1 Linux kernel release 2.6.xx <http://kernel.org/>
2
3These are the release notes for Linux version 2.6. Read them carefully,
4as they tell you what this is all about, explain how to install the
5kernel, and what to do if something goes wrong.
6
7WHAT IS LINUX?
8
9 Linux is a clone of the operating system Unix, written from scratch by
10 Linus Torvalds with assistance from a loosely-knit team of hackers across
11 the Net. It aims towards POSIX and Single UNIX Specification compliance.
12
13 It has all the features you would expect in a modern fully-fledged Unix,
14 including true multitasking, virtual memory, shared libraries, demand
15 loading, shared copy-on-write executables, proper memory management,
16 and multistack networking including IPv4 and IPv6.
17
18 It is distributed under the GNU General Public License - see the
19 accompanying COPYING file for more details.
20
21ON WHAT HARDWARE DOES IT RUN?
22
23 Although originally developed first for 32-bit x86-based PCs (386 or higher),
24 today Linux also runs on (at least) the Compaq Alpha AXP, Sun SPARC and
25 UltraSPARC, Motorola 68000, PowerPC, PowerPC64, ARM, Hitachi SuperH, Cell,
26 IBM S/390, MIPS, HP PA-RISC, Intel IA-64, DEC VAX, AMD x86-64, AXIS CRIS,
27 Xtensa, AVR32 and Renesas M32R architectures.
28
29 Linux is easily portable to most general-purpose 32- or 64-bit architectures
30 as long as they have a paged memory management unit (PMMU) and a port of the
31 GNU C compiler (gcc) (part of The GNU Compiler Collection, GCC). Linux has
32 also been ported to a number of architectures without a PMMU, although
33 functionality is then obviously somewhat limited.
34 Linux has also been ported to itself. You can now run the kernel as a
35 userspace application - this is called UserMode Linux (UML).
36
37DOCUMENTATION:
38
39 - There is a lot of documentation available both in electronic form on
40 the Internet and in books, both Linux-specific and pertaining to
41 general UNIX questions. I'd recommend looking into the documentation
42 subdirectories on any Linux FTP site for the LDP (Linux Documentation
43 Project) books. This README is not meant to be documentation on the
44 system: there are much better sources available.
45
46 - There are various README files in the Documentation/ subdirectory:
47 these typically contain kernel-specific installation notes for some
48 drivers for example. See Documentation/00-INDEX for a list of what
49 is contained in each file. Please read the Changes file, as it
50 contains information about the problems, which may result by upgrading
51 your kernel.
52
53 - The Documentation/DocBook/ subdirectory contains several guides for
54 kernel developers and users. These guides can be rendered in a
55 number of formats: PostScript (.ps), PDF, and HTML, among others.
56 After installation, "make psdocs", "make pdfdocs", or "make htmldocs"
57 will render the documentation in the requested format.
58
59INSTALLING the kernel:
60
61 - If you install the full sources, put the kernel tarball in a
62 directory where you have permissions (eg. your home directory) and
63 unpack it:
64
65 gzip -cd linux-2.6.XX.tar.gz | tar xvf -
66
67 or
68 bzip2 -dc linux-2.6.XX.tar.bz2 | tar xvf -
69
70
71 Replace "XX" with the version number of the latest kernel.
72
73 Do NOT use the /usr/src/linux area! This area has a (usually
74 incomplete) set of kernel headers that are used by the library header
75 files. They should match the library, and not get messed up by
76 whatever the kernel-du-jour happens to be.
77
78 - You can also upgrade between 2.6.xx releases by patching. Patches are
79 distributed in the traditional gzip and the newer bzip2 format. To
80 install by patching, get all the newer patch files, enter the
81 top level directory of the kernel source (linux-2.6.xx) and execute:
82
83 gzip -cd ../patch-2.6.xx.gz | patch -p1
84
85 or
86 bzip2 -dc ../patch-2.6.xx.bz2 | patch -p1
87
88 (repeat xx for all versions bigger than the version of your current
89 source tree, _in_order_) and you should be ok. You may want to remove
90 the backup files (xxx~ or xxx.orig), and make sure that there are no
91 failed patches (xxx# or xxx.rej). If there are, either you or me has
92 made a mistake.
93
94 Unlike patches for the 2.6.x kernels, patches for the 2.6.x.y kernels
95 (also known as the -stable kernels) are not incremental but instead apply
96 directly to the base 2.6.x kernel. Please read
97 Documentation/applying-patches.txt for more information.
98
99 Alternatively, the script patch-kernel can be used to automate this
100 process. It determines the current kernel version and applies any
101 patches found.
102
103 linux/scripts/patch-kernel linux
104
105 The first argument in the command above is the location of the
106 kernel source. Patches are applied from the current directory, but
107 an alternative directory can be specified as the second argument.
108
109 - If you are upgrading between releases using the stable series patches
110 (for example, patch-2.6.xx.y), note that these "dot-releases" are
111 not incremental and must be applied to the 2.6.xx base tree. For
112 example, if your base kernel is 2.6.12 and you want to apply the
113 2.6.12.3 patch, you do not and indeed must not first apply the
114 2.6.12.1 and 2.6.12.2 patches. Similarly, if you are running kernel
115 version 2.6.12.2 and want to jump to 2.6.12.3, you must first
116 reverse the 2.6.12.2 patch (that is, patch -R) _before_ applying
117 the 2.6.12.3 patch.
118 You can read more on this in Documentation/applying-patches.txt
119
120 - Make sure you have no stale .o files and dependencies lying around:
121
122 cd linux
123 make mrproper
124
125 You should now have the sources correctly installed.
126
127SOFTWARE REQUIREMENTS
128
129 Compiling and running the 2.6.xx kernels requires up-to-date
130 versions of various software packages. Consult
131 Documentation/Changes for the minimum version numbers required
132 and how to get updates for these packages. Beware that using
133 excessively old versions of these packages can cause indirect
134 errors that are very difficult to track down, so don't assume that
135 you can just update packages when obvious problems arise during
136 build or operation.
137
138BUILD directory for the kernel:
139
140 When compiling the kernel all output files will per default be
141 stored together with the kernel source code.
142 Using the option "make O=output/dir" allow you to specify an alternate
143 place for the output files (including .config).
144 Example:
145 kernel source code: /usr/src/linux-2.6.N
146 build directory: /home/name/build/kernel
147
148 To configure and build the kernel use:
149 cd /usr/src/linux-2.6.N
150 make O=/home/name/build/kernel menuconfig
151 make O=/home/name/build/kernel
152 sudo make O=/home/name/build/kernel modules_install install
153
154 Please note: If the 'O=output/dir' option is used then it must be
155 used for all invocations of make.
156
157CONFIGURING the kernel:
158
159 Do not skip this step even if you are only upgrading one minor
160 version. New configuration options are added in each release, and
161 odd problems will turn up if the configuration files are not set up
162 as expected. If you want to carry your existing configuration to a
163 new version with minimal work, use "make oldconfig", which will
164 only ask you for the answers to new questions.
165
166 - Alternate configuration commands are:
167 "make config" Plain text interface.
168 "make menuconfig" Text based color menus, radiolists & dialogs.
169 "make xconfig" X windows (Qt) based configuration tool.
170 "make gconfig" X windows (Gtk) based configuration tool.
171 "make oldconfig" Default all questions based on the contents of
172 your existing ./.config file and asking about
173 new config symbols.
174 "make silentoldconfig"
175 Like above, but avoids cluttering the screen
176 with questions already answered.
177 "make defconfig" Create a ./.config file by using the default
178 symbol values from arch/$ARCH/defconfig.
179 "make allyesconfig"
180 Create a ./.config file by setting symbol
181 values to 'y' as much as possible.
182 "make allmodconfig"
183 Create a ./.config file by setting symbol
184 values to 'm' as much as possible.
185 "make allnoconfig" Create a ./.config file by setting symbol
186 values to 'n' as much as possible.
187 "make randconfig" Create a ./.config file by setting symbol
188 values to random values.
189
190 The allyesconfig/allmodconfig/allnoconfig/randconfig variants can
191 also use the environment variable KCONFIG_ALLCONFIG to specify a
192 filename that contains config options that the user requires to be
193 set to a specific value. If KCONFIG_ALLCONFIG=filename is not used,
194 "make *config" checks for a file named "all{yes/mod/no/random}.config"
195 for symbol values that are to be forced. If this file is not found,
196 it checks for a file named "all.config" to contain forced values.
197
198 NOTES on "make config":
199 - having unnecessary drivers will make the kernel bigger, and can
200 under some circumstances lead to problems: probing for a
201 nonexistent controller card may confuse your other controllers
202 - compiling the kernel with "Processor type" set higher than 386
203 will result in a kernel that does NOT work on a 386. The
204 kernel will detect this on bootup, and give up.
205 - A kernel with math-emulation compiled in will still use the
206 coprocessor if one is present: the math emulation will just
207 never get used in that case. The kernel will be slightly larger,
208 but will work on different machines regardless of whether they
209 have a math coprocessor or not.
210 - the "kernel hacking" configuration details usually result in a
211 bigger or slower kernel (or both), and can even make the kernel
212 less stable by configuring some routines to actively try to
213 break bad code to find kernel problems (kmalloc()). Thus you
214 should probably answer 'n' to the questions for
215 "development", "experimental", or "debugging" features.
216
217COMPILING the kernel:
218
219 - Make sure you have at least gcc 3.2 available.
220 For more information, refer to Documentation/Changes.
221
222 Please note that you can still run a.out user programs with this kernel.
223
224 - Do a "make" to create a compressed kernel image. It is also
225 possible to do "make install" if you have lilo installed to suit the
226 kernel makefiles, but you may want to check your particular lilo setup first.
227
228 To do the actual install you have to be root, but none of the normal
229 build should require that. Don't take the name of root in vain.
230
231 - If you configured any of the parts of the kernel as `modules', you
232 will also have to do "make modules_install".
233
234 - Keep a backup kernel handy in case something goes wrong. This is
235 especially true for the development releases, since each new release
236 contains new code which has not been debugged. Make sure you keep a
237 backup of the modules corresponding to that kernel, as well. If you
238 are installing a new kernel with the same version number as your
239 working kernel, make a backup of your modules directory before you
240 do a "make modules_install".
241 Alternatively, before compiling, use the kernel config option
242 "LOCALVERSION" to append a unique suffix to the regular kernel version.
243 LOCALVERSION can be set in the "General Setup" menu.
244
245 - In order to boot your new kernel, you'll need to copy the kernel
246 image (e.g. .../linux/arch/i386/boot/bzImage after compilation)
247 to the place where your regular bootable kernel is found.
248
249 - Booting a kernel directly from a floppy without the assistance of a
250 bootloader such as LILO, is no longer supported.
251
252 If you boot Linux from the hard drive, chances are you use LILO which
253 uses the kernel image as specified in the file /etc/lilo.conf. The
254 kernel image file is usually /vmlinuz, /boot/vmlinuz, /bzImage or
255 /boot/bzImage. To use the new kernel, save a copy of the old image
256 and copy the new image over the old one. Then, you MUST RERUN LILO
257 to update the loading map!! If you don't, you won't be able to boot
258 the new kernel image.
259
260 Reinstalling LILO is usually a matter of running /sbin/lilo.
261 You may wish to edit /etc/lilo.conf to specify an entry for your
262 old kernel image (say, /vmlinux.old) in case the new one does not
263 work. See the LILO docs for more information.
264
265 After reinstalling LILO, you should be all set. Shutdown the system,
266 reboot, and enjoy!
267
268 If you ever need to change the default root device, video mode,
269 ramdisk size, etc. in the kernel image, use the 'rdev' program (or
270 alternatively the LILO boot options when appropriate). No need to
271 recompile the kernel to change these parameters.
272
273 - Reboot with the new kernel and enjoy.
274
275IF SOMETHING GOES WRONG:
276
277 - If you have problems that seem to be due to kernel bugs, please check
278 the file MAINTAINERS to see if there is a particular person associated
279 with the part of the kernel that you are having trouble with. If there
280 isn't anyone listed there, then the second best thing is to mail
281 them to me (torvalds@linux-foundation.org), and possibly to any other
282 relevant mailing-list or to the newsgroup.
283
284 - In all bug-reports, *please* tell what kernel you are talking about,
285 how to duplicate the problem, and what your setup is (use your common
286 sense). If the problem is new, tell me so, and if the problem is
287 old, please try to tell me when you first noticed it.
288
289 - If the bug results in a message like
290
291 unable to handle kernel paging request at address C0000010
292 Oops: 0002
293 EIP: 0010:XXXXXXXX
294 eax: xxxxxxxx ebx: xxxxxxxx ecx: xxxxxxxx edx: xxxxxxxx
295 esi: xxxxxxxx edi: xxxxxxxx ebp: xxxxxxxx
296 ds: xxxx es: xxxx fs: xxxx gs: xxxx
297 Pid: xx, process nr: xx
298 xx xx xx xx xx xx xx xx xx xx
299
300 or similar kernel debugging information on your screen or in your
301 system log, please duplicate it *exactly*. The dump may look
302 incomprehensible to you, but it does contain information that may
303 help debugging the problem. The text above the dump is also
304 important: it tells something about why the kernel dumped code (in
305 the above example it's due to a bad kernel pointer). More information
306 on making sense of the dump is in Documentation/oops-tracing.txt
307
308 - If you compiled the kernel with CONFIG_KALLSYMS you can send the dump
309 as is, otherwise you will have to use the "ksymoops" program to make
310 sense of the dump (but compiling with CONFIG_KALLSYMS is usually preferred).
311 This utility can be downloaded from
312 ftp://ftp.<country>.kernel.org/pub/linux/utils/kernel/ksymoops/ .
313 Alternately you can do the dump lookup by hand:
314
315 - In debugging dumps like the above, it helps enormously if you can
316 look up what the EIP value means. The hex value as such doesn't help
317 me or anybody else very much: it will depend on your particular
318 kernel setup. What you should do is take the hex value from the EIP
319 line (ignore the "0010:"), and look it up in the kernel namelist to
320 see which kernel function contains the offending address.
321
322 To find out the kernel function name, you'll need to find the system
323 binary associated with the kernel that exhibited the symptom. This is
324 the file 'linux/vmlinux'. To extract the namelist and match it against
325 the EIP from the kernel crash, do:
326
327 nm vmlinux | sort | less
328
329 This will give you a list of kernel addresses sorted in ascending
330 order, from which it is simple to find the function that contains the
331 offending address. Note that the address given by the kernel
332 debugging messages will not necessarily match exactly with the
333 function addresses (in fact, that is very unlikely), so you can't
334 just 'grep' the list: the list will, however, give you the starting
335 point of each kernel function, so by looking for the function that
336 has a starting address lower than the one you are searching for but
337 is followed by a function with a higher address you will find the one
338 you want. In fact, it may be a good idea to include a bit of
339 "context" in your problem report, giving a few lines around the
340 interesting one.
341
342 If you for some reason cannot do the above (you have a pre-compiled
343 kernel image or similar), telling me as much about your setup as
344 possible will help. Please read the REPORTING-BUGS document for details.
345
346 - Alternately, you can use gdb on a running kernel. (read-only; i.e. you
347 cannot change values or set break points.) To do this, first compile the
348 kernel with -g; edit arch/i386/Makefile appropriately, then do a "make
349 clean". You'll also need to enable CONFIG_PROC_FS (via "make config").
350
351 After you've rebooted with the new kernel, do "gdb vmlinux /proc/kcore".
352 You can now use all the usual gdb commands. The command to look up the
353 point where your system crashed is "l *0xXXXXXXXX". (Replace the XXXes
354 with the EIP value.)
355
356 gdb'ing a non-running kernel currently fails because gdb (wrongly)
357 disregards the starting offset for which the kernel is compiled.
358