Linux 内核发行版本 2.6.xx

http://kernel.org/

本文是 linux 2.6 的版本说明。本文主要介绍什么是 linux，如何安装 kernel 以及如果 出现问题该怎么处理。

什么是 LINUX?

Linux 是 Unix 操作系统的一个克隆，是由 Linus Torvalds 和一群网络黑客从头开始写 的一个操作系统。Linux 的目标是更加符合 POSIX 和 Single Unix 规格标准。

它拥有在现代成熟的 Unix 中所有的特性，包括真正的多任务处理、虚拟内存、共享库、 加载器、执行程序的共享写时拷贝技术(STL)、优化的内存管理，还有多网络协议如 IPv4 和 IPv6。

它在GNU公共许可证的保护下发行。

硬件运行环境

虽然最初的 Linux 运行在 x86 架构的 32 位机上，但是随着 Linux 的发展，目前至少 可以运行下以下架构的处理器上：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.

只要含有分页机制的内存管理单元(PMMU) 和 GNU C 编译器接口(The GNU Compiler Collection 的组成部分，GCC)，Linux 就能很容易的移植到主流的 32 或 64 位体系结 构的处理器上。Linux也能在一些没有 PMMU 的架构上进行移植，虽然功能性上面或多或 少有所限制。

Linux 还能移植到它自己身上，可以像用户空间的应用程序一样运行内核 -- 这叫 "用户 模式 Linux" (UserMode Linux，简称 UML)。

文档

• 已经有大量针对 Linux 或关于通用 Unix 问题的文档，或以电子档的形式在网络上、或 以书本的形式发行。这里建议在任何地方分享的 Linux 的文档都值得好好看看，这份注 记不是作为系统的文档而提供的，有很多更好的资源适合你去阅读。

• 在 Documentation/ 的子目录下有许多不同的 README 文件，比如其中会有关于一些驱 动的内核安装说明。Documentation/00-INDEX 文件中包含关于各文件主要内容介绍的索 引。也看下 Changes 文件，其中有关于升级内核的一些信息。

• Documentation/DocBook/ 子目录下包含一些内核开发人员和用户的指南。这些指南提供 多种格式：PostScript(.ps), PDF, HTML, 和 man-pages 等。内核代码安装好之后，可 以通过使用 "make psdocs", "make pdfdocs", "make htmldocs" 或 "make mandocs" 命令来生成相应格式的文档。

安装内核源码

• If you install the full sources, put the kernel tarball in a directory where you have permissions (eg. your home directory) and unpack it:

• 如果安装所有的源代码，将压缩包放在某个你有相应权限的目录下(在你的 home 目录下 就可以了)，然后解压：

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

  或者

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

  其中 "XX" 指对应的内核版本号(一般升级时我们都选择最新的内核版本)。

  请不要使用 /usr/src/linux 这个区域。这个区域包含库头文件需要使用的大量(通常不 完全)的内核头文件。它们必须与库相匹配，而不应该因为内核变更弄的一团糟。

• 你可以通过打补丁在 2.6.xx 发布版之间升级。补丁以传统的 gzip 格式和较新的 bzip2格式提供。打补丁时，先下载所有新的补丁文件，进入内核源码的顶层目录，然后 执行以下命令：

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

  或者

   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.

  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.

  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.

• 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.

软件要求

编译并运行 2.6.xx 内核需要一些较新的软件包。从 Documentation/Changes 中可以查 找到有关于所需软件包的最低版本号，以及如何升级这些软件。

值得注意的是，使用一些过老版本的软件包会导致间接的错误，且这些错误非常难去跟 踪，所以不要在很明显的问题发生后再升级包。

构建内核路径

默认情况下，编译内核源代码所有生成的文件会与内核源代码在同个目录下。 "make O=output/dir" 命令允许你指定特定的目录来放生成的文件(包括 .config)。 例如 kernel 和编译输出目录如下：

kernel source code:     /usr/src/linux-2.6.N
build directory:        /home/name/build/kernel

则需要使用下面的命令来配置和编译内核:

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

请注意：一旦使用了 'O=output/dir' 这个选项，则后面的命令都要使用这个选项。

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.

• Alternate configuration commands are: "make config" Plain text interface. "make menuconfig" Text based color menus, radiolists & dialogs. "make xconfig" X windows (Qt) based configuration tool. "make gconfig" X windows (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 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.

  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
  • 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.
  • 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.

编译内核

• 确认 gcc 至少为 3.2 版本。在 Documentation/Changes 中可查阅到更多的信息。 请注意当前的内核仍能够运行 a.out 形式的用户程序。

• 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.

  真正安装时需要root权限，但其他的编译动作不需要。尽量不要使用root身份来执行命 令。

• 如果将某个部份编译成了模块 "modules"，还需要运行 "make modules_install" 命令。

• 内核编译/构建时的详细输出信息：

  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.:

   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/i386/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.

  重装完LILO之后，所有的工作都作完了。然后关掉系统。

  如果还需要更改内核中默认的根设备、视频模式、ramdisk 的大小等，使用 "rdev" 程 序(如果可能的话用使用 LILO 加载选项)，而不必重新编译内核来改变这些参数。

• 重启后开始愉快的 Linux 之旅吧。

倘若出现了错误

• 如果问题看起来像是内核的 bug，请检查 MAINTAINERS 来查看出错的部份是否有专门的 人来维护，如果没有，请向 torvalds@linux-foundation.org 发邮件，如果可能的话， 也可向相关的邮件列表发邮件。

• 在报告 bug 时，请详细描述你所用的是什么内核、如何重现你所遇到的问题、你做了哪 设置(你感觉会是什么问题)。如果是新问题，告诉我这些，如果是旧问题(该问题以前可 能被讨论过), 请告诉我你是什么时候开始注意该问题的。

• 如果出现 bug 的时候打印类似这样的 log 信息

   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
  

  屏幕上或系统 log 里记录了类似上面的信息，请准确地将它们复制下来。这些可能看 起来毫无意义，但其中却可能包含了用于调试该问题的信息。它上部的字符也很重要： 它记录了内核崩溃代码(上面的例子里的错误代码表示出错的原因是错误的内核指针)。 更多关于这类的信息可查看 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..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.