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1 Linux kernel release 3.x <http://kernel.org/>
2
3These are the release notes for Linux version 3. 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, Tilera TILE, 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, 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
59INSTALLING 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-3.X.tar.gz | tar xvf -
66
67 or
68 bzip2 -dc linux-3.X.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 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:
82
83 gzip -cd ../patch-3.x.gz | patch -p1
84
85 or
86 bzip2 -dc ../patch-3.x.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 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.
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-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
117 the 3.0.3 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 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
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-3.N
146 build directory: /home/name/build/kernel
147
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
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 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
174 new config symbols.
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 ${PLATFORM}_defconfig"
184 Create a ./.config file by using the default
185 symbol values from
186 arch/$ARCH/configs/${PLATFORM}_defconfig.
187 Use "make help" to get a list of all available
188 platforms of your architecture.
189 "make allyesconfig"
190 Create a ./.config file by setting symbol
191 values to 'y' as much as possible.
192 "make allmodconfig"
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.
199
200 You can find more information on using the Linux kernel config tools
201 in Documentation/kbuild/kconfig.txt.
202
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.
221
222COMPILING the kernel:
223
224 - Make sure you have at least gcc 3.2 available.
225 For more information, refer to Documentation/Changes.
226
227 Please note that you can still run a.out user programs with this kernel.
228
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.
232
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.
235
236 - If you configured any of the parts of the kernel as `modules', you
237 will also have to do "make modules_install".
238
239 - Verbose kernel compile/build output:
240
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.:
246
247 make V=1 all
248
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".
251
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.
262
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.
266
267 - Booting a kernel directly from a floppy without the assistance of a
268 bootloader such as LILO, is no longer supported.
269
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.
277
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.
282
283 After reinstalling LILO, you should be all set. Shutdown the system,
284 reboot, and enjoy!
285
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.
290
291 - Reboot with the new kernel and enjoy.
292
293IF SOMETHING GOES WRONG:
294
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.
301
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.
306
307 - If the bug results in a message like
308
309 unable to handle kernel paging request at address C0000010
310 Oops: 0002
311 EIP: 0010:XXXXXXXX
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
317
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
325
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:
332
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.
339
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:
344
345 nm vmlinux | sort | less
346
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
358 interesting one.
359
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.
363
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").
368
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
372 with the EIP value.)
373
374 gdb'ing a non-running kernel currently fails because gdb (wrongly)
375 disregards the starting offset for which the kernel is compiled.
376
1 Linux kernel release 3.x <http://kernel.org/>
2
3These are the release notes for Linux version 3. 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, Tilera TILE, 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, 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
59INSTALLING 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-3.X.tar.gz | tar xvf -
66
67 or
68
69 bzip2 -dc linux-3.X.tar.bz2 | tar xvf -
70
71 Replace "X" 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 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:
82
83 gzip -cd ../patch-3.x.gz | patch -p1
84
85 or
86
87 bzip2 -dc ../patch-3.x.bz2 | patch -p1
88
89 Replace "x" for all versions bigger than the version "X" of your current
90 source tree, _in_order_, and you should be ok. You may want to remove
91 the backup files (some-file-name~ or some-file-name.orig), and make sure
92 that there are no failed patches (some-file-name# or some-file-name.rej).
93 If there are, either you or I have made a mistake.
94
95 Unlike patches for the 3.x kernels, patches for the 3.x.y kernels
96 (also known as the -stable kernels) are not incremental but instead apply
97 directly to the base 3.x kernel. For example, if your base kernel is 3.0
98 and you want to apply the 3.0.3 patch, you must not first apply the 3.0.1
99 and 3.0.2 patches. Similarly, if you are running kernel version 3.0.2 and
100 want to jump to 3.0.3, you must first reverse the 3.0.2 patch (that is,
101 patch -R) _before_ applying the 3.0.3 patch. You can read more on this in
102 Documentation/applying-patches.txt
103
104 Alternatively, the script patch-kernel can be used to automate this
105 process. It determines the current kernel version and applies any
106 patches found.
107
108 linux/scripts/patch-kernel linux
109
110 The first argument in the command above is the location of the
111 kernel source. Patches are applied from the current directory, but
112 an alternative directory can be specified as the second argument.
113
114 - Make sure you have no stale .o files and dependencies lying around:
115
116 cd linux
117 make mrproper
118
119 You should now have the sources correctly installed.
120
121SOFTWARE REQUIREMENTS
122
123 Compiling and running the 3.x kernels requires up-to-date
124 versions of various software packages. Consult
125 Documentation/Changes for the minimum version numbers required
126 and how to get updates for these packages. Beware that using
127 excessively old versions of these packages can cause indirect
128 errors that are very difficult to track down, so don't assume that
129 you can just update packages when obvious problems arise during
130 build or operation.
131
132BUILD directory for the kernel:
133
134 When compiling the kernel, all output files will per default be
135 stored together with the kernel source code.
136 Using the option "make O=output/dir" allow you to specify an alternate
137 place for the output files (including .config).
138 Example:
139
140 kernel source code: /usr/src/linux-3.X
141 build directory: /home/name/build/kernel
142
143 To configure and build the kernel, use:
144
145 cd /usr/src/linux-3.X
146 make O=/home/name/build/kernel menuconfig
147 make O=/home/name/build/kernel
148 sudo make O=/home/name/build/kernel modules_install install
149
150 Please note: If the 'O=output/dir' option is used, then it must be
151 used for all invocations of make.
152
153CONFIGURING the kernel:
154
155 Do not skip this step even if you are only upgrading one minor
156 version. New configuration options are added in each release, and
157 odd problems will turn up if the configuration files are not set up
158 as expected. If you want to carry your existing configuration to a
159 new version with minimal work, use "make oldconfig", which will
160 only ask you for the answers to new questions.
161
162 - Alternative configuration commands are:
163
164 "make config" Plain text interface.
165
166 "make menuconfig" Text based color menus, radiolists & dialogs.
167
168 "make nconfig" Enhanced text based color menus.
169
170 "make xconfig" X windows (Qt) based configuration tool.
171
172 "make gconfig" X windows (Gtk) based configuration tool.
173
174 "make oldconfig" Default all questions based on the contents of
175 your existing ./.config file and asking about
176 new config symbols.
177
178 "make silentoldconfig"
179 Like above, but avoids cluttering the screen
180 with questions already answered.
181 Additionally updates the dependencies.
182
183 "make defconfig" Create a ./.config file by using the default
184 symbol values from either arch/$ARCH/defconfig
185 or arch/$ARCH/configs/${PLATFORM}_defconfig,
186 depending on the architecture.
187
188 "make ${PLATFORM}_defconfig"
189 Create a ./.config file by using the default
190 symbol values from
191 arch/$ARCH/configs/${PLATFORM}_defconfig.
192 Use "make help" to get a list of all available
193 platforms of your architecture.
194
195 "make allyesconfig"
196 Create a ./.config file by setting symbol
197 values to 'y' as much as possible.
198
199 "make allmodconfig"
200 Create a ./.config file by setting symbol
201 values to 'm' as much as possible.
202
203 "make allnoconfig" Create a ./.config file by setting symbol
204 values to 'n' as much as possible.
205
206 "make randconfig" Create a ./.config file by setting symbol
207 values to random values.
208
209 You can find more information on using the Linux kernel config tools
210 in Documentation/kbuild/kconfig.txt.
211
212 - NOTES on "make config":
213
214 - Having unnecessary drivers will make the kernel bigger, and can
215 under some circumstances lead to problems: probing for a
216 nonexistent controller card may confuse your other controllers
217
218 - Compiling the kernel with "Processor type" set higher than 386
219 will result in a kernel that does NOT work on a 386. The
220 kernel will detect this on bootup, and give up.
221
222 - A kernel with math-emulation compiled in will still use the
223 coprocessor if one is present: the math emulation will just
224 never get used in that case. The kernel will be slightly larger,
225 but will work on different machines regardless of whether they
226 have a math coprocessor or not.
227
228 - The "kernel hacking" configuration details usually result in a
229 bigger or slower kernel (or both), and can even make the kernel
230 less stable by configuring some routines to actively try to
231 break bad code to find kernel problems (kmalloc()). Thus you
232 should probably answer 'n' to the questions for "development",
233 "experimental", or "debugging" features.
234
235COMPILING the kernel:
236
237 - Make sure you have at least gcc 3.2 available.
238 For more information, refer to Documentation/Changes.
239
240 Please note that you can still run a.out user programs with this kernel.
241
242 - Do a "make" to create a compressed kernel image. It is also
243 possible to do "make install" if you have lilo installed to suit the
244 kernel makefiles, but you may want to check your particular lilo setup first.
245
246 To do the actual install, you have to be root, but none of the normal
247 build should require that. Don't take the name of root in vain.
248
249 - If you configured any of the parts of the kernel as `modules', you
250 will also have to do "make modules_install".
251
252 - Verbose kernel compile/build output:
253
254 Normally, the kernel build system runs in a fairly quiet mode (but not
255 totally silent). However, sometimes you or other kernel developers need
256 to see compile, link, or other commands exactly as they are executed.
257 For this, use "verbose" build mode. This is done by inserting
258 "V=1" in the "make" command. E.g.:
259
260 make V=1 all
261
262 To have the build system also tell the reason for the rebuild of each
263 target, use "V=2". The default is "V=0".
264
265 - Keep a backup kernel handy in case something goes wrong. This is
266 especially true for the development releases, since each new release
267 contains new code which has not been debugged. Make sure you keep a
268 backup of the modules corresponding to that kernel, as well. If you
269 are installing a new kernel with the same version number as your
270 working kernel, make a backup of your modules directory before you
271 do a "make modules_install".
272
273 Alternatively, before compiling, use the kernel config option
274 "LOCALVERSION" to append a unique suffix to the regular kernel version.
275 LOCALVERSION can be set in the "General Setup" menu.
276
277 - In order to boot your new kernel, you'll need to copy the kernel
278 image (e.g. .../linux/arch/i386/boot/bzImage after compilation)
279 to the place where your regular bootable kernel is found.
280
281 - Booting a kernel directly from a floppy without the assistance of a
282 bootloader such as LILO, is no longer supported.
283
284 If you boot Linux from the hard drive, chances are you use LILO, which
285 uses the kernel image as specified in the file /etc/lilo.conf. The
286 kernel image file is usually /vmlinuz, /boot/vmlinuz, /bzImage or
287 /boot/bzImage. To use the new kernel, save a copy of the old image
288 and copy the new image over the old one. Then, you MUST RERUN LILO
289 to update the loading map!! If you don't, you won't be able to boot
290 the new kernel image.
291
292 Reinstalling LILO is usually a matter of running /sbin/lilo.
293 You may wish to edit /etc/lilo.conf to specify an entry for your
294 old kernel image (say, /vmlinux.old) in case the new one does not
295 work. See the LILO docs for more information.
296
297 After reinstalling LILO, you should be all set. Shutdown the system,
298 reboot, and enjoy!
299
300 If you ever need to change the default root device, video mode,
301 ramdisk size, etc. in the kernel image, use the 'rdev' program (or
302 alternatively the LILO boot options when appropriate). No need to
303 recompile the kernel to change these parameters.
304
305 - Reboot with the new kernel and enjoy.
306
307IF SOMETHING GOES WRONG:
308
309 - If you have problems that seem to be due to kernel bugs, please check
310 the file MAINTAINERS to see if there is a particular person associated
311 with the part of the kernel that you are having trouble with. If there
312 isn't anyone listed there, then the second best thing is to mail
313 them to me (torvalds@linux-foundation.org), and possibly to any other
314 relevant mailing-list or to the newsgroup.
315
316 - In all bug-reports, *please* tell what kernel you are talking about,
317 how to duplicate the problem, and what your setup is (use your common
318 sense). If the problem is new, tell me so, and if the problem is
319 old, please try to tell me when you first noticed it.
320
321 - If the bug results in a message like
322
323 unable to handle kernel paging request at address C0000010
324 Oops: 0002
325 EIP: 0010:XXXXXXXX
326 eax: xxxxxxxx ebx: xxxxxxxx ecx: xxxxxxxx edx: xxxxxxxx
327 esi: xxxxxxxx edi: xxxxxxxx ebp: xxxxxxxx
328 ds: xxxx es: xxxx fs: xxxx gs: xxxx
329 Pid: xx, process nr: xx
330 xx xx xx xx xx xx xx xx xx xx
331
332 or similar kernel debugging information on your screen or in your
333 system log, please duplicate it *exactly*. The dump may look
334 incomprehensible to you, but it does contain information that may
335 help debugging the problem. The text above the dump is also
336 important: it tells something about why the kernel dumped code (in
337 the above example, it's due to a bad kernel pointer). More information
338 on making sense of the dump is in Documentation/oops-tracing.txt
339
340 - If you compiled the kernel with CONFIG_KALLSYMS you can send the dump
341 as is, otherwise you will have to use the "ksymoops" program to make
342 sense of the dump (but compiling with CONFIG_KALLSYMS is usually preferred).
343 This utility can be downloaded from
344 ftp://ftp.<country>.kernel.org/pub/linux/utils/kernel/ksymoops/ .
345 Alternatively, you can do the dump lookup by hand:
346
347 - In debugging dumps like the above, it helps enormously if you can
348 look up what the EIP value means. The hex value as such doesn't help
349 me or anybody else very much: it will depend on your particular
350 kernel setup. What you should do is take the hex value from the EIP
351 line (ignore the "0010:"), and look it up in the kernel namelist to
352 see which kernel function contains the offending address.
353
354 To find out the kernel function name, you'll need to find the system
355 binary associated with the kernel that exhibited the symptom. This is
356 the file 'linux/vmlinux'. To extract the namelist and match it against
357 the EIP from the kernel crash, do:
358
359 nm vmlinux | sort | less
360
361 This will give you a list of kernel addresses sorted in ascending
362 order, from which it is simple to find the function that contains the
363 offending address. Note that the address given by the kernel
364 debugging messages will not necessarily match exactly with the
365 function addresses (in fact, that is very unlikely), so you can't
366 just 'grep' the list: the list will, however, give you the starting
367 point of each kernel function, so by looking for the function that
368 has a starting address lower than the one you are searching for but
369 is followed by a function with a higher address you will find the one
370 you want. In fact, it may be a good idea to include a bit of
371 "context" in your problem report, giving a few lines around the
372 interesting one.
373
374 If you for some reason cannot do the above (you have a pre-compiled
375 kernel image or similar), telling me as much about your setup as
376 possible will help. Please read the REPORTING-BUGS document for details.
377
378 - Alternatively, you can use gdb on a running kernel. (read-only; i.e. you
379 cannot change values or set break points.) To do this, first compile the
380 kernel with -g; edit arch/i386/Makefile appropriately, then do a "make
381 clean". You'll also need to enable CONFIG_PROC_FS (via "make config").
382
383 After you've rebooted with the new kernel, do "gdb vmlinux /proc/kcore".
384 You can now use all the usual gdb commands. The command to look up the
385 point where your system crashed is "l *0xXXXXXXXX". (Replace the XXXes
386 with the EIP value.)
387
388 gdb'ing a non-running kernel currently fails because gdb (wrongly)
389 disregards the starting offset for which the kernel is compiled.
390