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Diffstat (limited to 'documentation/poky-ref-manual/ref-classes.xml')
| -rw-r--r-- | documentation/poky-ref-manual/ref-classes.xml | 50 |
1 files changed, 46 insertions, 4 deletions
diff --git a/documentation/poky-ref-manual/ref-classes.xml b/documentation/poky-ref-manual/ref-classes.xml index cf39680..93e9ea8 100644 --- a/documentation/poky-ref-manual/ref-classes.xml +++ b/documentation/poky-ref-manual/ref-classes.xml @@ -265,17 +265,59 @@ The packaging classes add support for generating packages from a build's output. The core generic functionality is in <filename>package.bbclass</filename>. - The code specific - to particular package types is contained in various sub-classes such as + The code specific to particular package types is contained in various sub-classes such as <filename>package_deb.bbclass</filename>, <filename>package_ipk.bbclass</filename>, and <filename>package_rpm.bbclass</filename>. Most users will want one or more of these classes. + </para> + + <para> You can control the list of resulting package formats by using the <filename><link linkend='var-PACKAGE_CLASSES'>PACKAGE_CLASSES</link></filename> - variable. - The first class listed in this variable is be used for image generation. + variable defined in the <filename>local.conf</filename> configuration file + found in the Yocto Project file's <filename>conf</filename> directory. + 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. + </para> + + <para> + 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 <filename>PACKAGE_CLASSES</filename> + to "package_ipk" if you are building smaller systems. + </para> + + <para> + 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. + </para> + + <para> + 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. + </para> + + <para> + You can find additional information on the effects of the package class at these + two Yocto Project mailing list links: + <itemizedlist> + <listitem><para><ulink url='https://lists.yoctoproject.org/pipermail/poky/2011-May/006362.html'> + https://lists.yoctoproject.org/pipermail/poky/2011-May/006362.html</ulink></para></listitem> + <listitem><para><ulink url='https://lists.yoctoproject.org/pipermail/poky/2011-May/006363.html'> + https://lists.yoctoproject.org/pipermail/poky/2011-May/006363.html</ulink></para></listitem> + </itemizedlist> </para> </section> |
