410 lines
18 KiB
ReStructuredText
410 lines
18 KiB
ReStructuredText
.. _readme:
|
|
|
|
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?
|
|
--------------
|
|
|
|
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. See Documentation/00-INDEX for a list of what
|
|
is contained in each file. 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-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
|
|
: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 4.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-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 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.
|
|
|
|
"make kvmconfig" Enable additional options for kvm guest kernel support.
|
|
|
|
"make xenconfig" 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.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 :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,
|
|
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/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 the :ref:`admin-guide/reporting-bugs.rst <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``).
|
|
|
|
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.
|