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Linux kernel release 4.x <http://kernel.org/>

=============================================

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.

WHAT IS LINUX?

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

  It is distributed under the GNU General Public License - see the

  accompanying COPYING file for more details.

ON WHAT HARDWARE DOES IT RUN?

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

  Linux has also been ported to itself. You can now run the kernel as a

  userspace application - this is called UserMode Linux (UML).

DOCUMENTATION:

Documentation

-------------

 - There is a lot of documentation available both in electronic form on

   the Internet and in books, both Linux-specific and pertaining to

 - 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.

   After installation, ``make psdocs``, ``make pdfdocs``, ``make htmldocs``,

   or ``make mandocs`` will render the documentation in the requested format.

INSTALLING the kernel source:

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:

   unpack it::

     xz -cd linux-4.X.tar.xz | tar xvf -

 - 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:

   (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

   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.

   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

   patch -R) **before** applying the 4.0.3 patch. You can read more on this in

   :ref:`Documentation/applying-patches.txt <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.

   patches found::

     linux/scripts/patch-kernel linux

   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:

 - 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

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

   :ref:`Documentation/Changes <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:

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

   Using the option ``make O=output/dir`` allows you to specify an alternate

   place for the output files (including .config).

   Example:

   Example::

     kernel source code: /usr/src/linux-4.X

     build directory:    /home/name/build/kernel

   To configure and build the kernel, use:

   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

   Please note: If the ``O=output/dir`` option is used, then it must be

   used for all invocations of make.

CONFIGURING the kernel:

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

   new version with minimal work, use ``make oldconfig``, which will

   only ask you for the answers to new questions.

 - Alternative configuration commands are:

 - Alternative configuration commands are::

     "make config"      Plain text interface.

   You can find more information on using the Linux kernel config tools

   in Documentation/kbuild/kconfig.txt.

 - NOTES on "make config":

 - NOTES on ``make config``:

    - Having unnecessary drivers will make the kernel bigger, and can

      under some circumstances lead to problems: probing for a

      should probably answer 'n' to the questions for "development",

      "experimental", or "debugging" features.

COMPILING the kernel:

Compiling the kernel

--------------------

 - Make sure you have at least gcc 3.2 available.

   For more information, refer to Documentation/Changes.

   For more information, refer to :ref:`Documentation/Changes <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

 - 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".

 - 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:

   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.

   ``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".

   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

   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".

   do a ``make modules_install``.

   Alternatively, before compiling, use the kernel config option

   "LOCALVERSION" to append a unique suffix to the regular kernel version.

   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

   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 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

   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

 - If the bug results in a message like::

     unable to handle kernel paging request at address C0000010

     Oops: 0002

   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

   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/ .

   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

   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:

   the EIP from the kernel crash, do::

     nm vmlinux | sort | less

   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.

   possible will help.  Please read the :ref:`REPORTING-BUGS <reportingbugs>`

   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").

   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".

   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

   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)

   gdb'ing a non-running kernel currently fails because ``gdb`` (wrongly)

   disregards the starting offset for which the kernel is compiled.