            <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#build-directory" target="_top">Build Directory</a>:
            </p><pre class="literallayout">
     INHERIT += "buildhistory"
     BUILDHISTORY_COMMIT = "1"
            </pre><p>
            Enabling build history as previously described
            causes the build process to collect build
            output information and commit it to a local
            <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#git" target="_top">Git</a> repository.
            </p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
                Enabling build history increases your build times slightly,
                particularly for images, and increases the amount of disk
                space used during the build.
            </div><p>
        </p><p>
            You can disable build history by removing the previous statements
            from your <code class="filename">conf/local.conf</code> file.
            However, you should realize that enabling and disabling
            build history in this manner can change the
            <code class="filename">do_package</code> task checksums, which if you
            are using the OEBasicHash signature generator (the default
            for many current distro configurations including
            <code class="filename">DISTRO = "poky"</code> and
            <code class="filename">DISTRO = ""</code>) will result in the packaging
            tasks being re-run during the subsequent build.
        </p><p>
            To disable the build history functionality without causing the
            packaging tasks to be re-run, add just this statement to your
            <code class="filename">conf/local.conf</code> file:
            </p><pre class="literallayout">
     BUILDHISTORY_FEATURES = ""
            </pre><p>
        </p></div><div class="section" title="2.4.2. Understanding What the Build History Contains"><div class="titlepage"><div><div><h3 class="title"><a id="understanding-what-the-build-history-contains"></a>2.4.2. Understanding What the Build History Contains</h3></div></div></div><p>
            Build history information is kept in
            <a class="link" href="#var-TMPDIR" title="TMPDIR"><code class="filename">$TMPDIR</code></a><code class="filename">/buildhistory</code>
            in the Build Directory.
            The following is an example abbreviated listing:
            </p><table border="0" summary="manufactured viewport for HTML img" cellspacing="0" cellpadding="0" width="540"><tr style="height: 360px"><td align="center"><img src="figures/buildhistory.png" align="middle" width="540" /></td></tr></table><p>
        </p><div class="section" title="2.4.2.1. Build History Package Information"><div class="titlepage"><div><div><h4 class="title"><a id="build-history-package-information"></a>2.4.2.1. Build History Package Information</h4></div></div></div><p>
                The history for each package contains a text file that has
                name-value pairs with information about the package.
                For example, <code class="filename">buildhistory/packages/core2-poky-linux/busybox/busybox/latest</code>
                contains the following:
                </p><pre class="literallayout">
     PV = 1.19.3
     PR = r3
     RDEPENDS = update-rc.d eglibc (&gt;= 2.13)
     RRECOMMENDS = busybox-syslog busybox-udhcpc
     PKGSIZE = 564701
     FILES = /usr/bin/* /usr/sbin/* /usr/libexec/* /usr/lib/lib*.so.* \
        /etc /com /var /bin/* /sbin/* /lib/*.so.* /usr/share/busybox \
        /usr/lib/busybox/* /usr/share/pixmaps /usr/share/applications \
        /usr/share/idl /usr/share/omf /usr/share/sounds /usr/lib/bonobo/servers
     FILELIST = /etc/busybox.links /etc/init.d/hwclock.sh /bin/busybox /bin/sh
                </pre><p>
                Most of these name-value pairs corresponds to variables used
                to produce the package.
                The exceptions are <code class="filename">FILELIST</code>, which is the
                actual list of files in the package, and
                <code class="filename">PKGSIZE</code>, which is the total size of files
                in the package in bytes.
            </p><p>
                There is also a file corresponding to the recipe from which the
                package came (e.g.
                <code class="filename">buildhistory/packages/core2-poky-linux/busybox/latest</code>):
                </p><pre class="literallayout">
     PV = 1.19.3
     PR = r3
     DEPENDS = virtual/i586-poky-linux-gcc virtual/i586-poky-linux-compilerlibs \
        virtual/libc update-rc.d-native
     PACKAGES = busybox-httpd busybox-udhcpd busybox-udhcpc busybox-syslog \
        busybox-mdev busybox-dbg busybox busybox-doc busybox-dev \
        busybox-staticdev busybox-locale
                </pre><p>
            </p></div><div class="section" title="2.4.2.2. Build History Image Information"><div class="titlepage"><div><div><h4 class="title"><a id="build-history-image-information"></a>2.4.2.2. Build History Image Information</h4></div></div></div><p>
                The files produced for each image are as follows:
                </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em>build-id:</em></span>
                        Human-readable information about the build configuration
                        and metadata source revisions.</p></li><li class="listitem"><p><span class="emphasis"><em>*.dot:</em></span>
                        Dependency graphs for the image that are
                        compatible with <code class="filename">graphviz</code>.
                        </p></li><li class="listitem"><p><span class="emphasis"><em>files-in-image.txt:</em></span>
 	                    A list of files in the image with permissions,
                        owner, group, size, and symlink information.
                        </p></li><li class="listitem"><p><span class="emphasis"><em>image-info.txt:</em></span>
                        A text file containing name-value pairs with information
                        about the image.
                        See the following listing example for more information.
                        </p></li><li class="listitem"><p><span class="emphasis"><em>installed-package-names.txt:</em></span>
                        A list of installed packages by name only.</p></li><li class="listitem"><p><span class="emphasis"><em>installed-package-sizes.txt:</em></span>
                        A list of installed packages ordered by size.
                        </p></li><li class="listitem"><p><span class="emphasis"><em>installed-packages.txt:</em></span>
                        A list of installed packages with fuill package
                        filenames.</p></li></ul></div><p>
                </p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
                    Installed package information is able to be gathered and
                    produced even if package management is disabled for the final
                    image.
                </div><p>
            </p><p>
                Here is an example of <code class="filename">image-info.txt</code>:
                </p><pre class="literallayout">
     DISTRO = poky
     DISTRO_VERSION = 1.1+snapshot-20120207
     USER_CLASSES = image-mklibs image-prelink
     IMAGE_CLASSES = image_types
     IMAGE_FEATURES = debug-tweaks x11-base apps-x11-core \
        package-management ssh-server-dropbear package-management
     IMAGE_LINGUAS = en-us en-gb
     IMAGE_INSTALL = task-core-boot task-base-extended
     BAD_RECOMMENDATIONS =
     ROOTFS_POSTPROCESS_COMMAND = buildhistory_get_image_installed ;   rootfs_update_timestamp ;
     IMAGE_POSTPROCESS_COMMAND = buildhistory_get_imageinfo ;
     IMAGESIZE = 171816
                </pre><p>
                Other than <code class="filename">IMAGESIZE</code>, which is the
                total size of the files in the image in Kbytes, the
                name-value pairs are variables that may have influenced the
                content of the image.
                This information is often useful when you are trying to determine
                why a change in the package or file listings has occurred.
            </p></div><div class="section" title="2.4.2.3. Using Build History to Gather Image Information Only"><div class="titlepage"><div><div><h4 class="title"><a id="using-build-history-to-gather-image-information-only"></a>2.4.2.3. Using Build History to Gather Image Information Only</h4></div></div></div><p>
                As you can see, build history produces image information,
                including dependency graphs, so you can see why something
                was pulled into the image.
                If you are just interested in this information and not
                interested in collecting history or any package information,
                you can enable writing only image information without
                any history by adding the following
                to your <code class="filename">conf/local.conf</code> file found in the
                <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#build-directory" target="_top">Build Directory</a>:
                </p><pre class="literallayout">
     INHERIT += "buildhistory"
     BUILDHISTORY_COMMIT = "0"
     BUILDHISTORY_FEATURES = "image"
                </pre><p>
            </p></div><div class="section" title="2.4.2.4. Examining Build History Information"><div class="titlepage"><div><div><h4 class="title"><a id="examining-build-history-information"></a>2.4.2.4. Examining Build History Information</h4></div></div></div><p>
                You can examine build history output from the command line or
                from a web interface.
            </p><p>
                To see any changes that have occurred (assuming you have
                <code class="filename">BUILDHISTORY_COMMIT = "1"</code>), you can simply
                use any Git command that allows you to view the history of
                a repository.
                Here is one method:
                </p><pre class="literallayout">
      $ git log -p
                </pre><p>
                You need to realize, however, that this method does show
                changes that are not significant (e.g. a package's size
                changing by a few bytes).
            </p><p>
                A command-line tool called <code class="filename">buildhistory-diff</code>
                does exist though that queries the Git repository and prints just
                the differences that might be significant in human-readable form.
                Here is an example:
                </p><pre class="literallayout">
     $ ~/poky/poky/scripts/buildhistory-diff . HEAD^
     Changes to images/qemux86_64/eglibc/core-image-minimal (files-in-image.txt):
        /etc/anotherpkg.conf was added
        /sbin/anotherpkg was added
        * (installed-package-names.txt):
        *   anotherpkg was added
     Changes to images/qemux86_64/eglibc/core-image-minimal (installed-package-names.txt):
        anotherpkg was added
     packages/qemux86_64-poky-linux/v86d: PACKAGES: added "v86d-extras"
        * PR changed from "r0" to "r1"
        * PV changed from "0.1.10" to "0.1.12"
     packages/qemux86_64-poky-linux/v86d/v86d: PKGSIZE changed from 110579 to 144381 (+30%)
        * PR changed from "r0" to "r1"
        * PV changed from "0.1.10" to "0.1.12"
                </pre><p>
            </p><p>
                To see changes to the build history using a web interface, follow
                the instruction in the <code class="filename">README</code> file here.
                <a class="ulink" href="http://git.yoctoproject.org/cgit/cgit.cgi/buildhistory-web/" target="_top">http://git.yoctoproject.org/cgit/cgit.cgi/buildhistory-web/</a>.
            </p><p>
                Here is a sample screenshot of the interface:
                </p><table border="0" summary="manufactured viewport for HTML img" cellspacing="0" cellpadding="0" width="130%"><tr><td align="center"><img src="figures/buildhistory-web.png" align="middle" height="468" /></td></tr></table><p>
            </p></div></div></div></div>

    <div class="chapter" title="Chapter 3. Technical Details"><div class="titlepage"><div><div><h2 class="title"><a id="technical-details"></a>Chapter 3. Technical Details</h2></div></div></div><div class="toc"><p><strong>Table of Contents</strong></p><dl><dt><span class="section"><a href="#usingpoky-components">3.1. Yocto Project Components</a></span></dt><dd><dl><dt><span class="section"><a href="#usingpoky-components-bitbake">3.1.1. BitBake</a></span></dt><dt><span class="section"><a href="#usingpoky-components-metadata">3.1.2. Metadata (Recipes)</a></span></dt><dt><span class="section"><a href="#usingpoky-components-classes">3.1.3. Classes</a></span></dt><dt><span class="section"><a href="#usingpoky-components-configuration">3.1.4. Configuration</a></span></dt></dl></dd><dt><span class="section"><a href="#shared-state-cache">3.2. Shared State Cache</a></span></dt><dd><dl><dt><span class="section"><a href="#overall-architecture">3.2.1. Overall Architecture</a></span></dt><dt><span class="section"><a href="#checksums">3.2.2. Checksums (Signatures)</a></span></dt><dt><span class="section"><a href="#shared-state">3.2.3. Shared State</a></span></dt><dt><span class="section"><a href="#tips-and-tricks">3.2.4. Tips and Tricks</a></span></dt></dl></dd><dt><span class="section"><a href="#x32">3.3. x32</a></span></dt><dd><dl><dt><span class="section"><a href="#support">3.3.1. Support</a></span></dt><dt><span class="section"><a href="#future-development-and-limitations">3.3.2. Future Development and Limitations</a></span></dt><dt><span class="section"><a href="#using-x32-right-now">3.3.3. Using x32 Right Now</a></span></dt></dl></dd><dt><span class="section"><a href="#licenses">3.4. Licenses</a></span></dt><dd><dl><dt><span class="section"><a href="#usingpoky-configuring-LIC_FILES_CHKSUM">3.4.1. Tracking License Changes</a></span></dt><dt><span class="section"><a href="#enabling-commercially-licensed-recipes">3.4.2. Enabling Commercially Licensed Recipes</a></span></dt></dl></dd></dl></div><p>
        This chapter provides technical details for various parts of the Yocto Project.
        Currently, topics include Yocto Project components and shared state (sstate) cache.
    </p><div class="section" title="3.1. Yocto Project Components"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="usingpoky-components"></a>3.1. Yocto Project Components</h2></div></div></div><p>
        The BitBake task executor together with various types of configuration files form the
        OpenEmbedded Core.
        This section overviews the BitBake task executor and the
        configuration files by describing what they are used for and how they interact.
    </p><p>
        BitBake handles the parsing and execution of the data files.
        The data itself is of various types:
    </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em>Recipes:</em></span>  Provides details about particular
            pieces of software</p></li><li class="listitem"><p><span class="emphasis"><em>Class Data:</em></span>  An abstraction of common build
            information (e.g. how to build a Linux kernel).</p></li><li class="listitem"><p><span class="emphasis"><em>Configuration Data:</em></span>  Defines machine-specific settings,
            policy decisions, etc.
            Configuration data acts as the glue to bind everything together.</p></li></ul></div><p>
        For more information on data, see the
        "<a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#yocto-project-terms" target="_top">Yocto Project Terms</a>"
        section in the Yocto Project Development Manual.
    </p><p>
        BitBake knows how to combine multiple data sources together and refers to each data source
        as a layer.
        For information on layers, see the
        "<a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#understanding-and-creating-layers" target="_top">Understanding and
        Creating Layers</a>" section of the Yocto Project Development Manual.
    </p><p>
        Following are some brief details on these core components.
        For more detailed information on these components see the
        "<a class="link" href="#ref-structure" title="Chapter 5. Source Directory Structure">Directory Structure</a>" chapter.
    </p><div class="section" title="3.1.1. BitBake"><div class="titlepage"><div><div><h3 class="title"><a id="usingpoky-components-bitbake"></a>3.1.1. BitBake</h3></div></div></div><p>
            BitBake is the tool at the heart of the OpenEmbedded build system and is responsible
            for parsing the metadata, generating a list of tasks from it,
            and then executing those tasks.
            To see a list of the options BitBake supports, use the following help command:
            </p><pre class="literallayout">
     $ bitbake --help
            </pre><p>
        </p><p>
            The most common usage for BitBake is <code class="filename">bitbake &lt;packagename&gt;</code>, where
            <code class="filename">packagename</code> is the name of the package you want to build
            (referred to as the "target" in this manual).
            The target often equates to the first part of a <code class="filename">.bb</code> filename.
            So, to run the <code class="filename">matchbox-desktop_1.2.3.bb</code> file, you
            might type the following:
            </p><pre class="literallayout">
     $ bitbake matchbox-desktop
            </pre><p>
            Several different versions of <code class="filename">matchbox-desktop</code> might exist.
            BitBake chooses the one selected by the distribution configuration.
            You can get more details about how BitBake chooses between different
            target versions and providers in the
            "<a class="link" href="#ref-bitbake-providers" title="6.2. Preferences and Providers">Preferences and Providers</a>" section.
        </p><p>
            BitBake also tries to execute any dependent tasks first.
            So for example, before building <code class="filename">matchbox-desktop</code>, BitBake
            would build a cross compiler and <code class="filename">eglibc</code> if they had not already
            been built.
            </p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>This release of the Yocto Project does not support the <code class="filename">glibc</code>
                GNU version of the Unix standard C library.  By default, the OpenEmbedded build system
                builds with <code class="filename">eglibc</code>.</div><p>
        </p><p>
            A useful BitBake option to consider is the <code class="filename">-k</code> or
            <code class="filename">--continue</code> option.
            This option instructs BitBake to try and continue processing the job as much
            as possible even after encountering an error.
            When an error occurs, the target that
            failed and those that depend on it cannot be remade.
            However, when you use this option other dependencies can still be processed.
        </p></div><div class="section" title="3.1.2. Metadata (Recipes)"><div class="titlepage"><div><div><h3 class="title"><a id="usingpoky-components-metadata"></a>3.1.2. Metadata (Recipes)</h3></div></div></div><p>
            The <code class="filename">.bb</code> files are usually referred to as "recipes."
            In general, a recipe contains information about a single piece of software.
            The information includes the location from which to download the source patches
            (if any are needed), which special configuration options to apply,
            how to compile the source files, and how to package the compiled output.
        </p><p>
            The term "package" can also be used to describe recipes.
            However, since the same word is used for the packaged output from the OpenEmbedded
            build system (i.e. <code class="filename">.ipk</code> or <code class="filename">.deb</code> files),
            this document avoids using the term "package" when referring to recipes.
        </p></div><div class="section" title="3.1.3. Classes"><div class="titlepage"><div><div><h3 class="title"><a id="usingpoky-components-classes"></a>3.1.3. Classes</h3></div></div></div><p>
            Class files (<code class="filename">.bbclass</code>) contain information that is useful to share
            between metadata files.
            An example is the Autotools class, which contains
            common settings for any application that Autotools uses.
            The "<a class="link" href="#ref-classes" title="Chapter 7. Classes">Classes</a>" chapter provides details
            about common classes and how to use them.
        </p></div><div class="section" title="3.1.4. Configuration"><div class="titlepage"><div><div><h3 class="title"><a id="usingpoky-components-configuration"></a>3.1.4. Configuration</h3></div></div></div><p>
            The configuration files (<code class="filename">.conf</code>) define various configuration variables
            that govern the OpenEmbedded build process.
            These files fall into several areas that define machine configuration options,
            distribution configuration options, compiler tuning options, general common configuration
            options and user configuration options (<code class="filename">local.conf</code>, which is found
            in the <a class="ulink" href="build-directory" target="_top">Build Directory</a>).
        </p></div></div><div class="section" title="3.2. Shared State Cache"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="shared-state-cache"></a>3.2. Shared State Cache</h2></div></div></div><p>
        By design, the OpenEmbedded build system builds everything from scratch unless
        BitBake can determine that parts don't need to be rebuilt.
        Fundamentally, building from scratch is attractive as it means all parts are
        built fresh and there is no possibility of stale data causing problems.
        When developers hit problems, they typically default back to building from scratch
        so they know the state of things from the start.
    </p><p>
        Building an image from scratch is both an advantage and a disadvantage to the process.
        As mentioned in the previous paragraph, building from scratch ensures that
        everything is current and starts from a known state.
        However, building from scratch also takes much longer as it generally means
        rebuilding things that don't necessarily need rebuilt.
    </p><p>
        The Yocto Project implements shared state code that supports incremental builds.
        The implementation of the shared state code answers the following questions that
        were fundamental roadblocks within the OpenEmbedded incremental build support system:
        </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem">What pieces of the system have changed and what pieces have not changed?</li><li class="listitem">How are changed pieces of software removed and replaced?</li><li class="listitem">How are pre-built components that don't need to be rebuilt from scratch
                used when they are available?</li></ul></div><p>
    </p><p>
        For the first question, the build system detects changes in the "inputs" to a given task by
        creating a checksum (or signature) of the task's inputs.
        If the checksum changes, the system assumes the inputs have changed and the task needs to be
        rerun.
        For the second question, the shared state (sstate) code tracks which tasks add which output
        to the build process.
        This means the output from a given task can be removed, upgraded or otherwise manipulated.
        The third question is partly addressed by the solution for the second question
        assuming the build system can fetch the sstate objects from remote locations and
        install them if they are deemed to be valid.
    </p><p>
        The rest of this section goes into detail about the overall incremental build
        architecture, the checksums (signatures), shared state, and some tips and tricks.
    </p><div class="section" title="3.2.1. Overall Architecture"><div class="titlepage"><div><div><h3 class="title"><a id="overall-architecture"></a>3.2.1. Overall Architecture</h3></div></div></div><p>
            When determining what parts of the system need to be built, BitBake
            uses a per-task basis and does not use a per-recipe basis.
            You might wonder why using a per-task basis is preferred over a per-recipe basis.
            To help explain, consider having the IPK packaging backend enabled and then switching to DEB.
            In this case, <code class="filename">do_install</code> and <code class="filename">do_package</code>
            output are still valid.
            However, with a per-recipe approach, the build would not include the
            <code class="filename">.deb</code> files.
            Consequently, you would have to invalidate the whole build and rerun it.
            Rerunning everything is not the best situation.
            Also in this case, the core must be "taught" much about specific tasks.
            This methodology does not scale well and does not allow users to easily add new tasks
            in layers or as external recipes without touching the packaged-staging core.
        </p></div><div class="section" title="3.2.2. Checksums (Signatures)"><div class="titlepage"><div><div><h3 class="title"><a id="checksums"></a>3.2.2. Checksums (Signatures)</h3></div></div></div><p>
            The shared state code uses a checksum, which is a unique signature of a task's
            inputs, to determine if a task needs to be run again.
            Because it is a change in a task's inputs that triggers a rerun, the process
            needs to detect all the inputs to a given task.
            For shell tasks, this turns out to be fairly easy because
            the build process generates a "run" shell script for each task and
            it is possible to create a checksum that gives you a good idea of when
            the task's data changes.
        </p><p>
            To complicate the problem, there are things that should not be included in
            the checksum.
            First, there is the actual specific build path of a given task -
            the <a class="link" href="#var-WORKDIR" title="WORKDIR"><code class="filename">WORKDIR</code></a>.
            It does not matter if the working directory changes because it should not
            affect the output for target packages.
            Also, the build process has the objective of making native/cross packages relocatable.
            The checksum therefore needs to exclude <code class="filename">WORKDIR</code>.
            The simplistic approach for excluding the working directory is to set
            <code class="filename">WORKDIR</code> to some fixed value and create the checksum
            for the "run" script.
        </p><p>
            Another problem results from the "run" scripts containing functions that
            might or might not get called.
            The incremental build solution contains code that figures out dependencies
            between shell functions.
            This code is used to prune the "run" scripts down to the minimum set,
            thereby alleviating this problem and making the "run" scripts much more
            readable as a bonus.
        </p><p>
            So far we have solutions for shell scripts.
            What about python tasks?
            The same approach applies even though these tasks are more difficult.
            The process needs to figure out what variables a python function accesses
            and what functions it calls.
            Again, the incremental build solution contains code that first figures out
            the variable and function dependencies, and then creates a checksum for the data
            used as the input to the task.
        </p><p>
            Like the <code class="filename">WORKDIR</code> case, situations exist where dependencies
            should be ignored.
            For these cases, you can instruct the build process to ignore a dependency
            by using a line like the following:
            </p><pre class="literallayout">
     PACKAGE_ARCHS[vardepsexclude] = "MACHINE"
            </pre><p>
            This example ensures that the <code class="filename">PACKAGE_ARCHS</code> variable does not
            depend on the value of <code class="filename">MACHINE</code>, even if it does reference it.
        </p><p>
            Equally, there are cases where we need to add dependencies BitBake is not able to find.
            You can accomplish this by using a line like the following:
            </p><pre class="literallayout">
      PACKAGE_ARCHS[vardeps] = "MACHINE"
            </pre><p>
            This example explicitly adds the <code class="filename">MACHINE</code> variable as a
            dependency for <code class="filename">PACKAGE_ARCHS</code>.
        </p><p>
            Consider a case with inline python, for example, where BitBake is not
            able to figure out dependencies.
            When running in debug mode (i.e. using <code class="filename">-DDD</code>), BitBake
            produces output when it discovers something for which it cannot figure out
            dependencies.
            The Yocto Project team has currently not managed to cover those dependencies
            in detail and is aware of the need to fix this situation.
        </p><p>
            Thus far, this section has limited discussion to the direct inputs into a task.
            Information based on direct inputs is referred to as the "basehash" in the
            code.
            However, there is still the question of a task's indirect inputs - the
            things that were already built and present in the Build Directory.
            The checksum (or signature) for a particular task needs to add the hashes
            of all the tasks on which the particular task depends.
            Choosing which dependencies to add is a policy decision.
            However, the effect is to generate a master checksum that combines the basehash
            and the hashes of the task's dependencies.
        </p><p>
            At the code level, there are a variety of ways both the basehash and the
            dependent task hashes can be influenced.
            Within the BitBake configuration file, we can give BitBake some extra information
            to help it construct the basehash.
            The following statements effectively result in a list of global variable
            dependency excludes - variables never included in any checksum:
            </p><pre class="literallayout">
  BB_HASHBASE_WHITELIST ?= "TMPDIR FILE PATH PWD BB_TASKHASH BBPATH"
  BB_HASHBASE_WHITELIST += "DL_DIR SSTATE_DIR THISDIR FILESEXTRAPATHS"
  BB_HASHBASE_WHITELIST += "FILE_DIRNAME HOME LOGNAME SHELL TERM USER"
  BB_HASHBASE_WHITELIST += "FILESPATH USERNAME STAGING_DIR_HOST STAGING_DIR_TARGET"
            </pre><p>
            The previous example actually excludes
            <a class="link" href="#var-WORKDIR" title="WORKDIR"><code class="filename">WORKDIR</code></a>
            since it is actually constructed as a path within
            <a class="link" href="#var-TMPDIR" title="TMPDIR"><code class="filename">TMPDIR</code></a>, which is on
            the whitelist.
        </p><p>
            The rules for deciding which hashes of dependent tasks to include through
            dependency chains are more complex and are generally accomplished with a
            python function.
            The code in <code class="filename">meta/lib/oe/sstatesig.py</code> shows two examples
            of this and also illustrates how you can insert your own policy into the system
            if so desired.
            This file defines the two basic signature generators <code class="filename">OE-Core</code>
            uses:  "OEBasic" and "OEBasicHash".
            By default, there is a dummy "noop" signature handler enabled in BitBake.
            This means that behavior is unchanged from previous versions.
            <code class="filename">OE-Core</code> uses the "OEBasic" signature handler by default
            through this setting in the <code class="filename">bitbake.conf</code> file:
            </p><pre class="literallayout">
  BB_SIGNATURE_HANDLER ?= "OEBasic"
            </pre><p>
            The "OEBasicHash" <code class="filename">BB_SIGNATURE_HANDLER</code> is the same as the
            "OEBasic" version but adds the task hash to the stamp files.
            This results in any metadata change that changes the task hash, automatically
            causing the task to be run again.
            This removes the need to bump <a class="link" href="#var-PR" title="PR"><code class="filename">PR</code></a>
            values and changes to metadata automatically ripple across the build.
            Currently, this behavior is not the default behavior for <code class="filename">OE-Core</code>
            but is the default in <code class="filename">poky</code>.
        </p><p>
            It is also worth noting that the end result of these signature generators is to
            make some dependency and hash information available to the build.
            This information includes:
            </p><pre class="literallayout">
  BB_BASEHASH_task-&lt;taskname&gt; - the base hashes for each task in the recipe
  BB_BASEHASH_&lt;filename:taskname&gt; - the base hashes for each dependent task
  BBHASHDEPS_&lt;filename:taskname&gt; - The task dependencies for each task
  BB_TASKHASH - the hash of the currently running task
            </pre><p>
        </p></div><div class="section" title="3.2.3. Shared State"><div class="titlepage"><div><div><h3 class="title"><a id="shared-state"></a>3.2.3. Shared State</h3></div></div></div><p>
            Checksums and dependencies, as discussed in the previous section, solve half the
            problem.
            The other part of the problem is being able to use checksum information during the build
            and being able to reuse or rebuild specific components.
        </p><p>
            The shared state class (<code class="filename">sstate.bbclass</code>)
            is a relatively generic implementation of how to "capture" a snapshot of a given task.
            The idea is that the build process does not care about the source of a task's output.
            Output could be freshly built or it could be downloaded and unpacked from
            somewhere - the build process doesn't need to worry about its source.
        </p><p>
            There are two types of output, one is just about creating a directory
            in <a class="link" href="#var-WORKDIR" title="WORKDIR"><code class="filename">WORKDIR</code></a>.
            A good example is the output of either <code class="filename">do_install</code> or
            <code class="filename">do_package</code>.
            The other type of output occurs when a set of data is merged into a shared directory
            tree such as the sysroot.
        </p><p>
            The Yocto Project team has tried to keep the details of the implementation hidden in
            <code class="filename">sstate.bbclass</code>.
            From a user's perspective, adding shared state wrapping to a task
            is as simple as this <code class="filename">do_deploy</code> example taken from
            <code class="filename">do_deploy.bbclass</code>:
            </p><pre class="literallayout">
     DEPLOYDIR = "${WORKDIR}/deploy-${PN}"
     SSTATETASKS += "do_deploy"
     do_deploy[sstate-name] = "deploy"
     do_deploy[sstate-inputdirs] = "${DEPLOYDIR}"
     do_deploy[sstate-outputdirs] = "${DEPLOY_DIR_IMAGE}"

     python do_deploy_setscene () {
         sstate_setscene(d)
     }
     addtask do_deploy_setscene
            </pre><p>
            In the example, we add some extra flags to the task, a name field ("deploy"), an
            input directory where the task sends data, and the output
            directory where the data from the task should eventually be copied.
            We also add a <code class="filename">_setscene</code> variant of the task and add the task
            name to the <code class="filename">SSTATETASKS</code> list.
        </p><p>
            If you have a directory whose contents you need to preserve, you can do this with
            a line like the following:
            </p><pre class="literallayout">
     do_package[sstate-plaindirs] = "${PKGD} ${PKGDEST}"
            </pre><p>
            This method, as well as the following example, also works for multiple directories.
            </p><pre class="literallayout">
     do_package[sstate-inputdirs] = "${PKGDESTWORK} ${SHLIBSWORKDIR}"
     do_package[sstate-outputdirs] = "${PKGDATA_DIR} ${SHLIBSDIR}"
     do_package[sstate-lockfile] = "${PACKAGELOCK}"
            </pre><p>
            These methods also include the ability to take a lockfile when manipulating
            shared state directory structures since some cases are sensitive to file
            additions or removals.
        </p><p>
            Behind the scenes, the shared state code works by looking in
            <a class="link" href="#var-SSTATE_DIR" title="SSTATE_DIR"><code class="filename">SSTATE_DIR</code></a> and
            <a class="link" href="#var-SSTATE_MIRRORS" title="SSTATE_MIRRORS"><code class="filename">SSTATE_MIRRORS</code></a>
            for shared state files.
            Here is an example:
            </p><pre class="literallayout">
     SSTATE_MIRRORS ?= "\
     file://.* http://someserver.tld/share/sstate/PATH \n \
     file://.* file:///some/local/dir/sstate/PATH"
            </pre><p>
            </p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
                The shared state directory (<code class="filename">SSTATE_DIR</code>) is
                organized into two-character subdirectories, where the subdirectory
                names are based on the first two characters of the hash.
                If the shared state directory structure for a mirror has the
                same structure as <code class="filename">SSTATE_DIR</code>, you must
                specify "PATH" as part of the URI to enable the build system
                to map to the appropriate subdirectory.
            </div><p>
        </p><p>
            The shared state package validity can be detected just by looking at the
            filename since the filename contains the task checksum (or signature) as
            described earlier in this section.
            If a valid shared state package is found, the build process downloads it
            and uses it to accelerate the task.
        </p><p>
            The build processes uses the <code class="filename">*_setscene</code> tasks
            for the task acceleration phase.
            BitBake goes through this phase before the main execution code and tries
            to accelerate any tasks for which it can find shared state packages.
            If a shared state package for a task is available, the shared state
            package is used.
            This means the task and any tasks on which it is dependent are not
            executed.
        </p><p>
            As a real world example, the aim is when building an IPK-based image,
            only the <code class="filename">do_package_write_ipk</code> tasks would have their
            shared state packages fetched and extracted.
            Since the sysroot is not used, it would never get extracted.
            This is another reason why a task-based approach is preferred over a
            recipe-based approach, which would have to install the output from every task.
        </p></div><div class="section" title="3.2.4. Tips and Tricks"><div class="titlepage"><div><div><h3 class="title"><a id="tips-and-tricks"></a>3.2.4. Tips and Tricks</h3></div></div></div><p>
            The code in the build system that supports incremental builds is not
            simple code.
            This section presents some tips and tricks that help you work around
            issues related to shared state code.
        </p><div class="section" title="3.2.4.1. Debugging"><div class="titlepage"><div><div><h4 class="title"><a id="debugging"></a>3.2.4.1. Debugging</h4></div></div></div><p>
                When things go wrong, debugging needs to be straightforward.
                Because of this, the Yocto Project team included strong debugging
                tools:
                </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>Whenever a shared state package is written out, so is a
                        corresponding <code class="filename">.siginfo</code> file.
                        This practice results in a pickled python database of all
                        the metadata that went into creating the hash for a given shared state
                        package.</p></li><li class="listitem"><p>If BitBake is run with the <code class="filename">--dump-signatures</code>
                        (or <code class="filename">-S</code>) option, BitBake dumps out
                        <code class="filename">.siginfo</code> files in
                        the stamp directory for every task it would have executed instead of
                        building the specified target package.</p></li><li class="listitem"><p>There is a <code class="filename">bitbake-diffsigs</code> command that
                        can process these <code class="filename">.siginfo</code> files.
                        If one file is specified, it will dump out the dependency
                        information in the file.
                        If two files are specified, it will compare the two files and dump out
                        the differences between the two.
                        This allows the question of "What changed between X and Y?" to be
                        answered easily.</p></li></ul></div><p>
            </p></div><div class="section" title="3.2.4.2. Invalidating Shared State"><div class="titlepage"><div><div><h4 class="title"><a id="invalidating-shared-state"></a>3.2.4.2. Invalidating Shared State</h4></div></div></div><p>
                The shared state code uses checksums and shared state
                cache to avoid unnecessarily rebuilding tasks.
                As with all schemes, this one has some drawbacks.
                It is possible that you could make implicit changes that are not factored
                into the checksum calculation, but do affect a task's output.
                A good example is perhaps when a tool changes its output.
                Let's say that the output of <code class="filename">rpmdeps</code> needed to change.
                The result of the change should be that all the "package", "package_write_rpm",
                and "package_deploy-rpm" shared state cache items would become invalid.
                But, because this is a change that is external to the code and therefore implicit,
                the associated shared state cache items do not become invalidated.
                In this case, the build process would use the cached items rather than running the
                task again.
                Obviously, these types of implicit changes can cause problems.
            </p><p>
                To avoid these problems during the build, you need to understand the effects of any
                change you make.
                Note that any changes you make directly to a function automatically are factored into
                the checksum calculation and thus, will invalidate the associated area of sstate cache.
                You need to be aware of any implicit changes that are not obvious changes to the
                code and could affect the output of a given task.
                Once you are aware of such a change, you can take steps to invalidate the cache
                and force the task to run.
                The step to take is as simple as changing a function's comments in the source code.
                For example, to invalidate package shared state files, change the comment statements
                of <code class="filename">do_package</code> or the comments of one of the functions it calls.
                The change is purely cosmetic, but it causes the checksum to be recalculated and
                forces the task to be run again.
            </p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
                For an example of a commit that makes a cosmetic change to invalidate
                a shared state, see this
                <a class="ulink" href="http://git.yoctoproject.org/cgit.cgi/poky/commit/meta/classes/package.bbclass?id=737f8bbb4f27b4837047cb9b4fbfe01dfde36d54" target="_top">commit</a>.
            </div></div></div></div><div class="section" title="3.3. x32"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="x32"></a>3.3. x32</h2></div></div></div><p>
        x32 is a new processor-specific Application Binary Interface (psABI) for x86_64.
        An ABI defines the calling conventions between functions in a processing environment.
        The interface determines what registers are used and what the sizes are for various C data types.
    </p><p>
        Some processing environments prefer using 32-bit applications even when running
        on Intel 64-bit platforms.
        Consider the i386 psABI, which is a very old 32-bit ABI for Intel 64-bit platforms.
        The i386 psABI does not provide efficient use and access of the Intel 64-bit processor resources,
        leaving the system underutilized.
        Now consider the x86_64 psABI.
        This ABI is newer and uses 64-bits for data sizes and program pointers.
        The extra bits increase the footprint size of the programs, libraries,
        and also increases the memory and file system size requirements.
        Executing under the x32 psABI enables user programs to utilize CPU and system resources
        more efficiently while keeping the memory footprint of the applications low.
        Extra bits are used for registers but not for addressing mechanisms.
    </p><div class="section" title="3.3.1. Support"><div class="titlepage"><div><div><h3 class="title"><a id="support"></a>3.3.1. Support</h3></div></div></div><p>
            While the x32 psABI specifications are not fully finalized, this Yocto Project
            release supports current development specifications of x32 psABI.
            As of this release of the Yocto Project, x32 psABI support exists as follows:
            </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>You can create packages and images in x32 psABI format on x86_64 architecture targets.
                    </p></li><li class="listitem"><p>You can use the x32 psABI support through the <code class="filename">meta-x32</code>
                    layer on top of the OE-core/Yocto layer.</p></li><li class="listitem"><p>The toolchain from the <code class="filename">experimental/meta-x32</code> layer
                    is used for building x32 psABI program binaries.</p></li><li class="listitem"><p>You can successfully build many recipes with the x32 toolchain.</p></li><li class="listitem"><p>You can create and boot <code class="filename">core-image-minimal</code> and
                    <code class="filename">core-image-sato</code> images.</p></li></ul></div><p>
        </p></div><div class="section" title="3.3.2. Future Development and Limitations"><div class="titlepage"><div><div><h3 class="title"><a id="future-development-and-limitations"></a>3.3.2. Future Development and Limitations</h3></div></div></div><p>
            As of this Yocto Project release, the x32 psABI kernel and library interfaces
            specifications are not finalized.
        </p><p>
            Future Plans for the x32 psABI in the Yocto Project include the following:
            </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>Enhance and fix the few remaining recipes so they
                    work with and support x32 toolchains.</p></li><li class="listitem"><p>Enhance RPM Package Manager (RPM) support for x32 binaries.</p></li><li class="listitem"><p>Support larger images.</p></li><li class="listitem"><p>Integrate x32 recipes, toolchain, and kernel changes from
                    <code class="filename">experimental/meta-x32</code> into OE-core.</p></li></ul></div><p>
        </p></div><div class="section" title="3.3.3. Using x32 Right Now"><div class="titlepage"><div><div><h3 class="title"><a id="using-x32-right-now"></a>3.3.3. Using x32 Right Now</h3></div></div></div><p>
            Despite the fact the x32 psABI support is in development state for this release of the
            Yocto Project, you can follow these steps to use the x32 spABI:
            </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>Add the <code class="filename">experimental/meta-x32</code> layer to your local
                    <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#build-directory" target="_top">Build Directory</a>.
                    You can find the <code class="filename">experimental/meta-x32</code> source repository at
                    <a class="ulink" href="http://git.yoctoproject.org" target="_top">http://git.yoctoproject.org</a>.</p></li><li class="listitem"><p>Edit your <code class="filename">conf/bblayers.conf</code> file so that it includes
                    the <code class="filename">meta-x32</code>.
                    Here is an example:
                    </p><pre class="literallayout">
     BBLAYERS ?= " \
        /home/nitin/prj/poky.git/meta \
        /home/nitin/prj/poky.git/meta-yocto \
        /home/nitin/prj/poky.git/meta-yocto-bsp \
        /home/nitin/prj/meta-x32.git \
        "
     BBLAYERS_NON_REMOVABLE ?= " \
        /home/nitin/prj/poky.git/meta \
        /home/nitin/prj/poky.git/meta-yocto \
        "
                    </pre></li><li class="listitem"><p>Enable the x32 psABI tuning file for <code class="filename">x86_64</code>
                    machines by editing the <code class="filename">conf/local.conf</code> like this:
                    </p><pre class="literallayout">
      MACHINE = "qemux86-64"
      DEFAULTTUNE = "x86-64-x32"
      baselib = "${@d.getVar('BASE_LIB_tune-' + (d.getVar('DEFAULTTUNE', True) \
         or 'INVALID'), True) or 'lib'}"
      #MACHINE = "atom-pc"
      #DEFAULTTUNE = "core2-64-x32"
                    </pre></li><li class="listitem"><p>As usual, use BitBake to build an image that supports the x32 psABI.
                    Here is an example:
                    </p><pre class="literallayout">
     $ bitake core-image-sato
                    </pre></li><li class="listitem"><p>As usual, run your image using QEMU:
                    </p><pre class="literallayout">
     $ runqemu qemux86-64 core-image-sato
                    </pre></li></ul></div><p>
        </p></div></div><div class="section" title="3.4. Licenses"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="licenses"></a>3.4. Licenses</h2></div></div></div><p>
        This section describes the mechanism by which the OpenEmbedded build system
        tracks changes to licensing text.
        The section also describes how to enable commercially licensed recipes,
        which by default are disabled.
    </p><p>
        For information that can help you maintain compliance with various open
        source licensing during the lifecycle of the product, see the
        "<a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#maintaining-open-source-license-compliance-during-your-products-lifecycle" target="_top">Maintaining Open Source License Compliance During Your Project's Lifecycle</a>" section
        in the Yocto Project Development Manual.
    </p><div class="section" title="3.4.1. Tracking License Changes"><div class="titlepage"><div><div><h3 class="title"><a id="usingpoky-configuring-LIC_FILES_CHKSUM"></a>3.4.1. Tracking License Changes</h3></div></div></div><p>
            The license of an upstream project might change in the future.
            In order to prevent these changes going unnoticed, the
            <code class="filename"><a class="link" href="#var-LIC_FILES_CHKSUM" title="LIC_FILES_CHKSUM">LIC_FILES_CHKSUM</a></code>
            variable tracks changes to the license text. The checksums are validated at the end of the
            configure step, and if the checksums do not match, the build will fail.
        </p><div class="section" title="3.4.1.1. Specifying the LIC_FILES_CHKSUM Variable"><div class="titlepage"><div><div><h4 class="title"><a id="usingpoky-specifying-LIC_FILES_CHKSUM"></a>3.4.1.1. Specifying the <code class="filename">LIC_FILES_CHKSUM</code> Variable</h4></div></div></div><p>
                The <code class="filename">LIC_FILES_CHKSUM</code>
                variable contains checksums of the license text in the source code for the recipe.
                Following is an example of how to specify <code class="filename">LIC_FILES_CHKSUM</code>:
                </p><pre class="literallayout">
     LIC_FILES_CHKSUM = "file://COPYING;md5=xxxx \
                         file://licfile1.txt;beginline=5;endline=29;md5=yyyy \
                         file://licfile2.txt;endline=50;md5=zzzz \
                         ..."
                </pre><p>
            </p><p>
                The build system uses the
                <code class="filename"><a class="link" href="#var-S" title="S">S</a></code> variable as the
                default directory used when searching files listed in
                <code class="filename">LIC_FILES_CHKSUM</code>.
                The previous example employs the default directory.
            </p><p>
                You can also use relative paths as shown in the following example:
                </p><pre class="literallayout">
     LIC_FILES_CHKSUM = "file://src/ls.c;startline=5;endline=16;\
                                         md5=bb14ed3c4cda583abc85401304b5cd4e"
     LIC_FILES_CHKSUM = "file://../license.html;md5=5c94767cedb5d6987c902ac850ded2c6"
                </pre><p>
            </p><p>
                In this example, the first line locates a file in
                <code class="filename">${S}/src/ls.c</code>.
                The second line refers to a file in
                <code class="filename"><a class="link" href="#var-WORKDIR" title="WORKDIR">WORKDIR</a></code>, which is the parent
                of <code class="filename"><a class="link" href="#var-S" title="S">S</a></code>.
            </p><p>
                Note that this variable is mandatory for all recipes, unless the
                <code class="filename">LICENSE</code> variable is set to "CLOSED".
            </p></div><div class="section" title="3.4.1.2. Explanation of Syntax"><div class="titlepage"><div><div><h4 class="title"><a id="usingpoky-LIC_FILES_CHKSUM-explanation-of-syntax"></a>3.4.1.2. Explanation of Syntax</h4></div></div></div><p>
                As mentioned in the previous section, the
                <code class="filename">LIC_FILES_CHKSUM</code> variable lists all the
                important files that contain the license text for the source code.
                It is possible to specify a checksum for an entire file, or a specific section of a
                file (specified by beginning and ending line numbers with the "beginline" and "endline"
                parameters, respectively).
                The latter is useful for source files with a license notice header,
                README documents, and so forth.
                If you do not use the "beginline" parameter, then it is assumed that the text begins on the
                first line of the file.
                Similarly, if you do not use the "endline" parameter, it is assumed that the license text
                ends with the last line of the file.
            </p><p>
                The "md5" parameter stores the md5 checksum of the license text.
                If the license text changes in any way as compared to this parameter
                then a mismatch occurs.
                This mismatch triggers a build failure and notifies the developer.
                Notification allows the developer to review and address the license text changes.
                Also note that if a mismatch occurs during the build, the correct md5
                checksum is placed in the build log and can be easily copied to the recipe.
            </p><p>
                There is no limit to how many files you can specify using the
                <code class="filename">LIC_FILES_CHKSUM</code> variable.
                Generally, however, every project requires a few specifications for license tracking.
                Many projects have a "COPYING" file that stores the license information for all the source
                code files.
                This practice allows you to just track the "COPYING" file as long as it is kept up to date.
            </p><div class="tip" title="Tip" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Tip</h3>
                If you specify an empty or invalid "md5" parameter, BitBake returns an md5 mis-match
                error and displays the correct "md5" parameter value during the build.
                The correct parameter is also captured in the build log.
            </div><div class="tip" title="Tip" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Tip</h3>
                If the whole file contains only license text, you do not need to use the "beginline" and
                "endline" parameters.
            </div></div></div><div class="section" title="3.4.2. Enabling Commercially Licensed Recipes"><div class="titlepage"><div><div><h3 class="title"><a id="enabling-commercially-licensed-recipes"></a>3.4.2. Enabling Commercially Licensed Recipes</h3></div></div></div><p>
            By default, the OpenEmbedded build system disables
            components that have commercial or other special licensing
            requirements.
            Such requirements are defined on a
            recipe-by-recipe basis through the <code class="filename">LICENSE_FLAGS</code> variable
            definition in the affected recipe.
            For instance, the
            <code class="filename">$HOME/poky/meta/recipes-multimedia/gstreamer/gst-plugins-ugly</code>
            recipe contains the following statement:
            </p><pre class="literallayout">
     LICENSE_FLAGS = "commercial"
            </pre><p>
            Here is a slightly more complicated example that contains both an
            explicit recipe name and version (after variable expansion):
            </p><pre class="literallayout">
     LICENSE_FLAGS = "license_${PN}_${PV}"
            </pre><p>
	        In order for a component restricted by a <code class="filename">LICENSE_FLAGS</code>
	        definition to be enabled and included in an image, it
	        needs to have a matching entry in the global
	        <code class="filename">LICENSE_FLAGS_WHITELIST</code> variable, which is a variable
	        typically defined in your <code class="filename">local.conf</code> file.
            For example, to enable
	        the <code class="filename">$HOME/poky/meta/recipes-multimedia/gstreamer/gst-plugins-ugly</code>
	        package, you could add either the string
	        "commercial_gst-plugins-ugly" or the more general string
	        "commercial" to <code class="filename">LICENSE_FLAGS_WHITELIST</code>.
            See the
            "<a class="link" href="#license-flag-matching" title="3.4.2.1. License Flag Matching">License Flag Matching</a>" section
            for a full explanation of how <code class="filename">LICENSE_FLAGS</code> matching works.
            Here is the example:
            </p><pre class="literallayout">
     LICENSE_FLAGS_WHITELIST = "commercial_gst-plugins-ugly"
            </pre><p>
	        Likewise, to additionally enable the package built from the recipe containing
	        <code class="filename">LICENSE_FLAGS = "license_${PN}_${PV}"</code>, and assuming
	        that the actual recipe name was <code class="filename">emgd_1.10.bb</code>,
	        the following string would enable that package as well as
	        the original <code class="filename">gst-plugins-ugly</code> package:
            </p><pre class="literallayout">
     LICENSE_FLAGS_WHITELIST = "commercial_gst-plugins-ugly license_emgd_1.10"
            </pre><p>
	        As a convenience, you do not need to specify the complete license string
	        in the whitelist for every package.
            you can use an abbreviated form, which consists
	        of just the first portion or portions of the license string before
	        the initial underscore character or characters.
            A partial string will match
	        any license that contains the given string as the first
	        portion of its license.
            For example, the following
	        whitelist string will also match both of the packages
	        previously mentioned as well as any other packages that have
	        licenses starting with "commercial" or "license".
            </p><pre class="literallayout">
     LICENSE_FLAGS_WHITELIST = "commercial license"
            </pre><p>
        </p><div class="section" title="3.4.2.1. License Flag Matching"><div class="titlepage"><div><div><h4 class="title"><a id="license-flag-matching"></a>3.4.2.1. License Flag Matching</h4></div></div></div><p>
		        The definition of 'matching' in reference to a
		        recipe's <code class="filename">LICENSE_FLAGS</code> setting is simple.
                However, some things exist that you should know about in order to
                correctly and effectively use it.
            </p><p>
                Before a flag
                defined by a particular recipe is tested against the
                contents of the <code class="filename">LICENSE_FLAGS_WHITELIST</code> variable, the
                string <code class="filename">_${PN}</code> (with
                <a class="link" href="#var-PN" title="PN"><code class="filename">PN</code></a> expanded of course) is
                appended to the flag, thus automatically making each
                <code class="filename">LICENSE_FLAGS</code> value recipe-specific.
                That string is
                then matched against the whitelist.
                So if you specify <code class="filename">LICENSE_FLAGS = "commercial"</code> in recipe
		        "foo" for example, the string <code class="filename">"commercial_foo"</code>
                would normally be what is specified in the whitelist in order for it to
                match.
            </p><p>
                You can broaden the match by
                putting any "_"-separated beginning subset of a
                <code class="filename">LICENSE_FLAGS</code> flag in the whitelist, which will also
                match.
                For example, simply specifying "commercial" in
                the whitelist would match any expanded <code class="filename">LICENSE_FLAGS</code>
                definition starting with "commercial" such as
                "commercial_foo" and "commercial_bar", which are the
                strings that would be automatically generated for
                hypothetical "foo" and "bar" recipes assuming those
                recipes had simply specified the following:
                </p><pre class="literallayout">
     LICENSE_FLAGS = "commercial"
                </pre><p>
            </p><p>
                Broadening the match allows for a range of specificity for the items
                in the whitelist, from more general to perfectly
                specific.
                So you have the choice of exhaustively
                enumerating each license flag in the whitelist to
                allow only those specific recipes into the image, or
                of using a more general string to pick up anything
                matching just the first component or components of the specified
                string.
            </p><p>
                This scheme works even if the flag already
                has <code class="filename">_${PN}</code> appended - the extra <code class="filename">_${PN}</code> is
                redundant, but does not affect the outcome.
                For example, a license flag of "commercial_1.2_foo" would
                turn into "commercial_1.2_foo_foo" and would match
                both the general "commercial" and the specific
                "commercial_1.2_foo", as expected.
                The flag would also match
                "commercial_1.2_foo_foo" and "commercial_1.2", which
                does not make much sense regarding use in the whitelist.
            </p><p>
                For a versioned string, you could instead specify
                "commercial_foo_1.2", which would turn into
                "commercial_foo_1.2_foo".
                And, as expected, this flag allows
                you to pick up this package along with
                anything else "commercial" when you specify "commercial"
                in the whitelist.
                Or, the flag allows you to pick up this package along with anything "commercial_foo"
                regardless of version when you use "commercial_foo" in the whitelist.
                Finally, you can be completely specific about the package and version and specify
                "commercial_foo_1.2" package and version.
            </p></div><div class="section" title="3.4.2.2. Other Variables Related to Commercial Licenses"><div class="titlepage"><div><div><h4 class="title"><a id="other-variables-related-to-commercial-licenses"></a>3.4.2.2. Other Variables Related to Commercial Licenses</h4></div></div></div><p>
                Other helpful variables related to commercial
                license handling exist and are defined in the
                <code class="filename">$HOME/poky/meta/conf/distro/include/default-distrovars.inc</code> file:
                </p><pre class="literallayout">
     COMMERCIAL_AUDIO_PLUGINS ?= ""
     COMMERCIAL_VIDEO_PLUGINS ?= ""
     COMMERCIAL_QT = ""
                </pre><p>
                If you want to enable these components, you can do so by making sure you have
                the following statements in your <code class="filename">local.conf</code> configuration file:
                </p><pre class="literallayout">
     COMMERCIAL_AUDIO_PLUGINS = "gst-plugins-ugly-mad \
        gst-plugins-ugly-mpegaudioparse"
     COMMERCIAL_VIDEO_PLUGINS = "gst-plugins-ugly-mpeg2dec \
        gst-plugins-ugly-mpegstream gst-plugins-bad-mpegvideoparse"
     COMMERCIAL_QT ?= "qmmp"
     LICENSE_FLAGS_WHITELIST = "commercial_gst-plugins-ugly commercial_gst-plugins-bad commercial_qmmp"
                </pre><p>
                Of course, you could also create a matching whitelist
                for those components using the more general "commercial"
                in the whitelist, but that would also enable all the
                other packages with <code class="filename">LICENSE_FLAGS</code> containing
                "commercial", which you may or may not want:
                </p><pre class="literallayout">
     LICENSE_FLAGS_WHITELIST = "commercial"
                </pre><p>
            </p><p>
                Specifying audio and video plug-ins as part of the
                <code class="filename">COMMERCIAL_AUDIO_PLUGINS</code> and
                <code class="filename">COMMERCIAL_VIDEO_PLUGINS</code> statements
                or commercial qt components as part of
                the <code class="filename">COMMERCIAL_QT</code> statement (along
                with the enabling <code class="filename">LICENSE_FLAGS_WHITELIST</code>) includes the
                plug-ins or components into built images, thus adding
                support for media formats or components.
            </p></div></div></div></div>

    <div class="chapter" title="Chapter 4. Migrating to a Newer Yocto Project Release"><div class="titlepage"><div><div><h2 class="title"><a id="migration"></a>Chapter 4. Migrating to a Newer Yocto Project Release</h2></div></div></div><div class="toc"><p><strong>Table of Contents</strong></p><dl><dt><span class="section"><a href="#moving-to-the-yocto-project-1.3-release">4.1. Moving to the Yocto Project 1.3 Release</a></span></dt><dd><dl><dt><span class="section"><a href="#1.3-local-configuration">4.1.1. Local Configuration</a></span></dt><dt><span class="section"><a href="#1.3-recipes">4.1.2. Recipes</a></span></dt></dl></dd></dl></div><p>
        This chapter provides information you can use to migrate work to a
        newer Yocto Project release.  You can find the same information in the
        release notes for a given release.
    </p><div class="section" title="4.1. Moving to the Yocto Project 1.3 Release"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="moving-to-the-yocto-project-1.3-release"></a>4.1. Moving to the Yocto Project 1.3 Release</h2></div></div></div><p>
        This section provides migration information for moving to the
        Yocto Project 1.3 Release.
    </p><div class="section" title="4.1.1. Local Configuration"><div class="titlepage"><div><div><h3 class="title"><a id="1.3-local-configuration"></a>4.1.1. Local Configuration</h3></div></div></div><p>
            Differences include changes for
            <a class="link" href="#var-SSTATE_MIRRORS" title="SSTATE_MIRRORS"><code class="filename">SSTATE_MIRRORS</code></a>
            and <code class="filename">bblayers.conf</code>.
        </p><div class="section" title="4.1.1.1. SSTATE_MIRRORS"><div class="titlepage"><div><div><h4 class="title"><a id="migration-1.3-sstate-mirrors"></a>4.1.1.1. SSTATE_MIRRORS</h4></div></div></div><p>
                The shared state cache (sstate-cache) as pointed to by
                <a class="link" href="#var-SSTATE_DIR" title="SSTATE_DIR"><code class="filename">SSTATE_DIR</code></a> by default
                now has two-character subdirectories to prevent there being an issue with too
                many files in the same directory.
                Also, native sstate-cache packages will go into a subdirectory named using
                the distro ID string.
                If you copy the newly structured sstate-cache to a mirror location
                (either local or remote) and then point to it in
                <a class="link" href="#var-SSTATE_MIRRORS" title="SSTATE_MIRRORS"><code class="filename">SSTATE_MIRRORS</code></a>,
                you need to append "PATH" to the end of the mirror URL so that
                the path used by BitBake before the mirror substitution is
                appended to the path used to access the mirror.
                Here is an example:
                </p><pre class="literallayout">
     SSTATE_MIRRORS = "file://.* http://someserver.tld/share/sstate/PATH"
                </pre><p>
            </p></div><div class="section" title="4.1.1.2. bblayers.conf"><div class="titlepage"><div><div><h4 class="title"><a id="migration-1.3-bblayers-conf"></a>4.1.1.2. bblayers.conf</h4></div></div></div><p>
                The <code class="filename">meta-yocto</code> layer has been split into
                two parts: <code class="filename">meta-yocto</code> and
                <code class="filename">meta-yocto-bsp</code>, corresponding to the
                Poky reference distro configuration and the reference
                hardware Board Support Packages (BSPs), respectively.
                When running BitBake or Hob for the first time after upgrading,
                your <code class="filename">conf/bblayers.conf</code> file will be
                updated to handle this change and you will be asked to
                re-run/restart for the changes to take effect.
            </p></div></div><div class="section" title="4.1.2. Recipes"><div class="titlepage"><div><div><h3 class="title"><a id="1.3-recipes"></a>4.1.2. Recipes</h3></div></div></div><p>
            Differences include changes for the following:
            </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>Python function whitespace</p></li><li class="listitem"><p><code class="filename">proto=</code> in <code class="filename">SRC_URI</code></p></li><li class="listitem"><p><code class="filename">nativesdk</code></p></li><li class="listitem"><p>Task recipes</p></li><li class="listitem"><p><code class="filename">IMAGE_FEATURES</code></p></li><li class="listitem"><p>Removed recipes</p></li></ul></div><p>
        </p><div class="section" title="4.1.2.1. Python Function Whitespace"><div class="titlepage"><div><div><h4 class="title"><a id="migration-1.3-python-function-whitespace"></a>4.1.2.1. Python Function Whitespace</h4></div></div></div><p>
                All Python functions must now use four spaces for indentation.
                Previously, an inconsistent mix of spaces and tabs existed,
                which made extending these functions using
                <code class="filename">_append</code> or <code class="filename">_prepend</code>
                complicated given that Python treats whitespace as
                syntactically significant.
                If you are defining or extending any Python functions (e.g.
                <code class="filename">populate_packages</code>, <code class="filename">do_unpack</code>,
                <code class="filename">do_patch</code> and so forth) in custom recipes
                or classes, you need to ensure you are using consistent
                four-space indentation.
            </p></div><div class="section" title="4.1.2.2. proto= in SRC_URI"><div class="titlepage"><div><div><h4 class="title"><a id="migration-1.3-proto=-in-src-uri"></a>4.1.2.2. proto= in SRC_URI</h4></div></div></div><p>
                Any use of <code class="filename">proto=</code> in
                <a class="link" href="#var-SRC_URI" title="SRC_URI"><code class="filename">SRC_URI</code></a>
                needs to be changed to <code class="filename">protocol=</code>.
                In particular, this applies to the following URIs:
                </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><code class="filename">svn://</code></p></li><li class="listitem"><p><code class="filename">bzr://</code></p></li><li class="listitem"><p><code class="filename">hg://</code></p></li><li class="listitem"><p><code class="filename">osc://</code></p></li></ul></div><p>
                Other URIs were already using <code class="filename">protocol=</code>.
                This change improves consistency.
            </p></div><div class="section" title="4.1.2.3. nativesdk"><div class="titlepage"><div><div><h4 class="title"><a id="migration-1.3-nativesdk"></a>4.1.2.3. nativesdk</h4></div></div></div><p>
                The suffix <code class="filename">nativesdk</code> is now implemented
                as a prefix, which simplifies a lot of the packaging code for
                <code class="filename">nativesdk</code> recipes.
                All custom <code class="filename">nativesdk</code> recipes and any
                references need to be updated to use
                <code class="filename">nativesdk-*</code> instead of
                <code class="filename">*-nativesdk</code>.
            </p></div><div class="section" title="4.1.2.4. Task Recipes"><div class="titlepage"><div><div><h4 class="title"><a id="migration-1.3-task-recipes"></a>4.1.2.4. Task Recipes</h4></div></div></div><p>
                "Task" recipes are now known as "Package groups" and have
                been renamed from <code class="filename">task-*.bb</code> to
                <code class="filename">packagegroup-*.bb</code>.
                Existing references to the previous <code class="filename">task-*</code>
                names should work in most cases as there is an automatic
                upgrade path for most packages.
                However, you should update references in your own recipes and
                configurations as they could be removed in future releases.
                You should also rename any custom <code class="filename">task-*</code>
                recipes to <code class="filename">packagegroup-*</code>, and change
                them to inherit <code class="filename">packagegroup</code> instead of
                <code class="filename">task</code>, as well as taking the opportunity
                to remove anything now handled by
                <code class="filename">packagegroup.bbclass</code>, such as providing
                <code class="filename">-dev</code> and <code class="filename">-dbg</code>
                packages, setting
                <a class="link" href="#var-LIC_FILES_CHKSUM" title="LIC_FILES_CHKSUM"><code class="filename">LIC_FILES_CHKSUM</code></a>,
                and so forth.
                See the
                "<a class="link" href="#ref-classes-packagegroup" title="7.12. Package Groups - packagegroup.bbclass">Package Groups - packagegroup.bbclass</a>"
                section for further details.
            </p></div><div class="section" title="4.1.2.5. IMAGE_FEATURES"><div class="titlepage"><div><div><h4 class="title"><a id="migration-1.3-image-features"></a>4.1.2.5. IMAGE_FEATURES</h4></div></div></div><p>
                Image recipes that previously included "apps-console-core"
                in <a class="link" href="#var-IMAGE_FEATURES" title="IMAGE_FEATURES"><code class="filename">IMAGE_FEATURES</code></a>
                should now include "splash" instead to enable the boot-up
                splash screen.
                Retaining "apps-console-core" will still include the splash
                screen generates a warning.
                The "apps-x11-core" and "apps-x11-games"
                <code class="filename">IMAGE_FEATURES</code> features have been removed.
            </p></div><div class="section" title="4.1.2.6. Removed Recipes"><div class="titlepage"><div><div><h4 class="title"><a id="migration-1.3-removed-recipes"></a>4.1.2.6. Removed Recipes</h4></div></div></div><p>
                The following recipes have been removed.
                For most of them, it is unlikely that you would have any
                references to them in your own metadata.
                However, you should check your metadata against this list to be sure:
                </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em><code class="filename">libx11-trim</code></em></span>:
                        Replaced by <code class="filename">libx11</code>, which has a negligible
                        size difference with modern Xorg.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">xserver-xorg-lite</code></em></span>:
                        Use <code class="filename">xserver-xorg</code>, which has a negligible
                        size difference when DRI and GLX modules are not installed.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">xserver-kdrive</code></em></span>:
                        Effectively unmaintained for many years.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">mesa-xlib</code></em></span>:
                        No longer serves any purpose.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">galago</code></em></span>:
                        Replaced by telepathy.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">gail</code></em></span>:
                        Functionality was integrated into GTK+ 2.13.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">eggdbus</code></em></span>:
                        No longer needed.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">gcc-*-intermediate</code></em></span>:
                        The build has been restructured to avoid the need for
                        this step.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">libgsmd</code></em></span>:
                        Unmaintained for many years.
                        Functionality now provided by
                        <code class="filename">ofono</code> instead.</p></li><li class="listitem"><p><span class="emphasis"><em>contacts, dates, tasks, eds-tools</em></span>:
                        Largely unmaintained PIM application suite.
                        It has been moved to <code class="filename">meta-gnome</code>
                        in <code class="filename">meta-openembedded</code>.</p></li></ul></div><p>
                In addition to the previously listed changes, the
                <code class="filename">meta-demoapps</code> directory has also been removed
                because the recipes in it were not being maintained and many
                had become obsolete or broken.
                Additionally, these recipes were not parsed in the default configuration.
                Many of these recipes are already provided in an updated and
                maintained form within OpenEmbedded community layers such as
                <code class="filename">meta-oe</code> and <code class="filename">meta-gnome</code>.
                For the remainder, you can now find them in the
                <code class="filename">meta-extras</code> repository, which is in the
                Yocto Project source repositories.
            </p></div></div></div></div>

    <div class="chapter" title="Chapter 5. Source Directory Structure"><div class="titlepage"><div><div><h2 class="title"><a id="ref-structure"></a>Chapter 5. Source Directory Structure</h2></div></div></div><div class="toc"><p><strong>Table of Contents</strong></p><dl><dt><span class="section"><a href="#structure-core">5.1. Top level core components</a></span></dt><dd><dl><dt><span class="section"><a href="#structure-core-bitbake">5.1.1. <code class="filename">bitbake/</code></a></span></dt><dt><span class="section"><a href="#structure-core-build">5.1.2. <code class="filename">build/</code></a></span></dt><dt><span class="section"><a href="#handbook">5.1.3. <code class="filename">documentation</code></a></span></dt><dt><span class="section"><a href="#structure-core-meta">5.1.4. <code class="filename">meta/</code></a></span></dt><dt><span class="section"><a href="#structure-core-meta-yocto">5.1.5. <code class="filename">meta-yocto/</code></a></span></dt><dt><span class="section"><a href="#structure-core-meta-yocto-bsp">5.1.6. <code class="filename">meta-yocto-bsp/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-hob">5.1.7. <code class="filename">meta-hob/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-skeleton">5.1.8. <code class="filename">meta-skeleton/</code></a></span></dt><dt><span class="section"><a href="#structure-core-scripts">5.1.9. <code class="filename">scripts/</code></a></span></dt><dt><span class="section"><a href="#structure-core-script">5.1.10. <code class="filename">oe-init-build-env</code></a></span></dt><dt><span class="section"><a href="#structure-basic-top-level">5.1.11. <code class="filename">LICENSE, README, and README.hardware</code></a></span></dt></dl></dd><dt><span class="section"><a href="#structure-build">5.2. The Build Directory - <code class="filename">build/</code></a></span></dt><dd><dl><dt><span class="section"><a href="#structure-build-pseudodone">5.2.1. <code class="filename">build/pseudodone</code></a></span></dt><dt><span class="section"><a href="#structure-build-conf-local.conf">5.2.2. <code class="filename">build/conf/local.conf</code></a></span></dt><dt><span class="section"><a href="#structure-build-conf-bblayers.conf">5.2.3. <code class="filename">build/conf/bblayers.conf</code></a></span></dt><dt><span class="section"><a href="#structure-build-conf-sanity_info">5.2.4. <code class="filename">build/conf/sanity_info</code></a></span></dt><dt><span class="section"><a href="#structure-build-downloads">5.2.5. <code class="filename">build/downloads/</code></a></span></dt><dt><span class="section"><a href="#structure-build-sstate-cache">5.2.6. <code class="filename">build/sstate-cache/</code></a></span></dt><dt><span class="section"><a href="#structure-build-tmp">5.2.7. <code class="filename">build/tmp/</code></a></span></dt><dt><span class="section"><a href="#structure-build-tmp-buildstats">5.2.8. <code class="filename">build/tmp/buildstats/</code></a></span></dt><dt><span class="section"><a href="#structure-build-tmp-cache">5.2.9. <code class="filename">build/tmp/cache/</code></a></span></dt><dt><span class="section"><a href="#structure-build-tmp-deploy">5.2.10. <code class="filename">build/tmp/deploy/</code></a></span></dt><dt><span class="section"><a href="#structure-build-tmp-deploy-deb">5.2.11. <code class="filename">build/tmp/deploy/deb/</code></a></span></dt><dt><span class="section"><a href="#structure-build-tmp-deploy-rpm">5.2.12. <code class="filename">build/tmp/deploy/rpm/</code></a></span></dt><dt><span class="section"><a href="#structure-build-tmp-deploy-licenses">5.2.13. <code class="filename">build/tmp/deploy/licenses/</code></a></span></dt><dt><span class="section"><a href="#structure-build-tmp-deploy-images">5.2.14. <code class="filename">build/tmp/deploy/images/</code></a></span></dt><dt><span class="section"><a href="#structure-build-tmp-deploy-ipk">5.2.15. <code class="filename">build/tmp/deploy/ipk/</code></a></span></dt><dt><span class="section"><a href="#structure-build-tmp-sysroots">5.2.16. <code class="filename">build/tmp/sysroots/</code></a></span></dt><dt><span class="section"><a href="#structure-build-tmp-stamps">5.2.17. <code class="filename">build/tmp/stamps/</code></a></span></dt><dt><span class="section"><a href="#structure-build-tmp-log">5.2.18. <code class="filename">build/tmp/log/</code></a></span></dt><dt><span class="section"><a href="#structure-build-tmp-pkgdata">5.2.19. <code class="filename">build/tmp/pkgdata/</code></a></span></dt><dt><span class="section"><a href="#structure-build-tmp-work">5.2.20. <code class="filename">build/tmp/work/</code></a></span></dt></dl></dd><dt><span class="section"><a href="#structure-meta">5.3. The Metadata - <code class="filename">meta/</code></a></span></dt><dd><dl><dt><span class="section"><a href="#structure-meta-classes">5.3.1. <code class="filename">meta/classes/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-conf">5.3.2. <code class="filename">meta/conf/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-conf-machine">5.3.3. <code class="filename">meta/conf/machine/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-conf-distro">5.3.4. <code class="filename">meta/conf/distro/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-recipes-bsp">5.3.5. <code class="filename">meta/recipes-bsp/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-recipes-connectivity">5.3.6. <code class="filename">meta/recipes-connectivity/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-recipes-core">5.3.7. <code class="filename">meta/recipes-core/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-recipes-devtools">5.3.8. <code class="filename">meta/recipes-devtools/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-recipes-extended">5.3.9. <code class="filename">meta/recipes-extended/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-recipes-gnome">5.3.10. <code class="filename">meta/recipes-gnome/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-recipes-graphics">5.3.11. <code class="filename">meta/recipes-graphics/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-recipes-kernel">5.3.12. <code class="filename">meta/recipes-kernel/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-recipes-multimedia">5.3.13. <code class="filename">meta/recipes-multimedia/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-recipes-qt">5.3.14. <code class="filename">meta/recipes-qt/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-recipes-rt">5.3.15. <code class="filename">meta/recipes-rt/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-recipes-sato">5.3.16. <code class="filename">meta/recipes-sato/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-recipes-support">5.3.17. <code class="filename">meta/recipes-support/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-site">5.3.18. <code class="filename">meta/site/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-recipes-txt">5.3.19. <code class="filename">meta/recipes.txt</code></a></span></dt></dl></dd></dl></div><p>
    The <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#source-directory" target="_top">Source Directory</a> consists of several components.
    Understanding them and knowing where they are located is key to using the Yocto Project well.
    This chapter describes the Source Directory and gives information about the various
    files and directories.
</p><p>
    For information on how to establish a local Source Directory on your development system, see the
    "<a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#getting-setup" target="_top">Getting Set Up</a>"
    section in the Yocto Project Development Manual.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
    The OpenEmbedded build system does not support file or directory names that
    contain spaces.
    Be sure that the Source Directory you use does not contain these types
    of names.
</div><div class="section" title="5.1. Top level core components"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="structure-core"></a>5.1. Top level core components</h2></div></div></div><div class="section" title="5.1.1. bitbake/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-core-bitbake"></a>5.1.1. <code class="filename">bitbake/</code></h3></div></div></div><p>
            The <a class="ulink" href="source-directory" target="_top">Source Directory</a>
            includes a copy of BitBake for ease of use.
            The copy usually matches the current stable BitBake release from the BitBake project.
            BitBake, a metadata interpreter, reads the Yocto Project metadata and runs the tasks
            defined by that data.
            Failures are usually from the metadata and not from BitBake itself.
            Consequently, most users do not need to worry about BitBake.
        </p><p>
            When you run the <code class="filename">bitbake</code> command, the wrapper script in
            <code class="filename">scripts/</code> is executed to run the main BitBake executable,
            which resides in the <code class="filename">bitbake/bin/</code> directory.
            Sourcing the <a class="link" href="#structure-core-script" title="5.1.10. oe-init-build-env">oe-init-build-env</a>
            script places the <code class="filename">scripts</code> and <code class="filename">bitbake/bin</code>
            directories (in that order) into the shell's <code class="filename">PATH</code> environment
            variable.
        </p><p>
            For more information on BitBake, see the BitBake documentation
            inculded in the <code class="filename">bitbake/doc/manual</code> directory of the
            <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#source-directory" target="_top">Source Directory</a>.
        </p></div><div class="section" title="5.1.2. build/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-core-build"></a>5.1.2. <code class="filename">build/</code></h3></div></div></div><p>
            This directory contains user configuration files and the output
            generated by the OpenEmbedded build system in its standard configuration where
            the source tree is combined with the output.
            The <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#build-directory" target="_top">Build Directory</a>
            is created initially when you <code class="filename">source</code>
            the OpenEmbedded build environment setup script <code class="filename">oe-init-build-env</code>.
        </p><p>
            It is also possible to place output and configuration
            files in a directory separate from the
            <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#source-directory" target="_top">Source Directory</a>
            by providing a directory name when you <code class="filename">source</code>
            the setup script.
            For information on separating output from your local Source Directory files, see <a class="link" href="#structure-core-script" title="5.1.10. oe-init-build-env">oe-init-build-env</a>.
        </p></div><div class="section" title="5.1.3. documentation"><div class="titlepage"><div><div><h3 class="title"><a id="handbook"></a>5.1.3. <code class="filename">documentation</code></h3></div></div></div><p>
            This directory holds the source for the Yocto Project documentation
            as well as templates and tools that allow you to generate PDF and HTML
            versions of the manuals.
            Each manual is contained in a sub-folder.
            For example, the files for this manual reside in
            <code class="filename">ref-manual</code>.
        </p></div><div class="section" title="5.1.4. meta/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-core-meta"></a>5.1.4. <code class="filename">meta/</code></h3></div></div></div><p>
            This directory contains the OpenEmbedded Core metadata.
            The directory holds recipes, common classes, and machine
            configuration for emulated targets (qemux86, qemuarm,
            and so on.)
        </p></div><div class="section" title="5.1.5. meta-yocto/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-core-meta-yocto"></a>5.1.5. <code class="filename">meta-yocto/</code></h3></div></div></div><p>
            This directory contains the configuration for the Poky
            reference distribution.
        </p></div><div class="section" title="5.1.6. meta-yocto-bsp/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-core-meta-yocto-bsp"></a>5.1.6. <code class="filename">meta-yocto-bsp/</code></h3></div></div></div><p>
            This directory contains the Yocto Project reference
            hardware BSPs.
        </p></div><div class="section" title="5.1.7. meta-hob/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-meta-hob"></a>5.1.7. <code class="filename">meta-hob/</code></h3></div></div></div><p>
            This directory contains template recipes used by the
            <a class="ulink" href="http://www.yoctoproject.org/projects/hob" target="_top">Hob</a>
            build UI.
        </p></div><div class="section" title="5.1.8. meta-skeleton/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-meta-skeleton"></a>5.1.8. <code class="filename">meta-skeleton/</code></h3></div></div></div><p>
            This directory contains template recipes for BSP and kernel development.
        </p></div><div class="section" title="5.1.9. scripts/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-core-scripts"></a>5.1.9. <code class="filename">scripts/</code></h3></div></div></div><p>
            This directory contains various integration scripts that implement
            extra functionality in the Yocto Project environment (e.g. QEMU scripts).
            The <a class="link" href="#structure-core-script" title="5.1.10. oe-init-build-env">oe-init-build-env</a> script appends this
            directory to the shell's <code class="filename">PATH</code> environment variable.
        </p><p>
            The <code class="filename">scripts</code> directory has useful scripts that assist contributing
            back to the Yocto Project, such as <code class="filename">create_pull_request</code> and
            <code class="filename">send_pull_request</code>.
        </p></div><div class="section" title="5.1.10. oe-init-build-env"><div class="titlepage"><div><div><h3 class="title"><a id="structure-core-script"></a>5.1.10. <code class="filename">oe-init-build-env</code></h3></div></div></div><p>
            This script sets up the OpenEmbedded build environment.
            Running this script with the <code class="filename">source</code> command in
            a shell makes changes to <code class="filename">PATH</code> and sets other core BitBake variables based on the
            current working directory.
            You need to run this script before running BitBake commands.
            The script uses other scripts within the <code class="filename">scripts</code> directory to do
            the bulk of the work.
        </p><p>
            By default, running this script without a Build Directory argument creates the
            <code class="filename">build</code> directory.
            If you provide a Build Directory argument when you <code class="filename">source</code>
            the script, you direct OpenEmbedded build system to create a
            <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#build-directory" target="_top">Build Directory</a> of your choice.
            For example, the following command creates a Build Directory named
            <code class="filename">mybuilds</code> that is outside of the
            <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#source-directory" target="_top">Source Directory</a>:
            </p><pre class="literallayout">
     $ source oe-init-build-env ~/mybuilds
            </pre><p>
            </p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
                The OpenEmbedded build system does not support file or directory names that
                contain spaces.
                If you attempt to run the <code class="filename">oe-init-build-env</code> script
                from a Source Directory that contains spaces in either the filenames
                or directory names, the script returns an error indicating no such
                file or directory.
                Be sure to use a Source Directory free of names containing spaces.
            </div><p>
        </p></div><div class="section" title="5.1.11. LICENSE, README, and README.hardware"><div class="titlepage"><div><div><h3 class="title"><a id="structure-basic-top-level"></a>5.1.11. <code class="filename">LICENSE, README, and README.hardware</code></h3></div></div></div><p>
            These files are standard top-level files.
        </p></div></div><div class="section" title="5.2. The Build Directory - build/"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="structure-build"></a>5.2. The Build Directory - <code class="filename">build/</code></h2></div></div></div><div class="section" title="5.2.1. build/pseudodone"><div class="titlepage"><div><div><h3 class="title"><a id="structure-build-pseudodone"></a>5.2.1. <code class="filename">build/pseudodone</code></h3></div></div></div><p>
            This tag file indicates that the initial pseudo binary was created.
            The file is built the first time BitBake is invoked.
        </p></div><div class="section" title="5.2.2. build/conf/local.conf"><div class="titlepage"><div><div><h3 class="title"><a id="structure-build-conf-local.conf"></a>5.2.2. <code class="filename">build/conf/local.conf</code></h3></div></div></div><p>
            This file contains all the local user configuration for your build environment.
            If there is no <code class="filename">local.conf</code> present, it is created from
            <code class="filename">local.conf.sample</code>.
            The <code class="filename">local.conf</code> file contains documentation on the various configuration options.
            Any variable set here overrides any variable set elsewhere within the environment unless
            that variable is hard-coded within a file (e.g. by using '=' instead of '?=').
            Some variables are hard-coded for various reasons but these variables are
            relatively rare.
        </p><p>
            Edit this file to set the <code class="filename"><a class="link" href="#var-MACHINE" title="MACHINE">MACHINE</a></code>
            for which you want to build, which package types you wish to use
            (<a class="link" href="#var-PACKAGE_CLASSES" title="PACKAGE_CLASSES"><code class="filename">PACKAGE_CLASSES</code></a>),
            where you want to downloaded files
            (<code class="filename"><a class="link" href="#var-DL_DIR" title="DL_DIR">DL_DIR</a></code>),
            and how you want your host machine to use resources
            (<a class="link" href="#var-BB_NUMBER_THREADS" title="BB_NUMBER_THREADS"><code class="filename">BB_NUMBER_THREADS</code></a> and
            <a class="link" href="#var-PARALLEL_MAKE" title="PARALLEL_MAKE"><code class="filename">PARALLEL_MAKE</code></a>).
        </p></div><div class="section" title="5.2.3. build/conf/bblayers.conf"><div class="titlepage"><div><div><h3 class="title"><a id="structure-build-conf-bblayers.conf"></a>5.2.3. <code class="filename">build/conf/bblayers.conf</code></h3></div></div></div><p>
            This file defines layers, which are directory trees, traversed (or walked) by BitBake.
            If <code class="filename">bblayers.conf</code>
            is not present, it is created from <code class="filename">bblayers.conf.sample</code> when
            you <code class="filename">source</code> the environment setup script.
        </p><p>
            The <code class="filename">bblayers.conf</code> file uses the
            <a class="link" href="#var-BBLAYERS" title="BBLAYERS"><code class="filename">BBLAYERS</code></a> variable to
            list the layers BitBake tries to find.
            The file uses the
            <a class="link" href="#var-BBLAYERS_NON_REMOVABLE" title="BBLAYERS_NON_REMOVABLE"><code class="filename">BBLAYERS_NON_REMOVABLE</code></a>
            variable to list layers that must not be removed.
        </p></div><div class="section" title="5.2.4. build/conf/sanity_info"><div class="titlepage"><div><div><h3 class="title"><a id="structure-build-conf-sanity_info"></a>5.2.4. <code class="filename">build/conf/sanity_info</code></h3></div></div></div><p>
            This file is created during the build to indicate the state of the sanity checks.
        </p></div><div class="section" title="5.2.5. build/downloads/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-build-downloads"></a>5.2.5. <code class="filename">build/downloads/</code></h3></div></div></div><p>
            This directory is used for the upstream source tarballs.
            The directory can be reused by multiple builds or moved to another location.
            You can control the location of this directory through the
            <code class="filename"><a class="link" href="#var-DL_DIR" title="DL_DIR">DL_DIR</a></code> variable.
        </p></div><div class="section" title="5.2.6. build/sstate-cache/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-build-sstate-cache"></a>5.2.6. <code class="filename">build/sstate-cache/</code></h3></div></div></div><p>
            This directory is used for the shared state cache.
            The directory can be reused by multiple builds or moved to another location.
            You can control the location of this directory through the
            <code class="filename"><a class="link" href="#var-SSTATE_DIR" title="SSTATE_DIR">SSTATE_DIR</a></code> variable.
        </p></div><div class="section" title="5.2.7. build/tmp/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-build-tmp"></a>5.2.7. <code class="filename">build/tmp/</code></h3></div></div></div><p>
            This directory receives all the OpenEmbedded build system's output.
            BitBake creates this directory if it does not exist.
            As a last resort, to clean up a build and start it from scratch (other than the downloads),
            you can remove everything in the <code class="filename">tmp</code> directory or get rid of the
            directory completely.
            If you do, you should also completely remove the <code class="filename">build/sstate-cache</code>
            directory as well.
        </p></div><div class="section" title="5.2.8. build/tmp/buildstats/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-build-tmp-buildstats"></a>5.2.8. <code class="filename">build/tmp/buildstats/</code></h3></div></div></div><p>
            This directory stores the build statistics.
        </p></div><div class="section" title="5.2.9. build/tmp/cache/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-build-tmp-cache"></a>5.2.9. <code class="filename">build/tmp/cache/</code></h3></div></div></div><p>
            When BitBake parses the metadata, it creates a cache file of the result that can
            be used when subsequently running commands.
            These results are stored here on a per-machine basis.
        </p></div><div class="section" title="5.2.10. build/tmp/deploy/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-build-tmp-deploy"></a>5.2.10. <code class="filename">build/tmp/deploy/</code></h3></div></div></div><p>
            This directory contains any 'end result' output from the OpenEmbedded build process.
        </p></div><div class="section" title="5.2.11. build/tmp/deploy/deb/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-build-tmp-deploy-deb"></a>5.2.11. <code class="filename">build/tmp/deploy/deb/</code></h3></div></div></div><p>
            This directory receives any <code class="filename">.deb</code> packages produced by
            the build process.
            The packages are sorted into feeds for different architecture types.
        </p></div><div class="section" title="5.2.12. build/tmp/deploy/rpm/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-build-tmp-deploy-rpm"></a>5.2.12. <code class="filename">build/tmp/deploy/rpm/</code></h3></div></div></div><p>
            This directory receives any <code class="filename">.rpm</code> packages produced by
            the build process.
            The packages are sorted into feeds for different architecture types.
        </p></div><div class="section" title="5.2.13. build/tmp/deploy/licenses/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-build-tmp-deploy-licenses"></a>5.2.13. <code class="filename">build/tmp/deploy/licenses/</code></h3></div></div></div><p>
            This directory receives package licensing information.
            For example, the directory contains sub-directories for <code class="filename">bash</code>,
            <code class="filename">busybox</code>, and <code class="filename">eglibc</code> (among others) that in turn
            contain appropriate <code class="filename">COPYING</code> license files with other licensing information.
        </p></div><div class="section" title="5.2.14. build/tmp/deploy/images/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-build-tmp-deploy-images"></a>5.2.14. <code class="filename">build/tmp/deploy/images/</code></h3></div></div></div><p>
            This directory receives complete filesystem images.
            If you want to flash the resulting image from a build onto a device, look here for the image.
        </p><p>
            Be careful when deleting files in this directory.
            You can safely delete old images from this directory (e.g.
            <code class="filename">core-image-*</code>, <code class="filename">hob-image-*</code>,
            etc.).
            However, the kernel (<code class="filename">*zImage*</code>, <code class="filename">*uImage*</code>, etc.),
            bootloader and other supplementary files might be deployed here prior to building an
            image.
            Because these files, however, are not directly produced from the image, if you
            delete them they will not be automatically re-created when you build the image again.
        </p><p>
            If you do accidentally delete files here, you will need to force them to be
            re-created.
            In order to do that, you will need to know the target that produced them.
            For example, these commands rebuild and re-create the kernel files:
            </p><pre class="literallayout">
     $ bitbake -c clean virtual/kernel
     $ bitbake virtual/kernel
            </pre><p>
        </p></div><div class="section" title="5.2.15. build/tmp/deploy/ipk/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-build-tmp-deploy-ipk"></a>5.2.15. <code class="filename">build/tmp/deploy/ipk/</code></h3></div></div></div><p>
            This directory receives <code class="filename">.ipk</code> packages produced by
            the build process.</p></div><div class="section" title="5.2.16. build/tmp/sysroots/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-build-tmp-sysroots"></a>5.2.16. <code class="filename">build/tmp/sysroots/</code></h3></div></div></div><p>
            This directory contains shared header files and libraries as well as other shared
            data.
            Packages that need to share output with other packages do so within this directory.
            The directory is subdivided by architecture so multiple builds can run within
            the one Build Directory.
        </p></div><div class="section" title="5.2.17. build/tmp/stamps/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-build-tmp-stamps"></a>5.2.17. <code class="filename">build/tmp/stamps/</code></h3></div></div></div><p>
            This directory holds information that BitBake uses for accounting purposes
            to track what tasks have run and when they have run.
            The directory is sub-divided by architecture, package name, and
            version.
            Following is an example:
            </p><pre class="literallayout">
     stamps/all-poky-linux/distcc-config/1.0-r0.do_build-2fdd....2do
            </pre><p>
            Although the files in the directory are empty of data,
            BitBake uses the filenames and timestamps for tracking purposes.
        </p></div><div class="section" title="5.2.18. build/tmp/log/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-build-tmp-log"></a>5.2.18. <code class="filename">build/tmp/log/</code></h3></div></div></div><p>
            This directory contains general logs that are not otherwise placed using the
            package's <code class="filename"><a class="link" href="#var-WORKDIR" title="WORKDIR">WORKDIR</a></code>.
            Examples of logs are the output from the <code class="filename">check_pkg</code> or
            <code class="filename">distro_check</code> tasks.
            Running a build does not necessarily mean this directory is created.
        </p></div><div class="section" title="5.2.19. build/tmp/pkgdata/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-build-tmp-pkgdata"></a>5.2.19. <code class="filename">build/tmp/pkgdata/</code></h3></div></div></div><p>
            This directory contains intermediate packaging data that is used later in the packaging process.
            For more information, see the "<a class="link" href="#ref-classes-package" title="7.13. Packaging - package*.bbclass">Packaging - package*.bbclass</a>" section.
        </p></div><div class="section" title="5.2.20. build/tmp/work/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-build-tmp-work"></a>5.2.20. <code class="filename">build/tmp/work/</code></h3></div></div></div><p>
            This directory contains architecture-specific work sub-directories
            for packages built by BitBake.
            All tasks execute from the appropriate work directory.
            For example, the source for a particular package is unpacked,
            patched, configured and compiled all within its own work directory.
            Within the work directory, organization is based on the package group
            and version for which the source is being compiled
            as defined by the
            <a class="link" href="#var-WORKDIR" title="WORKDIR"><code class="filename">WORKDIR</code></a>.
        </p><p>
            It is worth considering the structure of a typical work directory.
            As an example, consider the <code class="filename">linux-yocto-kernel-3.0</code>
            on the machine <code class="filename">qemux86</code>
            built within the Yocto Project.
            For this package, a work directory of
            <code class="filename">tmp/work/qemux86-poky-linux/linux-yocto/3.0+git1+&lt;.....&gt;</code>,
            referred to as the
            <code class="filename"><a class="link" href="#var-WORKDIR" title="WORKDIR">WORKDIR</a></code>, is created.
            Within this directory, the source is unpacked to
            <code class="filename">linux-qemux86-standard-build</code> and then patched by Quilt
            (see the
            "<a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#using-a-quilt-workflow" target="_top">Modifying Package
            Source Code with Quilt</a>" section in the Yocto Project Development Manual.
            Within the <code class="filename">linux-qemux86-standard-build</code> directory,
            standard Quilt directories <code class="filename">linux-3.0/patches</code>
            and <code class="filename">linux-3.0/.pc</code> are created,
            and standard Quilt commands can be used.
        </p><p>
            There are other directories generated within <code class="filename">WORKDIR</code>.
            The most important directory is <code class="filename">WORKDIR/temp/</code>,
            which has log files for each task (<code class="filename">log.do_*.pid</code>)
            and contains the scripts BitBake runs for each task
            (<code class="filename">run.do_*.pid</code>).
            The <code class="filename">WORKDIR/image/</code> directory is where "make
            install" places its output that is then split into sub-packages
            within <code class="filename">WORKDIR/packages-split/</code>.
        </p></div></div><div class="section" title="5.3. The Metadata - meta/"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="structure-meta"></a>5.3. The Metadata - <code class="filename">meta/</code></h2></div></div></div><p>
        As mentioned previously, metadata is the core of the Yocto Project.
        Metadata has several important subdivisions:
    </p><div class="section" title="5.3.1. meta/classes/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-meta-classes"></a>5.3.1. <code class="filename">meta/classes/</code></h3></div></div></div><p>
            This directory contains the <code class="filename">*.bbclass</code> files.
            Class files are used to abstract common code so it can be reused by multiple
            packages.
            Every package inherits the <code class="filename">base.bbclass</code> file.
            Examples of other important classes are <code class="filename">autotools.bbclass</code>, which
            in theory allows any Autotool-enabled package to work with the Yocto Project with minimal effort.
            Another example is <code class="filename">kernel.bbclass</code> that contains common code and functions
            for working with the Linux kernel.
            Functions like image generation or packaging also have their specific class files
            such as <code class="filename">image.bbclass</code>, <code class="filename">rootfs_*.bbclass</code> and
            <code class="filename">package*.bbclass</code>.
        </p></div><div class="section" title="5.3.2. meta/conf/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-meta-conf"></a>5.3.2. <code class="filename">meta/conf/</code></h3></div></div></div><p>
            This directory contains the core set of configuration files that start from
            <code class="filename">bitbake.conf</code> and from which all other configuration
            files are included.
            See the include statements at the end of the file and you will note that even
            <code class="filename">local.conf</code> is loaded from there.
            While <code class="filename">bitbake.conf</code> sets up the defaults, you can often override
            these by using the (<code class="filename">local.conf</code>) file, machine file or
            the distribution configuration file.
        </p></div><div class="section" title="5.3.3. meta/conf/machine/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-meta-conf-machine"></a>5.3.3. <code class="filename">meta/conf/machine/</code></h3></div></div></div><p>
            This directory contains all the machine configuration files.
            If you set <code class="filename">MACHINE="qemux86"</code>,
            the OpenEmbedded build system looks for a <code class="filename">qemux86.conf</code> file in this
            directory.
            The <code class="filename">include</code> directory contains various data common to multiple machines.
            If you want to add support for a new machine to the Yocto Project, look in this directory.
        </p></div><div class="section" title="5.3.4. meta/conf/distro/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-meta-conf-distro"></a>5.3.4. <code class="filename">meta/conf/distro/</code></h3></div></div></div><p>
            Any distribution-specific configuration is controlled from this directory.
            For the Yocto Project, the <code class="filename">defaultsetup.conf</code> is the main file here.
            This directory includes the versions and the
            <code class="filename">SRCDATE</code> definitions for applications that are configured here.
            An example of an alternative configuration might be <code class="filename">poky-bleeding.conf</code>.
            Although this file mainly inherits its configuration from Poky.
        </p></div><div class="section" title="5.3.5. meta/recipes-bsp/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-meta-recipes-bsp"></a>5.3.5. <code class="filename">meta/recipes-bsp/</code></h3></div></div></div><p>
            This directory contains anything linking to specific hardware or hardware
            configuration information such as "u-boot" and "grub".
        </p></div><div class="section" title="5.3.6. meta/recipes-connectivity/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-meta-recipes-connectivity"></a>5.3.6. <code class="filename">meta/recipes-connectivity/</code></h3></div></div></div><p>
            This directory contains libraries and applications related to communication with other devices.
        </p></div><div class="section" title="5.3.7. meta/recipes-core/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-meta-recipes-core"></a>5.3.7. <code class="filename">meta/recipes-core/</code></h3></div></div></div><p>
            This directory contains what is needed to build a basic working Linux image
            including commonly used dependencies.
        </p></div><div class="section" title="5.3.8. meta/recipes-devtools/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-meta-recipes-devtools"></a>5.3.8. <code class="filename">meta/recipes-devtools/</code></h3></div></div></div><p>
            This directory contains tools that are primarily used by the build system.
            The tools, however, can also be used on targets.
        </p></div><div class="section" title="5.3.9. meta/recipes-extended/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-meta-recipes-extended"></a>5.3.9. <code class="filename">meta/recipes-extended/</code></h3></div></div></div><p>
            This directory contains non-essential applications that add features compared to the
            alternatives in core.
            You might need this directory for full tool functionality or for Linux Standard Base (LSB)
            compliance.
        </p></div><div class="section" title="5.3.10. meta/recipes-gnome/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-meta-recipes-gnome"></a>5.3.10. <code class="filename">meta/recipes-gnome/</code></h3></div></div></div><p>
            This directory contains all things related to the GTK+ application framework.
        </p></div><div class="section" title="5.3.11. meta/recipes-graphics/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-meta-recipes-graphics"></a>5.3.11. <code class="filename">meta/recipes-graphics/</code></h3></div></div></div><p>
            This directory contains X and other graphically related system libraries
        </p></div><div class="section" title="5.3.12. meta/recipes-kernel/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-meta-recipes-kernel"></a>5.3.12. <code class="filename">meta/recipes-kernel/</code></h3></div></div></div><p>
            This directory contains the kernel and generic applications and libraries that
            have strong kernel dependencies.
        </p></div><div class="section" title="5.3.13. meta/recipes-multimedia/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-meta-recipes-multimedia"></a>5.3.13. <code class="filename">meta/recipes-multimedia/</code></h3></div></div></div><p>
            This directory contains codecs and support utilities for audio, images and video.
        </p></div><div class="section" title="5.3.14. meta/recipes-qt/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-meta-recipes-qt"></a>5.3.14. <code class="filename">meta/recipes-qt/</code></h3></div></div></div><p>
            This directory contains all things related to the Qt application framework.
        </p></div><div class="section" title="5.3.15. meta/recipes-rt/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-meta-recipes-rt"></a>5.3.15. <code class="filename">meta/recipes-rt/</code></h3></div></div></div><p>
            This directory contains package and image recipes for using and testing
            the <code class="filename">PREEMPT_RT</code> kernel.
        </p></div><div class="section" title="5.3.16. meta/recipes-sato/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-meta-recipes-sato"></a>5.3.16. <code class="filename">meta/recipes-sato/</code></h3></div></div></div><p>
            This directory contains the Sato demo/reference UI/UX and its associated applications
            and configuration data.
        </p></div><div class="section" title="5.3.17. meta/recipes-support/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-meta-recipes-support"></a>5.3.17. <code class="filename">meta/recipes-support/</code></h3></div></div></div><p>
            This directory contains recipes that used by other recipes, but that are not directly
            included in images (i.e. dependencies of other recipes).
        </p></div><div class="section" title="5.3.18. meta/site/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-meta-site"></a>5.3.18. <code class="filename">meta/site/</code></h3></div></div></div><p>
            This directory contains a list of cached results for various architectures.
            Because certain "autoconf" test results cannot be determined when cross-compiling due to
            the tests not able to run on a live system, the information in this directory is
            passed to "autoconf" for the various architectures.
        </p></div><div class="section" title="5.3.19. meta/recipes.txt"><div class="titlepage"><div><div><h3 class="title"><a id="structure-meta-recipes-txt"></a>5.3.19. <code class="filename">meta/recipes.txt</code></h3></div></div></div><p>
            This file is a description of the contents of <code class="filename">recipes-*</code>.
        </p></div></div></div>

    <div class="chapter" title="Chapter 6. BitBake"><div class="titlepage"><div><div><h2 class="title"><a id="ref-bitbake"></a>Chapter 6. BitBake</h2></div></div></div><div class="toc"><p><strong>Table of Contents</strong></p><dl><dt><span class="section"><a href="#ref-bitbake-parsing">6.1. Parsing</a></span></dt><dt><span class="section"><a href="#ref-bitbake-providers">6.2. Preferences and Providers</a></span></dt><dt><span class="section"><a href="#ref-bitbake-dependencies">6.3. Dependencies</a></span></dt><dt><span class="section"><a href="#ref-bitbake-tasklist">6.4. The Task List</a></span></dt><dt><span class="section"><a href="#ref-bitbake-runtask">6.5. Running a Task</a></span></dt><dt><span class="section"><a href="#ref-bitbake-commandline">6.6. BitBake Command Line</a></span></dt><dt><span class="section"><a href="#ref-bitbake-fetchers">6.7. Fetchers</a></span></dt></dl></div><p>
        BitBake is a program written in Python that interprets the metadata used by the OpenEmbedded
        build system.
        At some point, developers wonder what actually happens when you enter:
        </p><pre class="literallayout">
     $ bitbake core-image-sato
        </pre><p>
    </p><p>
        This chapter provides an overview of what happens behind the scenes from BitBake's perspective.
    </p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
        BitBake strives to be a generic "task" executor that is capable of handling complex dependency relationships.
        As such, it has no real knowledge of what the tasks being executed actually do.
        BitBake just considers a list of tasks with dependencies and handles metadata
        that consists of variables in a certain format that get passed to the tasks.
    </div><div class="section" title="6.1. Parsing"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-bitbake-parsing"></a>6.1. Parsing</h2></div></div></div><p>
            BitBake parses configuration files, classes, and <code class="filename">.bb</code> files.
        </p><p>
            The first thing BitBake does is look for the <code class="filename">bitbake.conf</code> file.
            This file resides in the
            <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#source-directory" target="_top">Source Directory</a>
            within the <code class="filename">meta/conf/</code> directory.
            BitBake finds it by examining its
            <a class="link" href="#var-BBPATH" title="BBPATH"><code class="filename">BBPATH</code></a> environment
            variable and looking for the <code class="filename">meta/conf/</code>
            directory.
        </p><p>
            The <code class="filename">bitbake.conf</code> file lists other configuration
            files to include from a <code class="filename">conf/</code>
            directory below the directories listed in <code class="filename">BBPATH</code>.
            In general, the most important configuration file from a user's perspective
            is <code class="filename">local.conf</code>, which contains a user's customized
            settings for the OpenEmbedded build environment.
            Other notable configuration files are the distribution
            configuration file (set by the
            <code class="filename"><a class="link" href="#var-DISTRO" title="DISTRO">DISTRO</a></code> variable)
            and the machine configuration file
            (set by the
            <code class="filename"><a class="link" href="#var-MACHINE" title="MACHINE">MACHINE</a></code> variable).
            The <code class="filename">DISTRO</code> and <code class="filename">MACHINE</code> BitBake environment
            variables are both usually set in
            the <code class="filename">local.conf</code> file.
            Valid distribution
            configuration files are available in the <code class="filename">meta/conf/distro/</code> directory
            and valid machine configuration
            files in the <code class="filename">meta/conf/machine/</code> directory.
            Within the <code class="filename">meta/conf/machine/include/</code>
            directory are various <code class="filename">tune-*.inc</code> configuration files that provide common
            "tuning" settings specific to and shared between particular architectures and machines.
        </p><p>
            After the parsing of the configuration files, some standard classes are included.
            The <code class="filename">base.bbclass</code> file is always included.
            Other classes that are specified in the configuration using the
            <code class="filename"><a class="link" href="#var-INHERIT" title="INHERIT">INHERIT</a></code>
            variable are also included.
            Class files are searched for in a <code class="filename">classes</code> subdirectory
            under the paths in <code class="filename">BBPATH</code> in the same way as
            configuration files.
        </p><p>
            After classes are included, the variable
            <code class="filename"><a class="link" href="#var-BBFILES" title="BBFILES">BBFILES</a></code>
            is set, usually in
            <code class="filename">local.conf</code>, and defines the list of places to search for
            <code class="filename">.bb</code> files.
            By default, the <code class="filename">BBFILES</code> variable specifies the
            <code class="filename">meta/recipes-*/</code> directory within Poky.
            Adding extra content to <code class="filename">BBFILES</code> is best achieved through the use of
            BitBake layers as described in the
            "<a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#understanding-and-creating-layers" target="_top">Understanding and
            Creating Layers</a>" section of the Yocto Project Development Manual.
        </p><p>
            BitBake parses each <code class="filename">.bb</code> file in <code class="filename">BBFILES</code> and
            stores the values of various variables.
            In summary, for each <code class="filename">.bb</code>
            file the configuration plus the base class of variables are set, followed
            by the data in the <code class="filename">.bb</code> file
            itself, followed by any inherit commands that
            <code class="filename">.bb</code> file might contain.
        </p><p>
            Because parsing <code class="filename">.bb</code> files is a time
            consuming process, a cache is kept to speed up subsequent parsing.
            This cache is invalid if the timestamp of the <code class="filename">.bb</code>
            file itself changes, or if the timestamps of any of the include,
            configuration or class files the <code class="filename">.bb</code>
            file depends on changes.
        </p></div><div class="section" title="6.2. Preferences and Providers"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-bitbake-providers"></a>6.2. Preferences and Providers</h2></div></div></div><p>
            Once all the <code class="filename">.bb</code> files have been
            parsed, BitBake starts to build the target (<code class="filename">core-image-sato</code>
            in the previous section's example) and looks for providers of that target.
            Once a provider is selected, BitBake resolves all the dependencies for
            the target.
            In the case of <code class="filename">core-image-sato</code>, it would lead to
            <code class="filename">packagegroup-core-x11-sato</code>,
            which in turn leads to recipes like <code class="filename">matchbox-terminal</code>,
            <code class="filename">pcmanfm</code> and <code class="filename">gthumb</code>.
            These recipes in turn depend on <code class="filename">eglibc</code> and the toolchain.
        </p><p>
            Sometimes a target might have multiple providers.
            A common example is "virtual/kernel", which is provided by each kernel package.
            Each machine often selects the best kernel provider by using a line similar to the
            following in the machine configuration file:
        </p><pre class="literallayout">
     PREFERRED_PROVIDER_virtual/kernel = "linux-yocto"
        </pre><p>
            The default <code class="filename"><a class="link" href="#var-PREFERRED_PROVIDER" title="PREFERRED_PROVIDER">PREFERRED_PROVIDER</a></code>
            is the provider with the same name as the target.
        </p><p>
            Understanding how providers are chosen is made complicated by the fact
            that multiple versions might exist.
            BitBake defaults to the highest version of a provider.
            Version comparisons are made using the same method as Debian.
            You can use the
            <code class="filename"><a class="link" href="#var-PREFERRED_VERSION" title="PREFERRED_VERSION">PREFERRED_VERSION</a></code>
            variable to specify a particular version (usually in the distro configuration).
            You can influence the order by using the
            <code class="filename"><a class="link" href="#var-DEFAULT_PREFERENCE" title="DEFAULT_PREFERENCE">DEFAULT_PREFERENCE</a></code>
            variable.
            By default, files have a preference of "0".
            Setting the <code class="filename">DEFAULT_PREFERENCE</code> to "-1" makes the
            package unlikely to be used unless it is explicitly referenced.
            Setting the <code class="filename">DEFAULT_PREFERENCE</code> to "1" makes it likely the package is used.
            <code class="filename">PREFERRED_VERSION</code> overrides any <code class="filename">DEFAULT_PREFERENCE</code> setting.
            <code class="filename">DEFAULT_PREFERENCE</code> is often used to mark newer and more experimental package
            versions until they have undergone sufficient testing to be considered stable.
        </p><p>
            In summary, BitBake has created a list of providers, which is prioritized, for each target.
        </p></div><div class="section" title="6.3. Dependencies"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-bitbake-dependencies"></a>6.3. Dependencies</h2></div></div></div><p>
            Each target BitBake builds consists of multiple tasks such as
            <code class="filename">fetch</code>, <code class="filename">unpack</code>,
            <code class="filename">patch</code>, <code class="filename">configure</code>,
            and <code class="filename">compile</code>.
            For best performance on multi-core systems, BitBake considers each task as an independent
            entity with its own set of dependencies.
        </p><p>
            Dependencies are defined through several variables.
            You can find information about variables BitBake uses in the BitBake documentation,
            which is found in the <code class="filename">bitbake/doc/manual</code> directory within the
            <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#source-directory" target="_top">Source Directory</a>.
            At a basic level, it is sufficient to know that BitBake uses the
            <code class="filename"><a class="link" href="#var-DEPENDS" title="DEPENDS">DEPENDS</a></code> and
            <code class="filename"><a class="link" href="#var-RDEPENDS" title="RDEPENDS">RDEPENDS</a></code> variables when
            calculating dependencies.
        </p></div><div class="section" title="6.4. The Task List"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-bitbake-tasklist"></a>6.4. The Task List</h2></div></div></div><p>
            Based on the generated list of providers and the dependency information,
            BitBake can now calculate exactly what tasks it needs to run and in what
            order it needs to run them.
            The build now starts with BitBake forking off threads up to the limit set in the
            <code class="filename"><a class="link" href="#var-BB_NUMBER_THREADS" title="BB_NUMBER_THREADS">BB_NUMBER_THREADS</a></code> variable.
            BitBake continues to fork threads as long as there are tasks ready to run,
            those tasks have all their dependencies met, and the thread threshold has not been
            exceeded.
        </p><p>
            It is worth noting that you can greatly speed up the build time by properly setting
            the <code class="filename">BB_NUMBER_THREADS</code> variable.
            See the
            "<a class="ulink" href="http://www.yoctoproject.org/docs/1.4/yocto-project-qs/yocto-project-qs.html#building-image" target="_top">Building an Image</a>"
            section in the Yocto Project Quick Start for more information.
        </p><p>
            As each task completes, a timestamp is written to the directory specified by the
            <code class="filename"><a class="link" href="#var-STAMP" title="STAMP">STAMP</a></code> variable.
            On subsequent runs, BitBake looks within the <code class="filename">/build/tmp/stamps</code>
            directory and does not rerun
            tasks that are already completed unless a timestamp is found to be invalid.
            Currently, invalid timestamps are only considered on a per
            <code class="filename">.bb</code> file basis.
            So, for example, if the configure stamp has a timestamp greater than the
            compile timestamp for a given target, then the compile task would rerun.
            Running the compile task again, however, has no effect on other providers
            that depend on that target.
            This behavior could change or become configurable in future versions of BitBake.
        </p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
            Some tasks are marked as "nostamp" tasks.
            No timestamp file is created when these tasks are run.
            Consequently, "nostamp" tasks are always rerun.
        </div></div><div class="section" title="6.5. Running a Task"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-bitbake-runtask"></a>6.5. Running a Task</h2></div></div></div><p>
            Tasks can either be a shell task or a Python task.
            For shell tasks, BitBake writes a shell script to
            <code class="filename">${WORKDIR}/temp/run.do_taskname.pid</code> and then executes the script.
            The generated shell script contains all the exported variables, and the shell functions
            with all variables expanded.
            Output from the shell script goes to the file <code class="filename">${WORKDIR}/temp/log.do_taskname.pid</code>.
            Looking at the expanded shell functions in the run file and the output in the log files
            is a useful debugging technique.
        </p><p>
            For Python tasks, BitBake executes the task internally and logs information to the
            controlling terminal.
            Future versions of BitBake will write the functions to files similar to the way
            shell tasks are handled.
            Logging will be handled in way similar to shell tasks as well.
        </p><p>
            Once all the tasks have been completed BitBake exits.
        </p><p>
            When running a task, BitBake tightly controls the execution environment
            of the build tasks to make sure unwanted contamination from the build machine
            cannot influence the build.
            Consequently, if you do want something to get passed into the build
            task's environment, you must take a few steps:
            </p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>Tell BitBake to load what you want from the environment
                    into the data store.
                    You can do so through the <code class="filename">BB_ENV_EXTRAWHITE</code>
                    variable.
                    For example, assume you want to prevent the build system from
                    accessing your <code class="filename">$HOME/.ccache</code> directory.
                    The following command tells BitBake to load
                    <code class="filename">CCACHE_DIR</code> from the environment into the data
                    store:
                    </p><pre class="literallayout">
     export BB_ENV_EXTRAWHITE="$BB_ENV_EXTRAWHITE CCACHE_DIR"
                    </pre></li><li class="listitem"><p>Tell BitBake to export what you have loaded into the
                    environment store to the task environment of every running task.
                    Loading something from the environment into the data store
                    (previous step) only makes it available in the datastore.
                    To export it to the task environment of every running task,
                    use a command similar to the following in your
                    <code class="filename">local.conf</code> or distro configuration file:
                    </p><pre class="literallayout">
     export CCACHE_DIR
                    </pre></li></ol></div><p>
        </p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
            A side effect of the previous steps is that BitBake records the variable
            as a dependency of the build process in things like the shared state
            checksums.
            If doing so results in unnecessary rebuilds of tasks, you can whitelist the
            variable so that the shared state code ignores the dependency when it creates
            checksums.
            For information on this process, see the <code class="filename">BB_HASHBASE_WHITELIST</code>
            example in the "<a class="link" href="#checksums" title="3.2.2. Checksums (Signatures)">Checksums (Signatures)</a>" section.
        </div></div><div class="section" title="6.6. BitBake Command Line"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-bitbake-commandline"></a>6.6. BitBake Command Line</h2></div></div></div><p>
            Following is the BitBake help output:
        </p><pre class="screen">
$ bitbake --help
Usage: bitbake [options] [package ...]

Executes the specified task (default is 'build') for a given set of BitBake files.
It expects that BBFILES is defined, which is a space separated list of files to
be executed.  BBFILES does support wildcards.
Default BBFILES are the .bb files in the current directory.

Options:
  --version             show program's version number and exit
  -h, --help            show this help message and exit
  -b BUILDFILE, --buildfile=BUILDFILE
                        execute the task against this .bb file, rather than a
                        package from BBFILES. Does not handle any
                        dependencies.
  -k, --continue        continue as much as possible after an error. While the
                        target that failed, and those that depend on it,
                        cannot be remade, the other dependencies of these
                        targets can be processed all the same.
  -a, --tryaltconfigs   continue with builds by trying to use alternative
                        providers where possible.
  -f, --force           force run of specified cmd, regardless of stamp status
  -c CMD, --cmd=CMD     Specify task to execute. Note that this only executes
                        the specified task for the providee and the packages
                        it depends on, i.e. 'compile' does not implicitly call
                        stage for the dependencies (IOW: use only if you know
                        what you are doing). Depending on the base.bbclass a
                        listtasks tasks is defined and will show available
                        tasks
  -r PREFILE, --read=PREFILE
                        read the specified file before bitbake.conf
  -R POSTFILE, --postread=POSTFILE
                        read the specified file after bitbake.conf
  -v, --verbose         output more chit-chat to the terminal
  -D, --debug           Increase the debug level. You can specify this more
                        than once.
  -n, --dry-run         don't execute, just go through the motions
  -S, --dump-signatures
                        don't execute, just dump out the signature
                        construction information
  -p, --parse-only      quit after parsing the BB files (developers only)
  -s, --show-versions   show current and preferred versions of all packages
  -e, --environment     show the global or per-package environment (this is
                        what used to be bbread)
  -g, --graphviz        emit the dependency trees of the specified packages in
                        the dot syntax
  -I EXTRA_ASSUME_PROVIDED, --ignore-deps=EXTRA_ASSUME_PROVIDED
                        Assume these dependencies don't exist and are already
                        provided (equivalent to ASSUME_PROVIDED). Useful to
                        make dependency graphs more appealing
  -l DEBUG_DOMAINS, --log-domains=DEBUG_DOMAINS
                        Show debug logging for the specified logging domains
  -P, --profile         profile the command and print a report
  -u UI, --ui=UI        userinterface to use
  -t SERVERTYPE, --servertype=SERVERTYPE
                        Choose which server to use, none, process or xmlrpc
  --revisions-changed   Set the exit code depending on whether upstream
                        floating revisions have changed or not
        </pre></div><div class="section" title="6.7. Fetchers"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-bitbake-fetchers"></a>6.7. Fetchers</h2></div></div></div><p>
            BitBake also contains a set of "fetcher" modules that allow
            retrieval of source code from various types of sources.
            For example, BitBake can get source code from a disk with the metadata, from websites,
            from remote shell accounts or from Source Code Management (SCM) systems
            like <code class="filename">cvs/subversion/git</code>.
        </p><p>
            Fetchers are usually triggered by entries in
            <code class="filename"><a class="link" href="#var-SRC_URI" title="SRC_URI">SRC_URI</a></code>.
            You can find information about the options and formats of entries for specific
            fetchers in the BitBake manual located in the
            <code class="filename">bitbake/doc/manual</code> directory of the
            <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#source-directory" target="_top">Source Directory</a>.
        </p><p>
            One useful feature for certain Source Code Manager (SCM) fetchers is the ability to
            "auto-update" when the upstream SCM changes version.
            Since this ability requires certain functionality from the SCM, not all
            systems support it.
            Currently Subversion, Bazaar and to a limited extent, Git support the ability to "auto-update".
            This feature works using the <code class="filename"><a class="link" href="#var-SRCREV" title="SRCREV">SRCREV</a></code>
            variable.
            See the
            "<a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#platdev-appdev-srcrev" target="_top">Using an External SCM</a>" section
            in the Yocto Project Development Manual for more information.
        </p></div></div>

    <div class="chapter" title="Chapter 7. Classes"><div class="titlepage"><div><div><h2 class="title"><a id="ref-classes"></a>Chapter 7. Classes</h2></div></div></div><div class="toc"><p><strong>Table of Contents</strong></p><dl><dt><span class="section"><a href="#ref-classes-base">7.1. The base class - <code class="filename">base.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-autotools">7.2. Autotooled Packages - <code class="filename">autotools.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-update-alternatives">7.3. Alternatives - <code class="filename">update-alternatives.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-update-rc.d">7.4. Initscripts - <code class="filename">update-rc.d.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-binconfig">7.5. Binary config scripts - <code class="filename">binconfig.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-debian">7.6. Debian renaming - <code class="filename">debian.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-pkgconfig">7.7. Pkg-config - <code class="filename">pkgconfig.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-src-distribute">7.8. Distribution of sources - <code class="filename">src_distribute_local.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-perl">7.9. Perl modules - <code class="filename">cpan.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-distutils">7.10. Python extensions - <code class="filename">distutils.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-devshell">7.11. Developer Shell - <code class="filename">devshell.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-packagegroup">7.12. Package Groups - <code class="filename">packagegroup.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-package">7.13. Packaging - <code class="filename">package*.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-kernel">7.14. Building kernels - <code class="filename">kernel.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-image">7.15. Creating images - <code class="filename">image.bbclass</code> and <code class="filename">rootfs*.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-sanity">7.16. Host System sanity checks - <code class="filename">sanity.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-insane">7.17. Generated output quality assurance checks - <code class="filename">insane.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-siteinfo">7.18. Autotools configuration data cache - <code class="filename">siteinfo.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-useradd">7.19. Adding Users - <code class="filename">useradd.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-externalsrc">7.20. Using External Source - <code class="filename">externalsrc.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-others">7.21. Other Classes</a></span></dt></dl></div><p>
    Class files are used to abstract common functionality and share it amongst multiple
    <code class="filename">.bb</code> files.
    Any metadata usually found in a <code class="filename">.bb</code> file can also be placed in a class
    file.
    Class files are identified by the extension <code class="filename">.bbclass</code> and are usually placed
    in a <code class="filename">classes/</code> directory beneath the
    <code class="filename">meta*/</code> directory found in the
    <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#source-directory" target="_top">Source Directory</a>.
    Class files can also be pointed to by BUILDDIR (e.g. <code class="filename">build/</code>)in the same way as
    <code class="filename">.conf</code> files in the <code class="filename">conf</code> directory.
    Class files are searched for in <a class="link" href="#var-BBPATH" title="BBPATH"><code class="filename">BBPATH</code></a>
    using the same method by which <code class="filename">.conf</code> files are searched.
</p><p>
    In most cases inheriting the class is enough to enable its features, although
    for some classes you might need to set variables or override some of the
    default behaviour.
</p><div class="section" title="7.1. The base class - base.bbclass"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-classes-base"></a>7.1. The base class - <code class="filename">base.bbclass</code></h2></div></div></div><p>
        The base class is special in that every <code class="filename">.bb</code>
        file inherits it automatically.
        This class contains definitions for standard basic
        tasks such as fetching, unpacking, configuring (empty by default), compiling
        (runs any <code class="filename">Makefile</code> present), installing (empty by default) and packaging
        (empty by default).
        These classes are often overridden or extended by other classes
        such as <code class="filename">autotools.bbclass</code> or <code class="filename">package.bbclass</code>.
        The class also contains some commonly used functions such as <code class="filename">oe_runmake</code>.
    </p></div><div class="section" title="7.2. Autotooled Packages - autotools.bbclass"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-classes-autotools"></a>7.2. Autotooled Packages - <code class="filename">autotools.bbclass</code></h2></div></div></div><p>
        Autotools (<code class="filename">autoconf</code>, <code class="filename">automake</code>,
        and <code class="filename">libtool</code>) bring standardization.
        This class defines a set of tasks (configure, compile etc.) that
        work for all Autotooled packages.
        It should usually be enough to define a few standard variables
        and then simply <code class="filename">inherit autotools</code>.
        This class can also work with software that emulates Autotools.
        For more information, see the
        "<a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#usingpoky-extend-addpkg-autotools" target="_top">Autotooled Package</a>"
        section in the Yocto Project Development Manual.
    </p><p>
        It's useful to have some idea of how the tasks defined by this class work
        and what they do behind the scenes.
        </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><code class="filename">do_configure</code> ‐ regenerates the
                configure script (using <code class="filename">autoreconf</code>) and then launches it
                with a standard set of arguments used during cross-compilation.
                You can pass additional parameters to <code class="filename">configure</code> through the
                <code class="filename"><a class="link" href="#var-EXTRA_OECONF" title="EXTRA_OECONF">EXTRA_OECONF</a></code> variable.
                </p></li><li class="listitem"><p><code class="filename">do_compile</code> ‐ runs <code class="filename">make</code> with
                arguments that specify the compiler and linker.
                You can pass additional arguments through
                the <code class="filename"><a class="link" href="#var-EXTRA_OEMAKE" title="EXTRA_OEMAKE">EXTRA_OEMAKE</a></code> variable.
                </p></li><li class="listitem"><p><code class="filename">do_install</code> ‐ runs <code class="filename">make install</code>
                and passes a DESTDIR option, which takes its value from the standard
                <code class="filename"><a class="link" href="#var-DESTDIR" title="DESTDIR">DESTDIR</a></code> variable.
                </p></li></ul></div><p>
    </p></div><div class="section" title="7.3. Alternatives - update-alternatives.bbclass"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-classes-update-alternatives"></a>7.3. Alternatives - <code class="filename">update-alternatives.bbclass</code></h2></div></div></div><p>
        Several programs can fulfill the same or similar function and be installed with the same name.
        For example, the <code class="filename">ar</code> command is available from the
        <code class="filename">busybox</code>, <code class="filename">binutils</code> and
        <code class="filename">elfutils</code> packages.
        The <code class="filename">update-alternatives.bbclass</code> class handles renaming the
        binaries so that multiple packages can be installed without conflicts.
        The <code class="filename">ar</code> command still works regardless of which packages are installed
        or subsequently removed.
        The class renames the conflicting binary in each package and symlinks the highest
        priority binary during installation or removal of packages.
    </p><p>
        Four variables control this class:
        </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><code class="filename">ALTERNATIVE_NAME</code> ‐ The name of the
                binary that is replaced (<code class="filename">ar</code> in this example).</p></li><li class="listitem"><p><code class="filename">ALTERNATIVE_LINK</code> ‐ The path to
                the resulting binary (<code class="filename">/bin/ar</code> in this example).</p></li><li class="listitem"><p><code class="filename">ALTERNATIVE_PATH</code> ‐ The path to the
                real binary (<code class="filename">/usr/bin/ar.binutils</code> in this example).</p></li><li class="listitem"><p><code class="filename">ALTERNATIVE_PRIORITY</code> ‐ The priority of
                the binary.
                The version with the most features should have the highest priority.</p></li></ul></div><p>
    </p><p>
	Currently, the OpenEmbedded build system supports only one binary per package.
    </p></div><div class="section" title="7.4. Initscripts - update-rc.d.bbclass"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-classes-update-rc.d"></a>7.4. Initscripts - <code class="filename">update-rc.d.bbclass</code></h2></div></div></div><p>
        This class uses <code class="filename">update-rc.d</code> to safely install an
        initialization script on behalf of the package.
        The OpenEmbedded build system takes care of details such as making sure the script is stopped before
        a package is removed and started when the package is installed.
        Three variables control this class:
        <code class="filename"><a class="link" href="#var-INITSCRIPT_PACKAGES" title="INITSCRIPT_PACKAGES">INITSCRIPT_PACKAGES</a></code>,
        <code class="filename"><a class="link" href="#var-INITSCRIPT_NAME" title="INITSCRIPT_NAME">INITSCRIPT_NAME</a></code> and
        <code class="filename"><a class="link" href="#var-INITSCRIPT_PARAMS" title="INITSCRIPT_PARAMS">INITSCRIPT_PARAMS</a></code>.
        See the variable links for details.
    </p></div><div class="section" title="7.5. Binary config scripts - binconfig.bbclass"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-classes-binconfig"></a>7.5. Binary config scripts - <code class="filename">binconfig.bbclass</code></h2></div></div></div><p>
        Before <code class="filename">pkg-config</code> had become widespread, libraries shipped shell
        scripts to give information about the libraries and include paths needed
        to build software (usually named <code class="filename">LIBNAME-config</code>).
        This class assists any recipe using such scripts.
    </p><p>
        During staging, BitBake installs such scripts into the
        <code class="filename">sysroots/</code> directory.
        BitBake also changes all paths to point into the <code class="filename">sysroots/</code>
        directory so all builds that use the script will use the correct
        directories for the cross compiling layout.
    </p></div><div class="section" title="7.6. Debian renaming - debian.bbclass"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-classes-debian"></a>7.6. Debian renaming - <code class="filename">debian.bbclass</code></h2></div></div></div><p>
        This class renames packages so that they follow the Debian naming
        policy (i.e. <code class="filename">eglibc</code> becomes <code class="filename">libc6</code>
        and <code class="filename">eglibc-devel</code> becomes <code class="filename">libc6-dev</code>.
    </p></div><div class="section" title="7.7. Pkg-config - pkgconfig.bbclass"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-classes-pkgconfig"></a>7.7. Pkg-config - <code class="filename">pkgconfig.bbclass</code></h2></div></div></div><p>
        <code class="filename">pkg-config</code> brought standardization and this class aims to make its
        integration smooth for all libraries that make use of it.
    </p><p>
        During staging, BitBake installs <code class="filename">pkg-config</code> data into the
        <code class="filename">sysroots/</code> directory.
        By making use of sysroot functionality within <code class="filename">pkg-config</code>,
        this class no longer has to manipulate the files.
    </p></div><div class="section" title="7.8. Distribution of sources - src_distribute_local.bbclass"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-classes-src-distribute"></a>7.8. Distribution of sources - <code class="filename">src_distribute_local.bbclass</code></h2></div></div></div><p>
        Many software licenses require that source files be provided along with the binaries.
        To simplify this process, two classes were created:
        <code class="filename">src_distribute.bbclass</code> and
        <code class="filename">src_distribute_local.bbclass</code>.
    </p><p>
        The results of these classes are <code class="filename">tmp/deploy/source/</code>
        subdirs with sources sorted by
        <code class="filename"><a class="link" href="#var-LICENSE" title="LICENSE">LICENSE</a></code> field.
        If recipes list few licenses (or have entries like "Bitstream Vera"),
        the source archive is placed in each license directory.
    </p><p>
        This class operates using three modes:
        </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em>copy:</em></span> Copies the files to the
                distribute directory.</p></li><li class="listitem"><p><span class="emphasis"><em>symlink:</em></span> Symlinks the files to the
                distribute directory.</p></li><li class="listitem"><p><span class="emphasis"><em>move+symlink:</em></span> Moves the files into
                the distribute directory and then symlinks them back.</p></li></ul></div><p>
    </p></div><div class="section" title="7.9. Perl modules - cpan.bbclass"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-classes-perl"></a>7.9. Perl modules - <code class="filename">cpan.bbclass</code></h2></div></div></div><p>
        Recipes for Perl modules are simple.
        These recipes usually only need to point to the source's archive and then inherit the
        proper <code class="filename">.bbclass</code> file.
        Building is split into two methods depending on which method the module authors used.
    </p><p>
        Modules that use old <code class="filename">Makefile.PL</code>-based build system require
        <code class="filename">cpan.bbclass</code> in their recipes.
    </p><p>
        Modules that use <code class="filename">Build.PL</code>-based build system require
        using <code class="filename">cpan_build.bbclass</code> in their recipes.
    </p></div><div class="section" title="7.10. Python extensions - distutils.bbclass"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-classes-distutils"></a>7.10. Python extensions - <code class="filename">distutils.bbclass</code></h2></div></div></div><p>
        Recipes for Python extensions are simple.
        These recipes usually only need to point to the source's archive and then inherit
        the proper <code class="filename">.bbclass</code> file.
        Building is split into two methods dependling on which method the module authors used.
    </p><p>
        Extensions that use an Autotools-based build system require Autotools and
        <code class="filename">distutils</code>-based <code class="filename">.bbclasse</code> files in their recipes.
    </p><p>
        Extensions that use <code class="filename">distutils</code>-based build systems require
        <code class="filename">distutils.bbclass</code> in their recipes.
    </p></div><div class="section" title="7.11. Developer Shell - devshell.bbclass"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-classes-devshell"></a>7.11. Developer Shell - <code class="filename">devshell.bbclass</code></h2></div></div></div><p>
        This class adds the <code class="filename">devshell</code> task.
        Distribution policy dictates whether to include this class.
        See the
        "<a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#platdev-appdev-devshell" target="_top">Using a Development Shell</a>" section
        in the Yocto Project Development Manual for more information about using <code class="filename">devshell</code>.
    </p></div><div class="section" title="7.12. Package Groups - packagegroup.bbclass"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-classes-packagegroup"></a>7.12. Package Groups - <code class="filename">packagegroup.bbclass</code></h2></div></div></div><p>
        This class sets default values appropriate for package group recipes (such as
        <code class="filename"><a class="link" href="#var-PACKAGES" title="PACKAGES">PACKAGES</a></code>,
        <code class="filename"><a class="link" href="#var-PACKAGE_ARCH" title="PACKAGE_ARCH">PACKAGE_ARCH</a></code>,
        <code class="filename"><a class="link" href="#var-ALLOW_EMPTY" title="ALLOW_EMPTY">ALLOW_EMPTY</a></code>,
        and so forth.
        It is highly recommended that all package group recipes inherit this class.
    </p><p>
        For information on how to use this class, see the
        "<a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#usingpoky-extend-customimage-customtasks" target="_top">Customizing Images Using Custom Package Tasks</a>"
        section in the Yocto Project Development Manual.
    </p><p>
        Previously, this class was named <code class="filename">task.bbclass</code>.
    </p></div><div class="section" title="7.13. Packaging - package*.bbclass"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-classes-package"></a>7.13. Packaging - <code class="filename">package*.bbclass</code></h2></div></div></div><p>
        The packaging classes add support for generating packages from a build's
        output.
        The core generic functionality is in <code class="filename">package.bbclass</code>.
        The code specific to particular package types is contained in various sub-classes such as
        <code class="filename">package_deb.bbclass</code>, <code class="filename">package_ipk.bbclass</code>,
        and <code class="filename">package_rpm.bbclass</code>.
        Most users will want one or more of these classes.
    </p><p>
        You can control the list of resulting package formats by using the
        <code class="filename"><a class="link" href="#var-PACKAGE_CLASSES" title="PACKAGE_CLASSES">PACKAGE_CLASSES</a></code>
        variable defined in the <code class="filename">local.conf</code> configuration file,
        which is located in the <code class="filename">conf</code> folder of the
        <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#source-directory" target="_top">Source Directory</a>.
        When defining the variable, you can specify one or more package types.
        Since images are generated from packages, a packaging class is
        needed to enable image generation.
        The first class listed in this variable is used for image generation.
    </p><p>
        The package class you choose can affect build-time performance and has space
        ramifications.
        In general, building a package with RPM takes about thirty percent more time as
        compared to using IPK to build the same or similar package.
        This comparison takes into account a complete build of the package with all
        dependencies previously built.
        The reason for this discrepancy is because the RPM package manager creates and
        processes more metadata than the IPK package manager.
        Consequently, you might consider setting <code class="filename">PACKAGE_CLASSES</code>
        to "package_ipk" if you are building smaller systems.
    </p><p>
        Keep in mind, however, that RPM starts to provide more abilities than IPK due to
        the fact that it processes more metadata.
        For example, this information includes individual file types, file checksum generation
        and evaluation on install, sparse file support, conflict detection and resolution
        for multilib systems, ACID style upgrade, and repackaging abilities for rollbacks.
    </p><p>
        Another consideration for packages built using the RPM package manager is space.
        For smaller systems, the extra space used for the Berkley Database and the amount
        of metadata can affect your ability to do on-device upgrades.
    </p><p>
        You can find additional information on the effects of the package class at these
        two Yocto Project mailing list links:
        </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><a class="ulink" href="http://lists.yoctoproject.org/pipermail/poky/2011-May/006362.html" target="_top">
                https://lists.yoctoproject.org/pipermail/poky/2011-May/006362.html</a></p></li><li class="listitem"><p><a class="ulink" href="http://lists.yoctoproject.org/pipermail/poky/2011-May/006363.html" target="_top">
                https://lists.yoctoproject.org/pipermail/poky/2011-May/006363.html</a></p></li></ul></div><p>
    </p></div><div class="section" title="7.14. Building kernels - kernel.bbclass"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-classes-kernel"></a>7.14. Building kernels - <code class="filename">kernel.bbclass</code></h2></div></div></div><p>
        This class handles building Linux kernels.
        The class contains code to build all kernel trees.
        All needed headers are staged into the
        <code class="filename"><a class="link" href="#var-STAGING_KERNEL_DIR" title="STAGING_KERNEL_DIR">STAGING_KERNEL_DIR</a></code>
        directory to allow out-of-tree module builds using <code class="filename">module.bbclass</code>.
    </p><p>
        This means that each built kernel module is packaged separately and inter-module
        dependencies are created by parsing the <code class="filename">modinfo</code> output.
        If all modules are required, then installing the <code class="filename">kernel-modules</code>
        package installs all packages with modules and various other kernel packages
        such as <code class="filename">kernel-vmlinux</code>.
    </p><p>
        Various other classes are used by the kernel and module classes internally including
        <code class="filename">kernel-arch.bbclass</code>, <code class="filename">module_strip.bbclass</code>,
        <code class="filename">module-base.bbclass</code>, and <code class="filename">linux-kernel-base.bbclass</code>.
    </p></div><div class="section" title="7.15. Creating images - image.bbclass and rootfs*.bbclass"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-classes-image"></a>7.15. Creating images - <code class="filename">image.bbclass</code> and <code class="filename">rootfs*.bbclass</code></h2></div></div></div><p>
        These classes add support for creating images in several formats.
        First, the root filesystem is created from packages using
        one of the <code class="filename">rootfs_*.bbclass</code>
        files (depending on the package format used) and then the image is created.
    </p><p>
        The <code class="filename"><a class="link" href="#var-IMAGE_FSTYPES" title="IMAGE_FSTYPES">IMAGE_FSTYPES</a></code>
        variable controls the types of images to generate.
    </p><p>
        The <code class="filename"><a class="link" href="#var-IMAGE_INSTALL" title="IMAGE_INSTALL">IMAGE_INSTALL</a></code>
        variable controls the list of packages to install into the image.
    </p></div><div class="section" title="7.16. Host System sanity checks - sanity.bbclass"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-classes-sanity"></a>7.16. Host System sanity checks - <code class="filename">sanity.bbclass</code></h2></div></div></div><p>
        This class checks to see if prerequisite software is present so that
        users can be notified of potential problems that might affect their build.
        The class also performs basic user configuration checks from
        the <code class="filename">local.conf</code> configuration file to
        prevent common mistakes that cause build failures.
        Distribution policy usually determines whether to include this class.
    </p></div><div class="section" title="7.17. Generated output quality assurance checks - insane.bbclass"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-classes-insane"></a>7.17. Generated output quality assurance checks - <code class="filename">insane.bbclass</code></h2></div></div></div><p>
        This class adds a step to the package generation process that sanity checks the
        packages generated by the OpenEmbedded build system.
        A range of checks are performed that check the build's output
        for common problems that show up during runtime.
        Distribution policy usually dictates whether to include this class.
    </p><p>
        You can configure the sanity checks so that specific test failures either raise a warning or
        an error message.
        Typically, failures for new tests generate a warning.
        Subsequent failures for the same test would then generate an error message
        once the metadata is in a known and good condition.
        You use the <code class="filename">WARN_QA</code> variable to specify tests for which you
        want to generate a warning message on failure.
        You use the <code class="filename">ERROR_QA</code> variable to specify tests for which you
        want to generate an error message on failure.
    </p><p>
        The following list shows the tests you can list with the <code class="filename">WARN_QA</code>
        and <code class="filename">ERROR_QA</code> variables:
        </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em><code class="filename">ldflags:</code></em></span>
                Ensures that the binaries were linked with the
                <code class="filename">LDFLAGS</code> options provided by the build system.
                If this test fails, check that the <code class="filename">LDFLAGS</code> variable
                is being passed to the linker command.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">useless-rpaths:</code></em></span>
                Checks for dynamic library load paths (rpaths) in the binaries that
                by default on a standard system are searched by the linker (e.g.
                <code class="filename">/lib</code> and <code class="filename">/usr/lib</code>).
                While these paths will not cause any breakage, they do waste space and
                are unnecessary.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">rpaths:</code></em></span>
                Checks for rpaths in the binaries that contain build system paths such
                as <code class="filename">TMPDIR</code>.
                If this test fails, bad <code class="filename">-rpath</code> options are being
                passed to the linker commands and your binaries have potential security
                issues.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">dev-so:</code></em></span>
                Checks that the <code class="filename">.so</code> symbolic links are in the
                <code class="filename">-dev</code> package and not in any of the other packages.
                In general, these symlinks are only useful for development purposes.
                Thus, the <code class="filename">-dev</code> package is the correct location for
                them.
                Some very rare cases do exist for dynamically loaded modules where
                these symlinks are needed instead in the main package.
                </p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">debug-files:</code></em></span>
                Checks for <code class="filename">.debug</code> directories in anything but the
                <code class="filename">-dbg</code> package.
                The debug files should all be in the <code class="filename">-dbg</code> package.
                Thus, anything packaged elsewhere is incorrect packaging.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">arch:</code></em></span>
                Checks the Executable and Linkable Format (ELF) type, bit size and endianness
                of any binaries to ensure it matches the target architecture.
                This test fails if any binaries don't match the type since there would be an
                incompatibility.
                Sometimes software, like bootloaders, might need to bypass this check.
                </p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">debug-deps:</code></em></span>
                Checks that <code class="filename">-dbg</code> packages only depend on other
                <code class="filename">-dbg</code> packages and not on any other types of packages,
                which would cause a packaging bug.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">dev-deps:</code></em></span>
                Checks that <code class="filename">-dev</code> packages only depend on other
                <code class="filename">-dev</code> packages and not on any other types of packages,
                which would be a packaging bug.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">pkgconfig:</code></em></span>
                Checks <code class="filename">.pc</code> files for any
                <code class="filename">TMPDIR/WORKDIR</code> paths.
                Any <code class="filename">.pc</code> file containing these paths is incorrect
                since <code class="filename">pkg-config</code> itself adds the correct sysroot prefix
                when the files are accessed.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">la:</code></em></span>
                Checks <code class="filename">.la</code> files for any <code class="filename">TMPDIR</code>
                paths.
                Any <code class="filename">.la</code> file continaing these paths is incorrect since
                <code class="filename">libtool</code> adds the correct sysroot prefix when using the
                files automatically itself.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">desktop:</code></em></span>
                Runs the <code class="filename">desktop-file-validate</code> program against any
                <code class="filename">.desktop</code> files to validate their contents against
                the specification for <code class="filename">.desktop</code> files.</p></li></ul></div><p>
    </p></div><div class="section" title="7.18. Autotools configuration data cache - siteinfo.bbclass"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-classes-siteinfo"></a>7.18. Autotools configuration data cache - <code class="filename">siteinfo.bbclass</code></h2></div></div></div><p>
        Autotools can require tests that must execute on the target hardware.
        Since this is not possible in general when cross compiling, site information is
        used to provide cached test results so these tests can be skipped over but
        still make the correct values available.
        The <code class="filename"><a class="link" href="#structure-meta-site" title="5.3.18. meta/site/">meta/site directory</a></code>
        contains test results sorted into different categories such as architecture, endianness, and
        the <code class="filename">libc</code> used.
        Site information provides a list of files containing data relevant to
        the current build in the
        <code class="filename"><a class="link" href="#var-CONFIG_SITE" title="CONFIG_SITE">CONFIG_SITE</a></code> variable
        that Autotools automatically picks up.
    </p><p>
        The class also provides variables like
        <code class="filename"><a class="link" href="#var-SITEINFO_ENDIANNESS" title="SITEINFO_ENDIANNESS">SITEINFO_ENDIANNESS</a></code>
        and <code class="filename"><a class="link" href="#var-SITEINFO_BITS" title="SITEINFO_BITS">SITEINFO_BITS</a></code>
        that can be used elsewhere in the metadata.
    </p><p>
        Because this class is included from <code class="filename">base.bbclass</code>, it is always active.
    </p></div><div class="section" title="7.19. Adding Users - useradd.bbclass"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-classes-useradd"></a>7.19. Adding Users - <code class="filename">useradd.bbclass</code></h2></div></div></div><p>
        If you have packages that install files that are owned by custom users or groups,
        you can use this class to specify those packages and associate the users and groups
        with those packages.
        The <code class="filename">meta-skeleton/recipes-skeleton/useradd/useradd-example.bb</code>
        recipe in the <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#source-directory" target="_top">Source Directory</a>
        provides a simple exmample that shows how to add three
        users and groups to two packages.
        See the <code class="filename">useradd-example.bb</code> for more information on how to
        use this class.
    </p></div><div class="section" title="7.20. Using External Source - externalsrc.bbclass"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-classes-externalsrc"></a>7.20. Using External Source - <code class="filename">externalsrc.bbclass</code></h2></div></div></div><p>
        You can use this class to build software from source code that is external to the
        OpenEmbedded build system.
        In other words, your source code resides in an external tree outside of the Yocto Project.
        Building software from an external source tree means that the normal fetch, unpack, and
        patch process is not used.
    </p><p>
        To use the class, you need to define the
        <a class="link" href="#var-S" title="S"><code class="filename">S</code></a> variable to point to the directory that contains the source files.
        You also need to have your recipe inherit the <code class="filename">externalsrc.bbclass</code> class.
    </p><p>
        This class expects the source code to support recipe builds that use the
        <a class="link" href="#var-B" title="B"><code class="filename">B</code></a> variable to point to the directory in
        which the OpenEmbedded build system places the generated objects built from the recipes.
        By default, the <code class="filename">B</code> directory is set to the following, which is separate from the
        Source Directory (<code class="filename">S</code>):
        </p><pre class="literallayout">
     ${WORKDIR}/${BPN}/{PV}/
        </pre><p>
        See the glossary entries for the
        <a class="link" href="#var-WORKDIR" title="WORKDIR"><code class="filename">WORKDIR</code></a>,
        <a class="link" href="#var-BPN" title="BPN"><code class="filename">BPN</code></a>,
        <a class="link" href="#var-PV" title="PV"><code class="filename">PV</code></a>,
        <a class="link" href="#var-S" title="S"><code class="filename">S</code></a>, and
        <a class="link" href="#var-B" title="B"><code class="filename">B</code></a> for more information.
    </p><p>
        You can build object files in the external tree by setting the
        <code class="filename">B</code> variable equal to <code class="filename">"${S}"</code>.
        However, this practice does not work well if you use the source for more than one variant
        (i.e., "natives" such as <code class="filename">quilt-native</code>,
        or "crosses" such as <code class="filename">gcc-cross</code>).
        So, be sure there are no "native", "cross", or "multilib" variants of the recipe.
    </p><p>
        If you do want to build different variants of a recipe, you can use the
        <a class="link" href="#var-BBCLASSEXTEND" title="BBCLASSEXTEND"><code class="filename">BBCLASSEXTEND</code></a> variable.
        When you do, the <a class="link" href="#var-B" title="B"><code class="filename">B</code></a> variable must support the
        recipe's ability to build variants in different working directories.
        Most autotools-based recipes support separating these directories.
        The OpenEmbedded build system defaults to using separate directories for <code class="filename">gcc</code>
        and some kernel recipes.
        Alternatively, you can make sure that separate recipes exist that each
        use the <code class="filename">BBCLASSEXTEND</code> variable to build each variant.
        The separate recipes can inherit a single target recipe.
    </p><p>
        For information on how to use this class, see the
        "<a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#building-software-from-an-external-source" target="_top">Building
        Software from an External Source</a>" section in the Yocto Project Development Manual.
    </p></div><div class="section" title="7.21. Other Classes"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-classes-others"></a>7.21. Other Classes</h2></div></div></div><p>
        Thus far, this chapter has discussed only the most useful and important
        classes.
        However, other classes exist within the <code class="filename">meta/classes</code> directory
        in the <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#source-directory" target="_top">Source Directory</a>.
        You can examine the <code class="filename">.bbclass</code> files directly for more
        information.
    </p></div></div>

    <div class="chapter" title="Chapter 8. Images"><div class="titlepage"><div><div><h2 class="title"><a id="ref-images"></a>Chapter 8. Images</h2></div></div></div><p>
        The OpenEmbedded build process supports several types of images to satisfy different needs.
        When you issue the <code class="filename">bitbake</code> command you provide a “top-level” recipe
        that essentially begins the build for the type of image you want.
    </p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
        Building an image without GNU General Public License Version 3 (GPLv3) components
        is only supported for minimal and base images.
        Furthermore, if you are going to build an image using non-GPLv3 components,
        you must make the following changes in the <code class="filename">local.conf</code> file
        before using the BitBake command to build the minimal or base image:
        <pre class="literallayout">
     1. Comment out the EXTRA_IMAGE_FEATURES line
     2. Set INCOMPATIBLE_LICENSE = "GPLv3"
        </pre></div><p>
        From within the <code class="filename">poky</code> Git repository, use the following command to list
        the supported images:
        </p><pre class="literallayout">
     $ ls meta*/recipes*/images/*.bb
        </pre><p>
        These recipes reside in the <code class="filename">meta/recipes-core/images</code>,
        <code class="filename">meta/recipes-extended/images</code>,
        <code class="filename">meta/recipes-graphics/images</code>, and
        <code class="filename">meta/recipes-sato/images</code> directories
        within the <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#source-directory" target="_top">source directory</a>.
        Although the recipe names are somewhat explanatory, here is a list that describes them:
    </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em><code class="filename">core-image-base</code>:</em></span>
            A console-only image that fully supports the target device hardware.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">core-image-minimal</code>:</em></span>
            A small image just capable of allowing a device to boot.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">core-image-minimal-dev</code>:</em></span>
            A <code class="filename">core-image-minimal</code> image suitable for development work
            using the host.
            The image includes headers and libraries you can use in a host development
            environment.
            </p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">core-image-minimal-initramfs</code>:</em></span>
            A <code class="filename">core-image-minimal</code> image that has the Minimal RAM-based
            Initial Root Filesystem (<code class="filename">initramfs</code>) as part of the kernel,
            which allows the system to find the first “init” program more efficiently.
            </p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">core-image-minimal-mtdutils</code>:</em></span>
            A <code class="filename">core-image-minimal</code> image that has support
            for the Minimal MTD Utilities, which let the user interact with the
            MTD subsystem in the kernel to perform operations on flash devices.
            </p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">core-image-x11</code>:</em></span>
            A very basic X11 image with a terminal.
            </p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">core-image-basic</code>:</em></span>
            A console-only image with more full-featured Linux system
            functionality installed.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">core-image-lsb</code>:</em></span>
            An image that conforms to the Linux Standard Base (LSB) specification.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">core-image-lsb-dev</code>:</em></span>
            A <code class="filename">core-image-lsb</code> image that is suitable for development work
            using the host.
            The image includes headers and libraries you can use in a host development
            environment.
            </p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">core-image-lsb-sdk</code>:</em></span>
            A <code class="filename">core-image-lsb</code> that includes everything in meta-toolchain
            but also includes development headers and libraries to form a complete standalone SDK.
            This image is suitable for development using the target.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">core-image-clutter</code>:</em></span>
            An image with support for the Open GL-based toolkit Clutter, which enables development of
            rich and animated graphical user interfaces.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">core-image-sato</code>:</em></span>
            An image with Sato support, a mobile environment and visual style that works well
            with mobile devices.
            The image supports X11 with a Sato theme and applications such as
            a terminal, editor, file manager, media player, and so forth.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">core-image-sato-dev</code>:</em></span>
            A <code class="filename">core-image-sato</code> image suitable for development
            using the host.
            The image includes libraries needed to build applications on the device itself,
            testing and profiling tools, and debug symbols.
            This image was formerly <code class="filename">core-image-sdk</code>.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">core-image-sato-sdk</code>:</em></span>
            A <code class="filename">core-image-sato</code> image that includes everything in meta-toolchain.
            The image also includes development headers and libraries to form a complete standalone SDK
            and is suitable for development using the target.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">core-image-rt</code>:</em></span>
            A <code class="filename">core-image-minimal</code> image plus a real-time test suite and
            tools appropriate for real-time use.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">core-image-rt-sdk</code>:</em></span>
            A <code class="filename">core-image-rt</code> image that includes everything in
            <code class="filename">meta-toolchain</code>.
            The image also includes development headers and libraries to form a complete
            stand-alone SDK and is suitable for development using the target.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">core-image-gtk-directfb</code>:</em></span>
            An image that uses <code class="filename">gtk+</code> over <code class="filename">directfb</code>
            instead of X11.
            In order to build, this image requires specific distro configuration that enables
            <code class="filename">gtk</code> over <code class="filename">directfb</code>.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">build-appliance-image</code>:</em></span>
            An image you can boot and run using either the
            <a class="ulink" href="http://www.vmware.com/products/player/overview.html" target="_top">VMware Player</a>
            or <a class="ulink" href="http://www.vmware.com/products/workstation/overview.html" target="_top">VMware Workstation</a>.
            For more information on this image, see the
            <a class="ulink" href="http://www.yoctoproject.org/documentation/build-appliance" target="_top">Build Appliance</a> page on
            the Yocto Project website.</p></li></ul></div><div class="tip" title="Tip" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Tip</h3>
        From the Yocto Project release 1.1 onwards, <code class="filename">-live</code> and
        <code class="filename">-directdisk</code> images have been replaced by a "live"
        option in <code class="filename">IMAGE_FSTYPES</code> that will work with any image to produce an
        image file that can be
        copied directly to a CD or USB device and run as is.
        To build a live image, simply add
        "live" to <code class="filename">IMAGE_FSTYPES</code> within the <code class="filename">local.conf</code>
        file or wherever appropriate and then build the desired image as normal.
    </div></div>

    <div class="chapter" title="Chapter 9. Reference: Features"><div class="titlepage"><div><div><h2 class="title"><a id="ref-features"></a>Chapter 9. Reference: Features</h2></div></div></div><div class="toc"><p><strong>Table of Contents</strong></p><dl><dt><span class="section"><a href="#ref-features-distro">9.1. Distro</a></span></dt><dt><span class="section"><a href="#ref-features-machine">9.2. Machine</a></span></dt><dt><span class="section"><a href="#ref-features-image">9.3. Images</a></span></dt><dt><span class="section"><a href="#ref-features-backfill">9.4. Feature Backfilling</a></span></dt></dl></div><p>
        Features provide a mechanism for working out which packages
        should be included in the generated images.
        Distributions can select which features they want to support through the
        <code class="filename"><a class="link" href="#var-DISTRO_FEATURES" title="DISTRO_FEATURES">DISTRO_FEATURES</a></code>
        variable, which is set in the <code class="filename">poky.conf</code> distribution configuration file.
        Machine features are set in the
        <code class="filename"><a class="link" href="#var-MACHINE_FEATURES" title="MACHINE_FEATURES">MACHINE_FEATURES</a></code>
        variable, which is set in the machine configuration file and
        specifies the hardware features for a given machine.
    </p><p>
        These two variables combine to work out which kernel modules,
        utilities, and other packages to include.
        A given distribution can support a selected subset of features so some machine features might not
        be included if the distribution itself does not support them.
    </p><p>
        One method you can use to determine which recipes are checking to see if a
        particular feature is contained or not is to <code class="filename">grep</code> through
        the metadata for the feature.
        Here is an example that discovers the recipes whose build is potentially
        changed based on a given feature:
        </p><pre class="literallayout">
     $ cd $HOME/poky
     $ git grep 'contains.*MACHINE_FEATURES.*&lt;feature&gt;'
        </pre><p>
    </p><p>
        This chapter provides a reference of shipped machine and distro features
        you can include as part of the image, a reference on image types you can
        build, and a reference on feature backfilling.
    </p><div class="section" title="9.1. Distro"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-features-distro"></a>9.1. Distro</h2></div></div></div><p>
            The items below are features you can use with
            <a class="link" href="#var-DISTRO_FEATURES" title="DISTRO_FEATURES"><code class="filename">DISTRO_FEATURES</code></a>.
            Features do not have a one-to-one correspondence to packages, and they can
            go beyond simply controlling the installation of a package or packages.
            Sometimes a feature can influence how certain recipes are built.
            For example, a feature might determine whether a particular configure option
            is specified within <code class="filename">do_configure</code> for a particular
            recipe.
        </p><p>
            This list only represents features as shipped with the Yocto Project metadata:
            </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em>alsa:</em></span> ALSA support will be included (OSS compatibility
                    kernel modules will be installed if available).</p></li><li class="listitem"><p><span class="emphasis"><em>bluetooth:</em></span> Include bluetooth support (integrated BT only)
                    </p></li><li class="listitem"><p><span class="emphasis"><em>ext2:</em></span> Include tools for supporting for devices with internal
                    HDD/Microdrive for storing files (instead of Flash only devices)
                    </p></li><li class="listitem"><p><span class="emphasis"><em>irda:</em></span> Include Irda support
                    </p></li><li class="listitem"><p><span class="emphasis"><em>keyboard:</em></span> Include keyboard support (e.g. keymaps will be
                    loaded during boot).
                    </p></li><li class="listitem"><p><span class="emphasis"><em>pci:</em></span> Include PCI bus support
                    </p></li><li class="listitem"><p><span class="emphasis"><em>pcmcia:</em></span> Include PCMCIA/CompactFlash support
                    </p></li><li class="listitem"><p><span class="emphasis"><em>usbgadget:</em></span> USB Gadget Device support (for USB
                    networking/serial/storage)
                    </p></li><li class="listitem"><p><span class="emphasis"><em>usbhost:</em></span> USB Host support (allows to connect external
                    keyboard, mouse, storage, network etc)
                    </p></li><li class="listitem"><p><span class="emphasis"><em>wifi:</em></span> WiFi support (integrated only)
                    </p></li><li class="listitem"><p><span class="emphasis"><em>cramfs:</em></span> CramFS support
                    </p></li><li class="listitem"><p><span class="emphasis"><em>ipsec:</em></span> IPSec support
                    </p></li><li class="listitem"><p><span class="emphasis"><em>ipv6:</em></span> IPv6 support
                    </p></li><li class="listitem"><p><span class="emphasis"><em>nfs:</em></span> NFS client support (for mounting NFS exports on
                    device)</p></li><li class="listitem"><p><span class="emphasis"><em>ppp:</em></span> PPP dialup support</p></li><li class="listitem"><p><span class="emphasis"><em>smbfs:</em></span> SMB networks client support (for mounting
                    Samba/Microsoft Windows shares on device)</p></li></ul></div><p>
        </p></div><div class="section" title="9.2. Machine"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-features-machine"></a>9.2. Machine</h2></div></div></div><p>
            The items below are features you can use with
            <a class="link" href="#var-MACHINE_FEATURES" title="MACHINE_FEATURES"><code class="filename">MACHINE_FEATURES</code></a>.
            Features do not have a one-to-one correspondence to packages, and they can
            go beyond simply controlling the installation of a package or packages.
            Sometimes a feature can influence how certain recipes are built.
            For example, a feature might determine whether a particular configure option
            is specified within <code class="filename">do_configure</code> for a particular
            recipe.
        </p><p>
            This feature list only represents features as shipped with the Yocto Project metadata:
            </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em>acpi:</em></span> Hardware has ACPI (x86/x86_64 only)
                    </p></li><li class="listitem"><p><span class="emphasis"><em>alsa:</em></span> Hardware has ALSA audio drivers
                    </p></li><li class="listitem"><p><span class="emphasis"><em>apm:</em></span> Hardware uses APM (or APM emulation)
                    </p></li><li class="listitem"><p><span class="emphasis"><em>bluetooth:</em></span> Hardware has integrated BT
                    </p></li><li class="listitem"><p><span class="emphasis"><em>ext2:</em></span> Hardware HDD or Microdrive
                    </p></li><li class="listitem"><p><span class="emphasis"><em>irda:</em></span> Hardware has Irda support
                    </p></li><li class="listitem"><p><span class="emphasis"><em>keyboard:</em></span> Hardware has a keyboard
                    </p></li><li class="listitem"><p><span class="emphasis"><em>pci:</em></span> Hardware has a PCI bus
                    </p></li><li class="listitem"><p><span class="emphasis"><em>pcmcia:</em></span> Hardware has PCMCIA or CompactFlash sockets
                    </p></li><li class="listitem"><p><span class="emphasis"><em>screen:</em></span> Hardware has a screen
                    </p></li><li class="listitem"><p><span class="emphasis"><em>serial:</em></span> Hardware has serial support (usually RS232)
                    </p></li><li class="listitem"><p><span class="emphasis"><em>touchscreen:</em></span> Hardware has a touchscreen
                    </p></li><li class="listitem"><p><span class="emphasis"><em>usbgadget:</em></span> Hardware is USB gadget device capable
                    </p></li><li class="listitem"><p><span class="emphasis"><em>usbhost:</em></span> Hardware is USB Host capable
                    </p></li><li class="listitem"><p><span class="emphasis"><em>wifi:</em></span> Hardware has integrated WiFi
                    </p></li></ul></div><p>
        </p></div><div class="section" title="9.3. Images"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-features-image"></a>9.3. Images</h2></div></div></div><p>
            The contents of images generated by the OpenEmbedded build system can be controlled by the
            <code class="filename"><a class="link" href="#var-IMAGE_FEATURES" title="IMAGE_FEATURES">IMAGE_FEATURES</a></code>
            and <code class="filename"><a class="link" href="#var-EXTRA_IMAGE_FEATURES" title="EXTRA_IMAGE_FEATURES">EXTRA_IMAGE_FEATURES</a></code>
            variables that you typically configure in your image recipes.
            Through these variables you can add several different
            predefined packages such as development utilities or packages with debug
            information needed to investigate application problems or profile applications.
        </p><p>
            Current list of
            <code class="filename">IMAGE_FEATURES</code> contains the following:
            </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em>splash:</em></span> Enables showing a splash screen during boot.
                    By default, this screen is provided by <code class="filename">psplash</code>, which does
                    allow customization.
                    If you prefer to use an alternative splash screen package, you can do so by
                    setting the <code class="filename">SPLASH</code> variable
                    to a different package name (or names) within the image recipe or at the distro
                    configuration level.</p></li><li class="listitem"><p><span class="emphasis"><em>ssh-server-dropbear:</em></span> Installs the Dropbear minimal
                    SSH server.
                    </p></li><li class="listitem"><p><span class="emphasis"><em>ssh-server-openssh:</em></span> Installs the OpenSSH SSH server,
                    which is more full-featured than Dropbear.
                    Note that if both the OpenSSH SSH server and the Dropbear minimal SSH server
                    are present in <code class="filename">IMAGE_FEATURES</code>, then OpenSSH will take
                    precedence and Dropbear will not be installed.</p></li><li class="listitem"><p><span class="emphasis"><em>x11:</em></span> Installs the X server</p></li><li class="listitem"><p><span class="emphasis"><em>x11-base:</em></span> Installs the X server with a
                    minimal environment.</p></li><li class="listitem"><p><span class="emphasis"><em>x11-sato:</em></span> Installs the OpenedHand Sato environment.
                    </p></li><li class="listitem"><p><span class="emphasis"><em>tools-sdk:</em></span> Installs a full SDK that runs on the device.
                    </p></li><li class="listitem"><p><span class="emphasis"><em>tools-debug:</em></span> Installs debugging tools such as
                    <code class="filename">strace</code> and <code class="filename">gdb</code>.
                    </p></li><li class="listitem"><p><span class="emphasis"><em>tools-profile:</em></span> Installs profiling tools such as
                    <code class="filename">oprofile</code>, <code class="filename">exmap</code>, and
                    <code class="filename">LTTng</code>.</p></li><li class="listitem"><p><span class="emphasis"><em>tools-testapps:</em></span> Installs device testing tools (e.g.
                    touchscreen debugging).</p></li><li class="listitem"><p><span class="emphasis"><em>nfs-server:</em></span> Installs an NFS server.</p></li><li class="listitem"><p><span class="emphasis"><em>dev-pkgs:</em></span> Installs development packages (headers and
                    extra library links) for all packages installed in a given image.</p></li><li class="listitem"><p><span class="emphasis"><em>staticdev-pkgs:</em></span> Installs static development
                    packages (i.e. static libraries containing <code class="filename">*.a</code> files) for all
                    packages installed in a given image.</p></li><li class="listitem"><p><span class="emphasis"><em>dbg-pkgs:</em></span> Installs debug symbol packages for all packages
                    installed in a given image.</p></li><li class="listitem"><p><span class="emphasis"><em>doc-pkgs:</em></span> Installs documentation packages for all packages
                    installed in a given image.</p></li></ul></div><p>
        </p></div><div class="section" title="9.4. Feature Backfilling"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-features-backfill"></a>9.4. Feature Backfilling</h2></div></div></div><p>
            Sometimes it is necessary in the OpenEmbedded build system to extend
            <a class="link" href="#var-MACHINE_FEATURES" title="MACHINE_FEATURES"><code class="filename">MACHINE_FEATURES</code></a>
            or <a class="link" href="#var-DISTRO_FEATURES" title="DISTRO_FEATURES"><code class="filename">DISTRO_FEATURES</code></a>
            to control functionality that was previously enabled and not able
            to be disabled.
            For these cases, we need to add an
            additional feature item to appear in one of these variables,
            but we do not want to force developers who have existing values
            of the variables in their configuration to add the new feature
            in order to retain the same overall level of functionality.
            Thus, the OpenEmbedded build system has a mechanism to
            automatically "backfill" these added features into existing
            distro or machine configurations.
            You can see the list of features for which this is done by
            finding the
            <a class="link" href="#var-DISTRO_FEATURES_BACKFILL" title="DISTRO_FEATURES_BACKFILL"><code class="filename">DISTRO_FEATURES_BACKFILL</code></a>
            and <a class="link" href="#var-MACHINE_FEATURES_BACKFILL" title="MACHINE_FEATURES_BACKFILL"><code class="filename">MACHINE_FEATURES_BACKFILL</code></a>
            variables in the <code class="filename">meta/conf/bitbake.conf</code> file.
        </p><p>
            Because such features are backfilled by default into all
            configurations as described in the previous paragraph, developers
            who wish to disable the new features need to be able to selectively
            prevent the backfilling from occurring.
            They can do this by adding the undesired feature or features to the
            <a class="link" href="#var-DISTRO_FEATURES_BACKFILL_CONSIDERED" title="DISTRO_FEATURES_BACKFILL_CONSIDERED"><code class="filename">DISTRO_FEATURES_BACKFILL_CONSIDERED</code></a>
            or <a class="link" href="#var-MACHINE_FEATURES_BACKFILL_CONSIDERED" title="MACHINE_FEATURES_BACKFILL_CONSIDERED"><code class="filename">MACHINE_FEATURES_BACKFILL_CONSIDERED</code></a>
            variables for distro features and machine features respectively.
        </p><p>
            Here are two examples to help illustrate feature backfilling:
            </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em>The "pulseaudio" distro feature option</em></span>:
                    Previously, PulseAudio support was enabled within the Qt and
                    GStreamer frameworks.
                    Because of this, the feature is backfilled and thus
                    enabled for all distros through the
                    <code class="filename">DISTRO_FEATURES_BACKFILL</code>
                    variable in the <code class="filename">meta/conf/bitbake.conf</code> file.
                    However, your distro needs to disable the feature.
                    You can disable the feature without affecting
                    other existing distro configurations that need PulseAudio support
                    by adding "pulseaudio" to
                    <code class="filename">DISTRO_FEATURES_BACKFILL_CONSIDERED</code>
                    in your distro's <code class="filename">.conf</code> file.
                    Adding the feature to this variable when it also
                    exists in the <code class="filename">DISTRO_FEATURES_BACKFILL</code>
                    variable prevents the build system from adding the feature to
                    your configuration's <code class="filename">DISTRO_FEATURES</code>, effectively disabling
                    the feature for that particular distro.</p></li><li class="listitem"><p><span class="emphasis"><em>The "rtc" machine feature option</em></span>:
                    Previously, real time clock (RTC) support was enabled for all
                    target devices.
                    Because of this, the feature is backfilled and thus enabled
                    for all machines through the <code class="filename">MACHINE_FEATURES_BACKFILL</code>
                    variable in the <code class="filename">meta/conf/bitbake.conf</code> file.
                    However, your target device does not have this capability.
                    You can disable RTC support for your device without
                    affecting other machines that need RTC support
                    by adding the feature to your machine's
                    <code class="filename">MACHINE_FEATURES_BACKFILL_CONSIDERED</code>
                    list in the machine's <code class="filename">.conf</code> file.
                    Adding the feature to this variable when it also
                    exists in the <code class="filename">MACHINE_FEATURES_BACKFILL</code>
                    variable prevents the build system from adding the feature to
                    your configuration's <code class="filename">MACHINE_FEATURES</code>, effectively
                    disabling RTC support for that particular machine.</p></li></ul></div><p>
        </p></div></div>

    <div class="chapter" title="Chapter 10. Variables Glossary"><div class="titlepage"><div><div><h2 class="title"><a id="ref-variables-glos"></a>Chapter 10. Variables Glossary</h2></div></div></div><div class="toc"><p><strong>Table of Contents</strong></p><dl><dt><span class="glossary"><a href="#ref-variables-glossary">Glossary</a></span></dt></dl></div><p>
    This chapter lists common variables used in the OpenEmbedded build system and gives an overview
    of their function and contents.
</p><div class="glossary" title="Glossary"><div class="titlepage"><div><div><h2 class="title"><a id="ref-variables-glossary"></a>Glossary</h2></div></div></div><p>
       <a class="link" href="#var-ALLOW_EMPTY" title="ALLOW_EMPTY">A</a>
       <a class="link" href="#var-B" title="B">B</a>
       <a class="link" href="#var-CFLAGS" title="CFLAGS">C</a>
       <a class="link" href="#var-D" title="D">D</a>
       <a class="link" href="#var-ENABLE_BINARY_LOCALE_GENERATION" title="ENABLE_BINARY_LOCALE_GENERATION">E</a>
       <a class="link" href="#var-FILES" title="FILES">F</a>

       <a class="link" href="#var-HOMEPAGE" title="HOMEPAGE">H</a>
       <a class="link" href="#var-IMAGE_FEATURES" title="IMAGE_FEATURES">I</a>

       <a class="link" href="#var-KBRANCH" title="KBRANCH">K</a>
       <a class="link" href="#var-LAYERDIR" title="LAYERDIR">L</a>
       <a class="link" href="#var-MACHINE" title="MACHINE">M</a>

       <a class="link" href="#var-OE_TERMINAL" title="OE_TERMINAL">O</a>
       <a class="link" href="#var-P" title="P">P</a>

       <a class="link" href="#var-RCONFLICTS" title="RCONFLICTS">R</a>
       <a class="link" href="#var-S" title="S">S</a>
       <a class="link" href="#var-T" title="T">T</a>


       <a class="link" href="#var-WORKDIR" title="WORKDIR">W</a>



    </p><div class="glossdiv" title="A"><h3 class="title">A</h3><dl><dt><a id="var-ALLOW_EMPTY"></a>ALLOW_EMPTY</dt><dd><p>
                   Specifies if an output package should still be produced if it is empty.
                   By default, BitBake does not produce empty packages.
                   This default behavior can cause issues when there is an
                   <a class="link" href="#var-RDEPENDS" title="RDEPENDS"><code class="filename">RDEPENDS</code></a> or
                   some other runtime hard-requirement on the existence of the package.
                </p><p>
                   Like all package-controlling variables, you must always use them in
                   conjunction with a package name override.
                   Here is an example:
                   </p><pre class="literallayout">
     ALLOW_EMPTY_${PN} = "1"
                   </pre><p>
                </p></dd><dt><a id="var-AUTHOR"></a>AUTHOR</dt><dd><p>The email address used to contact the original author or authors in
                    order to send patches, forward bugs, etc.</p></dd><dt><a id="var-AUTOREV"></a>AUTOREV</dt><dd><p>When <code class="filename"><a class="link" href="#var-SRCREV" title="SRCREV">SRCREV</a></code>
                    is set to the value of this variable, it specifies that the latest
                    source revision in the repository should be used. Here is an example:
                    </p><pre class="literallayout">
     SRCREV = "${AUTOREV}"
                    </pre><p>
                </p></dd></dl></div><div class="glossdiv" title="B"><h3 class="title">B</h3><dl><dt><a id="var-B"></a>B</dt><dd><p>
                    The <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#build-directory" target="_top">Build Directory</a>.
                    The OpenEmbedded build system places generated objects into the Build Directory
                    during a recipe's build process.
                    By default, this directory is the same as the <a class="link" href="#var-S" title="S"><code class="filename">S</code></a>
                    directory:
                    </p><pre class="literallayout">
     B = ${WORKDIR}/${BPN}/{PV}/
                    </pre><p>
                    You can separate the (<code class="filename">S</code>) directory and the directory pointed to
                    by the <code class="filename">B</code> variable.
                    Most autotools-based recipes support separating these directories.
                    The build system defaults to using separate directories for <code class="filename">gcc</code>
                    and some kernel recipes.
                </p></dd><dt><a id="var-BAD_RECOMMENDATIONS"></a>BAD_RECOMMENDATIONS</dt><dd><p>
                    A list of packages not to install despite being recommended by a recipe.
                    Support for this variable exists only when using the
                    <code class="filename">ipk</code> packaging backend.
                </p></dd><dt><a id="var-BB_DISKMON_DIRS"></a>BB_DISKMON_DIRS</dt><dd><p>
                    Monitors disk space and available inodes during the build
                    and allows you to control the build based on these
                    parameters.
                </p><p>
                    Disk space monitoring is disabled by default.
                    To enable monitoring, add the <code class="filename">BB_DISKMON_DIRS</code>
                    variable to your <code class="filename">conf/local.conf</code> file found in the
                    <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#build-directory" target="_top">Build Directory</a>.
                    Use the following form:
                    </p><pre class="literallayout">
     BB_DISKMON_DIRS = "&lt;action&gt;,&lt;dir&gt;,&lt;threshold&gt; [...]"

     where:

        &lt;action&gt; is:
           ABORT:     Immediately abort the build when
                      a threshold is broken.
           STOPTASKS: Stop the build after the currently
                      executing tasks have finished when
                      a threshold is broken.
           WARN:      Issue a warning but continue the
                      build when a threshold is broken.
                      Subsequent warnings are issued as
                      defined by the
                      <a class="link" href="#var-BB_DISKMON_WARNINTERVAL" title="BB_DISKMON_WARNINTERVAL">BB_DISKMON_WARNINTERVAL</a> variable,
                      which must be defined in the
                      conf/local.conf file.

        &lt;dir&gt; is:
           Any directory you choose. You can specify one or
           more directories to monitor by separating the
           groupings with a space.  If two directories are
           on the same device, only the first directory
           is monitored.

        &lt;threshold&gt; is:
           Either the minimum available disk space,
           the minimum number of free inodes, or
           both.  You must specify at least one.  To
           omit one or the other, simply omit the value.
           Specify the threshold using G, M, K for Gbytes,
           Mbytes, and Kbytes, respectively. If you do
           not specify G, M, or K, Kbytes is assumed by
           default.  Do not use GB, MB, or KB.
                    </pre><p>
                </p><p>
                    Here are some examples:
                    </p><pre class="literallayout">
     BB_DISKMON_DIRS = "ABORT,${TMPDIR},1G,100K WARN,${SSTATE_DIR},1G,100K"
     BB_DISKMON_DIRS = "STOPTASKS,${TMPDIR},1G"
     BB_DISKMON_DIRS = "ABORT,${TMPDIR},,100K"
                    </pre><p>
                    The first example works only if you also provide
                    the <a class="link" href="#var-BB_DISKMON_WARNINTERVAL" title="BB_DISKMON_WARNINTERVAL"><code class="filename">BB_DISKMON_WARNINTERVAL</code></a> variable
                    in the <code class="filename">conf/local.conf</code>.
                    This example causes the build system to immediately
                    abort when either the disk space in <code class="filename">${TMPDIR}</code> drops
                    below 1 Gbyte or the available free inodes drops below
                    100 Kbytes.
                    Because two directories are provided with the variable, the
                    build system also issue a
                    warning when the disk space in the
                    <code class="filename">${SSTATE_DIR}</code> directory drops
                    below 1 Gbyte or the number of free inodes drops
                    below 100 Kbytes.
                    Subsequent warnings are issued during intervals as
                    defined by the <code class="filename">BB_DISKMON_WARNINTERVAL</code>
                    variable.
                </p><p>
                    The second example stops the build after all currently
                    executing tasks complete when the minimum disk space
                    in the <code class="filename">${TMPDIR}</code> directory drops
                    below 1 Gbyte.
                    No disk monitoring occurs for the free inodes in this case.
                </p><p>
                    The final example immediately aborts the build when the
                    number of free inodes in the <code class="filename">${TMPDIR}</code> directory
                    drops below 100 Kbytes.
                    No disk space monitoring for the directory itself occurs
                    in this case.
                </p></dd><dt><a id="var-BB_DISKMON_WARNINTERVAL"></a>BB_DISKMON_WARNINTERVAL</dt><dd><p>
                    Defines the disk space and free inode warning intervals.
                    To set these intervals, define the variable in your
                    <code class="filename">conf/local.conf</code> file in the
                    <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#build-directory" target="_top">Build Directory</a>.
                </p><p>
                    If you are going to use the
                    <code class="filename">BB_DISKMON_WARNINTERVAL</code> variable, you must
                    also use the
                    <a class="link" href="#var-BB_DISKMON_DIRS" title="BB_DISKMON_DIRS"><code class="filename">BB_DISKMON_DIRS</code></a> variable
                    and define its action as "WARN".
                    During the build, subsequent warnings are issued each time
                    disk space or number of free inodes further reduces by
                    the respective interval.
                </p><p>
                    If you do not provide a <code class="filename">BB_DISKMON_WARNINTERVAL</code>
                    variable and you do use <code class="filename">BB_DISKMON_DIRS</code> with
                    the "WARN" action, the disk monitoring interval defaults to
                    the following:
                    </p><pre class="literallayout">
     BB_DISKMON_WARNINTERVAL = "50M,5K"
                    </pre><p>
                </p><p>
                    When specifying the variable in your configuration file,
                    use the following form:
                    </p><pre class="literallayout">
     BB_DISKMON_WARNINTERVAL = "&lt;disk_space_interval&gt;,&lt;disk_inode_interval&gt;"

     where:

        &lt;disk_space_interval&gt; is:
           An interval of memory expressed in either
           G, M, or K for Gbytes, Mbytes, or Kbytes,
           respectively. You cannot use GB, MB, or KB.

        &lt;disk_inode_interval&gt; is:
           An interval of free inodes expressed in either
           G, M, or K for Gbytes, Mbytes, or Kbytes,
           respectively. You cannot use GB, MB, or KB.
                    </pre><p>
                </p><p>
                    Here is an example:
                    </p><pre class="literallayout">
     BB_DISKMON_DIRS = "WARN,${SSTATE_DIR},1G,100K"
     BB_DISKMON_WARNINTERVAL = "50M,5K"
                    </pre><p>
                    These variables cause the OpenEmbedded build system to
                    issue subsequent warnings each time the available
                    disk space further reduces by 50 Mbytes or the number
                    of free inodes further reduces by 5 Kbytes in the
                    <code class="filename">${SSTATE_DIR}</code> directory.
                    Subsequent warnings based on the interval occur each time
                    a respective interval is reached beyond the intial warning
                    (i.e. 1 Gbytes and 100 Kbytes).
                </p></dd><dt><a id="var-BBCLASSEXTEND"></a>BBCLASSEXTEND</dt><dd><p>
                    Allows you to extend a recipe so that it builds variants of the software.
                    Common variants for recipes exist such as "natives" like <code class="filename">quilt-native</code>,
                    which is a copy of quilt built to run on the build system;
                    "crosses" such as <code class="filename">gcc-cross</code>,
                    which is a compiler built to run on the build machine but produces binaries
                    that run on the target <a class="link" href="#var-MACHINE" title="MACHINE"><code class="filename">MACHINE</code></a>;
                    "nativesdk", which targets the SDK machine instead of <code class="filename">MACHINE</code>;
                    and "mulitlibs" in the form "<code class="filename">multilib:&lt;multilib_name&gt;</code>".
                </p><p>
                    To build a different variant of the recipe with a minimal amount of code, it usually
                    is as simple as adding the following to your recipe:
                    </p><pre class="literallayout">
     BBCLASSEXTEND =+ "native nativesdk"
     BBCLASSEXTEND =+ "multilib:&lt;multilib_name&gt;"
                    </pre><p>
                </p></dd><dt><a id="var-BBMASK"></a>BBMASK</dt><dd><p>Prevents BitBake from processing recipes and recipe append files.
                    You can use the <code class="filename">BBMASK</code> variable to "hide"
                    these <code class="filename">.bb</code> and <code class="filename">.bbappend</code> files.
                    BitBake ignores any recipe or recipe append files that match the expression.
                    It is as if BitBake does not see them at all.
                    Consequently, matching files are not parsed or otherwise used by
                    BitBake.</p><p>The value you provide is passed to python's regular expression compiler.
                    For complete syntax information, see python's documentation at
                    <a class="ulink" href="http://docs.python.org/release/2.3/lib/re-syntax.html" target="_top">http://docs.python.org/release/2.3/lib/re-syntax.html</a>.
                    The expression is compared against the full paths to the files.
                    For example, the following uses a complete regular expression to tell
                    BitBake to ignore all recipe and recipe append files in the
                    <code class="filename">.*/meta-ti/recipes-misc/</code> directory:
                    </p><pre class="literallayout">
     BBMASK = ".*/meta-ti/recipes-misc/"
                    </pre><p>Use the <code class="filename">BBMASK</code> variable from within the
                    <code class="filename">conf/local.conf</code> file found
                    in the <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#build-directory" target="_top">Build Directory</a>.</p></dd><dt><a id="var-BB_NUMBER_THREADS"></a>BB_NUMBER_THREADS</dt><dd><p>The maximum number of tasks BitBake should run in parallel at any one time.
                    If your host development system supports multiple cores a good rule of thumb
                    is to set this variable to twice the number of cores.</p></dd><dt><a id="var-BBFILE_COLLECTIONS"></a>BBFILE_COLLECTIONS</dt><dd><p>Lists the names of configured layers.
                    These names are used to find the other <code class="filename">BBFILE_*</code>
                    variables.
                    Typically, each layer will append its name to this variable in its
                    <code class="filename">conf/layer.conf</code> file.
                </p></dd><dt><a id="var-BBFILE_PATTERN"></a>BBFILE_PATTERN</dt><dd><p>Variable that expands to match files from <code class="filename">BBFILES</code> in a particular layer.
                    This variable is used in the <code class="filename">conf/layer.conf</code> file and must
                    be suffixed with the name of the specific layer (e.g.
                    <code class="filename">BBFILE_PATTERN_emenlow</code>).</p></dd><dt><a id="var-BBFILE_PRIORITY"></a>BBFILE_PRIORITY</dt><dd><p>Assigns the priority for recipe files in each layer.</p><p>This variable is useful in situations where the same recipe appears in
                    more than one layer.
                    Setting this variable allows you to prioritize a
                    layer against other layers that contain the same recipe - effectively
                    letting you control the precedence for the multiple layers.
                    The precedence established through this variable stands regardless of a
                    recipe's version (<code class="filename">PV</code> variable).
                    For example, a layer that has a recipe with a higher <code class="filename">PV</code> value but for
                    which the <code class="filename">BBFILE_PRIORITY</code> is set to have a lower precedence still has a
                    lower precedence.</p><p>A larger value for the <code class="filename">BBFILE_PRIORITY</code> variable results in a higher
                    precedence.
                    For example, the value 6 has a higher precedence than the value 5.
                    If not specified, the <code class="filename">BBFILE_PRIORITY</code> variable is set based on layer
                    dependencies (see the
                    <code class="filename"><a class="link" href="#var-LAYERDEPENDS" title="LAYERDEPENDS">LAYERDEPENDS</a></code> variable for
                    more information.
                    The default priority, if unspecified
                    for a layer with no dependencies, is the lowest defined priority + 1
                    (or 1 if no priorities are defined).</p><div class="tip" title="Tip" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Tip</h3>
                    You can use the command <code class="filename">bitbake-layers show_layers</code> to list
                    all configured layers along with their priorities.
                </div></dd><dt><a id="var-BBFILES"></a>BBFILES</dt><dd><p>List of recipe files used by BitBake to build software</p></dd><dt><a id="var-BBPATH"></a>BBPATH</dt><dd><p>Used by BitBake to locate <code class="filename">.bbclass</code> and configuration files.
                    This variable is analogous to the <code class="filename">PATH</code> variable.</p></dd><dt><a id="var-BBINCLUDELOGS"></a>BBINCLUDELOGS</dt><dd><p>Variable that controls how BitBake displays logs on build failure.</p></dd><dt><a id="var-BBLAYERS"></a>BBLAYERS</dt><dd><p>Lists the layers to enable during the build.
                    This variable is defined in the <code class="filename">bblayers.conf</code> configuration
                    file in the <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#build-directory" target="_top">Build Directory</a>.
                    Here is an example:
                    </p><pre class="literallayout">
     BBLAYERS = " \
       /home/scottrif/poky/meta \
       /home/scottrif/poky/meta-yocto \
       /home/scottrif/poky/meta-yocto-bsp \
       /home/scottrif/poky/meta-mykernel \
       "

     BBLAYERS_NON_REMOVABLE ?= " \
       /home/scottrif/poky/meta \
       /home/scottrif/poky/meta-yocto \
       "
                    </pre><p>
                    This example enables four layers, one of which is a custom, user-defined layer
                    named <code class="filename">meta-mykernel</code>.
                </p></dd><dt><a id="var-BBLAYERS_NON_REMOVABLE"></a>BBLAYERS_NON_REMOVABLE</dt><dd><p>Lists core layers that cannot be removed from the
                    <code class="filename">bblayers.conf</code> file.
                    In order for BitBake to build your image, your
                    <code class="filename">bblayers.conf</code> file must include the
                    <code class="filename">meta</code> and <code class="filename">meta-yocto</code>
                    core layers.
                    Here is an example that shows these two layers listed in
                    the <code class="filename">BBLAYERS_NON_REMOVABLE</code> statement:
                    </p><pre class="literallayout">
     BBLAYERS = " \
       /home/scottrif/poky/meta \
       /home/scottrif/poky/meta-yocto \
       /home/scottrif/poky/meta-yocto-bsp \
       /home/scottrif/poky/meta-mykernel \
       "

     BBLAYERS_NON_REMOVABLE ?= " \
       /home/scottrif/poky/meta \
       /home/scottrif/poky/meta-yocto \
       "
                    </pre><p>
                </p></dd><dt><a id="var-BP"></a>BP</dt><dd><p>The base recipe name and version but without any special
                    recipe name suffix (i.e. <code class="filename">-native</code>, <code class="filename">lib64-</code>,
                    and so forth).
                    <code class="filename">BP</code> is comprised of the following:
                    </p><pre class="literallayout">
     ${BPN}-${PV}
                    </pre></dd><dt><a id="var-BPN"></a>BPN</dt><dd><p>The bare name of the recipe.
                    This variable is a version of the <a class="link" href="#var-PN" title="PN"><code class="filename">PN</code></a> variable
                    but removes common suffixes such as "-native" and "-cross" as well
                    as removes common prefixes such as multilib's "lib64-" and "lib32-".
                    The exact list of suffixes removed is specified by the
                    <a class="link" href="#var-SPECIAL_PKGSUFFIX" title="SPECIAL_PKGSUFFIX"><code class="filename">SPECIAL_PKGSUFFIX</code></a> variable.
                    The exact list of prefixes removed is specified by the
                    <a class="link" href="#var-MLPREFIX" title="MLPREFIX"><code class="filename">MLPREFIX</code></a> variable.
                    Prefixes are removed for multilib and nativesdk cases.</p></dd></dl></div><div class="glossdiv" title="C"><h3 class="title">C</h3><dl><dt><a id="var-CFLAGS"></a>CFLAGS</dt><dd><p>
                    Flags passed to C compiler for the target system.
                    This variable evaluates to the same as
                    <code class="filename"><a class="link" href="#var-TARGET_CFLAGS" title="TARGET_CFLAGS">TARGET_CFLAGS</a></code>.
                </p></dd><dt><a id="var-COMBINED_FEATURES"></a>COMBINED_FEATURES</dt><dd><p>A set of features common between
                    <a class="link" href="#var-MACHINE_FEATURES" title="MACHINE_FEATURES"><code class="filename">MACHINE_FEATURES</code></a>
                    and <a class="link" href="#var-DISTRO_FEATURES" title="DISTRO_FEATURES"><code class="filename">DISTRO_FEATURES</code></a>.
                    See the glossary descriptions for these variables for more information.</p></dd><dt><a id="var-COMPATIBLE_MACHINE"></a>COMPATIBLE_MACHINE</dt><dd><p>A regular expression which evaluates to match the machines the recipe
                    works with.
                    It stops recipes being run on machines for which they are not compatible.
                    This is particularly useful with kernels.
                    It also helps to increase parsing speed as further parsing of the recipe is skipped
                    if it is found the current machine is not compatible.</p></dd><dt><a id="var-CONFFILES"></a>CONFFILES</dt><dd><p>
                    Identifies editable or configurable files that are part of a package.
                    If the Package Management System (PMS) is being used to update
                    packages on the target system, it is possible that
                    configuration files you have changed after the original installation
                    and that you now want to remain unchanged are overwritten.
                    In other words, editable files might exist in the package that you do not
                    want reset as part of the package update process.
                    You can use the <code class="filename">CONFFILES</code> variable to list the files in the
                    package that you wish to prevent the PMS from overwriting during this update process.
                </p><p>
                    To use the <code class="filename">CONFFILES</code> variable, provide a package name
                    override that identifies the resulting package.
                    Then, provide a space-separated list of files.
                    Here is an example:
                    </p><pre class="literallayout">
  CONFFILES_${PN} += "${sysconfdir}/file1 \
     ${sysconfdir}/file2 ${sysconfdir}/file3"
                    </pre><p>
                </p><p>
                    A relationship exists between the <code class="filename">CONFFILES</code> and
                    <code class="filename"><a class="link" href="#var-FILES" title="FILES">FILES</a></code> variables.
                    The files listed within <code class="filename">CONFFILES</code> must be a subset of
                    the files listed within <code class="filename">FILES</code>.
                    Because the configuration files you provide with <code class="filename">CONFFILES</code>
                    are simply being identified so that the PMS will not overwrite them,
                    it makes sense that
                    the files must already be included as part of the package through the
                    <code class="filename">FILES</code> variable.
                </p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
                    When specifying paths as part of the <code class="filename">CONFFILES</code> variable,
                    it is good practice to use appropriate path variables.
                    For example, <code class="filename">${sysconfdir}</code> rather than
                    <code class="filename">/etc</code> or <code class="filename">${bindir}</code> rather
                    than <code class="filename">/usr/bin</code>.
                    You can find a list of these variables at the top of the
                    <code class="filename">/meta/conf/bitbake.conf</code> file in the
                    <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#source-directory" target="_top">Source Directory</a>.
                </div></dd><dt><a id="var-CONFIG_SITE"></a>CONFIG_SITE</dt><dd><p>
                    A list of files that contains <code class="filename">autoconf</code> test results relevant
                    to the current build.
                    This variable is used by the Autotools utilities when running
                    <code class="filename">configure</code>.
                </p></dd><dt><a id="var-CORE_IMAGE_EXTRA_INSTALL"></a>CORE_IMAGE_EXTRA_INSTALL</dt><dd><p>
                    Specifies the list of packages to be added to the image.
                    This variable should only be set in the <code class="filename">local.conf</code>
                    configuration file found in the
                    <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#build-directory" target="_top">Build Directory</a>.
                </p><p>
                    This variable replaces <code class="filename">POKY_EXTRA_INSTALL</code>, which is no longer supported.
                </p></dd></dl></div><div class="glossdiv" title="D"><h3 class="title">D</h3><dl><dt><a id="var-D"></a>D</dt><dd><p>The destination directory.</p></dd><dt><a id="var-DEBUG_BUILD"></a>DEBUG_BUILD</dt><dd><p>
                    Specifies to build packages with debugging information.
                    This influences the value of the
                    <code class="filename"><a class="link" href="#var-SELECTED_OPTIMIZATION" title="SELECTED_OPTIMIZATION">SELECTED_OPTIMIZATION</a></code>
                    variable.
                </p></dd><dt><a id="var-DEBUG_OPTIMIZATION"></a>DEBUG_OPTIMIZATION</dt><dd><p>
                    The options to pass in
                    <code class="filename"><a class="link" href="#var-TARGET_CFLAGS" title="TARGET_CFLAGS">TARGET_CFLAGS</a></code>
                    and <code class="filename"><a class="link" href="#var-CFLAGS" title="CFLAGS">CFLAGS</a></code> when compiling
                    a system for debugging.
                    This variable defaults to "-O -fno-omit-frame-pointer -g".
                </p></dd><dt><a id="var-DEFAULT_PREFERENCE"></a>DEFAULT_PREFERENCE</dt><dd><p>Specifies the priority of recipes.</p></dd><dt><a id="var-DEPENDS"></a>DEPENDS</dt><dd><p>
                    Lists a recipe's build-time dependencies
                    (i.e. other recipe files).
                    The system ensures that all the dependencies listed
                    have been built and have their contents in the appropriate
                    sysroots before the recipe's configure task is executed.
                </p></dd><dt><a id="var-DESCRIPTION"></a>DESCRIPTION</dt><dd><p>The package description used by package managers.
                      If not set, <code class="filename">DESCRIPTION</code> takes
                      the value of the
                      <a class="link" href="#var-SUMMARY" title="SUMMARY"><code class="filename">SUMMARY</code></a>
                      variable.
                </p></dd><dt><a id="var-DESTDIR"></a>DESTDIR</dt><dd><p>the destination directory.</p></dd><dt><a id="var-DISTRO"></a>DISTRO</dt><dd><p>
                    The short name of the distribution.
                    This variable corresponds to a file with the
                    extension <code class="filename">.conf</code>
                    located in a <code class="filename">conf/distro</code> directory
                    within the metadata that contains the distribution configuration.
                    The
                    value must not contain spaces, and is typically all lower-case.
                </p><p>
                    If the variable is blank, a set of default configuration
                    will be used, which is specified
                    within <code class="filename">meta/conf/distro/defaultsetup.conf</code>.
                </p></dd><dt><a id="var-DISTRO_EXTRA_RDEPENDS"></a>DISTRO_EXTRA_RDEPENDS</dt><dd><p>
                    Specifies a list of distro-specific packages to add to all images.
                    This variable takes affect through
                    <code class="filename">packagegroup-base</code> so the
                    variable only really applies to the more full-featured
                    images that include <code class="filename">packagegroup-base</code>.
                    You can use this variable to keep distro policy out of
                    generic images.
                    As with all other distro variables, you set this variable
                    in the distro <code class="filename">.conf</code> file.
                </p></dd><dt><a id="var-DISTRO_EXTRA_RRECOMMENDS"></a>DISTRO_EXTRA_RRECOMMENDS</dt><dd><p>
                    Specifies a list of distro-specific packages to add to all images
                    if the packages exist.
                    The packages might not exist or be empty (e.g. kernel modules).
                    The list of packages are automatically installed but can be
                    removed by the user.
                </p></dd><dt><a id="var-DISTRO_FEATURES"></a>DISTRO_FEATURES</dt><dd><p>The features enabled for the distribution.
                    For a list of features supported by the Yocto Project as shipped,
                    see the "<a class="link" href="#ref-features-distro" title="9.1. Distro">Distro</a>"
                    section.
                </p></dd><dt><a id="var-DISTRO_FEATURES_BACKFILL"></a>DISTRO_FEATURES_BACKFILL</dt><dd><p>Features to be added to
                    <code class="filename"><a class="link" href="#var-DISTRO_FEATURES" title="DISTRO_FEATURES">DISTRO_FEATURES</a></code>
                    if not also present in
                    <code class="filename"><a class="link" href="#var-DISTRO_FEATURES_BACKFILL_CONSIDERED" title="DISTRO_FEATURES_BACKFILL_CONSIDERED">DISTRO_FEATURES_BACKFILL_CONSIDERED</a></code>.
                </p><p>
                    This variable is set in the <code class="filename">meta/conf/bitbake.conf</code> file.
                    It is not intended to be user-configurable.
                    It is best to just reference the variable to see which distro features are
                    being backfilled for all distro configurations.
                    See the <a class="link" href="#ref-features-backfill" title="9.4. Feature Backfilling">Feature backfilling</a> section for
                    more information.
                </p></dd><dt><a id="var-DISTRO_FEATURES_BACKFILL_CONSIDERED"></a>DISTRO_FEATURES_BACKFILL_CONSIDERED</dt><dd><p>Features from
                    <code class="filename"><a class="link" href="#var-DISTRO_FEATURES_BACKFILL" title="DISTRO_FEATURES_BACKFILL">DISTRO_FEATURES_BACKFILL</a></code>
                    that should not backfilled (i.e. added to
                    <code class="filename"><a class="link" href="#var-DISTRO_FEATURES" title="DISTRO_FEATURES">DISTRO_FEATURES</a></code>)
                    during the build.
                    See the "<a class="link" href="#ref-features-backfill" title="9.4. Feature Backfilling">Feature Backfilling</a>" section for
                    more information.
                    </p></dd><dt><a id="var-DISTRO_NAME"></a>DISTRO_NAME</dt><dd><p>The long name of the distribution.</p></dd><dt><a id="var-DISTRO_PN_ALIAS"></a>DISTRO_PN_ALIAS</dt><dd><p>Alias names used for the recipe in various Linux distributions.</p><p>See the
                    "<a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#usingpoky-configuring-DISTRO_PN_ALIAS" target="_top">Handling
                    a Package Name Alias</a>" section in the Yocto Project Development
                    Manual for more information.</p></dd><dt><a id="var-DISTRO_VERSION"></a>DISTRO_VERSION</dt><dd><p>the version of the distribution.</p></dd><dt><a id="var-DL_DIR"></a>DL_DIR</dt><dd><p>
                    The central download directory used by the build process to store downloads.
                    You can set this directory by defining the <code class="filename">DL_DIR</code>
                    variable in the <code class="filename">/conf/local.conf</code> file.
                    This directory is self-maintaining and you should not have
                    to touch it.
                    By default, the directory is <code class="filename">downloads</code> in the
                    <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#build-directory" target="_top">Build Directory</a>.
                    </p><pre class="literallayout">
     #DL_DIR ?= "${TOPDIR}/downloads"
                    </pre><p>
                    To specify a different download directory, simply uncomment the line
                    and provide your directory.
                </p><p>
                    During a first build, the system downloads many different source code
                    tarballs from various upstream projects.
                    Downloading can take a while, particularly if your network
                    connection is slow.
                    Tarballs are all stored in the directory defined by
                    <code class="filename">DL_DIR</code> and the build system looks there first
                    to find source tarballs.
                    </p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
                        When wiping and rebuilding, you can preserve this directory to speed
                        up this part of subsequent builds.
                    </div><p>
                </p><p>
                    You can safely share this directory between multiple builds on the
                    same development machine.
                    For additional information on how the build process gets source files
                    when working behind a firewall or proxy server, see the
                    "<a class="link" href="#how-does-the-yocto-project-obtain-source-code-and-will-it-work-behind-my-firewall-or-proxy-server">FAQ</a>"
                    chapter.
                </p></dd></dl></div><div class="glossdiv" title="E"><h3 class="title">E</h3><dl><dt><a id="var-ENABLE_BINARY_LOCALE_GENERATION"></a>ENABLE_BINARY_LOCALE_GENERATION</dt><dd><p></p><p>Variable that controls which locales for <code class="filename">eglibc</code> are
                    to be generated during the build (useful if the target device has 64Mbytes
                    of RAM or less).</p></dd><dt><a id="var-EXTENDPE"></a>EXTENDPE</dt><dd><p>
                    Used with file and pathnames to create a prefix for a recipe's
                    version based on the recipe's
                    <a class="link" href="#var-PE" title="PE"><code class="filename">PE</code></a> value.
                    If <code class="filename">PE</code> is set and greater than zero for a recipe,
                    <code class="filename">EXTENDPE</code> becomes that value (e.g if
                    <code class="filename">PE</code> is equal to "1" then <code class="filename">EXTENDPE</code>
                    becomes "1_").
                    If a recipe's <code class="filename">PE</code> is not set (the default) or is equal to
                    zero, <code class="filename">EXTENDPE</code> becomes "".</p><p>See the <a class="link" href="#var-STAMP" title="STAMP"><code class="filename">STAMP</code></a>
                    variable for an example.
                </p></dd><dt><a id="var-EXTRA_IMAGE_FEATURES"></a>EXTRA_IMAGE_FEATURES</dt><dd><p>Allows extra packages to be added to the generated images.
                    You set this variable in the <code class="filename">local.conf</code>
                    configuration file.
                    Note that some image features are also added using the
                    <code class="filename"><a class="link" href="#var-IMAGE_FEATURES" title="IMAGE_FEATURES">IMAGE_FEATURES</a></code>
                    variable generally configured in image recipes.
                    You can use this variable to add more features in addition to those.
                    Here are some examples of features you can add:</p><pre class="literallayout">
"dbg-pkgs" - Adds -dbg packages for all installed packages
             including symbol information for debugging and
             profiling.

"dev-pkgs" - Adds -dev packages for all installed packages.
             This is useful if you want to develop against
             the libraries in the image.

"tools-sdk" - Adds development tools such as gcc, make,
              pkgconfig and so forth.

"tools-debug" - Adds debugging tools such as gdb and
                strace.

"tools-profile" - Adds profiling tools such as oprofile,
                  exmap, lttng and valgrind (x86 only).

"tools-testapps" - Adds useful testing tools such as
                   ts_print, aplay, arecord and so
                   forth.

"debug-tweaks" - Makes an image suitable for development.
                 For example, ssh root access has a blank
                 password.  You should remove this feature
                 before you produce a production image.
                    </pre><p>There are other valid features too, see the
                 <a class="link" href="#ref-features-image" title="9.3. Images">Images</a>
                 section for more details.</p></dd><dt><a id="var-EXTRA_IMAGEDEPENDS"></a>EXTRA_IMAGEDEPENDS</dt><dd><p>A list of recipes to be built that do not provide packages to be installed in
                    the root filesystem.
                </p><p>Sometimes a recipe is required to build the final image but is not
                    needed in the root filesystem.
                    You can use the <code class="filename">EXTRA_IMAGEDEPENDS</code> variable to
                    list these recipes and thus, specify the dependencies.
                    A typical example is a required bootloader in a machine configuration.
                </p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
                    To add packages to the root filesystem, see the various
                    <code class="filename">*DEPENDS</code> and <code class="filename">*RECOMMENDS</code>
                    variables.
                </div></dd><dt><a id="var-EXTRA_OECMAKE"></a>EXTRA_OECMAKE</dt><dd><p>Additional <code class="filename">cmake</code> options.</p></dd><dt><a id="var-EXTRA_OECONF"></a>EXTRA_OECONF</dt><dd><p>Additional <code class="filename">configure</code> script options.</p></dd><dt><a id="var-EXTRA_OEMAKE"></a>EXTRA_OEMAKE</dt><dd><p>Additional GNU <code class="filename">make</code> options.</p></dd></dl></div><div class="glossdiv" title="F"><h3 class="title">F</h3><dl><dt><a id="var-FILES"></a>FILES</dt><dd><p>
                    The list of directories or files that are placed in packages.
                </p><p>
                    To use the <code class="filename">FILES</code> variable, provide a package name
                    override that identifies the resulting package.
                    Then, provide a space-separated list of files or paths that identifies the
                    files you want included as part of the resulting package.
                    Here is an example:
                    </p><pre class="literallayout">
  FILES_${PN} += "${bindir}/mydir1/ ${bindir}/mydir2/myfile"
                    </pre><p>
                </p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
                    When specifying paths as part of the <code class="filename">FILES</code> variable,
                    it is good practice to use appropriate path variables.
                    For example, <code class="filename">${sysconfdir}</code> rather than
                    <code class="filename">/etc</code> or <code class="filename">${bindir}</code> rather
                    than <code class="filename">/usr/bin</code>.
                    You can find a list of these variables at the top of the
                    <code class="filename">/meta/conf/bitbake.conf</code> file in the
                    <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#source-directory" target="_top">Source Directory</a>.
                </div><p>
                    If some of the files you provide with the <code class="filename">FILES</code> variable
                    are editable and you know they should not be
                    overwritten during the package update process by the Package Management
                    System (PMS), you can identify these files so that the PMS will not
                    overwrite them.
                    See the <code class="filename"><a class="link" href="#var-CONFFILES" title="CONFFILES">CONFFILES</a></code>
                    variable for information on how to identify these files to the PMS.
                </p></dd><dt><a id="var-FILESEXTRAPATHS"></a>FILESEXTRAPATHS</dt><dd><p>
                    Extends the search path the OpenEmbedded build system uses when
                    looking for files and patches as it processes recipes.
                    The directories BitBake uses when it processes recipes is defined by the
                    <a class="link" href="#var-FILESPATH" title="FILESPATH"><code class="filename">FILESPATH</code></a> variable.
                    You can add directories to the search path by defining the
                    <code class="filename">FILESEXTRAPATHS</code> variable.
                </p><p>
                    To add paths to the search order, provide a list of directories and separate
                    each path using a colon character as follows:
                    </p><pre class="literallayout">
     FILESEXTRAPATHS_prepend := "path_1:path_2:path_3:"
                    </pre><p>
                    Typically, you want your directories searched first.
                    To make sure that happens, use <code class="filename">_prepend</code> and
                    the immediate expansion (<code class="filename">:=</code>) operator as shown in the
                    previous example.
                    Finally, to maintain the integrity of the <code class="filename">FILESPATH</code> variable,
                    you must include the appropriate beginning or ending (as needed) colon character.
                </p><p>
                    The <code class="filename">FILESEXTRAPATHS</code> variable is intended for use in
                    <code class="filename">.bbappend</code> files to include any additional files provided in that layer.
                    You typically accomplish this with the following:
                    </p><pre class="literallayout">
     FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:"
                    </pre><p>
                </p></dd><dt><a id="var-FILESPATH"></a>FILESPATH</dt><dd><p>
                    The default set of directories the OpenEmbedded build system uses
                    when searching for patches and files.
                    During the build process, BitBake searches each directory in
                    <code class="filename">FILESPATH</code> in the specified order when looking for
                    files and patches specified by each <code class="filename">file://</code> URI in a recipe.
                </p><p>
                    The default value for the <code class="filename">FILESPATH</code> variable is defined
                    in the <code class="filename">base.bbclass</code> class found in
                    <code class="filename">meta/classes</code> in the
                    <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#source-directory" target="_top">Source Directory</a>:
                    </p><pre class="literallayout">
FILESPATH = "${@base_set_filespath([ "${FILE_DIRNAME}/${PF}", \
   "${FILE_DIRNAME}/${P}", "${FILE_DIRNAME}/${PN}", \
   "${FILE_DIRNAME}/${BP}", "${FILE_DIRNAME}/${BPN}", \
   "${FILE_DIRNAME}/files", "${FILE_DIRNAME}" ], d)}"
                    </pre><p>
                    Do not hand-edit the <code class="filename">FILESPATH</code> variable.
                    If you want to extend the set of pathnames that BitBake uses when searching for
                    files and patches, use the
                    <a class="link" href="#var-FILESEXTRAPATHS" title="FILESEXTRAPATHS"><code class="filename">FILESEXTRAPATHS</code></a> variable.
                </p></dd><dt><a id="var-FILESYSTEM_PERMS_TABLES"></a>FILESYSTEM_PERMS_TABLES</dt><dd><p>Allows you to define your own file permissions settings table as part of
                    your configuration for the packaging process.
                    For example, suppose you need a consistent set of custom permissions for
                    a set of groups and users across an entire work project.
                    It is best to do this in the packages themselves but this is not always
                    possible.
                </p><p>
                    By default, the OpenEmbedded build system uses the <code class="filename">fs-perms.txt</code>, which
                    is located in the <code class="filename">meta/files</code> folder in the
                    <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#source-directory" target="_top">Source Directory</a>.
                    If you create your own file permissions setting table, you should place it in your
                    layer or the distros layer.
                </p><p>
                    You define the <code class="filename">FILESYSTEM_PERMS_TABLES</code> variable in the
                    <code class="filename">conf/local.conf</code> file, which is found in the
                    <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#build-directory" target="_top">Build Directory</a>, to
                    point to your custom <code class="filename">fs-perms.txt</code>.
                    You can specify more than a single file permissions setting table.
                    The paths you specify to these files must be defined within the
                    <code class="filename">BBPATH</code> variable.
                </p><p>
                    For guidance on how to create your own file permissions settings table file,
                    examine the existing <code class="filename">fs-perms.txt</code>.
                </p></dd><dt><a id="var-FULL_OPTIMIZATION"></a>FULL_OPTIMIZATION</dt><dd><p>
                    The options to pass in
                    <code class="filename"><a class="link" href="#var-TARGET_CFLAGS" title="TARGET_CFLAGS">TARGET_CFLAGS</a></code>
                    and <code class="filename"><a class="link" href="#var-CFLAGS" title="CFLAGS">CFLAGS</a></code>
                    when compiling an optimized system.
                    This variable defaults to
                    "-fexpensive-optimizations -fomit-frame-pointer -frename-registers -O2".
                </p></dd></dl></div><div class="glossdiv" title="H"><h3 class="title">H</h3><dl><dt><a id="var-HOMEPAGE"></a>HOMEPAGE</dt><dd><p>Website where more information about the software the recipe is building
                    can be found.</p></dd></dl></div><div class="glossdiv" title="I"><h3 class="title">I</h3><dl><dt><a id="var-IMAGE_FEATURES"></a>IMAGE_FEATURES</dt><dd><p>The list of features to include in an image.
                Typically, you configure this variable in an image recipe.
                Note that you can also add extra features to the image by using the
                <code class="filename"><a class="link" href="#var-EXTRA_IMAGE_FEATURES" title="EXTRA_IMAGE_FEATURES">EXTRA_IMAGE_FEATURES</a></code> variable.
                See the "<a class="link" href="#ref-features-image" title="9.3. Images">Images</a>" section for the
                full list of features that can be included in images built by the
                OpenEmbedded build system.</p></dd><dt><a id="var-IMAGE_FSTYPES"></a>IMAGE_FSTYPES</dt><dd><p>Formats of root filesystem images that you want to have created.</p></dd><dt><a id="var-IMAGE_INSTALL"></a>IMAGE_INSTALL</dt><dd><p>
                    Specifies the packages to install into an image.
                    The <code class="filename">IMAGE_INSTALL</code> variable is a mechanism for an image
                    recipe and you should use it with care to avoid ordering issues.
                </p><p>
                    Image recipes set <code class="filename">IMAGE_INSTALL</code> to specify the
                    packages to install into an image through <code class="filename">image.bbclass</code>.
                    Additionally, "helper" classes exist, such as <code class="filename">core-image.bbclass</code>,
                    that can take
                    <code class="filename"><a class="link" href="#var-IMAGE_FEATURES" title="IMAGE_FEATURES">IMAGE_FEATURES</a></code> lists
                    and turn these into auto-generated entries in
                    <code class="filename">IMAGE_INSTALL</code> in addition to its default contents.
                </p><p>
                    Using <code class="filename">IMAGE_INSTALL</code> with the <code class="filename">+=</code>
                    operator from the <code class="filename">/conf/local.conf</code> file or from within
                    an image recipe is not recommended as it can cause ordering issues.
                    Since <code class="filename">core-image.bbclass</code> sets <code class="filename">IMAGE_INSTALL</code>
                    to a default value using the <code class="filename">?=</code> operator, using a
                    <code class="filename">+=</code> operation against <code class="filename">IMAGE_INSTALL</code>
                    will result in unexpected behavior when used in
                    <code class="filename">/conf/local.conf</code>.
                    Furthermore, the same operation from with an image recipe may or may not
                    succeed depending on the specific situation.
                    In both these cases, the behavior is contrary to how most users expect
                    the <code class="filename">+=</code> operator to work.
                </p><p>
                    When you use this variable, it is best to use it as follows:
                    </p><pre class="literallayout">
     IMAGE_INSTALL_append = " package-name"
                    </pre><p>
                    Be sure to include the space between the quotation character and the start of the
                    package name.
                </p></dd><dt><a id="var-IMAGE_OVERHEAD_FACTOR"></a>IMAGE_OVERHEAD_FACTOR</dt><dd><p>
                    Defines a multiplier that the build system applies to the initial image
                    size for cases when the multiplier times the returned disk usage value
                    for the image is greater than the sum of
                    <code class="filename"><a class="link" href="#var-IMAGE_ROOTFS_SIZE" title="IMAGE_ROOTFS_SIZE">IMAGE_ROOTFS_SIZE</a></code>
                    and
                    <code class="filename"><a class="link" href="#var-IMAGE_ROOTFS_EXTRA_SPACE" title="IMAGE_ROOTFS_EXTRA_SPACE">IMAGE_ROOTFS_EXTRA_SPACE</a></code>.
                    The result of the multiplier applied to the initial image size creates
                    free disk space in the image as overhead.
                    By default, the build process uses a multiplier of 1.3 for this variable.
                    This default value results in 30% free disk space added to the image when this
                    method is used to determine the final generated image size.
                    You should be aware that post install scripts and the package management
                    system uses disk space inside this overhead area.
                    Consequently, the multiplier does not produce an image with
                    all the theoretical free disk space.
                    See <code class="filename"><a class="link" href="#var-IMAGE_ROOTFS_SIZE" title="IMAGE_ROOTFS_SIZE">IMAGE_ROOTFS_SIZE</a></code>
                    for information on how the build system determines the overall image size.
                </p><p>
                    The default 30% free disk space typically gives the image enough room to boot
                    and allows for basic post installs while still leaving a small amount of
                    free disk space.
                    If 30% free space is inadequate, you can increase the default value.
                    For example, the following setting gives you 50% free space added to the image:
                    </p><pre class="literallayout">
     IMAGE_OVERHEAD_FACTOR = "1.5"
                    </pre><p>
                </p><p>
                    Alternatively, you can ensure a specific amount of free disk space is added
                    to the image by using
                    <code class="filename"><a class="link" href="#var-IMAGE_ROOTFS_EXTRA_SPACE" title="IMAGE_ROOTFS_EXTRA_SPACE">IMAGE_ROOTFS_EXTRA_SPACE</a></code>
                    the variable.
                </p></dd><dt><a id="var-IMAGE_ROOTFS_EXTRA_SPACE"></a>IMAGE_ROOTFS_EXTRA_SPACE</dt><dd><p>
                    Defines additional free disk space created in the image in Kbytes.
                    By default, this variable is set to "0".
                    This free disk space is added to the image after the build system determines
                    the image size as described in
                    <code class="filename"><a class="link" href="#var-IMAGE_ROOTFS_SIZE" title="IMAGE_ROOTFS_SIZE">IMAGE_ROOTFS_SIZE</a></code>.
                </p><p>
                    This variable is particularly useful when you want to ensure that a
                    specific amount of free disk space is available on a device after an image
                    is installed and running.
                    For example, to be sure 5 Gbytes of free disk space is available, set the
                    variable as follows:
                    </p><pre class="literallayout">
     IMAGE_ROOTFS_EXTRA_SPACE = "5242880"
                    </pre><p>
                </p></dd><dt><a id="var-IMAGE_ROOTFS_SIZE"></a>IMAGE_ROOTFS_SIZE</dt><dd><p>
                    Defines the size in Kbytes for the generated image.
                    The OpenEmbedded build system determines the final size for the generated
                    image using an algorithm that takes into account the initial disk space used
                    for the generated image, a requested size for the image, and requested
                    additional free disk space to be added to the image.
                    Programatically, the build system determines the final size of the
                    generated image as follows:
                    </p><pre class="literallayout">
    if (image-du * overhead) &lt; rootfs-size:
	internal-rootfs-size = rootfs-size + xspace
    else:
	internal-rootfs-size = (image-du * overhead) + xspace

    where:

      image-du = Returned value of the du command on
                 the image.

      overhead = IMAGE_OVERHEAD_FACTOR

      rootfs-size = IMAGE_ROOTFS_SIZE

      internal-rootfs-size = Initial root filesystem
                             size before any modifications.

      xspace = IMAGE_ROOTFS_EXTRA_SPACE
                    </pre><p>

                </p></dd><dt><a id="var-INC_PR"></a>INC_PR</dt><dd><p>Helps define the recipe revision for recipes that share
                    a common <code class="filename">include</code> file.
                    You can think of this variable as part of the recipe revision
                    as set from within an include file.</p><p>Suppose, for example, you have a set of recipes that
                    are used across several projects.
                    And, within each of those recipes the revision
                    (its <code class="filename">PR</code> value) is set accordingly.
                    In this case, when the revision of those recipes changes
                    the burden is on you to find all those recipes and
                    be sure that they get changed to reflect the updated
                    version of the recipe.
                    In this scenario, it can get complicated when recipes
                    used in many places and that provide common functionality
                    are upgraded to a new revision.</p><p>A more efficient way of dealing with this situation is
                    to set the <code class="filename">INC_PR</code> variable inside
                    the <code class="filename">include</code> files that the recipes
                    share and then expand the <code class="filename">INC_PR</code>
                    variable within the recipes to help
                    define the recipe revision.
                    </p><p>
                    The following provides an example that shows how to use
                    the <code class="filename">INC_PR</code> variable
                    given a common <code class="filename">include</code> file that
                    defines the variable.
                    Once the variable is defined in the
                    <code class="filename">include</code> file, you can use the
                    variable to set the <code class="filename">PR</code> values in
                    each recipe.
                    You will notice that when you set a recipe's
                    <code class="filename">PR</code> you can provide more granular
                    revisioning by appending values to the
                    <code class="filename">INC_PR</code> variable:
                    </p><pre class="literallayout">
recipes-graphics/xorg-font/xorg-font-common.inc:INC_PR = "r2"
recipes-graphics/xorg-font/encodings_1.0.4.bb:PR = "${INC_PR}.1"
recipes-graphics/xorg-font/font-util_1.3.0.bb:PR = "${INC_PR}.0"
recipes-graphics/xorg-font/font-alias_1.0.3.bb:PR = "${INC_PR}.3"
                    </pre><p>
                    The first line of the example establishes the baseline
                    revision to be used for all recipes that use the
                    <code class="filename">include</code> file.
                    The remaining lines in the example are from individual
                    recipes and show how the <code class="filename">PR</code> value
                    is set.</p></dd><dt><a id="var-INHIBIT_PACKAGE_STRIP"></a>INHIBIT_PACKAGE_STRIP</dt><dd><p>
                    Causes the build to not strip binaries in resulting packages.
                </p></dd><dt><a id="var-INHERIT"></a>INHERIT</dt><dd><p>
                    Causes the named class to be inherited at
                    this point during parsing.
                    The variable is only valid in configuration files.
                </p></dd><dt><a id="var-INITSCRIPT_PACKAGES"></a>INITSCRIPT_PACKAGES</dt><dd><p>
                    A list of the packages that contain initscripts.
                    If multiple packages are specified, you need to append the package name
                    to the other <code class="filename">INITSCRIPT_*</code> as an override.</p><p>
                    This variable is used in recipes when using <code class="filename">update-rc.d.bbclass</code>.
                    The variable is optional and defaults to the <code class="filename">PN</code> variable.
                </p></dd><dt><a id="var-INITSCRIPT_NAME"></a>INITSCRIPT_NAME</dt><dd><p>
                    The filename of the initscript (as installed to <code class="filename">${etcdir}/init.d)</code>.
                </p><p>
                    This variable is used in recipes when using <code class="filename">update-rc.d.bbclass</code>.
                    The variable is Mandatory.
                </p></dd><dt><a id="var-INITSCRIPT_PARAMS"></a>INITSCRIPT_PARAMS</dt><dd><p>
                    Specifies the options to pass to <code class="filename">update-rc.d</code>.
                    An example is <code class="filename">start 99 5 2 . stop 20 0 1 6 .</code>, which gives the script a
                    runlevel of 99, starts the script in initlevels 2 and 5, and
                    stops the script in levels 0, 1 and 6.
                </p><p>
                    The variable is mandatory and is used in recipes when using
                    <code class="filename">update-rc.d.bbclass</code>.
                </p></dd></dl></div><div class="glossdiv" title="K"><h3 class="title">K</h3><dl><dt><a id="var-KBRANCH"></a>KBRANCH</dt><dd><p>
                    A regular expression used by the build process to explicitly identify the kernel
                    branch that is validated, patched and configured during a build.
                    The <code class="filename">KBRANCH</code> variable is optional.
                    You can use it to trigger checks to ensure the exact kernel branch you want is
                    being used by the build process.
                </p><p>
                    Values for this variable are set in the kernel's recipe file and the kernel's
                    append file.
                    For example, if you are using the Yocto Project kernel that is based on the
                    Linux 3.4 kernel, the kernel recipe file is the
                    <code class="filename">meta/recipes-kernel/linux/linux-yocto_3.4.bb</code> file.
                    Following is the default value for <code class="filename">KBRANCH</code> and the default
                    override for the architectures the Yocto Project supports:
                    </p><pre class="literallayout">
     KBRANCH_DEFAULT = "standard/base"
     KBRANCH = "${KBRANCH_DEFAULT}"
                    </pre><p>
                    This branch exists in the <code class="filename">linux-yocto-3.4</code> kernel Git
                    repository <a class="ulink" href="http://git.yoctoproject.org/cgit.cgi/linux-yocto-3.4/refs/heads" target="_top">http://git.yoctoproject.org/cgit.cgi/linux-yocto-3.4/refs/heads</a>.
                </p><p>
                    This variable is also used from the kernel's append file to identify the kernel
                    branch specific to a particular machine or target hardware.
                    The kernel's append file is located in the BSP layer for a given machine.
                    For example, the kernel append file for the Crown Bay BSP is in the
                    <code class="filename">meta-intel</code> Git repository and is named
                    <code class="filename">meta-crownbay/recipes-kernel/linux/linux-yocto_3.4.bbappend</code>.
                    Here are the related statements from the append file:
                    </p><pre class="literallayout">
     COMPATIBLE_MACHINE_crownbay = "crownbay"
     KMACHINE_crownbay  = "crownbay"
     KBRANCH_crownbay  = "standard/crownbay"

     COMPATIBLE_MACHINE_crownbay-noemgd = "crownbay-noemgd"
     KMACHINE_crownbay-noemgd  = "crownbay"
     KBRANCH_crownbay-noemgd  = "standard/crownbay"
                    </pre><p>
                        The <code class="filename">KBRANCH_*</code> statements identify the kernel branch to
                        use when building for the Crown Bay BSP.
                        In this case there are two identical statements: one for each type of
                        Crown Bay machine.
                </p></dd><dt><a id="var-KERNEL_FEATURES"></a>KERNEL_FEATURES</dt><dd><p>Includes additional metadata from the Yocto Project kernel Git repository.
                    In the OpenEmbedded build system, the default Board Support Packages (BSPs)
                    metadata is provided through
                    the <code class="filename">KMACHINE</code> and <code class="filename">KBRANCH</code> variables.
                    You can use the <code class="filename">KERNEL_FEATURES</code> variable to further
                    add metadata for all BSPs.</p><p>The metadata you add through this variable includes config fragments and
                    features descriptions,
                    which usually includes patches as well as config fragments.
                    You typically override the <code class="filename">KERNEL_FEATURES</code> variable
                    for a specific machine.
                    In this way, you can provide validated, but optional, sets of kernel
                    configurations and features.</p><p>For example, the following adds <code class="filename">netfilter</code> to all
                    the Yocto Project kernels and adds sound support to the <code class="filename">qemux86</code>
                    machine:
                    </p><pre class="literallayout">
     # Add netfilter to all linux-yocto kernels
     KERNEL_FEATURES="features/netfilter"

     # Add sound support to the qemux86 machine
     KERNEL_FEATURES_append_qemux86=" cfg/sound"
                    </pre></dd><dt><a id="var-KERNEL_IMAGETYPE"></a>KERNEL_IMAGETYPE</dt><dd><p>The type of kernel to build for a device, usually set by the
                    machine configuration files and defaults to "zImage".
                    This variable is used
                    when building the kernel and is passed to <code class="filename">make</code> as the target to
                    build.</p></dd><dt><a id="var-KMACHINE"></a>KMACHINE</dt><dd><p>
                    The machine as known by the kernel.
                    Sometimes the machine name used by the kernel does not match the machine name
                    used by the OpenEmbedded build system.
                    For example, the machine name that the OpenEmbedded build system understands as
                    <code class="filename">qemuarm</code> goes by a different name in the Linux Yocto kernel.
                    The kernel understands that machine as <code class="filename">arm_versatile926ejs</code>.
                    For cases like these, the <code class="filename">KMACHINE</code> variable maps the
                    kernel machine name to the OpenEmbedded build system machine name.
                </p><p>
                    Kernel machine names are initially defined in the
                    <a class="ulink" href="http://git.yoctoproject.org/cgit.cgi" target="_top">Yocto Linux Kernel</a> in
                    the <code class="filename">meta</code> branch.
                    From the <code class="filename">meta</code> branch, look in
                    the <code class="filename">meta/cfg/kernel-cache/bsp/&lt;bsp_name&gt;/&lt;bsp-name&gt;-&lt;kernel-type&gt;.scc</code> file.
                    For example, from the <code class="filename">meta</code> branch in the
                    <code class="filename">linux-yocto-3.0</code> kernel, the
                    <code class="filename">meta/cfg/kernel-cache/bsp/cedartrail/cedartrail-standard.scc</code> file
                    has the following:
                    </p><pre class="literallayout">
     define KMACHINE cedartrail
     define KTYPE standard
     define KARCH i386

     include ktypes/standard
     branch cedartrail

     include cedartrail.scc
                    </pre><p>
                    You can see that the kernel understands the machine name for the Cedar Trail BSP as
                    <code class="filename">cedartrail</code>.
                </p><p>
                    If you look in the Cedar Trail BSP layer in the <code class="filename">meta-intel</code> source
                    repository at <code class="filename">meta-cedartrail/recipes-kernel/linux/linux-yocto_3.0.bbappend</code>,
                    you will find the following statements among others:
                    </p><pre class="literallayout">
     COMPATIBLE_MACHINE_cedartrail = "cedartrail"
     KMACHINE_cedartrail  = "cedartrail"
     KBRANCH_cedartrail  = "yocto/standard/cedartrail"
     KERNEL_FEATURES_append_cedartrail += "bsp/cedartrail/cedartrail-pvr-merge.scc"
     KERNEL_FEATURES_append_cedartrail += "cfg/efi-ext.scc"

     COMPATIBLE_MACHINE_cedartrail-nopvr = "cedartrail"
     KMACHINE_cedartrail-nopvr  = "cedartrail"
     KBRANCH_cedartrail-nopvr  = "yocto/standard/cedartrail"
     KERNEL_FEATURES_append_cedartrail-nopvr += " cfg/smp.scc"
                    </pre><p>
                    The <code class="filename">KMACHINE</code> statements in the kernel's append file make sure that
                    the OpenEmbedded build system and the Yocto Linux kernel understand the same machine
                    names.
                </p><p>
                    This append file uses two <code class="filename">KMACHINE</code> statements.
                    The first is not really necessary but does ensure that the machine known to the
                    OpenEmbedded build system as <code class="filename">cedartrail</code> maps to the machine
                    in the kernel also known as <code class="filename">cedartrail</code>:
                    </p><pre class="literallayout">
     KMACHINE_cedartrail  = "cedartrail"
                    </pre><p>
                </p><p>
                    The second statement is a good example of why the <code class="filename">KMACHINE</code> variable
                    is needed.
                    In this example, the OpenEmbedded build system uses the <code class="filename">cedartrail-nopvr</code>
                    machine name to refer to the Cedar Trail BSP that does not support the propriatory
                    PowerVR driver.
                    The kernel, however, uses the machine name <code class="filename">cedartrail</code>.
                    Thus, the append file must map the <code class="filename">cedartrail-nopvr</code> machine name to
                    the kernel's <code class="filename">cedartrail</code> name:
                    </p><pre class="literallayout">
     KMACHINE_cedartrail-nopvr  = "cedartrail"
                    </pre><p>
                </p><p>
                    BSPs that ship with the Yocto Project release provide all mappings between the Yocto
                    Project kernel machine names and the OpenEmbedded machine names.
                    Be sure to use the <code class="filename">KMACHINE</code> if you create a BSP and the machine
                    name you use is different than that used in the kernel.
                </p></dd></dl></div><div class="glossdiv" title="L"><h3 class="title">L</h3><dl><dt><a id="var-LAYERDEPENDS"></a>LAYERDEPENDS</dt><dd><p>Lists the layers that this recipe depends upon, separated by spaces.
                    Optionally, you can specify a specific layer version for a dependency
                    by adding it to the end of the layer name with a colon, (e.g. "anotherlayer:3"
                    to be compared against <code class="filename">LAYERVERSION_anotherlayer</code> in this case).
                    An error will be produced if any dependency is missing or
                    the version numbers do not match exactly (if specified).
                    This variable is used in the <code class="filename">conf/layer.conf</code> file
                    and must be suffixed with the name of the specific layer (e.g.
                    <code class="filename">LAYERDEPENDS_mylayer</code>).</p></dd><dt><a id="var-LAYERDIR"></a>LAYERDIR</dt><dd><p>When used inside the <code class="filename">layer.conf</code> configuration
                    file, this variable provides the path of the current layer.
                    This variable requires immediate expansion
                    (see the BitBake manual) as lazy expansion can result in
                    the expansion happening in the wrong directory and therefore
                    giving the wrong value.</p></dd><dt><a id="var-LAYERVERSION"></a>LAYERVERSION</dt><dd><p>Optionally specifies the version of a layer as a single number.
                    You can use this within <code class="filename">LAYERDEPENDS</code> for another layer in order to
                    depend on a specific version of the layer.
                    This variable is used in the <code class="filename">conf/layer.conf</code> file
                    and must be suffixed with the name of the specific layer (e.g.
                    <code class="filename">LAYERVERSION_mylayer</code>).</p></dd><dt><a id="var-LIC_FILES_CHKSUM"></a>LIC_FILES_CHKSUM</dt><dd><p>Checksums of the license text in the recipe source code.</p><p>This variable tracks changes in license text of the source
                    code files.
                    If the license text is changed, it will trigger a build
                    failure, which gives the developer an opportunity to review any
                    license change.</p><p>
                    This variable must be defined for all recipes (unless <code class="filename">LICENSE</code>
                    is set to "CLOSED")</p><p>For more information, see the
                    <a class="link" href="#usingpoky-configuring-LIC_FILES_CHKSUM" title="3.4.1. Tracking License Changes">
                    Tracking License Changes</a> section</p></dd><dt><a id="var-LICENSE"></a>LICENSE</dt><dd><p>
                    The list of source licenses for the recipe.
                    Follow these rules:
                    </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>Do not use spaces within individual
                            license names.</p></li><li class="listitem"><p>Separate license names using
                            | (pipe) when there is a choice between licenses.
                            </p></li><li class="listitem"><p>Separate license names using
                            &amp; (ampersand) when multiple licenses exist
                            that cover different parts of the source.
                            </p></li><li class="listitem"><p>You can use spaces between license
                            names.</p></li></ul></div><p>
                </p><p>
                    Here are some examples:
                    </p><pre class="literallayout">
     LICENSE = "LGPLv2.1 | GPLv3"
     LICENSE = "MPL-1 &amp; LGPLv2.1"
     LICENSE = "GPLv2+"
                    </pre><p>
                    The first example is from the recipes for Qt, which the user
                    may choose to distribute under either the LGPL version
                    2.1 or GPL version 3.
                    The second example is from Cairo where two licenses cover
                    different parts of the source code.
                    The final example is from <code class="filename">sysstat</code>,
                    which presents a single license.
                </p></dd><dt><a id="var-LICENSE_PATH"></a>LICENSE_PATH</dt><dd><p>Path to additional licenses used during the build.
                    By default, the OpenEmbedded build system uses <code class="filename">COMMON_LICENSE_DIR</code>
                    to define the directory that holds common license text used during the build.
                    The <code class="filename">LICENSE_PATH</code> variable allows you to extend that
                    location to other areas that have additional licenses:
                    </p><pre class="literallayout">
  LICENSE_PATH += "/path/to/additional/common/licenses"
                    </pre></dd></dl></div><div class="glossdiv" title="M"><h3 class="title">M</h3><dl><dt><a id="var-MACHINE"></a>MACHINE</dt><dd><p>
                    Specifies the target device for which the image is built.
                    You define <code class="filename">MACHINE</code> in the
                    <code class="filename">local.conf</code> file found in the
                    <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#build-directory" target="_top">Build Directory</a>.
                    By default, <code class="filename">MACHINE</code> is set to
                    "qemux86", which is an x86-based architecture machine to
                    be emulated using QEMU:
                    </p><pre class="literallayout">
     MACHINE ?= "qemux86"
                    </pre><p>
                    The variable corresponds to a machine configuration file of the
                    same name, through which machine-specific configurations are set.
                    Thus, when <code class="filename">MACHINE</code> is set to "qemux86" there
                    exists the corresponding <code class="filename">qemux86.conf</code> machine
                    configuration file, which can be found in the
                    <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#source-directory" target="_top">Source Directory</a>
                    in <code class="filename">meta/conf/machine</code>.
                </p><p>
                    The list of machines supported by the Yocto Project as
                    shipped include the following:
                    </p><pre class="literallayout">
     MACHINE ?= "qemuarm"
     MACHINE ?= "qemumips"
     MACHINE ?= "qemuppc"
     MACHINE ?= "qemux86"
     MACHINE ?= "qemux86-64"
     MACHINE ?= "atom-pc"
     MACHINE ?= "beagleboard"
     MACHINE ?= "mpc8315e-rdb"
     MACHINE ?= "routerstationpro"
                    </pre><p>
                    The last four are Yocto Project reference hardware boards, which
                    are provided in the <code class="filename">meta-yocto-bsp</code> layer.
                    </p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>Adding additional Board Support Package (BSP) layers
                        to your configuration adds new possible settings for
                        <code class="filename">MACHINE</code>.
                    </div><p>
                </p></dd><dt><a id="var-MACHINE_ESSENTIAL_EXTRA_RDEPENDS"></a>MACHINE_ESSENTIAL_EXTRA_RDEPENDS</dt><dd><p></p><p>
                    A list of required machine-specific packages to install as part of
                    the image being built.
                    The build process depends on these packages being present.
                    Furthermore, because this is a "machine essential" variable, the list of
                    packages are essential for the machine to boot.
                    The impact of this variable affects images based on
                    <code class="filename">packagegroup-core-boot</code>,
                    including the <code class="filename">core-image-minimal</code> image.
                </p><p>
                    This variable is similar to the
                    <code class="filename"><a class="link" href="#var-MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS" title="MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS">MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS</a></code>
                    variable with the exception that the image being built has a build
                    dependency on the variable's list of packages.
                    In other words, the image will not build if a file in this list is not found.
                </p><p>
                    As an example, suppose the machine for which you are building requires
                    <code class="filename">example-init</code> to be run during boot to initialize the hardware.
                    In this case, you would use the following in the machine's
                    <code class="filename">.conf</code> configuration file:
                    </p><pre class="literallayout">
     MACHINE_ESSENTIAL_EXTRA_RDEPENDS += "example-init"
                    </pre><p>
                </p></dd><dt><a id="var-MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS"></a>MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS</dt><dd><p></p><p>
                    A list of recommended machine-specific packages to install as part of
                    the image being built.
                    The build process does not depend on these packages being present.
                    However, because this is a "machine essential" variable, the list of
                    packages are essential for the machine to boot.
                    The impact of this variable affects images based on
                    <code class="filename">packagegroup-core-boot</code>,
                    including the <code class="filename">core-image-minimal</code> image.
                </p><p>
                    This variable is similar to the
                    <code class="filename"><a class="link" href="#var-MACHINE_ESSENTIAL_EXTRA_RDEPENDS" title="MACHINE_ESSENTIAL_EXTRA_RDEPENDS">MACHINE_ESSENTIAL_EXTRA_RDEPENDS</a></code>
                    variable with the exception that the image being built does not have a build
                    dependency on the variable's list of packages.
                    In other words, the image will still build if a package in this list is not found.
                    Typically, this variable is used to handle essential kernel modules, whose
                    functionality may be selected to be built into the kernel rather than as a module,
                    in which case a package will not be produced.
                </p><p>
                    Consider an example where you have a custom kernel where a specific touchscreen
                    driver is required for the machine to be usable.
                    However, the driver can be built as a module or
                    into the kernel depending on the kernel configuration.
                    If the driver is built as a module, you want it to be installed.
                    But, when the driver is built into the kernel, you still want the
                    build to succeed.
                    This variable sets up a "recommends" relationship so that in the latter case,
                    the build will not fail due to the missing package.
                    To accomplish this, assuming the package for the module was called
                    <code class="filename">kernel-module-ab123</code>, you would use the
                    following in the machine's <code class="filename">.conf</code> configuration
                    file:
                    </p><pre class="literallayout">
     MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS += "kernel-module-ab123"
                    </pre><p>
                </p><p>
                    Some examples of these machine essentials are flash, screen, keyboard, mouse,
                    or touchscreen drivers (depending on the machine).
                </p></dd><dt><a id="var-MACHINE_EXTRA_RDEPENDS"></a>MACHINE_EXTRA_RDEPENDS</dt><dd><p>
                    A list of machine-specific packages to install as part of the
                    image being built that are not essential for the machine to boot.
                    However, the build process for more fully-featured images
                    depends on the packages being present.
                </p><p>
                    This variable affects all images based on
                    <code class="filename">packagegroup-base</code>, which does not include the
                    <code class="filename">core-image-minimal</code> or <code class="filename">core-image-basic</code>
                    images.
                </p><p>
                    The variable is similar to the
                    <code class="filename"><a class="link" href="#var-MACHINE_EXTRA_RRECOMMENDS" title="MACHINE_EXTRA_RRECOMMENDS">MACHINE_EXTRA_RRECOMMENDS</a></code>
                    variable with the exception that the image being built has a build
                    dependency on the variable's list of packages.
                    In other words, the image will not build if a file in this list is not found.
                </p><p>
                    An example is a machine that has WiFi capability but is not essential
                    For the machine to boot the image.
                    However, if you are building a more fully-featured image, you want to enable
                    the WiFi.
                    The package containing the firmware for the WiFi hardware is always
                    expected to exist, so it is acceptable for the build process to depend upon
                    finding the package.
                    In this case, assuming the package for the firmware was called
                    <code class="filename">wifidriver-firmware</code>, you would use the following in the
                    <code class="filename">.conf</code> file for the machine:
                    </p><pre class="literallayout">
     MACHINE_EXTRA_RDEPENDS += "wifidriver-firmware"
                    </pre><p>
                </p></dd><dt><a id="var-MACHINE_EXTRA_RRECOMMENDS"></a>MACHINE_EXTRA_RRECOMMENDS</dt><dd><p></p><p>
                    A list of machine-specific packages to install as part of the
                    image being built that are not essential for booting the machine.
                    The image being built has no build dependency on this list of packages.
                </p><p>
                    This variable affects only images based on
                    <code class="filename">packagegroup-base</code>, which does not include the
                    <code class="filename">core-image-minimal</code> or <code class="filename">core-image-basic</code>
                    images.
                </p><p>
                    This variable is similar to the
                    <code class="filename"><a class="link" href="#var-MACHINE_EXTRA_RDEPENDS" title="MACHINE_EXTRA_RDEPENDS">MACHINE_EXTRA_RDEPENDS</a></code>
                    variable with the exception that the image being built does not have a build
                    dependency on the variable's list of packages.
                    In other words, the image will build if a file in this list is not found.
                </p><p>
                    An example is a machine that has WiFi capability but is not essential
                    For the machine to boot the image.
                    However, if you are building a more fully-featured image, you want to enable
                    WiFi.
                    In this case, the package containing the WiFi kernel module will not be produced
                    if the WiFi driver is built into the kernel, in which case you still want the
                    build to succeed instead of failing as a result of the package not being found.
                    To accomplish this, assuming the package for the module was called
                    <code class="filename">kernel-module-examplewifi</code>, you would use the
                    following in the <code class="filename">.conf</code> file for the machine:
                    </p><pre class="literallayout">
     MACHINE_EXTRA_RRECOMMENDS += "kernel-module-examplewifi"
                    </pre><p>
                </p></dd><dt><a id="var-MACHINE_FEATURES"></a>MACHINE_FEATURES</dt><dd><p>Specifies the list of hardware features the
                    <a class="link" href="#var-MACHINE" title="MACHINE">MACHINE</a> supports.
                    For example, including the "bluetooth" feature causes the
                    <code class="filename">bluez</code> bluetooth daemon to be built and
                    added to the image.
                    It also causes the <code class="filename">connman</code> recipe
                    to look at <code class="filename">MACHINE_FEATURES</code> and when it
                    finds "bluetooth" there it enables the bluetooth
                    support in ConnMan.
                </p><p>
                    For a list of features supported by the Yocto Project as shipped,
                    see the "<a class="link" href="#ref-features-machine" title="9.2. Machine">Machine</a>" section.
                </p></dd><dt><a id="var-MACHINE_FEATURES_BACKFILL"></a>MACHINE_FEATURES_BACKFILL</dt><dd><p>Features to be added to
                    <code class="filename"><a class="link" href="#var-MACHINE_FEATURES" title="MACHINE_FEATURES">MACHINE_FEATURES</a></code>
                    if not also present in
                    <code class="filename"><a class="link" href="#var-MACHINE_FEATURES_BACKFILL_CONSIDERED" title="MACHINE_FEATURES_BACKFILL_CONSIDERED">MACHINE_FEATURES_BACKFILL_CONSIDERED</a></code>.
                </p><p>
                    This variable is set in the <code class="filename">meta/conf/bitbake.conf</code> file.
                    It is not intended to be user-configurable.
                    It is best to just reference the variable to see which machine features are
                    being backfilled for all machine configurations.
                    See the <a class="link" href="#ref-features-backfill" title="9.4. Feature Backfilling">Feature backfilling</a> section for
                    more information.
                </p></dd><dt><a id="var-MACHINE_FEATURES_BACKFILL_CONSIDERED"></a>MACHINE_FEATURES_BACKFILL_CONSIDERED</dt><dd><p>Features from
                    <code class="filename"><a class="link" href="#var-MACHINE_FEATURES_BACKFILL" title="MACHINE_FEATURES_BACKFILL">MACHINE_FEATURES_BACKFILL</a></code>
                    that should not be backfilled (i.e. added to
                    <code class="filename"><a class="link" href="#var-MACHINE_FEATURES" title="MACHINE_FEATURES">MACHINE_FEATURES</a></code>)
                    during the build.
                    See the <a class="link" href="#ref-features-backfill" title="9.4. Feature Backfilling">Feature backfilling</a> section for
                    more information.
                    </p></dd><dt><a id="var-MAINTAINER"></a>MAINTAINER</dt><dd><p>The email address of the distribution maintainer.</p></dd><dt><a id="var-MLPREFIX"></a>MLPREFIX</dt><dd><p>
                    Specifies a prefix has been added to
                    <a class="link" href="#var-PN" title="PN"><code class="filename">PN</code></a> to create a special version
                    of a recipe or package, such as a multilib version.
                    The variable is used in places where the prefix needs to be
                    added to or removed from a the name (e.g. the
                    <a class="link" href="#var-BPN" title="BPN"><code class="filename">BPN</code></a> variable).
                    <code class="filename">MLPREFIX</code> gets set when a prefix has been
                    added to <code class="filename">PN</code>.
                </p></dd><dt><a id="var-MULTIMACH_TARGET_SYS"></a>MULTIMACH_TARGET_SYS</dt><dd><p>
                    Separates files for different machines such that you can build
                    for multiple target machines using the same output directories.
                    See the <a class="link" href="#var-STAMP" title="STAMP"><code class="filename">STAMP</code></a> variable
                    for an example.
                </p></dd></dl></div><div class="glossdiv" title="O"><h3 class="title">O</h3><dl><dt><a id="var-OE_TERMINAL"></a>OE_TERMINAL</dt><dd><p>
                    Controls how the OpenEmbedded build system spawns
                    interactive terminals on the host development system
                    (e.g. using the BitBake command with the
                    <code class="filename">-c devshell</code> command-line option).
                    For more information, see the
                    "<a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#platdev-appdev-devshell" target="_top">Using a Development Shell</a>" section
                    in the Yocto Project Development Manual.
                 </p><p>
                    You can use the following values for the
                    <code class="filename">OE_TERMINAL</code> variable:
                    </p><pre class="literallayout">
     auto
     gnome
     xfce
     rxvt
     screen
     konsole
     none
                    </pre><p>
                    </p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>Konsole support only works for KDE 3.x.
                        Also, "auto" is the default behavior for
                        <code class="filename">OE_TERMINAL</code></div><p>
                </p></dd></dl></div><div class="glossdiv" title="P"><h3 class="title">P</h3><dl><dt><a id="var-P"></a>P</dt><dd><p>The recipe name and version.
                    <code class="filename">P</code> is comprised of the following:
                    </p><pre class="literallayout">
     ${PN}-${PV}
                    </pre></dd><dt><a id="var-PACKAGE_ARCH"></a>PACKAGE_ARCH</dt><dd><p>The architecture of the resulting package or packages.</p></dd><dt><a id="var-PACKAGE_BEFORE_PN"></a>PACKAGE_BEFORE_PN</dt><dd><p>Enables easily adding packages to
                <code class="filename"><a class="link" href="#var-PACKAGES" title="PACKAGES">PACKAGES</a></code>
                before <code class="filename">${PN}</code> so that the packages can pick
                up files that would normally be included in the default package.</p></dd><dt><a id="var-PACKAGE_CLASSES"></a>PACKAGE_CLASSES</dt><dd><p>This variable, which is set in the <code class="filename">local.conf</code> configuration
                    file found in the <code class="filename">conf</code> folder of the
                    <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#source-directory" target="_top">Source Directory</a>,
                    specifies the package manager to use when packaging data.
                    You can provide one or more arguments for the variable with the first
                    argument being the package manager used to create images:
                    </p><pre class="literallayout">
     PACKAGE_CLASSES ?= "package_rpm package_deb package_ipk"
                    </pre><p>
                    For information on build performance effects as a result of the
                    package manager use, see
                    <a class="link" href="#ref-classes-package" title="7.13. Packaging - package*.bbclass">Packaging - <code class="filename">package*.bbclass</code></a>
                    in this manual.
                </p></dd><dt><a id="var-PACKAGE_EXTRA_ARCHS"></a>PACKAGE_EXTRA_ARCHS</dt><dd><p>Specifies the list of architectures compatible with the device CPU.
                    This variable is useful when you build for several different devices that use
                    miscellaneous processors such as XScale and ARM926-EJS).</p></dd><dt><a id="var-PACKAGECONFIG"></a>PACKAGECONFIG</dt><dd><p>
                    This variable provides a means of enabling or disabling
                    features of a recipe on a per-recipe basis.
                    The <code class="filename">PACKAGECONFIG</code>
                    variable itself specifies a space-separated list of the
                    features to enable.
                    The features themselves are specified as flags on the
                    <code class="filename">PACKAGECONFIG</code> variable.
                    You can provide up to four arguments, which are separated by
                    commas, to determine the behavior of each feature
                    when it is enabled or disabled.
                    You can omit any argument you like but must retain the
                    separating commas.
                    The arguments specify the following:
                    </p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>Extra arguments
                            that should be added to the configure script argument list
                            (<a class="link" href="#var-EXTRA_OECONF" title="EXTRA_OECONF"><code class="filename">EXTRA_OECONF</code></a>)
                            if the feature is enabled.</p></li><li class="listitem"><p>Extra arguments
                            that should be added to <code class="filename">EXTRA_OECONF</code>
                            if the feature is disabled.
                            </p></li><li class="listitem"><p>Additional build dependencies
                            (<a class="link" href="#var-DEPENDS" title="DEPENDS"><code class="filename">DEPENDS</code></a>)
                            that should be added if the feature is enabled.
                            </p></li><li class="listitem"><p>Additional runtime dependencies
                            (<a class="link" href="#var-RDEPENDS" title="RDEPENDS"><code class="filename">RDEPENDS</code></a>)
                            that should be added if the feature is enabled.
                            </p></li></ol></div><p>
                </p><p>
                    Consider the following example taken from the
                    <code class="filename">librsvg</code> recipe.
                    In this example the feature is <code class="filename">croco</code>, which
                    has three arguments that determine the feature's behavior.
                        </p><pre class="literallayout">
     PACKAGECONFIG ??= "croco"
     PACKAGECONFIG[croco] = "--with-croco,--without-croco,libcroco"
                        </pre><p>
                    The <code class="filename">--with-croco</code> and
                    <code class="filename">libcroco</code> arguments apply only if
                    the feature is enabled.
                    In this case, <code class="filename">--with-croco</code> is
                    added to the configure script argument list and
                    <code class="filename">libcroco</code> is added to
                    <code class="filename"><a class="link" href="#var-DEPENDS" title="DEPENDS">DEPENDS</a></code>.
                    On the other hand, if the feature is disabled say through
                    a <code class="filename">.bbappend</code> file in another layer, then
                    the second argument <code class="filename">--without-croco</code> is
                    added to the configure script rather than
                    <code class="filename">--with-croco</code>.
                </p></dd><dt><a id="var-PACKAGES"></a>PACKAGES</dt><dd><p>The list of packages to be created from the recipe.
                    The default value is the following:
                    </p><pre class="literallayout">
     ${PN}-dbg ${PN}-staticdev ${PN}-dev ${PN}-doc ${PN}-locale ${PACKAGE_BEFORE_PN} ${PN}
                    </pre></dd><dt><a id="var-PACKAGES_DYNAMIC"></a>PACKAGES_DYNAMIC</dt><dd><p>
                    A promise that your recipe satisfies runtime dependencies
                    for optional modules that are found in other recipes.
                    <code class="filename">PACKAGES_DYNAMIC</code>
                    does not actually satisfy the dependencies, it only states that
                    they should be satisfied.
                    For example, if a hard, runtime dependency
                    (<code class="filename">RDEPENDS</code>) of another package is satisfied
                    at build time through the <code class="filename">PACKAGES_DYNAMIC</code>
                    variable, but a package with the module name is never actually
                    produced, then the other package will be broken.
                    Thus, if you attempt to include that package in an image,
                    you will get a dependency failure from the packaging system
                    during <code class="filename">do_rootfs</code>.
                    Typically, if there is a chance that such a situation can
                    occur and the package that is not created is valid
                    without the dependency being satisfied, then you should use
                    <code class="filename">RRECOMMENDS</code> (a soft runtime dependency)
                    instead of <code class="filename">RDEPENDS</code>.
                </p><p>
                    For an example of how to use the <code class="filename">PACKAGES_DYNAMIC</code>
                    variable when you are splitting packages, see the
                    "<a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#handling-optional-module-packaging" target="_top">Handling Optional Module Packaging</a>" section
                    in the Yocto Project Development Manual.
                </p></dd><dt><a id="var-PARALLEL_MAKE"></a>PARALLEL_MAKE</dt><dd><p>Specifies extra options that are passed to the <code class="filename">make</code> command during the
                    compile tasks.
                    This variable is usually in the form <code class="filename">-j 4</code>, where the number
                    represents the maximum number of parallel threads make can run.
                    If you development host supports multiple cores a good rule of thumb is to set
                    this variable to twice the number of cores on the host.</p></dd><dt><a id="var-PF"></a>PF</dt><dd><p>Specifies the recipe or package name and includes all version and revision
                    numbers (i.e. <code class="filename">eglibc-2.13-r20+svnr15508/</code> and
                    <code class="filename">bash-4.2-r1/</code>).
                    This variable is comprised of the following:
                    </p><pre class="literallayout">
     ${PN}-${EXTENDPE}${PV}-${PR}
                    </pre></dd><dt><a id="var-PN"></a>PN</dt><dd><p>This variable can have two separate functions depending on the context: a recipe
                    name or a resulting package name.</p><p><code class="filename">PN</code> refers to a recipe name in the context of a file used
                    by the OpenEmbedded build system as input to create a package.
                    The name is normally extracted from the recipe file name.
                    For example, if the recipe is named
                    <code class="filename">expat_2.0.1.bb</code>, then the default value of <code class="filename">PN</code>
                    will be "expat".</p><p>
                    The variable refers to a package name in the context of a file created or produced by the
                    OpenEmbedded build system.</p><p>If applicable, the <code class="filename">PN</code> variable also contains any special
                    suffix or prefix.
                    For example, using <code class="filename">bash</code> to build packages for the native
                    machine, <code class="filename">PN</code> is <code class="filename">bash-native</code>.
                    Using <code class="filename">bash</code> to build packages for the target and for Multilib,
                    <code class="filename">PN</code> would be <code class="filename">bash</code> and
                    <code class="filename">lib64-bash</code>, respectively.
                </p></dd><dt><a id="var-PR"></a>PR</dt><dd><p>The revision of the recipe.
                    The default value for this variable is "r0".
                    </p></dd><dt><a id="var-PRINC"></a>PRINC</dt><dd><p>Causes the <code class="filename">PR</code> variable of
                    <code class="filename">.bbappend</code> files to dynamically increment.
                    This increment minimizes the impact of layer ordering.</p><p>In order to ensure multiple <code class="filename">.bbappend</code> files can co-exist,
                    <code class="filename">PRINC</code> should be self referencing.
                    This variable defaults to 0.</p><p>Following is an example that increments <code class="filename">PR</code> by two:
                    </p><pre class="literallayout">
     PRINC := "${@int(PRINC) + 2}"
                    </pre><p>
                    It is adviseable not to use strings such as ".= '.1'" with the variable because
                    this usage is very sensitive to layer ordering.
                    Explicit assignments should be avoided as they cannot adequately represent multiple
                    <code class="filename">.bbappend</code> files.</p></dd><dt><a id="var-PV"></a>PV</dt><dd><p>The version of the recipe.
                    The version is normally extracted from the recipe filename.
                    For example, if the recipe is named
                    <code class="filename">expat_2.0.1.bb</code>, then the default value of <code class="filename">PV</code>
                    will be "2.0.1".
                    <code class="filename">PV</code> is generally not overridden within
                    a recipe unless it is building an unstable (i.e. development) version from a source code repository
                    (e.g. Git or Subversion).
                 </p></dd><dt><a id="var-PE"></a>PE</dt><dd><p>
                    the epoch of the recipe.
                    The default value is "0".
                    The field is used to make upgrades possible when the versioning scheme changes in
                    some backwards incompatible way.
                </p></dd><dt><a id="var-PREFERRED_PROVIDER"></a>PREFERRED_PROVIDER</dt><dd><p>
                    If multiple recipes provide an item, this variable
                    determines which recipe should be given preference.
                    The variable must always be suffixed with the name of the
                    provided item, and should be set to the
                    <code class="filename">PN</code> of the recipe
                    to which you want to give precedence.
                    Here is an example:
                    </p><pre class="literallayout">
     PREFERRED_PROVIDER_virtual/xserver = "xserver-xf86"
                    </pre><p>
                </p></dd><dt><a id="var-PREFERRED_VERSION"></a>PREFERRED_VERSION</dt><dd><p>
                    If there are multiple versions of recipes available, this
                    variable determines which recipe should be given preference.
                    The variable must always be suffixed with the <code class="filename">PN</code>
                    for which to select, and should be set to the
                    <code class="filename">PV</code> to which you want to give precedence.
                    You can use the "<code class="filename">%</code>" character as a wildcard
                    to match any number of characters, which can be useful when
                    specifying versions that contain long revision number that could
                    potentially change.
                    Here are two examples:
                    </p><pre class="literallayout">
     PREFERRED_VERSION_python = "2.6.6"
     PREFERRED_VERSION_linux-yocto = "3.0+git%"
                    </pre><p>
                </p></dd></dl></div><div class="glossdiv" title="R"><h3 class="title">R</h3><dl><dt><a id="var-RCONFLICTS"></a>RCONFLICTS</dt><dd><p>The list of packages that conflict with a package.
                    Note that the package will not be installed if the conflicting packages are not
                    first removed.</p><p>
                   Like all package-controlling variables, you must always use them in
                   conjunction with a package name override.
                   Here is an example:
                   </p><pre class="literallayout">
     RCONFLICTS_${PN} = "another-conflicting-package-name"
                   </pre><p>
                </p></dd><dt><a id="var-RDEPENDS"></a>RDEPENDS</dt><dd><p>
                    Lists a package's run-time dependencies (i.e. other packages)
                    that must be installed for the package to be built.
                    In other words, in order for the package to be built and
                    run correctly, it depends on the listed packages.
                    If a package in this list cannot be found, it is probable
                    that a dependency error would occur before the build.
                </p><p>
                    The names of the variables you list with
                    <code class="filename">RDEPENDS</code> must be the names of other
                    packages as listed in the
                    <a class="link" href="#var-PACKAGES" title="PACKAGES"><code class="filename">PACKAGES</code></a>
                    variable.
                    You should not list recipe names (<code class="filename">PN</code>).
                </p><p>
                    Because the <code class="filename">RDEPENDS</code> variable applies
                    to packages being built, you should
                    always attach a package name to the variable to specify the
                    particular run-time package that has the dependency.
                    For example, suppose you are building a development package
                    that depends on the <code class="filename">perl</code> package.
                    In this case, you would use the following
                    <code class="filename">RDEPENDS</code> statement:
                    </p><pre class="literallayout">
     RDEPENDS_${PN}-dev += "perl"
                    </pre><p>
                    In the example, the package name
                    (<code class="filename">${PN}-dev</code>) must appear as it would
                    in the
                    <code class="filename"><a class="link" href="#var-PACKAGES" title="PACKAGES">PACKAGES</a></code>
                    namespace before any renaming of the output package by
                    classes like <code class="filename">debian.bbclass</code>.
                </p><p>
                    In many cases you do not need to explicitly add dependencies
                    to <code class="filename">RDEPENDS</code> since some automatic
                    handling occurs:
                    </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em><code class="filename">shlibdeps</code></em></span>:  If
                            a run-time package contains a shared library
                            (<code class="filename">.so</code>), the build
                            processes the library in order to determine other
                            libraries to which it is dynamically linked.
                            The build process adds these libraries to
                            <code class="filename">RDEPENDS</code> when creating the run-time
                            package.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">pcdeps</code></em></span>:  If
                            the package ships a <code class="filename">pkg-config</code>
                            information file, the build process uses this file
                            to add items to the <code class="filename">RDEPENDS</code>
                            variable to create the run-time packages.
                            </p></li></ul></div><p>
                </p></dd><dt><a id="var-RRECOMMENDS"></a>RRECOMMENDS</dt><dd><p>
                    A list of packages that extend the usability of a package being
                    built.
                    The package being built does not depend on this list of packages in
                    order to successfully build, but needs them for the extended usability.
                    To specify runtime dependencies for packages, see the
                    <code class="filename"><a class="link" href="#var-RDEPENDS" title="RDEPENDS">RDEPENDS</a></code> variable.
                </p><p>
                    The OpenEmbedded build process automatically installs the list of packages
                    as part of the built package.
                    However, you can remove them later if you want.
                    If, during the build, a package from the list cannot be found, the build
                    process continues without an error.
                </p><p>
                    Because the <code class="filename">RRECOMMENDS</code> variable applies to packages
                    being built, you should
                    always attach an override to the variable to specify the particular package
                    whose usability is being extended.
                    For example, suppose you are building a development package that is extended
                    to support wireless functionality.
                    In this case, you would use the following:
                    </p><pre class="literallayout">
     RRECOMMENDS_${PN}-dev += "&lt;wireless_package_name&gt;"
                    </pre><p>
                    In the example, the package name (<code class="filename">${PN}-dev</code>) must
                    appear as it would in the
                    <code class="filename"><a class="link" href="#var-PACKAGES" title="PACKAGES">PACKAGES</a></code> namespace before any
                    renaming of the output package by classes like <code class="filename">debian.bbclass</code>.
                </p></dd><dt><a id="var-RREPLACES"></a>RREPLACES</dt><dd><p>The list of packages that are replaced with this package.</p></dd></dl></div><div class="glossdiv" title="S"><h3 class="title">S</h3><dl><dt><a id="var-S"></a>S</dt><dd><p>
                    The location in the <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#build-directory" target="_top">Build Directory</a>
                    where unpacked package source code resides.
                    This location is within the working directory
                    (<code class="filename"><a class="link" href="#var-WORKDIR" title="WORKDIR">WORKDIR</a></code>), which
                    is not static.
                    The unpacked source location depends on the package name
                    (<code class="filename"><a class="link" href="#var-PN" title="PN">PN</a></code>) and
                    package version (<code class="filename"><a class="link" href="#var-PV" title="PV">PV</a></code>) as
                    follows:
                    </p><pre class="literallayout">
 ${WORKDIR}/${PN}/${PV}
                    </pre><p>
                    As an example, assume a
                    <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#source-directory" target="_top">Source Directory</a> top-level
                    folder named <code class="filename">poky</code>
                    and a default <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#build-directory" target="_top">Build Directory</a>
                    at <code class="filename">poky/build</code>.
                    In this case, the working directory the build system uses to build
                    the <code class="filename">db</code> package is the following:
                    </p><pre class="literallayout">
 ~/poky/build/tmp/work/qemux86-poky-linux/db/5.1.19-r3/db-5.1.19
                    </pre><p>
                </p></dd><dt><a id="var-SDKIMAGE_FEATURES"></a>SDKIMAGE_FEATURES</dt><dd><p>Equivalent to
                <code class="filename"><a class="link" href="#var-IMAGE_FEATURES" title="IMAGE_FEATURES">IMAGE_FEATURES</a></code>.
                However, this variable applies to the SDK generated from an image using
                <code class="filename">bitbake -c populate_sdk imagename</code>).
                </p></dd><dt><a id="var-SECTION"></a>SECTION</dt><dd><p>The section in which packages should be categorized.
                    Package management utilities can make use of this variable.</p></dd><dt><a id="var-SELECTED_OPTIMIZATION"></a>SELECTED_OPTIMIZATION</dt><dd><p>
                    The variable takes the value of
                    <code class="filename"><a class="link" href="#var-FULL_OPTIMIZATION" title="FULL_OPTIMIZATION">FULL_OPTIMIZATION</a></code>
                    unless <code class="filename"><a class="link" href="#var-DEBUG_BUILD" title="DEBUG_BUILD">DEBUG_BUILD</a></code> = "1".
                    In this case the value of
                    <code class="filename"><a class="link" href="#var-DEBUG_OPTIMIZATION" title="DEBUG_OPTIMIZATION">DEBUG_OPTIMIZATION</a></code> is used.
                </p></dd><dt><a id="var-SERIAL_CONSOLE"></a>SERIAL_CONSOLE</dt><dd><p>The speed and device for the serial port used to attach the serial console.
                    This variable is given to the kernel as the "console"
                    parameter and after booting occurs <code class="filename">getty</code> is started on that port
                    so remote login is possible.</p></dd><dt><a id="var-SITEINFO_ENDIANNESS"></a>SITEINFO_ENDIANNESS</dt><dd><p>
                    Specifies the endian byte order of the target system.
                    The value should be either "le" for little-endian or "be" for big-endian.
                </p></dd><dt><a id="var-SITEINFO_BITS"></a>SITEINFO_BITS</dt><dd><p>
                    Specifies the number of bits for the target system CPU.
                    The value should be either "32" or "64".
                </p></dd><dt><a id="var-SPECIAL_PKGSUFFIX"></a>SPECIAL_PKGSUFFIX</dt><dd><p>
                    A list of prefixes for <a class="link" href="#var-PN" title="PN"><code class="filename">PN</code></a> used by the
                    OpenEmbedded build system to create variants of recipes or packages.
                    The list specifies the prefixes to strip off during certain circumstances
                    such as the generation of the <a class="link" href="#var-BPN" title="BPN"><code class="filename">BPN</code></a> variable.
                </p></dd><dt><a id="var-SRC_URI"></a>SRC_URI</dt><dd><p>The list of source files - local or remote.
                    This variable tells the OpenEmbedded build system which bits to pull
                    in for the build and how to pull them in.
                    For example, if the recipe only needs to fetch a tarball from the
                    internet, the recipe uses a single <code class="filename">SRC_URI</code> entry.
                    On the other hand, if the recipe needs to fetch a tarball, apply
                    two patches, and include a custom file, the recipe would include four
                    instances of the variable.</p><p>The following list explains the available URI protocols:
                    </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em><code class="filename">file://</code> -</em></span> Fetches files, which is usually
                            a file shipped with the metadata, from the local machine.
                            The path is relative to the
                            <a class="link" href="#var-FILESPATH" title="FILESPATH"><code class="filename">FILESPATH</code></a>
                            variable.
                            Thus, the build system searches, in order, from the following directories,
                            which are assumed to be a subdirectories of the directory in which the
                            recipe file resides:
                            </p><div class="itemizedlist"><ul class="itemizedlist" type="circle"><li class="listitem"><p><span class="emphasis"><em><code class="filename">${PN}</code> -</em></span> The recipe name
                                    with any special suffix or prefix, if applicable.
                                    For example, using <code class="filename">bash</code> to build for the native
                                    machine, <code class="filename">PN</code> is <code class="filename">bash-native</code>.
                                    Using <code class="filename">bash</code> to build for the target and for Multilib,
                                    <code class="filename">PN</code> would be <code class="filename">bash</code> and
                                    <code class="filename">lib64-bash</code>, respectively.
                                    </p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">${PF}</code> - </em></span>
                                    <code class="filename">${PN}-${EXTENDPE}${PV}-${PR}</code>.
                                    The recipe name including all version and revision numbers
                                    (i.e. <code class="filename">eglibc-2.13-r20+svnr15508/</code> and
                                    <code class="filename">bash-4.2-r1/</code>).</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">${P}</code> -</em></span>
                                    <code class="filename">${PN}-${PV}</code>.
                                    The recipe name and version (i.e. <code class="filename">bash-4.2</code>).
                                    </p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">${BPN}</code> -</em></span> The
                                    base recipe name without any special suffix or version numbers.
                                    </p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">${BP}</code> -</em></span>
                                    <code class="filename">${BPN}-${PV}</code>.
                                    The base recipe name and version but without any special
                                    package name suffix.</p></li><li class="listitem"><p><span class="emphasis"><em>Files -</em></span> Files beneath the directory in which the recipe
                                    resides.</p></li><li class="listitem"><p><span class="emphasis"><em>Directory -</em></span> The directory itself in which the recipe
                                    resides.</p></li></ul></div></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">bzr://</code> -</em></span> Fetches files from a
                            Bazaar revision control repository.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">git://</code> -</em></span> Fetches files from a
                            Git revision control repository.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">osc://</code> -</em></span> Fetches files from
                            an OSC (OpenSuse Build service) revision control repository.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">repo://</code> -</em></span> Fetches files from
                            a repo (Git) repository.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">svk://</code> -</em></span> Fetches files from
                            an SVK revision control repository.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">http://</code> -</em></span> Fetches files from
                            the Internet using <code class="filename">http</code>.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">https://</code> -</em></span> Fetches files
                            from the Internet using <code class="filename">https</code>.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">ftp://</code> -</em></span> Fetches files
                            from the Internet using <code class="filename">ftp</code>.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">cvs://</code> -</em></span> Fetches files from
                            a CVS revision control repository.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">hg://</code> -</em></span> Fetches files from
                            a Mercurial (<code class="filename">hg</code>) revision control repository.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">p4://</code> -</em></span> Fetches files from
                            a Perforce (<code class="filename">p4</code>) revision control repository.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">ssh://</code> -</em></span> Fetches files from
                            a secure shell.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">svn://</code> -</em></span> Fetches files from
                            a Subversion (<code class="filename">svn</code>) revision control repository.</p></li></ul></div><p>
                </p><p>Standard and recipe-specific options for <code class="filename">SRC_URI</code> exist.
                    Here are standard options:
                    </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em><code class="filename">apply</code> -</em></span> Whether to apply
                            the patch or not.
                            The default action is to apply the patch.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">striplevel</code> -</em></span> Which
                            striplevel to use when applying the patch.
                            The default level is 1.</p></li></ul></div><p>
                </p><p>Here are options specific to recipes building code from a revision control system:
                    </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em><code class="filename">mindate</code> -</em></span> Only applies
                            the patch if <a class="link" href="#var-SRCDATE" title="SRCDATE"><code class="filename">SRCDATE</code></a>
                            is equal to or greater than <code class="filename">mindate</code>.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">maxdate</code> -</em></span> Only applies
                            the patch if <a class="link" href="#var-SRCDATE" title="SRCDATE"><code class="filename">SRCDATE</code></a>
                            is not later than <code class="filename">mindate</code>.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">minrev</code> -</em></span> Only applies
                            the patch if <a class="link" href="#var-SRCREV" title="SRCREV"><code class="filename">SRCREV</code></a>
                            is equal to or greater than <code class="filename">minrev</code>.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">maxrev</code> -</em></span> Only applies
                            the patch if <a class="link" href="#var-SRCREV" title="SRCREV"><code class="filename">SRCREV</code></a>
                            is not later than <code class="filename">maxrev</code>.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">rev</code> -</em></span> Only applies the
                            patch if <a class="link" href="#var-SRCREV" title="SRCREV"><code class="filename">SRCREV</code></a>
                            is equal to <code class="filename">rev</code>.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">notrev</code> -</em></span> Only applies
                            the patch if <a class="link" href="#var-SRCREV" title="SRCREV"><code class="filename">SRCREV</code></a>
                            is not equal to <code class="filename">rev</code>.</p></li></ul></div><p>
                </p><p>Here are some additional options worth mentioning:
                    </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em><code class="filename">unpack</code> -</em></span> Controls
                            whether or not to unpack the file if it is an archive.
                            The default action is to upack the file.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">subdir</code> -</em></span> Places the file
                            (or extracts its contents) into the specified
                            subdirectory of <a class="link" href="#var-WORKDIR" title="WORKDIR"><code class="filename">WORKDIR</code></a>.
                            This option is useful for unusual tarballs or other archives that
                            don't have their files already in a subdirectory within the archive.
                            </p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">name</code> -</em></span> Specifies a
                            name to be used for association with <code class="filename">SRC_URI</code> checksums
                            when you have more than one file specified in <code class="filename">SRC_URI</code>.
                            </p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">downloadfilename</code> -</em></span> Specifies
                            the filename used when storing the downloaded file.</p></li></ul></div><p>
                </p></dd><dt><a id="var-SRC_URI_OVERRIDES_PACKAGE_ARCH"></a>SRC_URI_OVERRIDES_PACKAGE_ARCH</dt><dd><p></p><p>
                    By default, the OpenEmbedded build system automatically detects whether
                    <code class="filename"><a class="link" href="#var-SRC_URI" title="SRC_URI">SRC_URI</a></code>
                    contains files that are machine-specific.
                    If so, the build system automatically changes
                    <code class="filename"><a class="link" href="#var-PACKAGE_ARCH" title="PACKAGE_ARCH">PACKAGE_ARCH</a></code>.
                    Setting this variable to "0" disables this behavior.
                </p></dd><dt><a id="var-SRCDATE"></a>SRCDATE</dt><dd><p>
                    The date of the source code used to build the package.
                    This variable applies only if the source was fetched from a Source Code Manager (SCM).
                </p></dd><dt><a id="var-SRCREV"></a>SRCREV</dt><dd><p>
                    The revision of the source code used to build the package.
                    This variable applies to Subversion, Git, Mercurial and Bazaar
                    only.
                    Note that if you wish to build a fixed revision and you wish
                    to avoid performing a query on the remote repository every time
                    BitBake parses your recipe, you should specify a <code class="filename">SRCREV</code> that is a
                    full revision identifier and not just a tag.
                </p></dd><dt><a id="var-SSTATE_DIR"></a>SSTATE_DIR</dt><dd><p>The directory for the shared state.</p></dd><dt><a id="var-SSTATE_MIRRORS"></a>SSTATE_MIRRORS</dt><dd><p>
                    Configures the OpenEmbedded build system to search other
                    mirror locations for prebuilt cache data objects before
                    building out the data.
                    This variable works like fetcher
                    <code class="filename">MIRRORS</code>/<code class="filename">PREMIRRORS</code>
                    and points to the cache locations to check for the shared
                    objects.
                </p><p>
                    You can specify a filesystem directory or a remote URL such
                    as HTTP or FTP.
                    The locations you specify need to contain the shared state
                    cache (sstate-cache) results from previous builds.
                    The sstate-cache you point to can also be from builds on
                    other machines.
                </p><p>
                    If a mirror uses the same structure as
                    <a class="link" href="#var-SSTATE_DIR" title="SSTATE_DIR"><code class="filename">SSTATE_DIR</code></a>,
                    you need to add
                    "PATH" at the end as shown in the examples below.
                    The build system substitues the correct path within the
                    directory structure.
                    </p><pre class="literallayout">
     SSTATE_MIRRORS ?= "\
     file://.* http://someserver.tld/share/sstate/PATH \n \
     file://.* file:///some/local/dir/sstate/PATH"
                    </pre><p>
                </p></dd><dt><a id="var-STAGING_KERNEL_DIR"></a>STAGING_KERNEL_DIR</dt><dd><p>
                    The directory with kernel headers that are required to build out-of-tree
                    modules.
                </p></dd><dt><a id="var-STAMP"></a>STAMP</dt><dd><p>
                    Specifies the base path used to create recipe stamp files.
                    The path to an actual stamp file is constructed by evaluating this
                    string and then appending additional information.
                    Currently, the default assignment for <code class="filename">STAMP</code>
                    as set in the <code class="filename">meta/conf/bitbake.conf</code> file
                    is:
                    </p><pre class="literallayout">
     STAMP = "${TMPDIR}/stamps/${MULTIMACH_TARGET_SYS}/${PN}/${EXTENDPE}${PV}-${PR}"
                    </pre><p>
                    See <a class="link" href="#var-TMPDIR" title="TMPDIR"><code class="filename">TMPDIR</code></a>,
                    <a class="link" href="#var-MULTIMACH_TARGET_SYS" title="MULTIMACH_TARGET_SYS"><code class="filename">MULTIMACH_TARGET_SYS</code></a>,
                    <a class="link" href="#var-PN" title="PN"><code class="filename">PN</code></a>,
                    <a class="link" href="#var-EXTENDPE" title="EXTENDPE"><code class="filename">EXTENDPE</code></a>,
                    <a class="link" href="#var-PV" title="PV"><code class="filename">PV</code></a>, and
                    <a class="link" href="#var-PR" title="PR"><code class="filename">PR</code></a> for related variable
                    information.
                </p></dd><dt><a id="var-SUMMARY"></a>SUMMARY</dt><dd><p>The short (72 characters or less) summary of the binary package for packaging
                    systems such as <code class="filename">opkg</code>, <code class="filename">rpm</code> or
                    <code class="filename">dpkg</code>.
                    By default, <code class="filename">SUMMARY</code> is used to define
                    the <a class="link" href="#var-DESCRIPTION" title="DESCRIPTION"><code class="filename">DESCRIPTION</code></a>
                    variable if <code class="filename">DESCRIPTION</code> is not set
                    in the recipe.
                </p></dd></dl></div><div class="glossdiv" title="T"><h3 class="title">T</h3><dl><dt><a id="var-T"></a>T</dt><dd><p>This variable points to a directory were Bitbake places temporary
                    files when building a particular package.
                    It is typically set as follows:
                    </p><pre class="literallayout">
     T = ${WORKDIR}/temp
                    </pre><p>
                    The <a class="link" href="#var-WORKDIR" title="WORKDIR"><code class="filename">WORKDIR</code></a>
                    is the directory into which Bitbake unpacks and builds the package.
                    The default <code class="filename">bitbake.conf</code> file sets this variable.</p><p>The <code class="filename">T</code> variable is not to be confused with
                    the <a class="link" href="#var-TMPDIR" title="TMPDIR"><code class="filename">TMPDIR</code></a> variable,
                    which points to the root of the directory tree where Bitbake
                    places the output of an entire build.
                </p></dd><dt><a id="var-TARGET_ARCH"></a>TARGET_ARCH</dt><dd><p>The architecture of the device being built.
                While a number of values are possible, the OpenEmbedded build system primarily supports
                <code class="filename">arm</code> and <code class="filename">i586</code>.</p></dd><dt><a id="var-TARGET_CFLAGS"></a>TARGET_CFLAGS</dt><dd><p>
                    Flags passed to the C compiler for the target system.
                    This variable evaluates to the same as
                    <code class="filename"><a class="link" href="#var-CFLAGS" title="CFLAGS">CFLAGS</a></code>.
                </p></dd><dt><a id="var-TARGET_FPU"></a>TARGET_FPU</dt><dd><p>Specifies the method for handling FPU code.
                    For FPU-less targets, which include most ARM CPUs, the variable must be
                    set to "soft".
                    If not, the kernel emulation gets used, which results in a performance penalty.</p></dd><dt><a id="var-TARGET_OS"></a>TARGET_OS</dt><dd><p>Specifies the target's operating system.
                    The variable can be set to "linux" for <code class="filename">eglibc</code>-based systems and
                    to "linux-uclibc" for <code class="filename">uclibc</code>.
                    For ARM/EABI targets, there are also "linux-gnueabi" and
                    "linux-uclibc-gnueabi" values possible.</p></dd><dt><a id="var-TCLIBC"></a>TCLIBC</dt><dd><p>
                    Specifies which variant of the GNU standard C library (<code class="filename">libc</code>)
                    to use during the build process.
                    This variable replaces <code class="filename">POKYLIBC</code>, which is no longer
                    supported.
                </p><p>
                    You can select <code class="filename">eglibc</code> or <code class="filename">uclibc</code>.
                    </p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
                        This release of the Yocto Project does not support the
                        <code class="filename">glibc</code> implementation of <code class="filename">libc</code>.
                    </div><p>
                </p></dd><dt><a id="var-TCMODE"></a>TCMODE</dt><dd><p>
                    The toolchain selector.
                    This variable replaces <code class="filename">POKYMODE</code>, which is no longer
                    supported.
                </p><p>
                    The <code class="filename">TCMODE</code> variable selects the external toolchain
                    built using the OpenEmbedded build system or a few supported combinations of
                    the upstream GCC or CodeSourcery Labs toolchain.
                    The variable identifies the <code class="filename">tcmode-*</code> files used in
                    the <code class="filename">meta/conf/distro/include</code> directory, which is found in the
                    <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#source-directory" target="_top">Source Directory</a>.
                </p><p>
                    By default, <code class="filename">TCMODE</code> is set to "default", which
                    chooses the <code class="filename">tcmode-default.inc</code> file.
                    The variable is similar to
                    <a class="link" href="#var-TCLIBC" title="TCLIBC"><code class="filename">TCLIBC</code></a>, which controls
                    the variant of the GNU standard C library (<code class="filename">libc</code>)
                    used during the build process: <code class="filename">eglibc</code> or <code class="filename">uclibc</code>.
                </p></dd><dt><a id="var-TMPDIR"></a>TMPDIR</dt><dd><p>
                    This variable is the temporary directory the OpenEmbedded build system
                    uses when it does its work building images.
                    By default, the <code class="filename">TMPDIR</code> variable is named
                    <code class="filename">tmp</code> within the
                    <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#build-directory" target="_top">Build Directory</a>.
                </p><p>
                    If you want to establish this directory in a location other than the
                    default, you can uncomment the following statement in the
                    <code class="filename">conf/local.conf</code> file in the
                    <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#source-directory" target="_top">Source Directory</a>:
                    </p><pre class="literallayout">
     #TMPDIR = "${TOPDIR}/tmp"
                    </pre><p>
                </p></dd><dt><a id="var-TOPDIR"></a>TOPDIR</dt><dd><p>
                    This variable is the
                    <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#build-directory" target="_top">Build Directory</a>.
                    BitBake automatically sets this variable.
                    The OpenEmbedded build system uses the Build Directory when building images.
                </p></dd></dl></div><div class="glossdiv" title="W"><h3 class="title">W</h3><dl><dt><a id="var-WORKDIR"></a>WORKDIR</dt><dd><p>
                    The pathname of the working directory in which the OpenEmbedded build system
                    builds a recipe.
                    This directory is located within the
                    <a class="link" href="#var-TMPDIR" title="TMPDIR"><code class="filename">TMPDIR</code></a> directory structure and changes
                    as different packages are built.
                </p><p>
                    The actual <code class="filename">WORKDIR</code> directory depends on several things:
                    </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem">The temporary directory - <a class="link" href="#var-TMPDIR" title="TMPDIR"><code class="filename">TMPDIR</code></a></li><li class="listitem">The package architecture - <a class="link" href="#var-PACKAGE_ARCH" title="PACKAGE_ARCH"><code class="filename">PACKAGE_ARCH</code></a></li><li class="listitem">The target machine - <a class="link" href="#var-MACHINE" title="MACHINE"><code class="filename">MACHINE</code></a></li><li class="listitem">The target operating system - <a class="link" href="#var-TARGET_OS" title="TARGET_OS"><code class="filename">TARGET_OS</code></a></li><li class="listitem">The recipe name - <a class="link" href="#var-PN" title="PN"><code class="filename">PN</code></a></li><li class="listitem">The recipe version - <a class="link" href="#var-PV" title="PV"><code class="filename">PV</code></a></li><li class="listitem">The recipe revision - <a class="link" href="#var-PR" title="PR"><code class="filename">PR</code></a></li></ul></div><p>
                </p><p>
                    For packages that are not dependent on a particular machine,
                    <code class="filename">WORKDIR</code> is defined as follows:
                    </p><pre class="literallayout">
 ${TMPDIR}/work/${PACKAGE_ARCH}-poky-${TARGET_OS}/${PN}/${PV}-${PR}
                    </pre><p>
                    As an example, assume a
                    <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#source-directory" target="_top">Source Directory</a> top-level
                    folder name <code class="filename">poky</code> and a default
                    <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#build-directory" target="_top">Build Directory</a>
                    at <code class="filename">poky/build</code>.
                    In this case, the working directory the build system uses to build
                    the <code class="filename">v86d</code> package is the following:
                    </p><pre class="literallayout">
     ~/poky/build/tmp/work/qemux86-poky-linux/v86d/01.9-r0
                    </pre><p>
                </p><p>
                    For packages that are dependent on a particular machine, <code class="filename">WORKDIR</code>
                    is defined slightly different:
                    </p><pre class="literallayout">
 ${TMPDIR}/work/${MACHINE}-poky-${TARGET_OS}/${PN}/${PV}-${PR}
                    </pre><p>
                    As an example, again assume a Source Directory top-level folder
                    named <code class="filename">poky</code> and a default Build Directory
                    at <code class="filename">poky/build</code>.
                    In this case, the working directory the build system uses to build
                    the <code class="filename">acl</code> recipe, which is being built for a
                    MIPS-based device, is the following:
                    </p><pre class="literallayout">
     ~/poky/build/tmp/work/mips-poky-linux/acl/2.2.51-r2
                    </pre><p>
                </p></dd></dl></div></div></div>

    <div class="chapter" title="Chapter 11. Variable Context"><div class="titlepage"><div><div><h2 class="title"><a id="ref-varlocality"></a>Chapter 11. Variable Context</h2></div></div></div><div class="toc"><p><strong>Table of Contents</strong></p><dl><dt><span class="section"><a href="#ref-varlocality-configuration">11.1. Configuration</a></span></dt><dd><dl><dt><span class="section"><a href="#ref-varlocality-config-distro">11.1.1. Distribution (Distro)</a></span></dt><dt><span class="section"><a href="#ref-varlocality-config-machine">11.1.2. Machine</a></span></dt><dt><span class="section"><a href="#ref-varlocality-config-local">11.1.3. Local</a></span></dt></dl></dd><dt><span class="section"><a href="#ref-varlocality-recipes">11.2. Recipes</a></span></dt><dd><dl><dt><span class="section"><a href="#ref-varlocality-recipe-required">11.2.1. Required</a></span></dt><dt><span class="section"><a href="#ref-varlocality-recipe-dependencies">11.2.2. Dependencies</a></span></dt><dt><span class="section"><a href="#ref-varlocality-recipe-paths">11.2.3. Paths</a></span></dt><dt><span class="section"><a href="#ref-varlocality-recipe-build">11.2.4. Extra Build Information</a></span></dt></dl></dd></dl></div><p>
        While most variables can be used in almost any context such as
        <code class="filename">.conf</code>, <code class="filename">.bbclass</code>,
        <code class="filename">.inc</code>, and <code class="filename">.bb</code> files,
        some variables are often associated with a particular locality or context.
        This chapter describes some common associations.
    </p><div class="section" title="11.1. Configuration"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-varlocality-configuration"></a>11.1. Configuration</h2></div></div></div><p>
            The following subsections provide lists of variables whose context is
            configuration: distribution, machine, and local.
        </p><div class="section" title="11.1.1. Distribution (Distro)"><div class="titlepage"><div><div><h3 class="title"><a id="ref-varlocality-config-distro"></a>11.1.1. Distribution (Distro)</h3></div></div></div><p>
               This section lists variables whose context is the distribution, or distro.
               </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><code class="filename"><a class="link" href="#var-DISTRO" title="DISTRO">DISTRO</a></code></p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-DISTRO_NAME" title="DISTRO_NAME">DISTRO_NAME</a></code>
                       </p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-DISTRO_VERSION" title="DISTRO_VERSION">DISTRO_VERSION</a>
                       </code></p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-MAINTAINER" title="MAINTAINER">MAINTAINER</a></code>
                       </p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-PACKAGE_CLASSES" title="PACKAGE_CLASSES">PACKAGE_CLASSES</a>
                       </code></p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-TARGET_OS" title="TARGET_OS">TARGET_OS</a></code>
                       </p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-TARGET_FPU" title="TARGET_FPU">TARGET_FPU</a></code>
                       </p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-TCMODE" title="TCMODE">TCMODE</a></code>
                       </p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-TCLIBC" title="TCLIBC">TCLIBC</a></code>
                       </p></li></ul></div><p>
            </p></div><div class="section" title="11.1.2. Machine"><div class="titlepage"><div><div><h3 class="title"><a id="ref-varlocality-config-machine"></a>11.1.2. Machine</h3></div></div></div><p>
                This section lists variables whose context is the machine.
                </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><code class="filename"><a class="link" href="#var-TARGET_ARCH" title="TARGET_ARCH">TARGET_ARCH</a></code>
                        </p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-SERIAL_CONSOLE" title="SERIAL_CONSOLE">SERIAL_CONSOLE</a>
                        </code></p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-PACKAGE_EXTRA_ARCHS" title="PACKAGE_EXTRA_ARCHS">PACKAGE_EXTRA_ARCHS</a>
                        </code></p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-IMAGE_FSTYPES" title="IMAGE_FSTYPES">IMAGE_FSTYPES</a>
                        </code></p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-MACHINE_FEATURES" title="MACHINE_FEATURES">MACHINE_FEATURES</a>
                        </code></p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-MACHINE_EXTRA_RDEPENDS" title="MACHINE_EXTRA_RDEPENDS">MACHINE_EXTRA_RDEPENDS
                        </a></code></p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-MACHINE_EXTRA_RRECOMMENDS" title="MACHINE_EXTRA_RRECOMMENDS">MACHINE_EXTRA_RRECOMMENDS
                        </a></code></p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-MACHINE_ESSENTIAL_EXTRA_RDEPENDS" title="MACHINE_ESSENTIAL_EXTRA_RDEPENDS">MACHINE_ESSENTIAL_EXTRA_RDEPENDS
                        </a></code></p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS" title="MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS">
                        MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS</a></code></p></li></ul></div><p>
            </p></div><div class="section" title="11.1.3. Local"><div class="titlepage"><div><div><h3 class="title"><a id="ref-varlocality-config-local"></a>11.1.3. Local</h3></div></div></div><p>
                This section lists variables whose context is the local configuration through the
                <code class="filename">local.conf</code> file.
                </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><code class="filename"><a class="link" href="#var-DISTRO" title="DISTRO">DISTRO</a></code>
                        </p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-MACHINE" title="MACHINE">MACHINE</a></code>
                        </p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-DL_DIR" title="DL_DIR">DL_DIR</a></code>
                        </p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-BBFILES" title="BBFILES">BBFILES</a></code>
                        </p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-EXTRA_IMAGE_FEATURES" title="EXTRA_IMAGE_FEATURES">EXTRA_IMAGE_FEATURES
                        </a></code></p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-PACKAGE_CLASSES" title="PACKAGE_CLASSES">PACKAGE_CLASSES</a>
                        </code></p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-BB_NUMBER_THREADS" title="BB_NUMBER_THREADS">BB_NUMBER_THREADS</a>
                        </code></p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-BBINCLUDELOGS" title="BBINCLUDELOGS">BBINCLUDELOGS</a>
                        </code></p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-ENABLE_BINARY_LOCALE_GENERATION" title="ENABLE_BINARY_LOCALE_GENERATION">
                        ENABLE_BINARY_LOCALE_GENERATION</a></code></p></li></ul></div><p>
            </p></div></div><div class="section" title="11.2. Recipes"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-varlocality-recipes"></a>11.2. Recipes</h2></div></div></div><p>
            The following subsections provide lists of variables whose context is
            recipes: required, dependencies, path, and extra build information.
        </p><div class="section" title="11.2.1. Required"><div class="titlepage"><div><div><h3 class="title"><a id="ref-varlocality-recipe-required"></a>11.2.1. Required</h3></div></div></div><p>
                This section lists variables that are required for recipes.
                </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><code class="filename"><a class="link" href="#var-LICENSE" title="LICENSE">LICENSE</a>
                        </code></p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-LIC_FILES_CHKSUM" title="LIC_FILES_CHKSUM">LIC_FILES_CHKSUM</a>
                        </code></p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-SRC_URI" title="SRC_URI">SRC_URI</a></code> - used
                        in recipes that fetch local or remote files.
                        </p></li></ul></div><p>
            </p></div><div class="section" title="11.2.2. Dependencies"><div class="titlepage"><div><div><h3 class="title"><a id="ref-varlocality-recipe-dependencies"></a>11.2.2. Dependencies</h3></div></div></div><p>
                This section lists variables that define recipe dependencies.
                </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><code class="filename"><a class="link" href="#var-DEPENDS" title="DEPENDS">DEPENDS</a>
                        </code></p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-RDEPENDS" title="RDEPENDS">RDEPENDS</a>
                        </code></p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-RRECOMMENDS" title="RRECOMMENDS">RRECOMMENDS</a>
                        </code></p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-RCONFLICTS" title="RCONFLICTS">RCONFLICTS</a>
                        </code></p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-RREPLACES" title="RREPLACES">RREPLACES</a>
                        </code></p></li></ul></div><p>
            </p></div><div class="section" title="11.2.3. Paths"><div class="titlepage"><div><div><h3 class="title"><a id="ref-varlocality-recipe-paths"></a>11.2.3. Paths</h3></div></div></div><p>
                This section lists variables that define recipe paths.
                </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><code class="filename"><a class="link" href="#var-WORKDIR" title="WORKDIR">WORKDIR</a>
                        </code></p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-S" title="S">S</a>
                        </code></p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-FILES" title="FILES">FILES</a>
                        </code></p></li></ul></div><p>
            </p></div><div class="section" title="11.2.4. Extra Build Information"><div class="titlepage"><div><div><h3 class="title"><a id="ref-varlocality-recipe-build"></a>11.2.4. Extra Build Information</h3></div></div></div><p>
                This section lists variables that define extra build information for recipes.
                </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><code class="filename"><a class="link" href="#var-EXTRA_OECMAKE" title="EXTRA_OECMAKE">EXTRA_OECMAKE</a>
                        </code></p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-EXTRA_OECONF" title="EXTRA_OECONF">EXTRA_OECONF</a>
                        </code></p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-EXTRA_OEMAKE" title="EXTRA_OEMAKE">EXTRA_OEMAKE</a>
                        </code></p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-PACKAGES" title="PACKAGES">PACKAGES</a></code>
                        </p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-DEFAULT_PREFERENCE" title="DEFAULT_PREFERENCE">DEFAULT_PREFERENCE
                        </a></code></p></li></ul></div><p>
            </p></div></div></div>

    <div class="chapter" title="Chapter 12. FAQ"><div class="titlepage"><div><div><h2 class="title"><a id="faq"></a>Chapter 12. FAQ</h2></div></div></div><div class="qandaset" title="Frequently Asked Questions"><a id="idm975296"></a><dl><dt>12.1. <a href="#idm974832">
                How does Poky differ from OpenEmbedded?
            </a></dt><dt>12.2. <a href="#idp1801248">
                I only have Python 2.4 or 2.5 but BitBake requires Python 2.6 or 2.7.
                Can I still use the Yocto Project?
            </a></dt><dt>12.3. <a href="#idm1781424">
                How can you claim Poky / OpenEmbedded-Core is stable?
            </a></dt><dt>12.4. <a href="#idm1777456">
                How do I get support for my board added to the Yocto Project?
            </a></dt><dt>12.5. <a href="#idm345792">
                Are there any products built using the OpenEmbedded build system?
            </a></dt><dt>12.6. <a href="#idm343136">
                What does the OpenEmbedded build system produce as output?
            </a></dt><dt>12.7. <a href="#idm341840">
                How do I add my package to the Yocto Project?
            </a></dt><dt>12.8. <a href="#idp1600368">
                Do I have to reflash my entire board with a new Yocto Project image when recompiling
                a package?
            </a></dt><dt>12.9. <a href="#idp1603824">
                What is GNOME Mobile and what is the difference between GNOME Mobile and GNOME?
            </a></dt><dt>12.10. <a href="#idp1605872">
                I see the error 'chmod: XXXXX new permissions are r-xrwxrwx, not r-xr-xr-x'.
                What is wrong?
            </a></dt><dt>12.11. <a href="#idp1662416">
                How do I make the Yocto Project work in RHEL/CentOS?
            </a></dt><dt>12.12. <a href="#idp562304">
                I see lots of 404 responses for files on
                http://www.yoctoproject.org/sources/*. Is something wrong?
            </a></dt><dt>12.13. <a href="#idp179952">
                I have machine-specific data in a package for one machine only but the package is
                being marked as machine-specific in all cases, how do I prevent this?
            </a></dt><dt>12.14. <a href="#idp184672">
                I'm behind a firewall and need to use a proxy server. How do I do that?
            </a></dt><dt>12.15. <a href="#idp1585952">
                What’s the difference between foo and foo-native?
            </a></dt><dt>12.16. <a href="#idp3269536">
                I'm seeing random build failures. Help?!
            </a></dt><dt>12.17. <a href="#idp3271104">
                What do we need to ship for license compliance?
            </a></dt><dt>12.18. <a href="#idp3272560">
                How do I disable the cursor on my touchscreen device?
            </a></dt><dt>12.19. <a href="#idp3244640">
                How do I make sure connected network interfaces are brought up by default?
            </a></dt><dt>12.20. <a href="#idp3248256">
                How do I create images with more free space?
            </a></dt><dt>12.21. <a href="#idp348464">
                Why don't you support directories with spaces in the pathnames?
            </a></dt><dt>12.22. <a href="#idp350512">
                How do I use an external toolchain?
            </a></dt><dt>12.23. <a href="#idm184288">
                How does the OpenEmbedded build system obtain source code and will it work behind my
                firewall or proxy server?
            </a></dt><dt>12.24. <a href="#idm1036560">
                Can I get rid of build output so I can start over?
            </a></dt></dl><table border="0" width="100%" summary="Q and A Set"><col align="left" width="1%" /><col /><tbody><tr class="question" title="12.1."><td align="left" valign="top"><a id="idm974832"></a><a id="idm974704"></a><p><strong>12.1.</strong></p></td><td align="left" valign="top"><p>
                How does Poky differ from <a class="ulink" href="http://www.openembedded.org" target="_top">OpenEmbedded</a>?
            </p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p>
                The term "Poky" refers to the specific reference build system that
                the Yocto Project provides.
                Poky is based on <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#oe-core" target="_top">OE-Core</a>
                and BitBake.
                Thus, the generic term used here for the build system is
                the "OpenEmbedded build system."
                Development in the Yocto Project using Poky is closely tied to OpenEmbedded, with
                changes always being merged to OE-Core or BitBake first before being pulled back
                into Poky.
                This practice benefits both projects immediately.
                For a fuller description of the term "Poky", see the
                <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#poky" target="_top">poky</a> term in the Yocto Project
                Development Manual.
            </p></td></tr><tr class="question" title="12.2."><td align="left" valign="top"><a id="idp1801248"></a><a id="idp1801376"></a><p><strong>12.2.</strong></p></td><td align="left" valign="top"><p>
                I only have Python 2.4 or 2.5 but BitBake requires Python 2.6 or 2.7.
                Can I still use the Yocto Project?
            </p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p>
                You can use a stand-alone tarball to provide Python 2.6.
                You can find pre-built 32 and 64-bit versions of Python 2.6 at the following locations:
                </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><a class="ulink" href="http://downloads.yoctoproject.org/releases/miscsupport/python-nativesdk-standalone-i686.tar.bz2" target="_top">32-bit tarball</a></p></li><li class="listitem"><p><a class="ulink" href="http://downloads.yoctoproject.org/releases/miscsupport/python-nativesdk-standalone-x86_64.tar.bz2" target="_top">64-bit tarball</a></p></li></ul></div><p>
            </p><p>
                These tarballs are self-contained with all required libraries and should work
                on most Linux systems.
                To use the tarballs extract them into the root
                directory and run the appropriate command:
                </p><pre class="literallayout">
     $ export PATH=/opt/poky/sysroots/i586-pokysdk-linux/usr/bin/:$PATH
     $ export PATH=/opt/poky/sysroots/x86_64-pokysdk-linux/usr/bin/:$PATH
                </pre><p>
            </p><p>
                Once you run the command, BitBake uses Python 2.6.
            </p></td></tr><tr class="question" title="12.3."><td align="left" valign="top"><a id="idm1781424"></a><a id="idm1781296"></a><p><strong>12.3.</strong></p></td><td align="left" valign="top"><p>
                How can you claim Poky / OpenEmbedded-Core is stable?
            </p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p>
                There are three areas that help with stability;
                </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>The Yocto Project team keeps
                        <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#oe-core" target="_top">OE-Core</a> small
                        and focused, containing around 830 recipes as opposed to the thousands
                        available in other OpenEmbedded community layers.
                        Keeping it small makes it easy to test and maintain.</p></li><li class="listitem"><p>The Yocto Project team runs manual and automated tests
                        using a small, fixed set of reference hardware as well as emulated
                        targets.</p></li><li class="listitem"><p>The Yocto Project uses an an autobuilder,
                        which provides continuous build and integration tests.</p></li></ul></div><p>
            </p></td></tr><tr class="question" title="12.4."><td align="left" valign="top"><a id="idm1777456"></a><a id="idm1777328"></a><p><strong>12.4.</strong></p></td><td align="left" valign="top"><p>
                How do I get support for my board added to the Yocto Project?
            </p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p>
                Support for an additional board is added by creating a BSP layer for it.
                For more information on how to create a BSP layer, see the
                <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/bsp-guide/bsp-guide.html" target="_top">Yocto Project Board Support Package (BSP) Developer's Guide</a>.
            </p><p>
                Usually, if the board is not completely exotic, adding support in
                the Yocto Project is fairly straightforward.
            </p></td></tr><tr class="question" title="12.5."><td align="left" valign="top"><a id="idm345792"></a><a id="idm345664"></a><p><strong>12.5.</strong></p></td><td align="left" valign="top"><p>
                Are there any products built using the OpenEmbedded build system?
            </p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p>
                The software running on the <a class="ulink" href="http://vernier.com/labquest/" target="_top">Vernier LabQuest</a>
                is built using the OpenEmbedded build system.
                See the <a class="ulink" href="http://www.vernier.com/products/interfaces/labq/" target="_top">Vernier LabQuest</a>
                website for more information.
                There are a number of pre-production devices using the OpenEmbedded build system
                and the Yocto Project team
                announces them as soon as they are released.
            </p></td></tr><tr class="question" title="12.6."><td align="left" valign="top"><a id="idm343136"></a><a id="idm343008"></a><p><strong>12.6.</strong></p></td><td align="left" valign="top"><p>
                What does the OpenEmbedded build system produce as output?
            </p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p>
                Because the same set of recipes can be used to create output of various formats, the
                output of an OpenEmbedded build depends on how it was started.
                Usually, the output is a flashable image ready for the target device.
            </p></td></tr><tr class="question" title="12.7."><td align="left" valign="top"><a id="idm341840"></a><a id="idm341712"></a><p><strong>12.7.</strong></p></td><td align="left" valign="top"><p>
                How do I add my package to the Yocto Project?
            </p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p>
                To add a package, you need to create a BitBake recipe.
                For information on how to add a package, see the section
                "<a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#usingpoky-extend-addpkg" target="_top">Adding a Package</a>"
                in the Yocto Project Development Manual.
            </p></td></tr><tr class="question" title="12.8."><td align="left" valign="top"><a id="idp1600368"></a><a id="idp1600496"></a><p><strong>12.8.</strong></p></td><td align="left" valign="top"><p>
                Do I have to reflash my entire board with a new Yocto Project image when recompiling
                a package?
            </p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p>
                The OpenEmbedded build system can build packages in various formats such as
                <code class="filename">ipk</code> for <code class="filename">opkg</code>,
                Debian package (<code class="filename">.deb</code>), or RPM.
                The packages can then be upgraded using the package tools on the device, much like
                on a desktop distribution such as Ubuntu or Fedora.
            </p></td></tr><tr class="question" title="12.9."><td align="left" valign="top"><a id="idp1603824"></a><a id="idp1603952"></a><p><strong>12.9.</strong></p></td><td align="left" valign="top"><p>
                What is GNOME Mobile and what is the difference between GNOME Mobile and GNOME?
            </p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p>
                GNOME Mobile is a subset of the <a class="ulink" href="http://www.gnome.org" target="_top">GNOME</a>
                platform targeted at mobile and embedded devices.
                The the main difference between GNOME Mobile and standard GNOME is that
                desktop-orientated libraries have been removed, along with deprecated libraries,
                creating a much smaller footprint.
            </p></td></tr><tr class="question" title="12.10."><td align="left" valign="top"><a id="idp1605872"></a><a id="idp1606000"></a><p><strong>12.10.</strong></p></td><td align="left" valign="top"><p>
                I see the error '<code class="filename">chmod: XXXXX new permissions are r-xrwxrwx, not r-xr-xr-x</code>'.
                What is wrong?
            </p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p>
                You are probably running the build on an NTFS filesystem.
                Use <code class="filename">ext2</code>, <code class="filename">ext3</code>, or <code class="filename">ext4</code> instead.
            </p></td></tr><tr class="question" title="12.11."><td align="left" valign="top"><a id="idp1662416"></a><a id="idp1662544"></a><p><strong>12.11.</strong></p></td><td align="left" valign="top"><p>
                How do I make the Yocto Project work in RHEL/CentOS?
            </p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p>
                To get the Yocto Project working under RHEL/CentOS 5.1 you need to first
                install some required packages.
                The standard CentOS packages needed are:
                </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>"Development tools" (selected during installation)</p></li><li class="listitem"><p><code class="filename">texi2html</code></p></li><li class="listitem"><p><code class="filename">compat-gcc-34</code></p></li></ul></div><p>
                On top of these, you need the following external packages:
                </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><code class="filename">python-sqlite2</code> from
                        <a class="ulink" href="http://dag.wieers.com/rpm/packages/python-sqlite2/" target="_top">DAG repository</a>
                        </p></li><li class="listitem"><p><code class="filename">help2man</code> from
                        <a class="ulink" href="http://centos.karan.org/el4/extras/stable/x86_64/RPMS/repodata/repoview/help2man-0-1.33.1-2.html" target="_top">Karan repository</a></p></li></ul></div><p>
            </p><p>
                Once these packages are installed, the OpenEmbedded build system will be able
                to build standard images.
                However, there might be a problem with the QEMU emulator segfaulting.
                You can either disable the generation of binary locales by setting
                <code class="filename"><a class="link" href="#var-ENABLE_BINARY_LOCALE_GENERATION" title="ENABLE_BINARY_LOCALE_GENERATION">ENABLE_BINARY_LOCALE_GENERATION</a>
                </code> to "0" or by removing the <code class="filename">linux-2.6-execshield.patch</code>
                from the kernel and rebuilding it since that is the patch that causes the problems with QEMU.
            </p></td></tr><tr class="question" title="12.12."><td align="left" valign="top"><a id="idp562304"></a><a id="idp562432"></a><p><strong>12.12.</strong></p></td><td align="left" valign="top"><p>
                I see lots of 404 responses for files on
                <code class="filename">http://www.yoctoproject.org/sources/*</code>. Is something wrong?
            </p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p>
                Nothing is wrong.
                The OpenEmbedded build system checks any configured source mirrors before downloading
                from the upstream sources.
                The build system does this searching for both source archives and
                pre-checked out versions of SCM managed software.
                These checks help in large installations because it can reduce load on the SCM servers
                themselves.
                The address above is one of the default mirrors configured into the
                build system.
                Consequently, if an upstream source disappears, the team
                can place sources there so builds continue to work.
            </p></td></tr><tr class="question" title="12.13."><td align="left" valign="top"><a id="idp179952"></a><a id="idp180080"></a><p><strong>12.13.</strong></p></td><td align="left" valign="top"><p>
                I have machine-specific data in a package for one machine only but the package is
                being marked as machine-specific in all cases, how do I prevent this?
            </p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p>
                Set <code class="filename"><a class="link" href="#var-SRC_URI_OVERRIDES_PACKAGE_ARCH" title="SRC_URI_OVERRIDES_PACKAGE_ARCH">SRC_URI_OVERRIDES_PACKAGE_ARCH</a>
                </code> = "0" in the <code class="filename">.bb</code> file but make sure the package is
                manually marked as
                machine-specific in the case that needs it.
                The code that handles <code class="filename">SRC_URI_OVERRIDES_PACKAGE_ARCH</code> is in <code class="filename">base.bbclass</code>.
            </p></td></tr><tr class="question" title="12.14."><td align="left" valign="top"><a id="idp184672"></a><a id="idp1581568"></a><p><strong>12.14.</strong></p></td><td align="left" valign="top"><p>
                I'm behind a firewall and need to use a proxy server. How do I do that?
            </p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p>
                Most source fetching by the OpenEmbedded build system is done by <code class="filename">wget</code>
                and you therefore need to specify the proxy settings in a
                <code class="filename">.wgetrc</code> file in your home directory.
                Example settings in that file would be
                </p><pre class="literallayout">
     http_proxy = http://proxy.yoyodyne.com:18023/
     ftp_proxy = http://proxy.yoyodyne.com:18023/
                </pre><p>
                The Yocto Project also includes a <code class="filename">site.conf.sample</code>
                file that shows how to configure CVS and Git proxy servers
                if needed.
            </p></td></tr><tr class="question" title="12.15."><td align="left" valign="top"><a id="idp1585952"></a><a id="idp1586080"></a><p><strong>12.15.</strong></p></td><td align="left" valign="top"><p>
                What’s the difference between <code class="filename">foo</code> and <code class="filename">foo-native</code>?
            </p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p>
                The <code class="filename">*-native</code> targets are designed to run on the system
                being used for the build.
                These are usually tools that are needed to assist the build in some way such as
                <code class="filename">quilt-native</code>, which is used to apply patches.
                The non-native version is the one that runs on the target device.
            </p></td></tr><tr class="question" title="12.16."><td align="left" valign="top"><a id="idp3269536"></a><a id="idp3269664"></a><p><strong>12.16.</strong></p></td><td align="left" valign="top"><p>
                I'm seeing random build failures. Help?!
            </p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p>
                If the same build is failing in totally different and random ways,
                the most likely explanation is that either the hardware you're running the
                build on has some problem, or, if you are running the build under virtualisation,
                the virtualisation probably has bugs.
                The OpenEmbedded build system processes a massive amount of data causing lots of network, disk and
                CPU activity and is sensitive to even single bit failures in any of these areas.
                True random failures have always been traced back to hardware or virtualisation issues.
            </p></td></tr><tr class="question" title="12.17."><td align="left" valign="top"><a id="idp3271104"></a><a id="idp3271232"></a><p><strong>12.17.</strong></p></td><td align="left" valign="top"><p>
                What do we need to ship for license compliance?
            </p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p>
                This is a difficult question and you need to consult your lawyer for the answer
                for your specific case.
                It is worth bearing in mind that for GPL compliance there needs to be enough
                information shipped to allow someone else to rebuild the same end result
                you are shipping.
                This means sharing the source code, any patches applied to it, and also any
                configuration information about how that package was configured and built.
            </p></td></tr><tr class="question" title="12.18."><td align="left" valign="top"><a id="idp3272560"></a><a id="idp3272688"></a><p><strong>12.18.</strong></p></td><td align="left" valign="top"><p>
                How do I disable the cursor on my touchscreen device?
            </p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p>
                You need to create a form factor file as described in the
                "<a class="ulink" href="http://www.yoctoproject.org/docs/1.4/bsp-guide/bsp-guide.html#bsp-filelayout-misc-recipes" target="_top">Miscellaneous Recipe Files</a>"
                section and set the <code class="filename">HAVE_TOUCHSCREEN</code> variable equal to one as follows:
                </p><pre class="literallayout">
     HAVE_TOUCHSCREEN=1
                </pre><p>
            </p></td></tr><tr class="question" title="12.19."><td align="left" valign="top"><a id="idp3244640"></a><a id="idp3244768"></a><p><strong>12.19.</strong></p></td><td align="left" valign="top"><p>
                How do I make sure connected network interfaces are brought up by default?
            </p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p>
                The default interfaces file provided by the netbase recipe does not
                automatically bring up network interfaces.
                Therefore, you will need to add a BSP-specific netbase that includes an interfaces
                file.
                See the "<a class="ulink" href="http://www.yoctoproject.org/docs/1.4/bsp-guide/bsp-guide.html#bsp-filelayout-misc-recipes" target="_top">Miscellaneous Recipe Files</a>"
                section for information on creating these types of miscellaneous recipe files.
            </p><p>
                For example, add the following files to your layer:
                </p><pre class="literallayout">
     meta-MACHINE/recipes-bsp/netbase/netbase/MACHINE/interfaces
     meta-MACHINE/recipes-bsp/netbase/netbase_5.0.bbappend
                </pre><p>
            </p></td></tr><tr class="question" title="12.20."><td align="left" valign="top"><a id="idp3248256"></a><a id="idp3248384"></a><p><strong>12.20.</strong></p></td><td align="left" valign="top"><p>
                How do I create images with more free space?
            </p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p>
                Images are created to be 1.2 times the size of the populated root filesystem.
                To modify this ratio so that there is more free space available, you need to
                set the configuration value <code class="filename">IMAGE_OVERHEAD_FACTOR</code>.
                For example, setting <code class="filename">IMAGE_OVERHEAD_FACTOR</code> to 1.5 sets
                the image size ratio to one and a half times the size of the populated
                root filesystem.
                </p><pre class="literallayout">
     IMAGE_OVERHEAD_FACTOR = "1.5"
                </pre><p>
            </p></td></tr><tr class="question" title="12.21."><td align="left" valign="top"><a id="idp348464"></a><a id="idp348592"></a><p><strong>12.21.</strong></p></td><td align="left" valign="top"><p>
                Why don't you support directories with spaces in the pathnames?
            </p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p>
                The Yocto Project team has tried to do this before but too many of the tools
                the OpenEmbedded build system depends on such as <code class="filename">autoconf</code>
                break when they find spaces in pathnames.
                Until that situation changes, the team will not support spaces in pathnames.
            </p></td></tr><tr class="question" title="12.22."><td align="left" valign="top"><a id="idp350512"></a><a id="idp350640"></a><p><strong>12.22.</strong></p></td><td align="left" valign="top"><p>
                How do I use an external toolchain?
            </p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p>
                The toolchain configuration is very flexible and customizable.
                It is primarily controlled with the
                <code class="filename"><a class="link" href="#var-TCMODE" title="TCMODE">TCMODE</a></code> variable.
                This variable controls which <code class="filename">tcmode-*.inc</code> file to include
                from the <code class="filename">meta/conf/distro/include</code> directory within the
                <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#source-directory" target="_top">source directory</a>.
            </p><p>
                The default value of <code class="filename">TCMODE</code> is "default"
                (i.e. <code class="filename">tcmode-default.inc</code>).
                However, other patterns are accepted.
                In particular, "external-*" refers to external toolchains of which there are some
                basic examples included in the OpenEmbedded Core (<code class="filename">meta</code>).
                You can use your own custom toolchain definition in your own layer
                (or as defined in the <code class="filename">local.conf</code> file) at the location
                <code class="filename">conf/distro/include/tcmode-*.inc</code>.
            </p><p>
                In addition to the toolchain configuration, you also need a corresponding toolchain recipe file.
                This recipe file needs to package up any pre-built objects in the toolchain such as
                <code class="filename">libgcc</code>, <code class="filename">libstdcc++</code>,
                any locales, and <code class="filename">libc</code>.
                An example is the <code class="filename">external-sourcery-toolchain.bb</code>, which is located
                in <code class="filename">meta/recipes-core/meta/</code> within the source directory.
            </p></td></tr><tr class="question" title="12.23."><td align="left" valign="top"><a id="idm184288"></a><a id="idm1835680"></a><p><strong>12.23.</strong></p></td><td align="left" valign="top"><p><a id="how-does-the-yocto-project-obtain-source-code-and-will-it-work-behind-my-firewall-or-proxy-server"></a>
                How does the OpenEmbedded build system obtain source code and will it work behind my
                firewall or proxy server?
            </p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p>
                The way the build system obtains source code is highly configurable.
                You can setup the build system to get source code in most environments if
                HTTP transport is available.
            </p><p>
                When the build system searches for source code, it first tries the local download directory.
                If that location fails, Poky tries PREMIRRORS, the upstream source,
                and then MIRRORS in that order.
            </p><p>
                By default, the OpenEmbedded build system uses the Yocto Project source PREMIRRORS
                for SCM-based sources,
                upstreams for normal tarballs, and then falls back to a number of other mirrors
                including the Yocto Project source mirror if those fail.
            </p><p>
                As an example, you could add a specific server for Poky to attempt before any
                others by adding something like the following to the <code class="filename">local.conf</code>
                configuration file:
                </p><pre class="literallayout">
     PREMIRRORS_prepend = "\
     git://.*/.* http://www.yoctoproject.org/sources/ \n \
     ftp://.*/.* http://www.yoctoproject.org/sources/ \n \
     http://.*/.* http://www.yoctoproject.org/sources/ \n \
     https://.*/.* http://www.yoctoproject.org/sources/ \n"
                </pre><p>
            </p><p>
                These changes cause Poky to intercept Git, FTP, HTTP, and HTTPS
                requests and direct them to the <code class="filename">http://</code> sources mirror.
                You can use <code class="filename">file://</code> URLs to point to local directories
                or network shares as well.
            </p><p>
                Aside from the previous technique, these options also exist:
                </p><pre class="literallayout">
     BB_NO_NETWORK = "1"
                </pre><p>
                 This statement tells BitBake to throw an error instead of trying to access the
                 Internet.
                 This technique is useful if you want to ensure code builds only from local sources.
             </p><p>
                 Here is another technique:
                 </p><pre class="literallayout">
     BB_FETCH_PREMIRRORONLY = "1"
                 </pre><p>
                 This statement limits Poky to pulling source from the PREMIRRORS only.
                 Again, this technique is useful for reproducing builds.
             </p><p>
                 Here is another technique:
                 </p><pre class="literallayout">
     BB_GENERATE_MIRROR_TARBALLS = "1"
                 </pre><p>
                 This statement tells Poky to generate mirror tarballs.
                 This technique is useful if you want to create a mirror server.
                 If not, however, the technique can simply waste time during the build.
             </p><p>
                 Finally, consider an example where you are behind an HTTP-only firewall.
                 You could make the following changes to the <code class="filename">local.conf</code>
                 configuration file as long as the PREMIRROR server is up to date:
                 </p><pre class="literallayout">
     PREMIRRORS_prepend = "\
     ftp://.*/.* http://www.yoctoproject.org/sources/ \n \
     http://.*/.* http://www.yoctoproject.org/sources/ \n \
     https://.*/.* http://www.yoctoproject.org/sources/ \n"
     BB_FETCH_PREMIRRORONLY = "1"
                 </pre><p>
                 These changes would cause Poky to successfully fetch source over HTTP and
                 any network accesses to anything other than the PREMIRROR would fail.
             </p><p>
                 The build system also honors the standard shell environment variables
                 <code class="filename">http_proxy</code>, <code class="filename">ftp_proxy</code>,
                 <code class="filename">https_proxy</code>, and <code class="filename">all_proxy</code>
                 to redirect requests through proxy servers.
             </p></td></tr><tr class="question" title="12.24."><td align="left" valign="top"><a id="idm1036560"></a><a id="idm1036432"></a><p><strong>12.24.</strong></p></td><td align="left" valign="top"><p>
                Can I get rid of build output so I can start over?
            </p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p>
                Yes - you can easily do this.
                When you use BitBake to build an image, all the build output goes into the
                directory created when you source the <code class="filename">oe-init-build-env</code>
                setup file.
                By default, this <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#build-directory" target="_top">build directory</a>
                is named <code class="filename">build</code> but can be named
                anything you want.
            </p><p>
                Within the build directory is the <code class="filename">tmp</code> directory.
                To remove all the build output yet preserve any source code or downloaded files
                from previous builds, simply remove the <code class="filename">tmp</code> directory.
            </p></td></tr></tbody></table></div></div>

    <div class="chapter" title="Chapter 13. Contributing to the Yocto Project"><div class="titlepage"><div><div><h2 class="title"><a id="resources"></a>Chapter 13. Contributing to the Yocto Project</h2></div></div></div><div class="toc"><p><strong>Table of Contents</strong></p><dl><dt><span class="section"><a href="#resources-intro">13.1. Introduction</a></span></dt><dt><span class="section"><a href="#resources-bugtracker">13.2. Tracking Bugs</a></span></dt><dt><span class="section"><a href="#resources-mailinglist">13.3. Mailing lists</a></span></dt><dt><span class="section"><a href="#resources-irc">13.4. Internet Relay Chat (IRC)</a></span></dt><dt><span class="section"><a href="#resources-links">13.5. Links</a></span></dt><dt><span class="section"><a href="#resources-contributions">13.6. Contributions</a></span></dt></dl></div><div class="section" title="13.1. Introduction"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="resources-intro"></a>13.1. Introduction</h2></div></div></div><p>
        The Yocto Project team is happy for people to experiment with the Yocto Project.
        A number of places exist to find help if you run into difficulties or find bugs.
        To find out how to download source code,
        see the "<a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#local-yp-release" target="_top">Yocto Project Release</a>"
        list item in the Yocto Project Development Manual.
    </p></div><div class="section" title="13.2. Tracking Bugs"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="resources-bugtracker"></a>13.2. Tracking Bugs</h2></div></div></div><p>
        If you find problems with the Yocto Project, you should report them using the
        Bugzilla application at <a class="ulink" href="http://bugzilla.yoctoproject.org" target="_top">http://bugzilla.yoctoproject.org</a>.
    </p></div><div class="section" title="13.3. Mailing lists"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="resources-mailinglist"></a>13.3. Mailing lists</h2></div></div></div><p>
        There are a number of mailing lists maintained by the Yocto Project as well as
        related OpenEmbedded mailing lists for discussion, patch submission and announcements.
        To subscribe to one of the following mailing lists, click on the appropriate URL
        in the following list and follow the instructions:
        </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><a class="ulink" href="http://lists.yoctoproject.org/listinfo/yocto" target="_top">http://lists.yoctoproject.org/listinfo/yocto</a> -
                General Yocto Project discussion mailing list. </p></li><li class="listitem"><p><a class="ulink" href="http://lists.linuxtogo.org/cgi-bin/mailman/listinfo/openembedded-core" target="_top">http://lists.linuxtogo.org/cgi-bin/mailman/listinfo/openembedded-core</a> -
                Discussion mailing list about OpenEmbedded-Core (the core metadata).</p></li><li class="listitem"><p><a class="ulink" href="http://lists.linuxtogo.org/cgi-bin/mailman/listinfo/openembedded-devel" target="_top">http://lists.linuxtogo.org/cgi-bin/mailman/listinfo/openembedded-devel</a> -
                Discussion mailing list about OpenEmbedded.</p></li><li class="listitem"><p><a class="ulink" href="http://lists.linuxtogo.org/cgi-bin/mailman/listinfo/bitbake-devel" target="_top">http://lists.linuxtogo.org/cgi-bin/mailman/listinfo/bitbake-devel</a> -
                Discussion mailing list about the BitBake build tool.</p></li><li class="listitem"><p><a class="ulink" href="http://lists.yoctoproject.org/listinfo/poky" target="_top">http://lists.yoctoproject.org/listinfo/poky</a> -
                Discussion mailing list about Poky.</p></li><li class="listitem"><p><a class="ulink" href="http://lists.yoctoproject.org/listinfo/yocto-announce" target="_top">http://lists.yoctoproject.org/listinfo/yocto-announce</a> -
                Mailing list to receive official Yocto Project release and milestone
                announcements.</p></li></ul></div><p>
    </p></div><div class="section" title="13.4. Internet Relay Chat (IRC)"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="resources-irc"></a>13.4. Internet Relay Chat (IRC)</h2></div></div></div><p>
        Two IRC channels on freenode are available for the Yocto Project and Poky discussions:
        </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><code class="filename">#yocto</code></p></li><li class="listitem"><p><code class="filename">#poky</code></p></li></ul></div><p>
    </p></div><div class="section" title="13.5. Links"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="resources-links"></a>13.5. Links</h2></div></div></div><p>
        Following is a list of resources you will find helpful:
        </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em><a class="ulink" href="http://www.yoctoproject.org" target="_top">The Yocto Project website</a>:
                </em></span> The home site for the Yocto Project.</p></li><li class="listitem"><p><span class="emphasis"><em><a class="ulink" href="http://www.intel.com/" target="_top">Intel Corporation</a>:</em></span>
                The company who acquired OpenedHand in 2008 and began development on the
                Yocto Project.</p></li><li class="listitem"><p><span class="emphasis"><em><a class="ulink" href="http://www.openembedded.org" target="_top">OpenEmbedded</a>:</em></span>
                The upstream, generic, embedded distribution used as the basis for the build system in the
                Yocto Project.
                Poky derives from and contributes back to the OpenEmbedded project.</p></li><li class="listitem"><p><span class="emphasis"><em><a class="ulink" href="http://developer.berlios.de/projects/bitbake/" target="_top">
                BitBake</a>:</em></span> The tool used to process metadata.</p></li><li class="listitem"><p><span class="emphasis"><em>BitBake User Manual:</em></span>
                A comprehensive guide to the BitBake tool.
                You can find the BitBake User Manual in the <code class="filename">bitbake/doc/manual</code>
                directory, which is found in the
                <a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#source-directory" target="_top">Source Directory</a>.
                </p></li><li class="listitem"><p><span class="emphasis"><em><a class="ulink" href="http://wiki.qemu.org/Index.html" target="_top">QEMU</a>:
                </em></span> An open source machine emulator and virtualizer.</p></li></ul></div><p>
    </p></div><div class="section" title="13.6. Contributions"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="resources-contributions"></a>13.6. Contributions</h2></div></div></div><p>
        The Yocto Project gladly accepts contributions.
        You can submit changes to the project either by creating and sending pull requests,
        or by submitting patches through email.
        For information on how to do both, see the
        "<a class="ulink" href="http://www.yoctoproject.org/docs/1.4/dev-manual/dev-manual.html#how-to-submit-a-change" target="_top">How to Submit a Change</a>"
        section in the Yocto Project Development Manual.
    </p></div></div>



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