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Linux Cross Reference



0001         Linux kernel release 3.x <>
0003 These are the release notes for Linux version 3.  Read them carefully,
0004 as they tell you what this is all about, explain how to install the
0005 kernel, and what to do if something goes wrong. 
0009   Linux is a clone of the operating system Unix, written from scratch by
0010   Linus Torvalds with assistance from a loosely-knit team of hackers across
0011   the Net. It aims towards POSIX and Single UNIX Specification compliance.
0013   It has all the features you would expect in a modern fully-fledged Unix,
0014   including true multitasking, virtual memory, shared libraries, demand
0015   loading, shared copy-on-write executables, proper memory management,
0016   and multistack networking including IPv4 and IPv6.
0018   It is distributed under the GNU General Public License - see the
0019   accompanying COPYING file for more details. 
0023   Although originally developed first for 32-bit x86-based PCs (386 or higher),
0024   today Linux also runs on (at least) the Compaq Alpha AXP, Sun SPARC and
0025   UltraSPARC, Motorola 68000, PowerPC, PowerPC64, ARM, Hitachi SuperH, Cell,
0026   IBM S/390, MIPS, HP PA-RISC, Intel IA-64, DEC VAX, AMD x86-64, AXIS CRIS,
0027   Xtensa, Tilera TILE, AVR32 and Renesas M32R architectures.
0029   Linux is easily portable to most general-purpose 32- or 64-bit architectures
0030   as long as they have a paged memory management unit (PMMU) and a port of the
0031   GNU C compiler (gcc) (part of The GNU Compiler Collection, GCC). Linux has
0032   also been ported to a number of architectures without a PMMU, although
0033   functionality is then obviously somewhat limited.
0034   Linux has also been ported to itself. You can now run the kernel as a
0035   userspace application - this is called UserMode Linux (UML).
0039  - There is a lot of documentation available both in electronic form on
0040    the Internet and in books, both Linux-specific and pertaining to
0041    general UNIX questions.  I'd recommend looking into the documentation
0042    subdirectories on any Linux FTP site for the LDP (Linux Documentation
0043    Project) books.  This README is not meant to be documentation on the
0044    system: there are much better sources available.
0046  - There are various README files in the Documentation/ subdirectory:
0047    these typically contain kernel-specific installation notes for some 
0048    drivers for example. See Documentation/00-INDEX for a list of what
0049    is contained in each file.  Please read the Changes file, as it
0050    contains information about the problems, which may result by upgrading
0051    your kernel.
0053  - The Documentation/DocBook/ subdirectory contains several guides for
0054    kernel developers and users.  These guides can be rendered in a
0055    number of formats:  PostScript (.ps), PDF, HTML, & man-pages, among others.
0056    After installation, "make psdocs", "make pdfdocs", "make htmldocs",
0057    or "make mandocs" will render the documentation in the requested format.
0059 INSTALLING the kernel source:
0061  - If you install the full sources, put the kernel tarball in a
0062    directory where you have permissions (eg. your home directory) and
0063    unpack it:
0065      gzip -cd linux-3.X.tar.gz | tar xvf -
0067    or
0069      bzip2 -dc linux-3.X.tar.bz2 | tar xvf -
0071    Replace "X" with the version number of the latest kernel.
0073    Do NOT use the /usr/src/linux area! This area has a (usually
0074    incomplete) set of kernel headers that are used by the library header
0075    files.  They should match the library, and not get messed up by
0076    whatever the kernel-du-jour happens to be.
0078  - You can also upgrade between 3.x releases by patching.  Patches are
0079    distributed in the traditional gzip and the newer bzip2 format.  To
0080    install by patching, get all the newer patch files, enter the
0081    top level directory of the kernel source (linux-3.X) and execute:
0083      gzip -cd ../patch-3.x.gz | patch -p1
0085    or
0087      bzip2 -dc ../patch-3.x.bz2 | patch -p1
0089    Replace "x" for all versions bigger than the version "X" of your current
0090    source tree, _in_order_, and you should be ok.  You may want to remove
0091    the backup files (some-file-name~ or some-file-name.orig), and make sure
0092    that there are no failed patches (some-file-name# or some-file-name.rej).
0093    If there are, either you or I have made a mistake.
0095    Unlike patches for the 3.x kernels, patches for the 3.x.y kernels
0096    (also known as the -stable kernels) are not incremental but instead apply
0097    directly to the base 3.x kernel.  For example, if your base kernel is 3.0
0098    and you want to apply the 3.0.3 patch, you must not first apply the 3.0.1
0099    and 3.0.2 patches. Similarly, if you are running kernel version 3.0.2 and
0100    want to jump to 3.0.3, you must first reverse the 3.0.2 patch (that is,
0101    patch -R) _before_ applying the 3.0.3 patch. You can read more on this in
0102    Documentation/applying-patches.txt
0104    Alternatively, the script patch-kernel can be used to automate this
0105    process.  It determines the current kernel version and applies any
0106    patches found.
0108      linux/scripts/patch-kernel linux
0110    The first argument in the command above is the location of the
0111    kernel source.  Patches are applied from the current directory, but
0112    an alternative directory can be specified as the second argument.
0114  - Make sure you have no stale .o files and dependencies lying around:
0116      cd linux
0117      make mrproper
0119    You should now have the sources correctly installed.
0123    Compiling and running the 3.x kernels requires up-to-date
0124    versions of various software packages.  Consult
0125    Documentation/Changes for the minimum version numbers required
0126    and how to get updates for these packages.  Beware that using
0127    excessively old versions of these packages can cause indirect
0128    errors that are very difficult to track down, so don't assume that
0129    you can just update packages when obvious problems arise during
0130    build or operation.
0132 BUILD directory for the kernel:
0134    When compiling the kernel, all output files will per default be
0135    stored together with the kernel source code.
0136    Using the option "make O=output/dir" allow you to specify an alternate
0137    place for the output files (including .config).
0138    Example:
0140      kernel source code: /usr/src/linux-3.X
0141      build directory:    /home/name/build/kernel
0143    To configure and build the kernel, use:
0145      cd /usr/src/linux-3.X
0146      make O=/home/name/build/kernel menuconfig
0147      make O=/home/name/build/kernel
0148      sudo make O=/home/name/build/kernel modules_install install
0150    Please note: If the 'O=output/dir' option is used, then it must be
0151    used for all invocations of make.
0153 CONFIGURING the kernel:
0155    Do not skip this step even if you are only upgrading one minor
0156    version.  New configuration options are added in each release, and
0157    odd problems will turn up if the configuration files are not set up
0158    as expected.  If you want to carry your existing configuration to a
0159    new version with minimal work, use "make oldconfig", which will
0160    only ask you for the answers to new questions.
0162  - Alternative configuration commands are:
0164      "make config"      Plain text interface.
0166      "make menuconfig"  Text based color menus, radiolists & dialogs.
0168      "make nconfig"     Enhanced text based color menus.
0170      "make xconfig"     X windows (Qt) based configuration tool.
0172      "make gconfig"     X windows (Gtk) based configuration tool.
0174      "make oldconfig"   Default all questions based on the contents of
0175                         your existing ./.config file and asking about
0176                         new config symbols.
0178      "make silentoldconfig"
0179                         Like above, but avoids cluttering the screen
0180                         with questions already answered.
0181                         Additionally updates the dependencies.
0183      "make olddefconfig"
0184                         Like above, but sets new symbols to their default
0185                         values without prompting.
0187      "make defconfig"   Create a ./.config file by using the default
0188                         symbol values from either arch/$ARCH/defconfig
0189                         or arch/$ARCH/configs/${PLATFORM}_defconfig,
0190                         depending on the architecture.
0192      "make ${PLATFORM}_defconfig"
0193                         Create a ./.config file by using the default
0194                         symbol values from
0195                         arch/$ARCH/configs/${PLATFORM}_defconfig.
0196                         Use "make help" to get a list of all available
0197                         platforms of your architecture.
0199      "make allyesconfig"
0200                         Create a ./.config file by setting symbol
0201                         values to 'y' as much as possible.
0203      "make allmodconfig"
0204                         Create a ./.config file by setting symbol
0205                         values to 'm' as much as possible.
0207      "make allnoconfig" Create a ./.config file by setting symbol
0208                         values to 'n' as much as possible.
0210      "make randconfig"  Create a ./.config file by setting symbol
0211                         values to random values.
0213      "make localmodconfig" Create a config based on current config and
0214                            loaded modules (lsmod). Disables any module
0215                            option that is not needed for the loaded modules.
0217                            To create a localmodconfig for another machine,
0218                            store the lsmod of that machine into a file
0219                            and pass it in as a LSMOD parameter.
0221                    target$ lsmod > /tmp/mylsmod
0222                    target$ scp /tmp/mylsmod host:/tmp
0224                    host$ make LSMOD=/tmp/mylsmod localmodconfig
0226                            The above also works when cross compiling.
0228      "make localyesconfig" Similar to localmodconfig, except it will convert
0229                            all module options to built in (=y) options.
0231    You can find more information on using the Linux kernel config tools
0232    in Documentation/kbuild/kconfig.txt.
0234  - NOTES on "make config":
0236     - Having unnecessary drivers will make the kernel bigger, and can
0237       under some circumstances lead to problems: probing for a
0238       nonexistent controller card may confuse your other controllers
0240     - Compiling the kernel with "Processor type" set higher than 386
0241       will result in a kernel that does NOT work on a 386.  The
0242       kernel will detect this on bootup, and give up.
0244     - A kernel with math-emulation compiled in will still use the
0245       coprocessor if one is present: the math emulation will just
0246       never get used in that case.  The kernel will be slightly larger,
0247       but will work on different machines regardless of whether they
0248       have a math coprocessor or not.
0250     - The "kernel hacking" configuration details usually result in a
0251       bigger or slower kernel (or both), and can even make the kernel
0252       less stable by configuring some routines to actively try to
0253       break bad code to find kernel problems (kmalloc()).  Thus you
0254       should probably answer 'n' to the questions for "development",
0255       "experimental", or "debugging" features.
0257 COMPILING the kernel:
0259  - Make sure you have at least gcc 3.2 available.
0260    For more information, refer to Documentation/Changes.
0262    Please note that you can still run a.out user programs with this kernel.
0264  - Do a "make" to create a compressed kernel image. It is also
0265    possible to do "make install" if you have lilo installed to suit the
0266    kernel makefiles, but you may want to check your particular lilo setup first.
0268    To do the actual install, you have to be root, but none of the normal
0269    build should require that. Don't take the name of root in vain.
0271  - If you configured any of the parts of the kernel as `modules', you
0272    will also have to do "make modules_install".
0274  - Verbose kernel compile/build output:
0276    Normally, the kernel build system runs in a fairly quiet mode (but not
0277    totally silent).  However, sometimes you or other kernel developers need
0278    to see compile, link, or other commands exactly as they are executed.
0279    For this, use "verbose" build mode.  This is done by inserting
0280    "V=1" in the "make" command.  E.g.:
0282      make V=1 all
0284    To have the build system also tell the reason for the rebuild of each
0285    target, use "V=2".  The default is "V=0".
0287  - Keep a backup kernel handy in case something goes wrong.  This is 
0288    especially true for the development releases, since each new release
0289    contains new code which has not been debugged.  Make sure you keep a
0290    backup of the modules corresponding to that kernel, as well.  If you
0291    are installing a new kernel with the same version number as your
0292    working kernel, make a backup of your modules directory before you
0293    do a "make modules_install".
0295    Alternatively, before compiling, use the kernel config option
0296    "LOCALVERSION" to append a unique suffix to the regular kernel version.
0297    LOCALVERSION can be set in the "General Setup" menu.
0299  - In order to boot your new kernel, you'll need to copy the kernel
0300    image (e.g. .../linux/arch/i386/boot/bzImage after compilation)
0301    to the place where your regular bootable kernel is found. 
0303  - Booting a kernel directly from a floppy without the assistance of a
0304    bootloader such as LILO, is no longer supported.
0306    If you boot Linux from the hard drive, chances are you use LILO, which
0307    uses the kernel image as specified in the file /etc/lilo.conf.  The
0308    kernel image file is usually /vmlinuz, /boot/vmlinuz, /bzImage or
0309    /boot/bzImage.  To use the new kernel, save a copy of the old image
0310    and copy the new image over the old one.  Then, you MUST RERUN LILO
0311    to update the loading map!! If you don't, you won't be able to boot
0312    the new kernel image.
0314    Reinstalling LILO is usually a matter of running /sbin/lilo. 
0315    You may wish to edit /etc/lilo.conf to specify an entry for your
0316    old kernel image (say, /vmlinux.old) in case the new one does not
0317    work.  See the LILO docs for more information. 
0319    After reinstalling LILO, you should be all set.  Shutdown the system,
0320    reboot, and enjoy!
0322    If you ever need to change the default root device, video mode,
0323    ramdisk size, etc.  in the kernel image, use the 'rdev' program (or
0324    alternatively the LILO boot options when appropriate).  No need to
0325    recompile the kernel to change these parameters. 
0327  - Reboot with the new kernel and enjoy. 
0331  - If you have problems that seem to be due to kernel bugs, please check
0332    the file MAINTAINERS to see if there is a particular person associated
0333    with the part of the kernel that you are having trouble with. If there
0334    isn't anyone listed there, then the second best thing is to mail
0335    them to me (, and possibly to any other
0336    relevant mailing-list or to the newsgroup.
0338  - In all bug-reports, *please* tell what kernel you are talking about,
0339    how to duplicate the problem, and what your setup is (use your common
0340    sense).  If the problem is new, tell me so, and if the problem is
0341    old, please try to tell me when you first noticed it.
0343  - If the bug results in a message like
0345      unable to handle kernel paging request at address C0000010
0346      Oops: 0002
0347      EIP:   0010:XXXXXXXX
0348      eax: xxxxxxxx   ebx: xxxxxxxx   ecx: xxxxxxxx   edx: xxxxxxxx
0349      esi: xxxxxxxx   edi: xxxxxxxx   ebp: xxxxxxxx
0350      ds: xxxx  es: xxxx  fs: xxxx  gs: xxxx
0351      Pid: xx, process nr: xx
0352      xx xx xx xx xx xx xx xx xx xx
0354    or similar kernel debugging information on your screen or in your
0355    system log, please duplicate it *exactly*.  The dump may look
0356    incomprehensible to you, but it does contain information that may
0357    help debugging the problem.  The text above the dump is also
0358    important: it tells something about why the kernel dumped code (in
0359    the above example, it's due to a bad kernel pointer). More information
0360    on making sense of the dump is in Documentation/oops-tracing.txt
0362  - If you compiled the kernel with CONFIG_KALLSYMS you can send the dump
0363    as is, otherwise you will have to use the "ksymoops" program to make
0364    sense of the dump (but compiling with CONFIG_KALLSYMS is usually preferred).
0365    This utility can be downloaded from
0366    ftp://ftp.<country> .
0367    Alternatively, you can do the dump lookup by hand:
0369  - In debugging dumps like the above, it helps enormously if you can
0370    look up what the EIP value means.  The hex value as such doesn't help
0371    me or anybody else very much: it will depend on your particular
0372    kernel setup.  What you should do is take the hex value from the EIP
0373    line (ignore the "0010:"), and look it up in the kernel namelist to
0374    see which kernel function contains the offending address.
0376    To find out the kernel function name, you'll need to find the system
0377    binary associated with the kernel that exhibited the symptom.  This is
0378    the file 'linux/vmlinux'.  To extract the namelist and match it against
0379    the EIP from the kernel crash, do:
0381      nm vmlinux | sort | less
0383    This will give you a list of kernel addresses sorted in ascending
0384    order, from which it is simple to find the function that contains the
0385    offending address.  Note that the address given by the kernel
0386    debugging messages will not necessarily match exactly with the
0387    function addresses (in fact, that is very unlikely), so you can't
0388    just 'grep' the list: the list will, however, give you the starting
0389    point of each kernel function, so by looking for the function that
0390    has a starting address lower than the one you are searching for but
0391    is followed by a function with a higher address you will find the one
0392    you want.  In fact, it may be a good idea to include a bit of
0393    "context" in your problem report, giving a few lines around the
0394    interesting one. 
0396    If you for some reason cannot do the above (you have a pre-compiled
0397    kernel image or similar), telling me as much about your setup as
0398    possible will help.  Please read the REPORTING-BUGS document for details.
0400  - Alternatively, you can use gdb on a running kernel. (read-only; i.e. you
0401    cannot change values or set break points.) To do this, first compile the
0402    kernel with -g; edit arch/i386/Makefile appropriately, then do a "make
0403    clean". You'll also need to enable CONFIG_PROC_FS (via "make config").
0405    After you've rebooted with the new kernel, do "gdb vmlinux /proc/kcore".
0406    You can now use all the usual gdb commands. The command to look up the
0407    point where your system crashed is "l *0xXXXXXXXX". (Replace the XXXes
0408    with the EIP value.)
0410    gdb'ing a non-running kernel currently fails because gdb (wrongly)
0411    disregards the starting offset for which the kernel is compiled.