README - Kernel Git Source Tree - This git is only for xburst cpu upstreaming works or co-works. nothing relate to openwrt-xburst.git, please use openwrt-xburst.git/target/linux/xburst/ for the last NanoNote kernel

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Linux kernel release 2.6.xx <http://kernel.org/>

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These are the release notes for Linux version 2.6. Read them carefully,

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as they tell you what this is all about, explain how to install the

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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

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Linus Torvalds with assistance from a loosely-knit team of hackers across

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the Net. It aims towards POSIX and Single UNIX Specification compliance.

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It has all the features you would expect in a modern fully-fledged Unix,

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including true multitasking, virtual memory, shared libraries, demand

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loading, shared copy-on-write executables, proper memory management,

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and multistack networking including IPv4 and IPv6.

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

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accompanying COPYING file for more details.

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ON WHAT HARDWARE DOES IT RUN?

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Although originally developed first for 32-bit x86-based PCs (386 or higher),

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today Linux also runs on (at least) the Compaq Alpha AXP, Sun SPARC and

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UltraSPARC, Motorola 68000, PowerPC, PowerPC64, ARM, Hitachi SuperH, Cell,

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IBM S/390, MIPS, HP PA-RISC, Intel IA-64, DEC VAX, AMD x86-64, AXIS CRIS,

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Xtensa, AVR32 and Renesas M32R architectures.

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Linux is easily portable to most general-purpose 32- or 64-bit architectures

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as long as they have a paged memory management unit (PMMU) and a port of the

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GNU C compiler (gcc) (part of The GNU Compiler Collection, GCC). Linux has

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also been ported to a number of architectures without a PMMU, although

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functionality is then obviously somewhat limited.

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

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

DOCUMENTATION:

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

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

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general UNIX questions. I'd recommend looking into the documentation

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subdirectories on any Linux FTP site for the LDP (Linux Documentation

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Project) books. This README is not meant to be documentation on the

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system: there are much better sources available.

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- There are various README files in the Documentation/ subdirectory:

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these typically contain kernel-specific installation notes for some

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drivers for example. See Documentation/00-INDEX for a list of what

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is contained in each file. Please read the Changes file, as it

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contains information about the problems, which may result by upgrading

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your kernel.

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- The Documentation/DocBook/ subdirectory contains several guides for

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kernel developers and users. These guides can be rendered in a

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number of formats: PostScript (.ps), PDF, HTML, & man-pages, among others.

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After installation, "make psdocs", "make pdfdocs", "make htmldocs",

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

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INSTALLING the kernel source:

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- If you install the full sources, put the kernel tarball in a

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directory where you have permissions (eg. your home directory) and

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unpack it:

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gzip -cd linux-2.6.XX.tar.gz | tar xvf -

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or

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bzip2 -dc linux-2.6.XX.tar.bz2 | tar xvf -

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Replace "XX" with the version number of the latest kernel.

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Do NOT use the /usr/src/linux area! This area has a (usually

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incomplete) set of kernel headers that are used by the library header

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files. They should match the library, and not get messed up by

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whatever the kernel-du-jour happens to be.

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- You can also upgrade between 2.6.xx releases by patching. Patches are

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distributed in the traditional gzip and the newer bzip2 format. To

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install by patching, get all the newer patch files, enter the

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top level directory of the kernel source (linux-2.6.xx) and execute:

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gzip -cd ../patch-2.6.xx.gz | patch -p1

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or

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bzip2 -dc ../patch-2.6.xx.bz2 | patch -p1

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(repeat xx for all versions bigger than the version of your current

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source tree, _in_order_) and you should be ok. You may want to remove

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the backup files (xxx~ or xxx.orig), and make sure that there are no

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failed patches (xxx# or xxx.rej). If there are, either you or me has

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made a mistake.

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Unlike patches for the 2.6.x kernels, patches for the 2.6.x.y kernels

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(also known as the -stable kernels) are not incremental but instead apply

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directly to the base 2.6.x kernel. Please read

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Documentation/applying-patches.txt for more information.

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Alternatively, the script patch-kernel can be used to automate this

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process. It determines the current kernel version and applies any

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patches found.

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linux/scripts/patch-kernel linux

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The first argument in the command above is the location of the

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kernel source. Patches are applied from the current directory, but

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an alternative directory can be specified as the second argument.

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- If you are upgrading between releases using the stable series patches

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(for example, patch-2.6.xx.y), note that these "dot-releases" are

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not incremental and must be applied to the 2.6.xx base tree. For

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example, if your base kernel is 2.6.12 and you want to apply the

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2.6.12.3 patch, you do not and indeed must not first apply the

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2.6.12.1 and 2.6.12.2 patches. Similarly, if you are running kernel

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version 2.6.12.2 and want to jump to 2.6.12.3, you must first

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reverse the 2.6.12.2 patch (that is, patch -R) _before_ applying

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the 2.6.12.3 patch.

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You can read more on this in Documentation/applying-patches.txt

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- Make sure you have no stale .o files and dependencies lying around:

cd linux

make mrproper

You should now have the sources correctly installed.

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SOFTWARE REQUIREMENTS

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Compiling and running the 2.6.xx kernels requires up-to-date

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versions of various software packages. Consult

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Documentation/Changes for the minimum version numbers required

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and how to get updates for these packages. Beware that using

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excessively old versions of these packages can cause indirect

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errors that are very difficult to track down, so don't assume that

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you can just update packages when obvious problems arise during

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build or operation.

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BUILD directory for the kernel:

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When compiling the kernel all output files will per default be

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stored together with the kernel source code.

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Using the option "make O=output/dir" allow you to specify an alternate

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place for the output files (including .config).

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Example:

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kernel source code: /usr/src/linux-2.6.N

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build directory: /home/name/build/kernel

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To configure and build the kernel use:

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cd /usr/src/linux-2.6.N

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make O=/home/name/build/kernel menuconfig

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make O=/home/name/build/kernel

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sudo make O=/home/name/build/kernel modules_install install

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

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used for all invocations of make.

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CONFIGURING the kernel:

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Do not skip this step even if you are only upgrading one minor

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version. New configuration options are added in each release, and

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odd problems will turn up if the configuration files are not set up

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as expected. If you want to carry your existing configuration to a

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

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only ask you for the answers to new questions.

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- Alternate configuration commands are:

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"make config" Plain text interface.

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"make menuconfig" Text based color menus, radiolists & dialogs.

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"make xconfig" X windows (Qt) based configuration tool.

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"make gconfig" X windows (Gtk) based configuration tool.

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"make oldconfig" Default all questions based on the contents of

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your existing ./.config file and asking about

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new config symbols.

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"make silentoldconfig"

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Like above, but avoids cluttering the screen

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with questions already answered.

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Additionally updates the dependencies.

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"make defconfig" Create a ./.config file by using the default

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symbol values from either arch/$ARCH/defconfig

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or arch/$ARCH/configs/${PLATFORM}_defconfig,

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depending on the architecture.

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"make ${PLATFORM}_defconfig"

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Create a ./.config file by using the default

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symbol values from

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arch/$ARCH/configs/${PLATFORM}_defconfig.

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Use "make help" to get a list of all available

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platforms of your architecture.

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"make allyesconfig"

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Create a ./.config file by setting symbol

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values to 'y' as much as possible.

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"make allmodconfig"

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Create a ./.config file by setting symbol

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values to 'm' as much as possible.

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"make allnoconfig" Create a ./.config file by setting symbol

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values to 'n' as much as possible.

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"make randconfig" Create a ./.config file by setting symbol

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values to random values.

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

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in Documentation/kbuild/kconfig.txt.

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NOTES on "make config":

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

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under some circumstances lead to problems: probing for a

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nonexistent controller card may confuse your other controllers

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- compiling the kernel with "Processor type" set higher than 386

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will result in a kernel that does NOT work on a 386. The

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kernel will detect this on bootup, and give up.

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- A kernel with math-emulation compiled in will still use the

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coprocessor if one is present: the math emulation will just

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never get used in that case. The kernel will be slightly larger,

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but will work on different machines regardless of whether they

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have a math coprocessor or not.

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- the "kernel hacking" configuration details usually result in a

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bigger or slower kernel (or both), and can even make the kernel

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less stable by configuring some routines to actively try to

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break bad code to find kernel problems (kmalloc()). Thus you

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should probably answer 'n' to the questions for

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"development", "experimental", or "debugging" features.

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COMPILING the kernel:

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- Make sure you have at least gcc 3.2 available.

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For more information, refer to Documentation/Changes.

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Please note that you can still run a.out user programs with this kernel.

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- Do a "make" to create a compressed kernel image. It is also

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possible to do "make install" if you have lilo installed to suit the

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kernel makefiles, but you may want to check your particular lilo setup first.

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To do the actual install you have to be root, but none of the normal

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build should require that. Don't take the name of root in vain.

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- If you configured any of the parts of the kernel as `modules', you

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will also have to do "make modules_install".

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- Verbose kernel compile/build output:

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Normally the kernel build system runs in a fairly quiet mode (but not

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totally silent). However, sometimes you or other kernel developers need

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to see compile, link, or other commands exactly as they are executed.

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For this, use "verbose" build mode. This is done by inserting

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"V=1" in the "make" command. E.g.:

make V=1 all

To have the build system also tell the reason for the rebuild of each

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target, use "V=2". The default is "V=0".

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- Keep a backup kernel handy in case something goes wrong. This is

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especially true for the development releases, since each new release

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contains new code which has not been debugged. Make sure you keep a

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backup of the modules corresponding to that kernel, as well. If you

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are installing a new kernel with the same version number as your

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working kernel, make a backup of your modules directory before you

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do a "make modules_install".

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Alternatively, before compiling, use the kernel config option

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

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LOCALVERSION can be set in the "General Setup" menu.

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- In order to boot your new kernel, you'll need to copy the kernel

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image (e.g. .../linux/arch/i386/boot/bzImage after compilation)

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to the place where your regular bootable kernel is found.

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- Booting a kernel directly from a floppy without the assistance of a

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bootloader such as LILO, is no longer supported.

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If you boot Linux from the hard drive, chances are you use LILO which

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uses the kernel image as specified in the file /etc/lilo.conf. The

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kernel image file is usually /vmlinuz, /boot/vmlinuz, /bzImage or

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/boot/bzImage. To use the new kernel, save a copy of the old image

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and copy the new image over the old one. Then, you MUST RERUN LILO

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to update the loading map!! If you don't, you won't be able to boot

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the new kernel image.

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Reinstalling LILO is usually a matter of running /sbin/lilo.

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You may wish to edit /etc/lilo.conf to specify an entry for your

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old kernel image (say, /vmlinux.old) in case the new one does not

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work. See the LILO docs for more information.

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After reinstalling LILO, you should be all set. Shutdown the system,

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reboot, and enjoy!

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If you ever need to change the default root device, video mode,

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ramdisk size, etc. in the kernel image, use the 'rdev' program (or

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alternatively the LILO boot options when appropriate). No need to

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recompile the kernel to change these parameters.

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- Reboot with the new kernel and enjoy.

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IF SOMETHING GOES WRONG:

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- If you have problems that seem to be due to kernel bugs, please check

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the file MAINTAINERS to see if there is a particular person associated

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with the part of the kernel that you are having trouble with. If there

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isn't anyone listed there, then the second best thing is to mail

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them to me (torvalds@linux-foundation.org), and possibly to any other

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relevant mailing-list or to the newsgroup.

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- In all bug-reports, *please* tell what kernel you are talking about,

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how to duplicate the problem, and what your setup is (use your common

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sense). If the problem is new, tell me so, and if the problem is

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old, please try to tell me when you first noticed it.

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- If the bug results in a message like

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unable to handle kernel paging request at address C0000010

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Oops: 0002

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EIP: 0010:XXXXXXXX

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eax: xxxxxxxx ebx: xxxxxxxx ecx: xxxxxxxx edx: xxxxxxxx

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esi: xxxxxxxx edi: xxxxxxxx ebp: xxxxxxxx

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ds: xxxx es: xxxx fs: xxxx gs: xxxx

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Pid: xx, process nr: xx

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xx xx xx xx xx xx xx xx xx xx

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or similar kernel debugging information on your screen or in your

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system log, please duplicate it *exactly*. The dump may look

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incomprehensible to you, but it does contain information that may

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help debugging the problem. The text above the dump is also

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important: it tells something about why the kernel dumped code (in

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the above example it's due to a bad kernel pointer). More information

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on making sense of the dump is in Documentation/oops-tracing.txt

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- If you compiled the kernel with CONFIG_KALLSYMS you can send the dump

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as is, otherwise you will have to use the "ksymoops" program to make

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sense of the dump (but compiling with CONFIG_KALLSYMS is usually preferred).

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This utility can be downloaded from

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ftp://ftp.<country>.kernel.org/pub/linux/utils/kernel/ksymoops/ .

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Alternately you can do the dump lookup by hand:

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- In debugging dumps like the above, it helps enormously if you can

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look up what the EIP value means. The hex value as such doesn't help

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me or anybody else very much: it will depend on your particular

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kernel setup. What you should do is take the hex value from the EIP

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line (ignore the "0010:"), and look it up in the kernel namelist to

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see which kernel function contains the offending address.

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To find out the kernel function name, you'll need to find the system

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binary associated with the kernel that exhibited the symptom. This is

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the file 'linux/vmlinux'. To extract the namelist and match it against

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the EIP from the kernel crash, do:

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nm vmlinux | sort | less

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This will give you a list of kernel addresses sorted in ascending

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order, from which it is simple to find the function that contains the

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offending address. Note that the address given by the kernel

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debugging messages will not necessarily match exactly with the

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function addresses (in fact, that is very unlikely), so you can't

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just 'grep' the list: the list will, however, give you the starting

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point of each kernel function, so by looking for the function that

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has a starting address lower than the one you are searching for but

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is followed by a function with a higher address you will find the one

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you want. In fact, it may be a good idea to include a bit of

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"context" in your problem report, giving a few lines around the

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interesting one.

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If you for some reason cannot do the above (you have a pre-compiled

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kernel image or similar), telling me as much about your setup as

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possible will help. Please read the REPORTING-BUGS document for details.

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- Alternately, you can use gdb on a running kernel. (read-only; i.e. you

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cannot change values or set break points.) To do this, first compile the

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kernel with -g; edit arch/i386/Makefile appropriately, then do a "make

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clean". You'll also need to enable CONFIG_PROC_FS (via "make config").

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After you've rebooted with the new kernel, do "gdb vmlinux /proc/kcore".

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You can now use all the usual gdb commands. The command to look up the

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point where your system crashed is "l *0xXXXXXXXX". (Replace the XXXes

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with the EIP value.)

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

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disregards the starting offset for which the kernel is compiled.

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