OSCL-LXR linux-6.0.1/​Documentation/​admin-guide/​README.rst	Source navigation Diff markup Identifier search General search
	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 .. _readme:
 
 Linux kernel release 6.x <http://kernel.org/>
 =============================================
 
 These are the release notes for Linux version 6.  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.
 
 What is Linux?
 --------------
 
   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.
 
   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 v2 - 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 Xtensa, and
   ARC 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. Please read the
    :ref:`Documentation/process/changes.rst <changes>` file, as it
    contains information about the problems, which may result by upgrading
    your kernel.
 
 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-6.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 6.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-6.x) and execute::
 
      xz -cd ../patch-6.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 6.x kernels, patches for the 6.x.y kernels
    (also known as the -stable kernels) are not incremental but instead apply
    directly to the base 6.x kernel.  For example, if your base kernel is 6.0
    and you want to apply the 6.0.3 patch, you must not first apply the 6.0.1
    and 6.0.2 patches. Similarly, if you are running kernel version 6.0.2 and
    want to jump to 6.0.3, you must first reverse the 6.0.2 patch (that is,
    patch -R) **before** applying the 6.0.3 patch. You can read more on this in
    :ref:`Documentation/process/applying-patches.rst <applying_patches>`.
 
    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 6.x kernels requires up-to-date
    versions of various software packages.  Consult
    :ref:`Documentation/process/changes.rst <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-6.x
      build directory:    /home/name/build/kernel
 
    To configure and build the kernel, use::
 
      cd /usr/src/linux-6.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 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.
 
                            Also, you can preserve modules in certain folders
                            or kconfig files by specifying their paths in
                            parameter LMC_KEEP.
 
                    target$ lsmod > /tmp/mylsmod
                    target$ scp /tmp/mylsmod host:/tmp
 
                    host$ make LSMOD=/tmp/mylsmod \
                            LMC_KEEP="drivers/usb:drivers/gpu:fs" \
                            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
                            also preserve modules by LMC_KEEP.
 
      "make kvm_guest.config"   Enable additional options for kvm guest kernel
                                support.
 
      "make xen.config"   Enable additional options for xen dom0 guest kernel
                          support.
 
      "make tinyconfig"  Configure the tiniest possible kernel.
 
    You can find more information on using the Linux kernel config tools
    in Documentation/kbuild/kconfig.rst.
 
  - 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 5.1 available.
    For more information, refer to :ref:`Documentation/process/changes.rst <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,
    etc. in the kernel image, use your bootloader's boot options
    where 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/admin-guide/bug-hunting.rst
 
  - 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
    https://www.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
    'Documentation/admin-guide/reporting-issues.rst' 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.

This page was automatically generated by the 2.1.0 LXR engine. The LXR team