1
Linux kernel release 3.x <http://kernel.org/>
3
These are the release notes for Linux version 3. 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.
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.
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.
18
It is distributed under the GNU General Public License - see the
19
accompanying COPYING file for more details.
21
ON WHAT HARDWARE DOES IT RUN?
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, Tilera TILE, AVR32 and Renesas M32R architectures.
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).
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.
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
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.
59
INSTALLING the kernel source:
61
- If you install the full sources, put the kernel tarball in a
62
directory where you have permissions (eg. your home directory) and
65
gzip -cd linux-3.X.tar.gz | tar xvf -
68
bzip2 -dc linux-3.X.tar.bz2 | tar xvf -
71
Replace "XX" with the version number of the latest kernel.
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.
78
- You can also upgrade between 3.x 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-3.x) and execute:
83
gzip -cd ../patch-3.x.gz | patch -p1
86
bzip2 -dc ../patch-3.x.bz2 | patch -p1
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
94
Unlike patches for the 3.x kernels, patches for the 3.x.y kernels
95
(also known as the -stable kernels) are not incremental but instead apply
96
directly to the base 3.x kernel. Please read
97
Documentation/applying-patches.txt for more information.
99
Alternatively, the script patch-kernel can be used to automate this
100
process. It determines the current kernel version and applies any
103
linux/scripts/patch-kernel linux
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.
109
- If you are upgrading between releases using the stable series patches
110
(for example, patch-3.x.y), note that these "dot-releases" are
111
not incremental and must be applied to the 3.x base tree. For
112
example, if your base kernel is 3.0 and you want to apply the
113
3.0.3 patch, you do not and indeed must not first apply the
114
3.0.1 and 3.0.2 patches. Similarly, if you are running kernel
115
version 3.0.2 and want to jump to 3.0.3, you must first
116
reverse the 3.0.2 patch (that is, patch -R) _before_ applying
118
You can read more on this in Documentation/applying-patches.txt
120
- Make sure you have no stale .o files and dependencies lying around:
125
You should now have the sources correctly installed.
127
SOFTWARE REQUIREMENTS
129
Compiling and running the 3.x 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
138
BUILD directory for the kernel:
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).
145
kernel source code: /usr/src/linux-3.N
146
build directory: /home/name/build/kernel
148
To configure and build the kernel use:
149
cd /usr/src/linux-3.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
154
Please note: If the 'O=output/dir' option is used then it must be
155
used for all invocations of make.
157
CONFIGURING the kernel:
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.
166
- Alternate configuration commands are:
167
"make config" Plain text interface.
168
"make menuconfig" Text based color menus, radiolists & dialogs.
169
"make nconfig" Enhanced text based color menus.
170
"make xconfig" X windows (Qt) based configuration tool.
171
"make gconfig" X windows (Gtk) based configuration tool.
172
"make oldconfig" Default all questions based on the contents of
173
your existing ./.config file and asking about
175
"make silentoldconfig"
176
Like above, but avoids cluttering the screen
177
with questions already answered.
178
Additionally updates the dependencies.
179
"make defconfig" Create a ./.config file by using the default
180
symbol values from either arch/$ARCH/defconfig
181
or arch/$ARCH/configs/${PLATFORM}_defconfig,
182
depending on the architecture.
183
"make ${PLATFORM}_defconfig"
184
Create a ./.config file by using the default
186
arch/$ARCH/configs/${PLATFORM}_defconfig.
187
Use "make help" to get a list of all available
188
platforms of your architecture.
190
Create a ./.config file by setting symbol
191
values to 'y' as much as possible.
193
Create a ./.config file by setting symbol
194
values to 'm' as much as possible.
195
"make allnoconfig" Create a ./.config file by setting symbol
196
values to 'n' as much as possible.
197
"make randconfig" Create a ./.config file by setting symbol
198
values to random values.
200
You can find more information on using the Linux kernel config tools
201
in Documentation/kbuild/kconfig.txt.
203
NOTES on "make config":
204
- having unnecessary drivers will make the kernel bigger, and can
205
under some circumstances lead to problems: probing for a
206
nonexistent controller card may confuse your other controllers
207
- compiling the kernel with "Processor type" set higher than 386
208
will result in a kernel that does NOT work on a 386. The
209
kernel will detect this on bootup, and give up.
210
- A kernel with math-emulation compiled in will still use the
211
coprocessor if one is present: the math emulation will just
212
never get used in that case. The kernel will be slightly larger,
213
but will work on different machines regardless of whether they
214
have a math coprocessor or not.
215
- the "kernel hacking" configuration details usually result in a
216
bigger or slower kernel (or both), and can even make the kernel
217
less stable by configuring some routines to actively try to
218
break bad code to find kernel problems (kmalloc()). Thus you
219
should probably answer 'n' to the questions for
220
"development", "experimental", or "debugging" features.
222
COMPILING the kernel:
224
- Make sure you have at least gcc 3.2 available.
225
For more information, refer to Documentation/Changes.
227
Please note that you can still run a.out user programs with this kernel.
229
- Do a "make" to create a compressed kernel image. It is also
230
possible to do "make install" if you have lilo installed to suit the
231
kernel makefiles, but you may want to check your particular lilo setup first.
233
To do the actual install you have to be root, but none of the normal
234
build should require that. Don't take the name of root in vain.
236
- If you configured any of the parts of the kernel as `modules', you
237
will also have to do "make modules_install".
239
- Verbose kernel compile/build output:
241
Normally the kernel build system runs in a fairly quiet mode (but not
242
totally silent). However, sometimes you or other kernel developers need
243
to see compile, link, or other commands exactly as they are executed.
244
For this, use "verbose" build mode. This is done by inserting
245
"V=1" in the "make" command. E.g.:
249
To have the build system also tell the reason for the rebuild of each
250
target, use "V=2". The default is "V=0".
252
- Keep a backup kernel handy in case something goes wrong. This is
253
especially true for the development releases, since each new release
254
contains new code which has not been debugged. Make sure you keep a
255
backup of the modules corresponding to that kernel, as well. If you
256
are installing a new kernel with the same version number as your
257
working kernel, make a backup of your modules directory before you
258
do a "make modules_install".
259
Alternatively, before compiling, use the kernel config option
260
"LOCALVERSION" to append a unique suffix to the regular kernel version.
261
LOCALVERSION can be set in the "General Setup" menu.
263
- In order to boot your new kernel, you'll need to copy the kernel
264
image (e.g. .../linux/arch/i386/boot/bzImage after compilation)
265
to the place where your regular bootable kernel is found.
267
- Booting a kernel directly from a floppy without the assistance of a
268
bootloader such as LILO, is no longer supported.
270
If you boot Linux from the hard drive, chances are you use LILO which
271
uses the kernel image as specified in the file /etc/lilo.conf. The
272
kernel image file is usually /vmlinuz, /boot/vmlinuz, /bzImage or
273
/boot/bzImage. To use the new kernel, save a copy of the old image
274
and copy the new image over the old one. Then, you MUST RERUN LILO
275
to update the loading map!! If you don't, you won't be able to boot
276
the new kernel image.
278
Reinstalling LILO is usually a matter of running /sbin/lilo.
279
You may wish to edit /etc/lilo.conf to specify an entry for your
280
old kernel image (say, /vmlinux.old) in case the new one does not
281
work. See the LILO docs for more information.
283
After reinstalling LILO, you should be all set. Shutdown the system,
286
If you ever need to change the default root device, video mode,
287
ramdisk size, etc. in the kernel image, use the 'rdev' program (or
288
alternatively the LILO boot options when appropriate). No need to
289
recompile the kernel to change these parameters.
291
- Reboot with the new kernel and enjoy.
293
IF SOMETHING GOES WRONG:
295
- If you have problems that seem to be due to kernel bugs, please check
296
the file MAINTAINERS to see if there is a particular person associated
297
with the part of the kernel that you are having trouble with. If there
298
isn't anyone listed there, then the second best thing is to mail
299
them to me (torvalds@linux-foundation.org), and possibly to any other
300
relevant mailing-list or to the newsgroup.
302
- In all bug-reports, *please* tell what kernel you are talking about,
303
how to duplicate the problem, and what your setup is (use your common
304
sense). If the problem is new, tell me so, and if the problem is
305
old, please try to tell me when you first noticed it.
307
- If the bug results in a message like
309
unable to handle kernel paging request at address C0000010
312
eax: xxxxxxxx ebx: xxxxxxxx ecx: xxxxxxxx edx: xxxxxxxx
313
esi: xxxxxxxx edi: xxxxxxxx ebp: xxxxxxxx
314
ds: xxxx es: xxxx fs: xxxx gs: xxxx
315
Pid: xx, process nr: xx
316
xx xx xx xx xx xx xx xx xx xx
318
or similar kernel debugging information on your screen or in your
319
system log, please duplicate it *exactly*. The dump may look
320
incomprehensible to you, but it does contain information that may
321
help debugging the problem. The text above the dump is also
322
important: it tells something about why the kernel dumped code (in
323
the above example it's due to a bad kernel pointer). More information
324
on making sense of the dump is in Documentation/oops-tracing.txt
326
- If you compiled the kernel with CONFIG_KALLSYMS you can send the dump
327
as is, otherwise you will have to use the "ksymoops" program to make
328
sense of the dump (but compiling with CONFIG_KALLSYMS is usually preferred).
329
This utility can be downloaded from
330
ftp://ftp.<country>.kernel.org/pub/linux/utils/kernel/ksymoops/ .
331
Alternately you can do the dump lookup by hand:
333
- In debugging dumps like the above, it helps enormously if you can
334
look up what the EIP value means. The hex value as such doesn't help
335
me or anybody else very much: it will depend on your particular
336
kernel setup. What you should do is take the hex value from the EIP
337
line (ignore the "0010:"), and look it up in the kernel namelist to
338
see which kernel function contains the offending address.
340
To find out the kernel function name, you'll need to find the system
341
binary associated with the kernel that exhibited the symptom. This is
342
the file 'linux/vmlinux'. To extract the namelist and match it against
343
the EIP from the kernel crash, do:
345
nm vmlinux | sort | less
347
This will give you a list of kernel addresses sorted in ascending
348
order, from which it is simple to find the function that contains the
349
offending address. Note that the address given by the kernel
350
debugging messages will not necessarily match exactly with the
351
function addresses (in fact, that is very unlikely), so you can't
352
just 'grep' the list: the list will, however, give you the starting
353
point of each kernel function, so by looking for the function that
354
has a starting address lower than the one you are searching for but
355
is followed by a function with a higher address you will find the one
356
you want. In fact, it may be a good idea to include a bit of
357
"context" in your problem report, giving a few lines around the
360
If you for some reason cannot do the above (you have a pre-compiled
361
kernel image or similar), telling me as much about your setup as
362
possible will help. Please read the REPORTING-BUGS document for details.
364
- Alternately, you can use gdb on a running kernel. (read-only; i.e. you
365
cannot change values or set break points.) To do this, first compile the
366
kernel with -g; edit arch/i386/Makefile appropriately, then do a "make
367
clean". You'll also need to enable CONFIG_PROC_FS (via "make config").
369
After you've rebooted with the new kernel, do "gdb vmlinux /proc/kcore".
370
You can now use all the usual gdb commands. The command to look up the
371
point where your system crashed is "l *0xXXXXXXXX". (Replace the XXXes
374
gdb'ing a non-running kernel currently fails because gdb (wrongly)
375
disregards the starting offset for which the kernel is compiled.