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1 Linux kernel release 2.6.xx
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 Unix clone written from scratch by Linus Torvalds with
10 assistance from a loosely-knit team of hackers across the Net.
11 It aims towards POSIX compliance.
12
13 It has all the features you would expect in a modern fully-fledged
14 Unix, including true multitasking, virtual memory, shared libraries,
15 demand loading, shared copy-on-write executables, proper memory
16 management and TCP/IP networking.
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 Linux was first developed for 386/486-based PCs. These days it also
24 runs on ARMs, DEC Alphas, SUN Sparcs, M68000 machines (like Atari and
25 Amiga), MIPS and PowerPC, and others.
26
27DOCUMENTATION:
28
29 - There is a lot of documentation available both in electronic form on
30 the Internet and in books, both Linux-specific and pertaining to
31 general UNIX questions. I'd recommend looking into the documentation
32 subdirectories on any Linux FTP site for the LDP (Linux Documentation
33 Project) books. This README is not meant to be documentation on the
34 system: there are much better sources available.
35
36 - There are various README files in the Documentation/ subdirectory:
37 these typically contain kernel-specific installation notes for some
38 drivers for example. See Documentation/00-INDEX for a list of what
39 is contained in each file. Please read the Changes file, as it
40 contains information about the problems, which may result by upgrading
41 your kernel.
42
43 - The Documentation/DocBook/ subdirectory contains several guides for
44 kernel developers and users. These guides can be rendered in a
45 number of formats: PostScript (.ps), PDF, and HTML, among others.
46 After installation, "make psdocs", "make pdfdocs", or "make htmldocs"
47 will render the documentation in the requested format.
48
49INSTALLING the kernel:
50
51 - If you install the full sources, put the kernel tarball in a
52 directory where you have permissions (eg. your home directory) and
53 unpack it:
54
55 gzip -cd linux-2.6.XX.tar.gz | tar xvf -
56
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57 or
58 bzip2 -dc linux-2.6.XX.tar.bz2 | tar xvf -
59
60
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61 Replace "XX" with the version number of the latest kernel.
62
63 Do NOT use the /usr/src/linux area! This area has a (usually
64 incomplete) set of kernel headers that are used by the library header
65 files. They should match the library, and not get messed up by
66 whatever the kernel-du-jour happens to be.
67
68 - You can also upgrade between 2.6.xx releases by patching. Patches are
69 distributed in the traditional gzip and the new bzip2 format. To
70 install by patching, get all the newer patch files, enter the
71 top level directory of the kernel source (linux-2.6.xx) and execute:
72
73 gzip -cd ../patch-2.6.xx.gz | patch -p1
74
75 or
76 bzip2 -dc ../patch-2.6.xx.bz2 | patch -p1
77
78 (repeat xx for all versions bigger than the version of your current
79 source tree, _in_order_) and you should be ok. You may want to remove
80 the backup files (xxx~ or xxx.orig), and make sure that there are no
81 failed patches (xxx# or xxx.rej). If there are, either you or me has
82 made a mistake.
83
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84 Unlike patches for the 2.6.x kernels, patches for the 2.6.x.y kernels
85 (also known as the -stable kernels) are not incremental but instead apply
86 directly to the base 2.6.x kernel. Please read
87 Documentation/applying-patches.txt for more information.
88
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89 Alternatively, the script patch-kernel can be used to automate this
90 process. It determines the current kernel version and applies any
91 patches found.
92
93 linux/scripts/patch-kernel linux
94
95 The first argument in the command above is the location of the
96 kernel source. Patches are applied from the current directory, but
97 an alternative directory can be specified as the second argument.
98
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99 - If you are upgrading between releases using the stable series patches
100 (for example, patch-2.6.xx.y), note that these "dot-releases" are
101 not incremental and must be applied to the 2.6.xx base tree. For
102 example, if your base kernel is 2.6.12 and you want to apply the
103 2.6.12.3 patch, you do not and indeed must not first apply the
104 2.6.12.1 and 2.6.12.2 patches. Similarly, if you are running kernel
105 version 2.6.12.2 and want to jump to 2.6.12.3, you must first
106 reverse the 2.6.12.2 patch (that is, patch -R) _before_ applying
107 the 2.6.12.3 patch.
108
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109 - Make sure you have no stale .o files and dependencies lying around:
110
111 cd linux
112 make mrproper
113
114 You should now have the sources correctly installed.
115
116SOFTWARE REQUIREMENTS
117
118 Compiling and running the 2.6.xx kernels requires up-to-date
119 versions of various software packages. Consult
120 Documentation/Changes for the minimum version numbers required
121 and how to get updates for these packages. Beware that using
122 excessively old versions of these packages can cause indirect
123 errors that are very difficult to track down, so don't assume that
124 you can just update packages when obvious problems arise during
125 build or operation.
126
127BUILD directory for the kernel:
128
129 When compiling the kernel all output files will per default be
130 stored together with the kernel source code.
131 Using the option "make O=output/dir" allow you to specify an alternate
132 place for the output files (including .config).
133 Example:
134 kernel source code: /usr/src/linux-2.6.N
135 build directory: /home/name/build/kernel
136
137 To configure and build the kernel use:
138 cd /usr/src/linux-2.6.N
139 make O=/home/name/build/kernel menuconfig
140 make O=/home/name/build/kernel
141 sudo make O=/home/name/build/kernel modules_install install
142
143 Please note: If the 'O=output/dir' option is used then it must be
144 used for all invocations of make.
145
146CONFIGURING the kernel:
147
148 Do not skip this step even if you are only upgrading one minor
149 version. New configuration options are added in each release, and
150 odd problems will turn up if the configuration files are not set up
151 as expected. If you want to carry your existing configuration to a
152 new version with minimal work, use "make oldconfig", which will
153 only ask you for the answers to new questions.
154
155 - Alternate configuration commands are:
156 "make menuconfig" Text based color menus, radiolists & dialogs.
157 "make xconfig" X windows (Qt) based configuration tool.
158 "make gconfig" X windows (Gtk) based configuration tool.
159 "make oldconfig" Default all questions based on the contents of
160 your existing ./.config file.
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161 "make silentoldconfig"
162 Like above, but avoids cluttering the screen
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164
165 NOTES on "make config":
166 - having unnecessary drivers will make the kernel bigger, and can
167 under some circumstances lead to problems: probing for a
168 nonexistent controller card may confuse your other controllers
169 - compiling the kernel with "Processor type" set higher than 386
170 will result in a kernel that does NOT work on a 386. The
171 kernel will detect this on bootup, and give up.
172 - A kernel with math-emulation compiled in will still use the
173 coprocessor if one is present: the math emulation will just
174 never get used in that case. The kernel will be slightly larger,
175 but will work on different machines regardless of whether they
176 have a math coprocessor or not.
177 - the "kernel hacking" configuration details usually result in a
178 bigger or slower kernel (or both), and can even make the kernel
179 less stable by configuring some routines to actively try to
180 break bad code to find kernel problems (kmalloc()). Thus you
181 should probably answer 'n' to the questions for
182 "development", "experimental", or "debugging" features.
183
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184COMPILING the kernel:
185
186 - Make sure you have gcc 2.95.3 available.
187 gcc 2.91.66 (egcs-1.1.2), and gcc 2.7.2.3 are known to miscompile
188 some parts of the kernel, and are *no longer supported*.
189 Also remember to upgrade your binutils package (for as/ld/nm and company)
190 if necessary. For more information, refer to Documentation/Changes.
191
192 Please note that you can still run a.out user programs with this kernel.
193
194 - Do a "make" to create a compressed kernel image. It is also
195 possible to do "make install" if you have lilo installed to suit the
196 kernel makefiles, but you may want to check your particular lilo setup first.
197
198 To do the actual install you have to be root, but none of the normal
199 build should require that. Don't take the name of root in vain.
200
201 - If you configured any of the parts of the kernel as `modules', you
202 will also have to do "make modules_install".
203
204 - Keep a backup kernel handy in case something goes wrong. This is
205 especially true for the development releases, since each new release
206 contains new code which has not been debugged. Make sure you keep a
207 backup of the modules corresponding to that kernel, as well. If you
208 are installing a new kernel with the same version number as your
209 working kernel, make a backup of your modules directory before you
210 do a "make modules_install".
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211 Alternatively, before compiling, use the kernel config option
212 "LOCALVERSION" to append a unique suffix to the regular kernel version.
213 LOCALVERSION can be set in the "General Setup" menu.
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214
215 - In order to boot your new kernel, you'll need to copy the kernel
216 image (e.g. .../linux/arch/i386/boot/bzImage after compilation)
217 to the place where your regular bootable kernel is found.
218
219 - Booting a kernel directly from a floppy without the assistance of a
220 bootloader such as LILO, is no longer supported.
221
222 If you boot Linux from the hard drive, chances are you use LILO which
223 uses the kernel image as specified in the file /etc/lilo.conf. The
224 kernel image file is usually /vmlinuz, /boot/vmlinuz, /bzImage or
225 /boot/bzImage. To use the new kernel, save a copy of the old image
226 and copy the new image over the old one. Then, you MUST RERUN LILO
227 to update the loading map!! If you don't, you won't be able to boot
228 the new kernel image.
229
230 Reinstalling LILO is usually a matter of running /sbin/lilo.
231 You may wish to edit /etc/lilo.conf to specify an entry for your
232 old kernel image (say, /vmlinux.old) in case the new one does not
233 work. See the LILO docs for more information.
234
235 After reinstalling LILO, you should be all set. Shutdown the system,
236 reboot, and enjoy!
237
238 If you ever need to change the default root device, video mode,
239 ramdisk size, etc. in the kernel image, use the 'rdev' program (or
240 alternatively the LILO boot options when appropriate). No need to
241 recompile the kernel to change these parameters.
242
243 - Reboot with the new kernel and enjoy.
244
245IF SOMETHING GOES WRONG:
246
247 - If you have problems that seem to be due to kernel bugs, please check
248 the file MAINTAINERS to see if there is a particular person associated
249 with the part of the kernel that you are having trouble with. If there
250 isn't anyone listed there, then the second best thing is to mail
251 them to me (torvalds@osdl.org), and possibly to any other relevant
252 mailing-list or to the newsgroup.
253
254 - In all bug-reports, *please* tell what kernel you are talking about,
255 how to duplicate the problem, and what your setup is (use your common
256 sense). If the problem is new, tell me so, and if the problem is
257 old, please try to tell me when you first noticed it.
258
259 - If the bug results in a message like
260
261 unable to handle kernel paging request at address C0000010
262 Oops: 0002
263 EIP: 0010:XXXXXXXX
264 eax: xxxxxxxx ebx: xxxxxxxx ecx: xxxxxxxx edx: xxxxxxxx
265 esi: xxxxxxxx edi: xxxxxxxx ebp: xxxxxxxx
266 ds: xxxx es: xxxx fs: xxxx gs: xxxx
267 Pid: xx, process nr: xx
268 xx xx xx xx xx xx xx xx xx xx
269
270 or similar kernel debugging information on your screen or in your
271 system log, please duplicate it *exactly*. The dump may look
272 incomprehensible to you, but it does contain information that may
273 help debugging the problem. The text above the dump is also
274 important: it tells something about why the kernel dumped code (in
275 the above example it's due to a bad kernel pointer). More information
276 on making sense of the dump is in Documentation/oops-tracing.txt
277
278 - If you compiled the kernel with CONFIG_KALLSYMS you can send the dump
279 as is, otherwise you will have to use the "ksymoops" program to make
280 sense of the dump. This utility can be downloaded from
281 ftp://ftp.<country>.kernel.org/pub/linux/utils/kernel/ksymoops.
282 Alternately you can do the dump lookup by hand:
283
284 - In debugging dumps like the above, it helps enormously if you can
285 look up what the EIP value means. The hex value as such doesn't help
286 me or anybody else very much: it will depend on your particular
287 kernel setup. What you should do is take the hex value from the EIP
288 line (ignore the "0010:"), and look it up in the kernel namelist to
289 see which kernel function contains the offending address.
290
291 To find out the kernel function name, you'll need to find the system
292 binary associated with the kernel that exhibited the symptom. This is
293 the file 'linux/vmlinux'. To extract the namelist and match it against
294 the EIP from the kernel crash, do:
295
296 nm vmlinux | sort | less
297
298 This will give you a list of kernel addresses sorted in ascending
299 order, from which it is simple to find the function that contains the
300 offending address. Note that the address given by the kernel
301 debugging messages will not necessarily match exactly with the
302 function addresses (in fact, that is very unlikely), so you can't
303 just 'grep' the list: the list will, however, give you the starting
304 point of each kernel function, so by looking for the function that
305 has a starting address lower than the one you are searching for but
306 is followed by a function with a higher address you will find the one
307 you want. In fact, it may be a good idea to include a bit of
308 "context" in your problem report, giving a few lines around the
309 interesting one.
310
311 If you for some reason cannot do the above (you have a pre-compiled
312 kernel image or similar), telling me as much about your setup as
313 possible will help.
314
315 - Alternately, you can use gdb on a running kernel. (read-only; i.e. you
316 cannot change values or set break points.) To do this, first compile the
317 kernel with -g; edit arch/i386/Makefile appropriately, then do a "make
318 clean". You'll also need to enable CONFIG_PROC_FS (via "make config").
319
320 After you've rebooted with the new kernel, do "gdb vmlinux /proc/kcore".
321 You can now use all the usual gdb commands. The command to look up the
322 point where your system crashed is "l *0xXXXXXXXX". (Replace the XXXes
323 with the EIP value.)
324
325 gdb'ing a non-running kernel currently fails because gdb (wrongly)
326 disregards the starting offset for which the kernel is compiled.
327