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@@ -1,400 +1,18 @@ - Linux kernel release 4.x <http://kernel.org/> +Linux kernel +============ -These are the release notes for Linux version 4. Read them carefully, -as they tell you what this is all about, explain how to install the -kernel, and what to do if something goes wrong. +This file was moved to Documentation/admin-guide/README.rst -WHAT IS LINUX? +Please notice that there are several guides for kernel developers and users. +These guides can be rendered in a number of formats, like HTML and PDF. - Linux is a clone of the operating system Unix, written from scratch by - Linus Torvalds with assistance from a loosely-knit team of hackers across - the Net. It aims towards POSIX and Single UNIX Specification compliance. +In order to build the documentation, use ``make htmldocs`` or +``make pdfdocs``. - It has all the features you would expect in a modern fully-fledged Unix, - including true multitasking, virtual memory, shared libraries, demand - loading, shared copy-on-write executables, proper memory management, - and multistack networking including IPv4 and IPv6. - - It is distributed under the GNU General Public License - see the - accompanying COPYING file for more details. - -ON WHAT HARDWARE DOES IT RUN? - - Although originally developed first for 32-bit x86-based PCs (386 or higher), - today Linux also runs on (at least) the Compaq Alpha AXP, Sun SPARC and - UltraSPARC, Motorola 68000, PowerPC, PowerPC64, ARM, Hitachi SuperH, Cell, - IBM S/390, MIPS, HP PA-RISC, Intel IA-64, DEC VAX, AMD x86-64, AXIS CRIS, - Xtensa, Tilera TILE, AVR32, ARC and Renesas M32R architectures. - - Linux is easily portable to most general-purpose 32- or 64-bit architectures - as long as they have a paged memory management unit (PMMU) and a port of the - GNU C compiler (gcc) (part of The GNU Compiler Collection, GCC). Linux has - also been ported to a number of architectures without a PMMU, although - functionality is then obviously somewhat limited. - Linux has also been ported to itself. You can now run the kernel as a - userspace application - this is called UserMode Linux (UML). - -DOCUMENTATION: - - - There is a lot of documentation available both in electronic form on - the Internet and in books, both Linux-specific and pertaining to - general UNIX questions. I'd recommend looking into the documentation - subdirectories on any Linux FTP site for the LDP (Linux Documentation - Project) books. This README is not meant to be documentation on the - system: there are much better sources available. - - - There are various README files in the Documentation/ subdirectory: - these typically contain kernel-specific installation notes for some - drivers for example. See Documentation/00-INDEX for a list of what - is contained in each file. Please read the Changes file, as it - contains information about the problems, which may result by upgrading - your kernel. - - - The Documentation/DocBook/ subdirectory contains several guides for - kernel developers and users. These guides can be rendered in a - number of formats: PostScript (.ps), PDF, HTML, & man-pages, among others. - After installation, "make psdocs", "make pdfdocs", "make htmldocs", - or "make mandocs" will render the documentation in the requested format. - -INSTALLING the kernel source: - - - If you install the full sources, put the kernel tarball in a - directory where you have permissions (e.g. your home directory) and - unpack it: - - xz -cd linux-4.X.tar.xz | tar xvf - - - Replace "X" with the version number of the latest kernel. - - Do NOT use the /usr/src/linux area! This area has a (usually - incomplete) set of kernel headers that are used by the library header - files. They should match the library, and not get messed up by - whatever the kernel-du-jour happens to be. - - - You can also upgrade between 4.x releases by patching. Patches are - distributed in the xz format. To install by patching, get all the - newer patch files, enter the top level directory of the kernel source - (linux-4.X) and execute: - - xz -cd ../patch-4.x.xz | patch -p1 - - Replace "x" for all versions bigger than the version "X" of your current - source tree, _in_order_, and you should be ok. You may want to remove - the backup files (some-file-name~ or some-file-name.orig), and make sure - that there are no failed patches (some-file-name# or some-file-name.rej). - If there are, either you or I have made a mistake. - - Unlike patches for the 4.x kernels, patches for the 4.x.y kernels - (also known as the -stable kernels) are not incremental but instead apply - directly to the base 4.x kernel. For example, if your base kernel is 4.0 - and you want to apply the 4.0.3 patch, you must not first apply the 4.0.1 - and 4.0.2 patches. Similarly, if you are running kernel version 4.0.2 and - want to jump to 4.0.3, you must first reverse the 4.0.2 patch (that is, - patch -R) _before_ applying the 4.0.3 patch. You can read more on this in - Documentation/applying-patches.txt - - Alternatively, the script patch-kernel can be used to automate this - process. It determines the current kernel version and applies any - patches found. - - linux/scripts/patch-kernel linux - - The first argument in the command above is the location of the - kernel source. Patches are applied from the current directory, but - an alternative directory can be specified as the second argument. - - - Make sure you have no stale .o files and dependencies lying around: - - cd linux - make mrproper - - You should now have the sources correctly installed. - -SOFTWARE REQUIREMENTS - - Compiling and running the 4.x kernels requires up-to-date - versions of various software packages. Consult - Documentation/Changes for the minimum version numbers required - and how to get updates for these packages. Beware that using - excessively old versions of these packages can cause indirect - errors that are very difficult to track down, so don't assume that - you can just update packages when obvious problems arise during - build or operation. - -BUILD directory for the kernel: - - When compiling the kernel, all output files will per default be - stored together with the kernel source code. - Using the option "make O=output/dir" allows you to specify an alternate - place for the output files (including .config). - Example: - - kernel source code: /usr/src/linux-4.X - build directory: /home/name/build/kernel - - To configure and build the kernel, use: - - cd /usr/src/linux-4.X - make O=/home/name/build/kernel menuconfig - make O=/home/name/build/kernel - sudo make O=/home/name/build/kernel modules_install install - - Please note: If the 'O=output/dir' option is used, then it must be - used for all invocations of make. - -CONFIGURING the kernel: - - Do not skip this step even if you are only upgrading one minor - version. New configuration options are added in each release, and - odd problems will turn up if the configuration files are not set up - as expected. If you want to carry your existing configuration to a - new version with minimal work, use "make oldconfig", which will - only ask you for the answers to new questions. - - - Alternative configuration commands are: - - "make config" Plain text interface. - - "make menuconfig" Text based color menus, radiolists & dialogs. - - "make nconfig" Enhanced text based color menus. - - "make xconfig" Qt based configuration tool. - - "make gconfig" GTK+ based configuration tool. - - "make oldconfig" Default all questions based on the contents of - your existing ./.config file and asking about - new config symbols. - - "make silentoldconfig" - Like above, but avoids cluttering the screen - with questions already answered. - Additionally updates the dependencies. - - "make olddefconfig" - Like above, but sets new symbols to their default - values without prompting. - - "make defconfig" Create a ./.config file by using the default - symbol values from either arch/$ARCH/defconfig - or arch/$ARCH/configs/${PLATFORM}_defconfig, - depending on the architecture. - - "make ${PLATFORM}_defconfig" - Create a ./.config file by using the default - symbol values from - arch/$ARCH/configs/${PLATFORM}_defconfig. - Use "make help" to get a list of all available - platforms of your architecture. - - "make allyesconfig" - Create a ./.config file by setting symbol - values to 'y' as much as possible. - - "make allmodconfig" - Create a ./.config file by setting symbol - values to 'm' as much as possible. - - "make allnoconfig" Create a ./.config file by setting symbol - values to 'n' as much as possible. - - "make randconfig" Create a ./.config file by setting symbol - values to random values. - - "make localmodconfig" Create a config based on current config and - loaded modules (lsmod). Disables any module - option that is not needed for the loaded modules. - - To create a localmodconfig for another machine, - store the lsmod of that machine into a file - and pass it in as a LSMOD parameter. - - target$ lsmod > /tmp/mylsmod - target$ scp /tmp/mylsmod host:/tmp - - host$ make LSMOD=/tmp/mylsmod localmodconfig - - The above also works when cross compiling. - - "make localyesconfig" Similar to localmodconfig, except it will convert - all module options to built in (=y) options. - - You can find more information on using the Linux kernel config tools - in Documentation/kbuild/kconfig.txt. - - - NOTES on "make config": - - - Having unnecessary drivers will make the kernel bigger, and can - under some circumstances lead to problems: probing for a - nonexistent controller card may confuse your other controllers - - - A kernel with math-emulation compiled in will still use the - coprocessor if one is present: the math emulation will just - never get used in that case. The kernel will be slightly larger, - but will work on different machines regardless of whether they - have a math coprocessor or not. - - - The "kernel hacking" configuration details usually result in a - bigger or slower kernel (or both), and can even make the kernel - less stable by configuring some routines to actively try to - break bad code to find kernel problems (kmalloc()). Thus you - should probably answer 'n' to the questions for "development", - "experimental", or "debugging" features. - -COMPILING the kernel: - - - Make sure you have at least gcc 3.2 available. - For more information, refer to Documentation/Changes. - - Please note that you can still run a.out user programs with this kernel. - - - Do a "make" to create a compressed kernel image. It is also - possible to do "make install" if you have lilo installed to suit the - kernel makefiles, but you may want to check your particular lilo setup first. - - To do the actual install, you have to be root, but none of the normal - build should require that. Don't take the name of root in vain. - - - If you configured any of the parts of the kernel as `modules', you - will also have to do "make modules_install". - - - Verbose kernel compile/build output: - - Normally, the kernel build system runs in a fairly quiet mode (but not - totally silent). However, sometimes you or other kernel developers need - to see compile, link, or other commands exactly as they are executed. - For this, use "verbose" build mode. This is done by passing - "V=1" to the "make" command, e.g. - - make V=1 all - - To have the build system also tell the reason for the rebuild of each - target, use "V=2". The default is "V=0". - - - Keep a backup kernel handy in case something goes wrong. This is - especially true for the development releases, since each new release - contains new code which has not been debugged. Make sure you keep a - backup of the modules corresponding to that kernel, as well. If you - are installing a new kernel with the same version number as your - working kernel, make a backup of your modules directory before you - do a "make modules_install". - - Alternatively, before compiling, use the kernel config option - "LOCALVERSION" to append a unique suffix to the regular kernel version. - LOCALVERSION can be set in the "General Setup" menu. - - - In order to boot your new kernel, you'll need to copy the kernel - image (e.g. .../linux/arch/x86/boot/bzImage after compilation) - to the place where your regular bootable kernel is found. - - - Booting a kernel directly from a floppy without the assistance of a - bootloader such as LILO, is no longer supported. - - If you boot Linux from the hard drive, chances are you use LILO, which - uses the kernel image as specified in the file /etc/lilo.conf. The - kernel image file is usually /vmlinuz, /boot/vmlinuz, /bzImage or - /boot/bzImage. To use the new kernel, save a copy of the old image - and copy the new image over the old one. Then, you MUST RERUN LILO - to update the loading map! If you don't, you won't be able to boot - the new kernel image. - - Reinstalling LILO is usually a matter of running /sbin/lilo. - You may wish to edit /etc/lilo.conf to specify an entry for your - old kernel image (say, /vmlinux.old) in case the new one does not - work. See the LILO docs for more information. - - After reinstalling LILO, you should be all set. Shutdown the system, - reboot, and enjoy! - - If you ever need to change the default root device, video mode, - ramdisk size, etc. in the kernel image, use the 'rdev' program (or - alternatively the LILO boot options when appropriate). No need to - recompile the kernel to change these parameters. - - - Reboot with the new kernel and enjoy. - -IF SOMETHING GOES WRONG: - - - If you have problems that seem to be due to kernel bugs, please check - the file MAINTAINERS to see if there is a particular person associated - with the part of the kernel that you are having trouble with. If there - isn't anyone listed there, then the second best thing is to mail - them to me (torvalds@linux-foundation.org), and possibly to any other - relevant mailing-list or to the newsgroup. - - - In all bug-reports, *please* tell what kernel you are talking about, - how to duplicate the problem, and what your setup is (use your common - sense). If the problem is new, tell me so, and if the problem is - old, please try to tell me when you first noticed it. - - - If the bug results in a message like - - unable to handle kernel paging request at address C0000010 - Oops: 0002 - EIP: 0010:XXXXXXXX - eax: xxxxxxxx ebx: xxxxxxxx ecx: xxxxxxxx edx: xxxxxxxx - esi: xxxxxxxx edi: xxxxxxxx ebp: xxxxxxxx - ds: xxxx es: xxxx fs: xxxx gs: xxxx - Pid: xx, process nr: xx - xx xx xx xx xx xx xx xx xx xx - - or similar kernel debugging information on your screen or in your - system log, please duplicate it *exactly*. The dump may look - incomprehensible to you, but it does contain information that may - help debugging the problem. The text above the dump is also - important: it tells something about why the kernel dumped code (in - the above example, it's due to a bad kernel pointer). More information - on making sense of the dump is in Documentation/oops-tracing.txt - - - If you compiled the kernel with CONFIG_KALLSYMS you can send the dump - as is, otherwise you will have to use the "ksymoops" program to make - sense of the dump (but compiling with CONFIG_KALLSYMS is usually preferred). - This utility can be downloaded from - ftp://ftp.<country>.kernel.org/pub/linux/utils/kernel/ksymoops/ . - Alternatively, you can do the dump lookup by hand: - - - In debugging dumps like the above, it helps enormously if you can - look up what the EIP value means. The hex value as such doesn't help - me or anybody else very much: it will depend on your particular - kernel setup. What you should do is take the hex value from the EIP - line (ignore the "0010:"), and look it up in the kernel namelist to - see which kernel function contains the offending address. - - To find out the kernel function name, you'll need to find the system - binary associated with the kernel that exhibited the symptom. This is - the file 'linux/vmlinux'. To extract the namelist and match it against - the EIP from the kernel crash, do: - - nm vmlinux | sort | less - - This will give you a list of kernel addresses sorted in ascending - order, from which it is simple to find the function that contains the - offending address. Note that the address given by the kernel - debugging messages will not necessarily match exactly with the - function addresses (in fact, that is very unlikely), so you can't - just 'grep' the list: the list will, however, give you the starting - point of each kernel function, so by looking for the function that - has a starting address lower than the one you are searching for but - is followed by a function with a higher address you will find the one - you want. In fact, it may be a good idea to include a bit of - "context" in your problem report, giving a few lines around the - interesting one. - - If you for some reason cannot do the above (you have a pre-compiled - kernel image or similar), telling me as much about your setup as - possible will help. Please read the REPORTING-BUGS document for details. - - - Alternatively, you can use gdb on a running kernel. (read-only; i.e. you - cannot change values or set break points.) To do this, first compile the - kernel with -g; edit arch/x86/Makefile appropriately, then do a "make - clean". You'll also need to enable CONFIG_PROC_FS (via "make config"). - - After you've rebooted with the new kernel, do "gdb vmlinux /proc/kcore". - You can now use all the usual gdb commands. The command to look up the - point where your system crashed is "l *0xXXXXXXXX". (Replace the XXXes - with the EIP value.) - - gdb'ing a non-running kernel currently fails because gdb (wrongly) - disregards the starting offset for which the kernel is compiled. +There are various text files in the Documentation/ subdirectory, +several of them using the Restructured Text markup notation. +See Documentation/00-INDEX for a list of what is contained in each file. +Please read the Documentation/process/changes.rst file, as it contains the +requirements for building and running the kernel, and information about +the problems which may result by upgrading your kernel. |
