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paulobrien authored Apr 6, 2011
1 Linux kernel release 2.6.xx <http://kernel.org/>
2
3 These are the release notes for Linux version 2.6. Read them carefully,
4 as they tell you what this is all about, explain how to install the
5 kernel, and what to do if something goes wrong.
6
7 WHAT 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
21 ON 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
37 DOCUMENTATION:
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, HTML, & man-pages, among others.
56 After installation, "make psdocs", "make pdfdocs", "make htmldocs",
57 or "make mandocs" will render the documentation in the requested format.
58
59 INSTALLING the kernel source:
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
127 SOFTWARE 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
138 BUILD 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
157 CONFIGURING 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 Additionally updates the dependencies.
178 "make defconfig" Create a ./.config file by using the default
179 symbol values from either arch/$ARCH/defconfig
180 or arch/$ARCH/configs/${PLATFORM}_defconfig,
181 depending on the architecture.
182 "make ${PLATFORM}_defconfig"
183 Create a ./.config file by using the default
184 symbol values from
185 arch/$ARCH/configs/${PLATFORM}_defconfig.
186 Use "make help" to get a list of all available
187 platforms of your architecture.
188 "make allyesconfig"
189 Create a ./.config file by setting symbol
190 values to 'y' as much as possible.
191 "make allmodconfig"
192 Create a ./.config file by setting symbol
193 values to 'm' as much as possible.
194 "make allnoconfig" Create a ./.config file by setting symbol
195 values to 'n' as much as possible.
196 "make randconfig" Create a ./.config file by setting symbol
197 values to random values.
198
199 You can find more information on using the Linux kernel config tools
200 in Documentation/kbuild/kconfig.txt.
201
202 NOTES on "make config":
203 - having unnecessary drivers will make the kernel bigger, and can
204 under some circumstances lead to problems: probing for a
205 nonexistent controller card may confuse your other controllers
206 - compiling the kernel with "Processor type" set higher than 386
207 will result in a kernel that does NOT work on a 386. The
208 kernel will detect this on bootup, and give up.
209 - A kernel with math-emulation compiled in will still use the
210 coprocessor if one is present: the math emulation will just
211 never get used in that case. The kernel will be slightly larger,
212 but will work on different machines regardless of whether they
213 have a math coprocessor or not.
214 - the "kernel hacking" configuration details usually result in a
215 bigger or slower kernel (or both), and can even make the kernel
216 less stable by configuring some routines to actively try to
217 break bad code to find kernel problems (kmalloc()). Thus you
218 should probably answer 'n' to the questions for
219 "development", "experimental", or "debugging" features.
220
221 COMPILING the kernel:
222
223 - Make sure you have at least gcc 3.2 available.
224 For more information, refer to Documentation/Changes.
225
226 Please note that you can still run a.out user programs with this kernel.
227
228 - Do a "make" to create a compressed kernel image. It is also
229 possible to do "make install" if you have lilo installed to suit the
230 kernel makefiles, but you may want to check your particular lilo setup first.
231
232 To do the actual install you have to be root, but none of the normal
233 build should require that. Don't take the name of root in vain.
234
235 - If you configured any of the parts of the kernel as `modules', you
236 will also have to do "make modules_install".
237
238 - Verbose kernel compile/build output:
239
240 Normally the kernel build system runs in a fairly quiet mode (but not
241 totally silent). However, sometimes you or other kernel developers need
242 to see compile, link, or other commands exactly as they are executed.
243 For this, use "verbose" build mode. This is done by inserting
244 "V=1" in the "make" command. E.g.:
245
246 make V=1 all
247
248 To have the build system also tell the reason for the rebuild of each
249 target, use "V=2". The default is "V=0".
250
251 - Keep a backup kernel handy in case something goes wrong. This is
252 especially true for the development releases, since each new release
253 contains new code which has not been debugged. Make sure you keep a
254 backup of the modules corresponding to that kernel, as well. If you
255 are installing a new kernel with the same version number as your
256 working kernel, make a backup of your modules directory before you
257 do a "make modules_install".
258 Alternatively, before compiling, use the kernel config option
259 "LOCALVERSION" to append a unique suffix to the regular kernel version.
260 LOCALVERSION can be set in the "General Setup" menu.
261
262 - In order to boot your new kernel, you'll need to copy the kernel
263 image (e.g. .../linux/arch/i386/boot/bzImage after compilation)
264 to the place where your regular bootable kernel is found.
265
266 - Booting a kernel directly from a floppy without the assistance of a
267 bootloader such as LILO, is no longer supported.
268
269 If you boot Linux from the hard drive, chances are you use LILO which
270 uses the kernel image as specified in the file /etc/lilo.conf. The
271 kernel image file is usually /vmlinuz, /boot/vmlinuz, /bzImage or
272 /boot/bzImage. To use the new kernel, save a copy of the old image
273 and copy the new image over the old one. Then, you MUST RERUN LILO
274 to update the loading map!! If you don't, you won't be able to boot
275 the new kernel image.
276
277 Reinstalling LILO is usually a matter of running /sbin/lilo.
278 You may wish to edit /etc/lilo.conf to specify an entry for your
279 old kernel image (say, /vmlinux.old) in case the new one does not
280 work. See the LILO docs for more information.
281
282 After reinstalling LILO, you should be all set. Shutdown the system,
283 reboot, and enjoy!
284
285 If you ever need to change the default root device, video mode,
286 ramdisk size, etc. in the kernel image, use the 'rdev' program (or
287 alternatively the LILO boot options when appropriate). No need to
288 recompile the kernel to change these parameters.
289
290 - Reboot with the new kernel and enjoy.
291
292 IF SOMETHING GOES WRONG:
293
294 - If you have problems that seem to be due to kernel bugs, please check
295 the file MAINTAINERS to see if there is a particular person associated
296 with the part of the kernel that you are having trouble with. If there
297 isn't anyone listed there, then the second best thing is to mail
298 them to me (torvalds@linux-foundation.org), and possibly to any other
299 relevant mailing-list or to the newsgroup.
300
301 - In all bug-reports, *please* tell what kernel you are talking about,
302 how to duplicate the problem, and what your setup is (use your common
303 sense). If the problem is new, tell me so, and if the problem is
304 old, please try to tell me when you first noticed it.
305
306 - If the bug results in a message like
307
308 unable to handle kernel paging request at address C0000010
309 Oops: 0002
310 EIP: 0010:XXXXXXXX
311 eax: xxxxxxxx ebx: xxxxxxxx ecx: xxxxxxxx edx: xxxxxxxx
312 esi: xxxxxxxx edi: xxxxxxxx ebp: xxxxxxxx
313 ds: xxxx es: xxxx fs: xxxx gs: xxxx
314 Pid: xx, process nr: xx
315 xx xx xx xx xx xx xx xx xx xx
316
317 or similar kernel debugging information on your screen or in your
318 system log, please duplicate it *exactly*. The dump may look
319 incomprehensible to you, but it does contain information that may
320 help debugging the problem. The text above the dump is also
321 important: it tells something about why the kernel dumped code (in
322 the above example it's due to a bad kernel pointer). More information
323 on making sense of the dump is in Documentation/oops-tracing.txt
324
325 - If you compiled the kernel with CONFIG_KALLSYMS you can send the dump
326 as is, otherwise you will have to use the "ksymoops" program to make
327 sense of the dump (but compiling with CONFIG_KALLSYMS is usually preferred).
328 This utility can be downloaded from
329 ftp://ftp.<country>.kernel.org/pub/linux/utils/kernel/ksymoops/ .
330 Alternately you can do the dump lookup by hand:
331
332 - In debugging dumps like the above, it helps enormously if you can
333 look up what the EIP value means. The hex value as such doesn't help
334 me or anybody else very much: it will depend on your particular
335 kernel setup. What you should do is take the hex value from the EIP
336 line (ignore the "0010:"), and look it up in the kernel namelist to
337 see which kernel function contains the offending address.
338
339 To find out the kernel function name, you'll need to find the system
340 binary associated with the kernel that exhibited the symptom. This is
341 the file 'linux/vmlinux'. To extract the namelist and match it against
342 the EIP from the kernel crash, do:
343
344 nm vmlinux | sort | less
345
346 This will give you a list of kernel addresses sorted in ascending
347 order, from which it is simple to find the function that contains the
348 offending address. Note that the address given by the kernel
349 debugging messages will not necessarily match exactly with the
350 function addresses (in fact, that is very unlikely), so you can't
351 just 'grep' the list: the list will, however, give you the starting
352 point of each kernel function, so by looking for the function that
353 has a starting address lower than the one you are searching for but
354 is followed by a function with a higher address you will find the one
355 you want. In fact, it may be a good idea to include a bit of
356 "context" in your problem report, giving a few lines around the
357 interesting one.
358
359 If you for some reason cannot do the above (you have a pre-compiled
360 kernel image or similar), telling me as much about your setup as
361 possible will help. Please read the REPORTING-BUGS document for details.
362
363 - Alternately, you can use gdb on a running kernel. (read-only; i.e. you
364 cannot change values or set break points.) To do this, first compile the
365 kernel with -g; edit arch/i386/Makefile appropriately, then do a "make
366 clean". You'll also need to enable CONFIG_PROC_FS (via "make config").
367
368 After you've rebooted with the new kernel, do "gdb vmlinux /proc/kcore".
369 You can now use all the usual gdb commands. The command to look up the
370 point where your system crashed is "l *0xXXXXXXXX". (Replace the XXXes
371 with the EIP value.)
372
373 gdb'ing a non-running kernel currently fails because gdb (wrongly)
374 disregards the starting offset for which the kernel is compiled.
375
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