Linux kernel release 2.6
  1.         Linux kernel release 2.6.xx <>
  2. These are the release notes for Linux version 2.6.  Read them carefully,
  3. as they tell you what this is all about, explain how to install the
  4. kernel, and what to do if something goes wrong.
  6.   Linux is a clone of the operating system Unix, written from scratch by
  7.   Linus Torvalds with assistance from a loosely-knit team of hackers across
  8.   the Net. It aims towards POSIX and Single UNIX Specification compliance.
  9.   It has all the features you would expect in a modern fully-fledged Unix,
  10.   including true multitasking, virtual memory, shared libraries, demand
  11.   loading, shared copy-on-write executables, proper memory management,
  12.   and multistack networking including IPv4 and IPv6.
  13.   It is distributed under the GNU General Public License - see the
  14.   accompanying COPYING file for more details.
  16.   Although originally developed first for 32-bit x86-based PCs (386 or higher),
  17.   today Linux also runs on (at least) the Compaq Alpha AXP, Sun SPARC and
  18.   UltraSPARC, Motorola 68000, PowerPC, PowerPC64, ARM, Hitachi SuperH, Cell,
  19.   IBM S/390, MIPS, HP PA-RISC, Intel IA-64, DEC VAX, AMD x86-64, AXIS CRIS,
  20.   Xtensa, AVR32 and Renesas M32R architectures.
  21.   Linux is easily portable to most general-purpose 32- or 64-bit architectures
  22.   as long as they have a paged memory management unit (PMMU) and a port of the
  23.   GNU C compiler (gcc) (part of The GNU Compiler Collection, GCC). Linux has
  24.   also been ported to a number of architectures without a PMMU, although
  25.   functionality is then obviously somewhat limited.
  26.   Linux has also been ported to itself. You can now run the kernel as a
  27.   userspace application - this is called UserMode Linux (UML).
  29.  - There is a lot of documentation available both in electronic form on
  30.    the Internet and in books, both Linux-specific and pertaining to
  31.    general UNIX questions.  I'd recommend looking into the documentation
  32.    subdirectories on any Linux FTP site for the LDP (Linux Documentation
  33.    Project) books.  This README is not meant to be documentation on the
  34.    system: there are much better sources available.
  35.  - There are various README files in the Documentation/ subdirectory:
  36.    these typically contain kernel-specific installation notes for some
  37.    drivers for example. See Documentation/00-INDEX for a list of what
  38.    is contained in each file.  Please read the Changes file, as it
  39.    contains information about the problems, which may result by upgrading
  40.    your kernel.
  41.  - The Documentation/DocBook/ subdirectory contains several guides for
  42.    kernel developers and users.  These guides can be rendered in a
  43.    number of formats:  PostScript (.ps), PDF, HTML, & man-pages, among others.
  44.    After installation, "make psdocs", "make pdfdocs", "make htmldocs",
  45.    or "make mandocs" will render the documentation in the requested format.
  46. INSTALLING the kernel source:
  47.  - If you install the full sources, put the kernel tarball in a
  48.    directory where you have permissions (eg. your home directory) and
  49.    unpack it:
  50.                 gzip -cd linux-2.6.XX.tar.gz | tar xvf -
  51.    or
  52.                 bzip2 -dc linux-2.6.XX.tar.bz2 | tar xvf -
  53.    Replace "XX" with the version number of the latest kernel.
  54.    Do NOT use the /usr/src/linux area! This area has a (usually
  55.    incomplete) set of kernel headers that are used by the library header
  56.    files.  They should match the library, and not get messed up by
  57.    whatever the kernel-du-jour happens to be.
  58.  - You can also upgrade between 2.6.xx releases by patching.  Patches are
  59.    distributed in the traditional gzip and the newer bzip2 format.  To
  60.    install by patching, get all the newer patch files, enter the
  61.    top level directory of the kernel source (linux-2.6.xx) and execute:
  62.                 gzip -cd ../patch-2.6.xx.gz | patch -p1
  63.    or
  64.                 bzip2 -dc ../patch-2.6.xx.bz2 | patch -p1
  65.    (repeat xx for all versions bigger than the version of your current
  66.    source tree, _in_order_) and you should be ok.  You may want to remove
  67.    the backup files (xxx~ or xxx.orig), and make sure that there are no
  68.    failed patches (xxx# or xxx.rej). If there are, either you or me has
  69.    made a mistake.
  70.    Unlike patches for the 2.6.x kernels, patches for the 2.6.x.y kernels
  71.    (also known as the -stable kernels) are not incremental but instead apply
  72.    directly to the base 2.6.x kernel.  Please read
  73.    Documentation/applying-patches.txt for more information.
  74.    Alternatively, the script patch-kernel can be used to automate this
  75.    process.  It determines the current kernel version and applies any
  76.    patches found.
  77.                 linux/scripts/patch-kernel linux
  78.    The first argument in the command above is the location of the
  79.    kernel source.  Patches are applied from the current directory, but
  80.    an alternative directory can be specified as the second argument.
  81.  - If you are upgrading between releases using the stable series patches
  82.    (for example, patch-2.6.xx.y), note that these "dot-releases" are
  83.    not incremental and must be applied to the 2.6.xx base tree. For
  84.    example, if your base kernel is 2.6.12 and you want to apply the
  85. patch, you do not and indeed must not first apply the
  86. and patches. Similarly, if you are running kernel
  87.    version and want to jump to, you must first
  88.    reverse the patch (that is, patch -R) _before_ applying
  89.    the patch.
  90.    You can read more on this in Documentation/applying-patches.txt
  91.  - Make sure you have no stale .o files and dependencies lying around:
  92.                 cd linux
  93.                 make mrproper
  94.    You should now have the sources correctly installed.
  96.    Compiling and running the 2.6.xx kernels requires up-to-date
  97.    versions of various software packages.  Consult
  98.    Documentation/Changes for the minimum version numbers required
  99.    and how to get updates for these packages.  Beware that using
  100.    excessively old versions of these packages can cause indirect
  101.    errors that are very difficult to track down, so don't assume that
  102.    you can just update packages when obvious problems arise during
  103.    build or operation.
  104. BUILD directory for the kernel:
  105.    When compiling the kernel all output files will per default be
  106.    stored together with the kernel source code.
  107.    Using the option "make O=output/dir" allow you to specify an alternate
  108.    place for the output files (including .config).
  109.    Example:
  110.      kernel source code:        /usr/src/linux-2.6.N
  111.      build directory:           /home/name/build/kernel
  112.    To configure and build the kernel use:
  113.    cd /usr/src/linux-2.6.N
  114.    make O=/home/name/build/kernel menuconfig
  115.    make O=/home/name/build/kernel
  116.    sudo make O=/home/name/build/kernel modules_install install
  117.    Please note: If the 'O=output/dir' option is used then it must be
  118.    used for all invocations of make.
  119. CONFIGURING the kernel:
  120.    Do not skip this step even if you are only upgrading one minor
  121.    version.  New configuration options are added in each release, and
  122.    odd problems will turn up if the configuration files are not set up
  123.    as expected.  If you want to carry your existing configuration to a
  124.    new version with minimal work, use "make oldconfig", which will
  125.    only ask you for the answers to new questions.
  126.  - Alternate configuration commands are:
  127.         "make config"      Plain text interface.
  128.         "make menuconfig"  Text based color menus, radiolists & dialogs.
  129.         "make xconfig"     X windows (Qt) based configuration tool.
  130.         "make gconfig"     X windows (Gtk) based configuration tool.
  131.         "make oldconfig"   Default all questions based on the contents of
  132.                            your existing ./.config file and asking about
  133.                            new config symbols.
  134.         "make silentoldconfig"
  135.                            Like above, but avoids cluttering the screen
  136.                            with questions already answered.
  137.                            Additionally updates the dependencies.
  138.         "make defconfig"   Create a ./.config file by using the default
  139.                            symbol values from either arch/$ARCH/defconfig
  140.                            or arch/$ARCH/configs/${PLATFORM}_defconfig,
  141.                            depending on the architecture.
  142.         "make ${PLATFORM}_defconfig"
  143.                           Create a ./.config file by using the default
  144.                           symbol values from
  145.                           arch/$ARCH/configs/${PLATFORM}_defconfig.
  146.                           Use "make help" to get a list of all available
  147.                           platforms of your architecture.
  148.         "make allyesconfig"
  149.                            Create a ./.config file by setting symbol
  150.                            values to 'y' as much as possible.
  151.         "make allmodconfig"
  152.                            Create a ./.config file by setting symbol
  153.                            values to 'm' as much as possible.
  154.         "make allnoconfig" Create a ./.config file by setting symbol
  155.                            values to 'n' as much as possible.
  156.         "make randconfig"  Create a ./.config file by setting symbol
  157.                            values to random values.
  158.    You can find more information on using the Linux kernel config tools
  159.    in Documentation/kbuild/kconfig.txt.
  160.         NOTES on "make config":
  161.         - having unnecessary drivers will make the kernel bigger, and can
  162.           under some circumstances lead to problems: probing for a
  163.           nonexistent controller card may confuse your other controllers
  164.         - compiling the kernel with "Processor type" set higher than 386
  165.           will result in a kernel that does NOT work on a 386.  The
  166.           kernel will detect this on bootup, and give up.
  167.         - A kernel with math-emulation compiled in will still use the
  168.           coprocessor if one is present: the math emulation will just
  169.           never get used in that case.  The kernel will be slightly larger,
  170.           but will work on different machines regardless of whether they
  171.           have a math coprocessor or not.
  172.         - the "kernel hacking" configuration details usually result in a
  173.           bigger or slower kernel (or both), and can even make the kernel
  174.           less stable by configuring some routines to actively try to
  175.           break bad code to find kernel problems (kmalloc()).  Thus you
  176.           should probably answer 'n' to the questions for
  177.           "development", "experimental", or "debugging" features.
  178. COMPILING the kernel:
  179.  - Make sure you have at least gcc 3.2 available.
  180.    For more information, refer to Documentation/Changes.
  181.    Please note that you can still run a.out user programs with this kernel.
  182.  - Do a "make" to create a compressed kernel image. It is also
  183.    possible to do "make install" if you have lilo installed to suit the
  184.    kernel makefiles, but you may want to check your particular lilo setup first.
  185.    To do the actual install you have to be root, but none of the normal
  186.    build should require that. Don't take the name of root in vain.
  187.  - If you configured any of the parts of the kernel as `modules', you
  188.    will also have to do "make modules_install".
  189.  - Verbose kernel compile/build output:
  190.    Normally the kernel build system runs in a fairly quiet mode (but not
  191.    totally silent).  However, sometimes you or other kernel developers need
  192.    to see compile, link, or other commands exactly as they are executed.
  193.    For this, use "verbose" build mode.  This is done by inserting
  194.    "V=1" in the "make" command.  E.g.:
  195.         make V=1 all
  196.    To have the build system also tell the reason for the rebuild of each
  197.    target, use "V=2".  The default is "V=0".
  198.  - Keep a backup kernel handy in case something goes wrong.  This is
  199.    especially true for the development releases, since each new release
  200.    contains new code which has not been debugged.  Make sure you keep a
  201.    backup of the modules corresponding to that kernel, as well.  If you
  202.    are installing a new kernel with the same version number as your
  203.    working kernel, make a backup of your modules directory before you
  204.    do a "make modules_install".
  205.    Alternatively, before compiling, use the kernel config option
  206.    "LOCALVERSION" to append a unique suffix to the regular kernel version.
  207.    LOCALVERSION can be set in the "General Setup" menu.
  208.  - In order to boot your new kernel, you'll need to copy the kernel
  209.    image (e.g. .../linux/arch/i386/boot/bzImage after compilation)
  210.    to the place where your regular bootable kernel is found.
  211.  - Booting a kernel directly from a floppy without the assistance of a
  212.    bootloader such as LILO, is no longer supported.
  213.    If you boot Linux from the hard drive, chances are you use LILO which
  214.    uses the kernel image as specified in the file /etc/lilo.conf.  The
  215.    kernel image file is usually /vmlinuz, /boot/vmlinuz, /bzImage or
  216.    /boot/bzImage.  To use the new kernel, save a copy of the old image
  217.    and copy the new image over the old one.  Then, you MUST RERUN LILO
  218.    to update the loading map!! If you don't, you won't be able to boot
  219.    the new kernel image.
  220.    Reinstalling LILO is usually a matter of running /sbin/lilo.
  221.    You may wish to edit /etc/lilo.conf to specify an entry for your
  222.    old kernel image (say, /vmlinux.old) in case the new one does not
  223.    work.  See the LILO docs for more information.
  224.    After reinstalling LILO, you should be all set.  Shutdown the system,
  225.    reboot, and enjoy!
  226.    If you ever need to change the default root device, video mode,
  227.    ramdisk size, etc.  in the kernel image, use the 'rdev' program (or
  228.    alternatively the LILO boot options when appropriate).  No need to
  229.    recompile the kernel to change these parameters.
  230.  - Reboot with the new kernel and enjoy.
  232.  - If you have problems that seem to be due to kernel bugs, please check
  233.    the file MAINTAINERS to see if there is a particular person associated
  234.    with the part of the kernel that you are having trouble with. If there
  235.    isn't anyone listed there, then the second best thing is to mail
  236.    them to me (, and possibly to any other
  237.    relevant mailing-list or to the newsgroup.
  238.  - In all bug-reports, *please* tell what kernel you are talking about,
  239.    how to duplicate the problem, and what your setup is (use your common
  240.    sense).  If the problem is new, tell me so, and if the problem is
  241.    old, please try to tell me when you first noticed it.
  242.  - If the bug results in a message like
  243.         unable to handle kernel paging request at address C0000010
  244.         Oops: 0002
  245.         EIP:   0010:XXXXXXXX
  246.         eax: xxxxxxxx   ebx: xxxxxxxx   ecx: xxxxxxxx   edx: xxxxxxxx
  247.         esi: xxxxxxxx   edi: xxxxxxxx   ebp: xxxxxxxx
  248.         ds: xxxx  es: xxxx  fs: xxxx  gs: xxxx
  249.         Pid: xx, process nr: xx
  250.         xx xx xx xx xx xx xx xx xx xx
  251.    or similar kernel debugging information on your screen or in your
  252.    system log, please duplicate it *exactly*.  The dump may look
  253.    incomprehensible to you, but it does contain information that may
  254.    help debugging the problem.  The text above the dump is also
  255.    important: it tells something about why the kernel dumped code (in
  256.    the above example it's due to a bad kernel pointer). More information
  257.    on making sense of the dump is in Documentation/oops-tracing.txt
  258.  - If you compiled the kernel with CONFIG_KALLSYMS you can send the dump
  259.    as is, otherwise you will have to use the "ksymoops" program to make
  260.    sense of the dump (but compiling with CONFIG_KALLSYMS is usually preferred).
  261.    This utility can be downloaded from
  262.    ftp://ftp.<country> .
  263.    Alternately you can do the dump lookup by hand:
  264.  - In debugging dumps like the above, it helps enormously if you can
  265.    look up what the EIP value means.  The hex value as such doesn't help
  266.    me or anybody else very much: it will depend on your particular
  267.    kernel setup.  What you should do is take the hex value from the EIP
  268.    line (ignore the "0010:"), and look it up in the kernel namelist to
  269.    see which kernel function contains the offending address.
  270.    To find out the kernel function name, you'll need to find the system
  271.    binary associated with the kernel that exhibited the symptom.  This is
  272.    the file 'linux/vmlinux'.  To extract the namelist and match it against
  273.    the EIP from the kernel crash, do:
  274.                 nm vmlinux | sort | less
  275.    This will give you a list of kernel addresses sorted in ascending
  276.    order, from which it is simple to find the function that contains the
  277.    offending address.  Note that the address given by the kernel
  278.    debugging messages will not necessarily match exactly with the
  279.    function addresses (in fact, that is very unlikely), so you can't
  280.    just 'grep' the list: the list will, however, give you the starting
  281.    point of each kernel function, so by looking for the function that
  282.    has a starting address lower than the one you are searching for but
  283.    is followed by a function with a higher address you will find the one
  284.    you want.  In fact, it may be a good idea to include a bit of
  285.    "context" in your problem report, giving a few lines around the
  286.    interesting one.
  287.    If you for some reason cannot do the above (you have a pre-compiled
  288.    kernel image or similar), telling me as much about your setup as
  289.    possible will help.  Please read the REPORTING-BUGS document for details.
  290.  - Alternately, you can use gdb on a running kernel. (read-only; i.e. you
  291.    cannot change values or set break points.) To do this, first compile the
  292.    kernel with -g; edit arch/i386/Makefile appropriately, then do a "make
  293.    clean". You'll also need to enable CONFIG_PROC_FS (via "make config").
  294.    After you've rebooted with the new kernel, do "gdb vmlinux /proc/kcore".
  295.    You can now use all the usual gdb commands. The command to look up the
  296.    point where your system crashed is "l *0xXXXXXXXX". (Replace the XXXes
  297.    with the EIP value.)
  298.    gdb'ing a non-running kernel currently fails because gdb (wrongly)
  299.    disregards the starting offset for which the kernel is compiled.
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