一个初学者如何可以在浩瀚的linux海洋里找到自己的小舟，遨游其中。我就是在寻觅的其中一员，希望你也是。接触linux内核，学习源代码，学习大师
们的杰作，这就是我的原动力，网上太多如何学习linux源代码的方法，可能适合一部分人，每个人都有自己的方法。而我，经过很常时间的思考，于是下定决
心，先攻破晦涩的英语这关，因为代码注释都是英文。我希望和有兴趣的初学者一起完成我们的遨游，那是无比的快乐和幸福！我英语只过了4级，翻译得很烂，只
是将我以为必要的翻译了，希望有爱好者能有时间将它补充完整，有些地方还翻译得不好。
来自linux-2.6.36.2/README
Linux kernel release 2.6.xx <http://kernel.org/>
These are the release notes for Linux version 2.6. 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 - see the
accompanying COPYING file for more details.
ON WHAT HARDWARE DOES IT RUN?
在什么机器上可以跑？
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, AXIS CRIS,
Xtensa, AVR32 and Renesas M32R architectures.
Linux is easily portable(方便的) 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（有点） limited.
Linux has also been ported to itself. You can now run the kernel as a
userspace application - this is called UserMode Linux (UML).
linux很容易就可以移植到32或者64位的机器上，只要它们有内存管理单元(PMMU)和一个GNU C编译工具。
linux也可以移植到一些没有PMMU的机器上，虽然功能上有点限制。linux也可以移植到自身。你现在就可以
将内核作为一个用户空间的应用程序（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.
这个文件夹下面包括了许多有用多文件，来自网络和书的电子版，还有linux和一般性unix的问题。
我推荐去看这个文件夹下面的那些linux FTP站点。此README在系统中并不意味着是完整的说明，站点里面
有更加好的资源。
- 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 Changes file, as it
contains information about the problems, which may result by upgrading
your kernel.
在每个子目录下面都有README文件，包含来内核安装的提示，比如某些驱动。看一下“Documentation/00-INDEX”
这个子目录，里面列出来每个文件。请读“Changs”这个文件，里面包含了一些难点信息，可能要导致你内核的升级。
- 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.
在“Documentation/DocBook/”这个子目录下包含了内核开发者和使用者的一些向导。可以作成.ps、PDF、
HTML等格式，用命令"make psdocs"、“make pdfdocs”、"make htmldocs"或者“make mandocs”。
INSTALLING the kernel source:
- If you install the full sources, put the kernel tarball in a
directory where you have permissions (eg. your home directory) and
unpack it:
如果你想安装源代码，请安装tar打包工具，然后用以下命令：
gzip -cd linux-2.6.XX.tar.gz | tar xvf -
or
bzip2 -dc linux-2.6.XX.tar.bz2 | tar xvf -
Replace "XX" with the version number of the latest kernel.
请用“XX”代替最近内核的版本号。
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.
不要使用“/usr/src/linux”作为目录，因为这个是内核库头文件的目录。
- You can also upgrade between 2.6.xx releases by patching. Patches are
distributed in the traditional gzip and the newer bzip2 format. To
install by patching, get all the newer patch files, enter the
top level directory of the kernel source (linux-2.6.xx) and execute:
你可以通过patch升级你的发行版。Patches一般都是用gzip和bzip2打包的。为了安装补丁，
要得到所有新的patch文件，然后进入内核源代码的顶级目录，使用以下命令：
gzip -cd ../patch-2.6.xx.gz | patch -p1
or
bzip2 -dc ../patch-2.6.xx.bz2 | patch -p1
(repeat xx for all versions bigger than the version of your current
source tree, _in_order_) and you should be ok. You may want to remove
the backup files (xxx~ or xxx.orig), and make sure that there are no
failed patches (xxx# or xxx.rej). If there are, either you or me has
made a mistake.
（打完补丁后，“xx”会替代当前源代码树的版本号），这样就ok了。你可能还要将一些备份文件删除掉，
(xxx~ or xxx.orig),确保没有失败的patches(xxx# or xxx.rej)。如果有，不是你犯错了，就是我。
Unlike patches for the 2.6.x kernels, patches for the 2.6.x.y kernels
(also known as the -stable kernels) are not incremental but instead apply
directly to the base 2.6.x kernel. Please read
Documentation/applying-patches.txt for more information.
不像“2.6.x”的内核补丁，“2.6.x.y”的内核补丁不是递增而是直接急于“2.6.x”内核的。请阅读“
Documentation/applying-patches.txt”文件，有更多信息。
Alternatively, the script patch-kernel can be used to automate this
process. It determines the current kernel version and applies any
patches found.
这个脚本“patch-kernel”被自动地使用在这个过程中，决定当前内核版本，运用在任何的补丁上。
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.
上面那个放在内核源代码中。补丁们可以用于当前目录，而且可以选择不同的目录。
- If you are upgrading between releases using the stable series patches
(for example, patch-2.6.xx.y), note that these "dot-releases" are
not incremental and must be applied to the 2.6.xx base tree. For
example, if your base kernel is 2.6.12 and you want to apply the
2.6.12.3 patch, you do not and indeed must not first apply the
2.6.12.1 and 2.6.12.2 patches. Similarly, if you are running kernel
version 2.6.12.2 and want to jump to 2.6.12.3, you must first
reverse the 2.6.12.2 patch (that is, patch -R) _before_ applying
the 2.6.12.3 patch.
You can read more on this in Documentation/applying-patches.txt
- 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 2.6.xx 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
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.
我们编译和运行内核时，需要一些软件包，并且这些软件包要符合内核更新的版本，否则会带来
很难追踪的错误。
BUILD directory for the kernel:
为内核建立目录：
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" allow you to specify an alternate
place for the output files (including .config).
Example:
kernel source code: /usr/src/linux-2.6.N
build directory: /home/name/build/kernel
我们编译内核时，可以将输出文件放在一起。
To configure and build the kernel use:
cd /usr/src/linux-2.6.N
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.
注意：所有的“make”命令都要带着“0=output/dir”。
CONFIGURING the kernel:
配置内核：
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.
不要跳过这个步骤，即使你仅仅只是升级一个小的版本。新的配置选项被增加到每个发行版中。
如果你想尽量用最小的工作量来配置，可以使用“use oldconfig”。
- Alternate configuration commands are:
"make config" Plain text interface.
简单的文本界面
"make menuconfig" Text based color menus, radiolists & dialogs.
有颜色的文本菜单，按钮列表和对话框
"make xconfig" X windows (Qt) based configuration tool.
图形界面（QT）
"make gconfig" X windows (Gtk) based configuration tool.
图形界面（GTK）
"make oldconfig" Default all questions based on the contents of
your existing ./.config file and asking about
new config symbols.
会默认一些基本内容，问一些新的配置
"make silentoldconfig"
Like above, but avoids cluttering the screen
with questions already answered.
Additionally updates the dependencies.
"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.
You can find more information on using the Linux kernel config tools
in Documentation/kbuild/kconfig.txt.
你可以通过“Documentation/kbuild/kconfig.txt”得到更多信息。
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
没有必要的驱动会使内核变大，在某些环境下可能会导致问题：探测一个不存在的控制器卡可能会
拒绝你另外一些控制器
- compiling the kernel with "Processor type" set higher than 386
will result in a kernel that does NOT work on a 386. The
kernel will detect this on bootup, and give up.
编译内核时，高于386的处理器在386的机器上无法工作。
- 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.
就是说如果内核将数学模拟编译进去后，不管运行在什么机器上，即使那个机器上有数学协处理器，
它都会进行模拟。
- 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.
像“kernel hacking”这样的选项会导致内核的不稳定。因此最好不要将它们编译进内核，比如有
"development", "experimental", or "debugging"特征的。
COMPILING the kernel:
编译内核：
- Make sure you have at least gcc 3.2 available.
For more information, refer to Documentation/Changes.
最低gcc本版为3.2，可以参考“Documentation/Changes”文件
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.
你可以使用“make”来创建压缩内核映像，也可以使用“make install”，不过要检查一下是否安装来lilo。
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".
如果你将内核配置成了模块，那么你得用“make modules_install”。
- Verbose kernel compile/build output:
- 编译/建立的详细输出：
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 inserting
"V=1" in the "make" command. E.g.:
一般来说内核建立步骤比较简单啦，然而，有些时候，需要学习一下编译、链接和另外一些命令。
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.
就是说让内核编译的模块时，有个备份，如果你不备份，也可以使用“General Setup”菜单下面的
“LOCALVERSION”选项。
- In order to boot your new kernel, you'll need to copy the kernel
image (e.g. .../linux/arch/i386/boot/bzImage after compilation)
to the place where your regular bootable kernel is found.
为了让你的新内核启动，要将内核映像放在boot可以找得到的地方。
- Booting a kernel directly from a floppy without the assistance of a
bootloader such as LILO, is no longer supported.
我们不提倡用软盘启动内核在没有bootloader“LILO”的情况下。
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.
如果用硬盘启动，你使用LILO，配置文件在“/etc/lilo.conf”，内核映像在"/boot/"目录下。
为了使用新的内核，为旧的内核保存一份拷贝，将新的内核映像覆盖旧的。然后重新运行一下LILO，更新
加载的map!!否则不能启动新的内核映像。
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.
下载后的LILO程序放在“/sbin/lilo”里，如果你将它的配置文件“/etc/lilo.conf”配置
成旧内核启动，那么新内核就无法工作了，可以查看LILO文档获得更多的信息。
After reinstalling LILO, you should be all set. Shutdown the system,
reboot, and enjoy!
重新启动，即可进入新内核了！
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.
如果你想改变内核映像的根设备、视频模式、虚拟盘的大小，可以使用"rdev"程序（或者在
LILO的选项中配置），不需要改变内核参数重新编译内核。
- Reboot with the new kernel and enjoy.
IF SOMETHING GOES WRONG:
如果出错了：
- 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/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
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/ .
Alternately 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 REPORTING-BUGS document for details.
- Alternately, 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/i386/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.