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  1. Linux kernel release 2.6.xx <http://kernel.org>
  2. These are the release notes for Linux version 2.6. Read them carefully,
  3. as they tell you what this is all about, explain how to install the
  4. kernel, and what to do if something goes wrong.
  5. WHAT IS LINUX?
  6. Linux is a clone of the operating system Unix, written from scratch by
  7. Linus Torvalds with assistance from a loosely-knit team of hackers across
  8. the Net. It aims towards POSIX and Single UNIX Specification compliance.
  9. It has all the features you would expect in a modern fully-fledged Unix,
  10. including true multitasking, virtual memory, shared libraries, demand
  11. loading, shared copy-on-write executables, proper memory management,
  12. and multistack networking including IPv4 and IPv6.
  13. It is distributed under the GNU General Public License - see the
  14. accompanying COPYING file for more details.
  15. ON WHAT HARDWARE DOES IT RUN?
  16. Although originally developed first for 32-bit x86-based PCs (386 or higher),
  17. today Linux also runs on (at least) the Compaq Alpha AXP, Sun SPARC and
  18. UltraSPARC, Motorola 68000, PowerPC, PowerPC64, ARM, Hitachi SuperH,
  19. IBM S/390, MIPS, HP PA-RISC, Intel IA-64, DEC VAX, AMD x86-64, AXIS CRIS,
  20. and Renesas M32R architectures.
  21. Linux is easily portable to most general-purpose 32- or 64-bit architectures
  22. as long as they have a paged memory management unit (PMMU) and a port of the
  23. GNU C compiler (gcc) (part of The GNU Compiler Collection, GCC). Linux has
  24. also been ported to a number of architectures without a PMMU, although
  25. functionality is then obviously somewhat limited.
  26. DOCUMENTATION:
  27. - There is a lot of documentation available both in electronic form on
  28. the Internet and in books, both Linux-specific and pertaining to
  29. general UNIX questions. I'd recommend looking into the documentation
  30. subdirectories on any Linux FTP site for the LDP (Linux Documentation
  31. Project) books. This README is not meant to be documentation on the
  32. system: there are much better sources available.
  33. - There are various README files in the Documentation/ subdirectory:
  34. these typically contain kernel-specific installation notes for some
  35. drivers for example. See Documentation/00-INDEX for a list of what
  36. is contained in each file. Please read the Changes file, as it
  37. contains information about the problems, which may result by upgrading
  38. your kernel.
  39. - The Documentation/DocBook/ subdirectory contains several guides for
  40. kernel developers and users. These guides can be rendered in a
  41. number of formats: PostScript (.ps), PDF, and HTML, among others.
  42. After installation, "make psdocs", "make pdfdocs", or "make htmldocs"
  43. will render the documentation in the requested format.
  44. INSTALLING the kernel:
  45. - If you install the full sources, put the kernel tarball in a
  46. directory where you have permissions (eg. your home directory) and
  47. unpack it:
  48. gzip -cd linux-2.6.XX.tar.gz | tar xvf -
  49. or
  50. bzip2 -dc linux-2.6.XX.tar.bz2 | tar xvf -
  51. Replace "XX" with the version number of the latest kernel.
  52. Do NOT use the /usr/src/linux area! This area has a (usually
  53. incomplete) set of kernel headers that are used by the library header
  54. files. They should match the library, and not get messed up by
  55. whatever the kernel-du-jour happens to be.
  56. - You can also upgrade between 2.6.xx releases by patching. Patches are
  57. distributed in the traditional gzip and the new bzip2 format. To
  58. install by patching, get all the newer patch files, enter the
  59. top level directory of the kernel source (linux-2.6.xx) and execute:
  60. gzip -cd ../patch-2.6.xx.gz | patch -p1
  61. or
  62. bzip2 -dc ../patch-2.6.xx.bz2 | patch -p1
  63. (repeat xx for all versions bigger than the version of your current
  64. source tree, _in_order_) and you should be ok. You may want to remove
  65. the backup files (xxx~ or xxx.orig), and make sure that there are no
  66. failed patches (xxx# or xxx.rej). If there are, either you or me has
  67. made a mistake.
  68. Unlike patches for the 2.6.x kernels, patches for the 2.6.x.y kernels
  69. (also known as the -stable kernels) are not incremental but instead apply
  70. directly to the base 2.6.x kernel. Please read
  71. Documentation/applying-patches.txt for more information.
  72. Alternatively, the script patch-kernel can be used to automate this
  73. process. It determines the current kernel version and applies any
  74. patches found.
  75. linux/scripts/patch-kernel linux
  76. The first argument in the command above is the location of the
  77. kernel source. Patches are applied from the current directory, but
  78. an alternative directory can be specified as the second argument.
  79. - If you are upgrading between releases using the stable series patches
  80. (for example, patch-2.6.xx.y), note that these "dot-releases" are
  81. not incremental and must be applied to the 2.6.xx base tree. For
  82. example, if your base kernel is 2.6.12 and you want to apply the
  83. 2.6.12.3 patch, you do not and indeed must not first apply the
  84. 2.6.12.1 and 2.6.12.2 patches. Similarly, if you are running kernel
  85. version 2.6.12.2 and want to jump to 2.6.12.3, you must first
  86. reverse the 2.6.12.2 patch (that is, patch -R) _before_ applying
  87. the 2.6.12.3 patch.
  88. - Make sure you have no stale .o files and dependencies lying around:
  89. cd linux
  90. make mrproper
  91. You should now have the sources correctly installed.
  92. SOFTWARE REQUIREMENTS
  93. Compiling and running the 2.6.xx kernels requires up-to-date
  94. versions of various software packages. Consult
  95. Documentation/Changes for the minimum version numbers required
  96. and how to get updates for these packages. Beware that using
  97. excessively old versions of these packages can cause indirect
  98. errors that are very difficult to track down, so don't assume that
  99. you can just update packages when obvious problems arise during
  100. build or operation.
  101. BUILD directory for the kernel:
  102. When compiling the kernel all output files will per default be
  103. stored together with the kernel source code.
  104. Using the option "make O=output/dir" allow you to specify an alternate
  105. place for the output files (including .config).
  106. Example:
  107. kernel source code: /usr/src/linux-2.6.N
  108. build directory: /home/name/build/kernel
  109. To configure and build the kernel use:
  110. cd /usr/src/linux-2.6.N
  111. make O=/home/name/build/kernel menuconfig
  112. make O=/home/name/build/kernel
  113. sudo make O=/home/name/build/kernel modules_install install
  114. Please note: If the 'O=output/dir' option is used then it must be
  115. used for all invocations of make.
  116. CONFIGURING the kernel:
  117. Do not skip this step even if you are only upgrading one minor
  118. version. New configuration options are added in each release, and
  119. odd problems will turn up if the configuration files are not set up
  120. as expected. If you want to carry your existing configuration to a
  121. new version with minimal work, use "make oldconfig", which will
  122. only ask you for the answers to new questions.
  123. - Alternate configuration commands are:
  124. "make menuconfig" Text based color menus, radiolists & dialogs.
  125. "make xconfig" X windows (Qt) based configuration tool.
  126. "make gconfig" X windows (Gtk) based configuration tool.
  127. "make oldconfig" Default all questions based on the contents of
  128. your existing ./.config file.
  129. "make silentoldconfig"
  130. Like above, but avoids cluttering the screen
  131. with questions already answered.
  132. NOTES on "make config":
  133. - having unnecessary drivers will make the kernel bigger, and can
  134. under some circumstances lead to problems: probing for a
  135. nonexistent controller card may confuse your other controllers
  136. - compiling the kernel with "Processor type" set higher than 386
  137. will result in a kernel that does NOT work on a 386. The
  138. kernel will detect this on bootup, and give up.
  139. - A kernel with math-emulation compiled in will still use the
  140. coprocessor if one is present: the math emulation will just
  141. never get used in that case. The kernel will be slightly larger,
  142. but will work on different machines regardless of whether they
  143. have a math coprocessor or not.
  144. - the "kernel hacking" configuration details usually result in a
  145. bigger or slower kernel (or both), and can even make the kernel
  146. less stable by configuring some routines to actively try to
  147. break bad code to find kernel problems (kmalloc()). Thus you
  148. should probably answer 'n' to the questions for
  149. "development", "experimental", or "debugging" features.
  150. COMPILING the kernel:
  151. - Make sure you have at least gcc 3.2 available.
  152. For more information, refer to Documentation/Changes.
  153. Please note that you can still run a.out user programs with this kernel.
  154. - Do a "make" to create a compressed kernel image. It is also
  155. possible to do "make install" if you have lilo installed to suit the
  156. kernel makefiles, but you may want to check your particular lilo setup first.
  157. To do the actual install you have to be root, but none of the normal
  158. build should require that. Don't take the name of root in vain.
  159. - If you configured any of the parts of the kernel as `modules', you
  160. will also have to do "make modules_install".
  161. - Keep a backup kernel handy in case something goes wrong. This is
  162. especially true for the development releases, since each new release
  163. contains new code which has not been debugged. Make sure you keep a
  164. backup of the modules corresponding to that kernel, as well. If you
  165. are installing a new kernel with the same version number as your
  166. working kernel, make a backup of your modules directory before you
  167. do a "make modules_install".
  168. Alternatively, before compiling, use the kernel config option
  169. "LOCALVERSION" to append a unique suffix to the regular kernel version.
  170. LOCALVERSION can be set in the "General Setup" menu.
  171. - In order to boot your new kernel, you'll need to copy the kernel
  172. image (e.g. .../linux/arch/i386/boot/bzImage after compilation)
  173. to the place where your regular bootable kernel is found.
  174. - Booting a kernel directly from a floppy without the assistance of a
  175. bootloader such as LILO, is no longer supported.
  176. If you boot Linux from the hard drive, chances are you use LILO which
  177. uses the kernel image as specified in the file /etc/lilo.conf. The
  178. kernel image file is usually /vmlinuz, /boot/vmlinuz, /bzImage or
  179. /boot/bzImage. To use the new kernel, save a copy of the old image
  180. and copy the new image over the old one. Then, you MUST RERUN LILO
  181. to update the loading map!! If you don't, you won't be able to boot
  182. the new kernel image.
  183. Reinstalling LILO is usually a matter of running /sbin/lilo.
  184. You may wish to edit /etc/lilo.conf to specify an entry for your
  185. old kernel image (say, /vmlinux.old) in case the new one does not
  186. work. See the LILO docs for more information.
  187. After reinstalling LILO, you should be all set. Shutdown the system,
  188. reboot, and enjoy!
  189. If you ever need to change the default root device, video mode,
  190. ramdisk size, etc. in the kernel image, use the 'rdev' program (or
  191. alternatively the LILO boot options when appropriate). No need to
  192. recompile the kernel to change these parameters.
  193. - Reboot with the new kernel and enjoy.
  194. IF SOMETHING GOES WRONG:
  195. - If you have problems that seem to be due to kernel bugs, please check
  196. the file MAINTAINERS to see if there is a particular person associated
  197. with the part of the kernel that you are having trouble with. If there
  198. isn't anyone listed there, then the second best thing is to mail
  199. them to me (torvalds@osdl.org), and possibly to any other relevant
  200. mailing-list or to the newsgroup.
  201. - In all bug-reports, *please* tell what kernel you are talking about,
  202. how to duplicate the problem, and what your setup is (use your common
  203. sense). If the problem is new, tell me so, and if the problem is
  204. old, please try to tell me when you first noticed it.
  205. - If the bug results in a message like
  206. unable to handle kernel paging request at address C0000010
  207. Oops: 0002
  208. EIP: 0010:XXXXXXXX
  209. eax: xxxxxxxx ebx: xxxxxxxx ecx: xxxxxxxx edx: xxxxxxxx
  210. esi: xxxxxxxx edi: xxxxxxxx ebp: xxxxxxxx
  211. ds: xxxx es: xxxx fs: xxxx gs: xxxx
  212. Pid: xx, process nr: xx
  213. xx xx xx xx xx xx xx xx xx xx
  214. or similar kernel debugging information on your screen or in your
  215. system log, please duplicate it *exactly*. The dump may look
  216. incomprehensible to you, but it does contain information that may
  217. help debugging the problem. The text above the dump is also
  218. important: it tells something about why the kernel dumped code (in
  219. the above example it's due to a bad kernel pointer). More information
  220. on making sense of the dump is in Documentation/oops-tracing.txt
  221. - If you compiled the kernel with CONFIG_KALLSYMS you can send the dump
  222. as is, otherwise you will have to use the "ksymoops" program to make
  223. sense of the dump. This utility can be downloaded from
  224. ftp://ftp.<country>.kernel.org/pub/linux/utils/kernel/ksymoops.
  225. Alternately you can do the dump lookup by hand:
  226. - In debugging dumps like the above, it helps enormously if you can
  227. look up what the EIP value means. The hex value as such doesn't help
  228. me or anybody else very much: it will depend on your particular
  229. kernel setup. What you should do is take the hex value from the EIP
  230. line (ignore the "0010:"), and look it up in the kernel namelist to
  231. see which kernel function contains the offending address.
  232. To find out the kernel function name, you'll need to find the system
  233. binary associated with the kernel that exhibited the symptom. This is
  234. the file 'linux/vmlinux'. To extract the namelist and match it against
  235. the EIP from the kernel crash, do:
  236. nm vmlinux | sort | less
  237. This will give you a list of kernel addresses sorted in ascending
  238. order, from which it is simple to find the function that contains the
  239. offending address. Note that the address given by the kernel
  240. debugging messages will not necessarily match exactly with the
  241. function addresses (in fact, that is very unlikely), so you can't
  242. just 'grep' the list: the list will, however, give you the starting
  243. point of each kernel function, so by looking for the function that
  244. has a starting address lower than the one you are searching for but
  245. is followed by a function with a higher address you will find the one
  246. you want. In fact, it may be a good idea to include a bit of
  247. "context" in your problem report, giving a few lines around the
  248. interesting one.
  249. If you for some reason cannot do the above (you have a pre-compiled
  250. kernel image or similar), telling me as much about your setup as
  251. possible will help.
  252. - Alternately, you can use gdb on a running kernel. (read-only; i.e. you
  253. cannot change values or set break points.) To do this, first compile the
  254. kernel with -g; edit arch/i386/Makefile appropriately, then do a "make
  255. clean". You'll also need to enable CONFIG_PROC_FS (via "make config").
  256. After you've rebooted with the new kernel, do "gdb vmlinux /proc/kcore".
  257. You can now use all the usual gdb commands. The command to look up the
  258. point where your system crashed is "l *0xXXXXXXXX". (Replace the XXXes
  259. with the EIP value.)
  260. gdb'ing a non-running kernel currently fails because gdb (wrongly)
  261. disregards the starting offset for which the kernel is compiled.