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1 Linux kernel release 2.5.xx
3 These are the release notes for Linux version 2.5. 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.
7 NOTE! As with all odd-numbered releases, 2.5.x is a development kernel.
8 For stable kernels, see the 2.4.x maintained by Marcelo Tosatti.
10 WHAT IS LINUX?
12 Linux is a Unix clone written from scratch by Linus Torvalds with
13 assistance from a loosely-knit team of hackers across the Net.
14 It aims towards POSIX compliance.
16 It has all the features you would expect in a modern fully-fledged
17 Unix, including true multitasking, virtual memory, shared libraries,
18 demand loading, shared copy-on-write executables, proper memory
19 management and TCP/IP networking.
21 It is distributed under the GNU General Public License - see the
22 accompanying COPYING file for more details.
24 ON WHAT HARDWARE DOES IT RUN?
26 Linux was first developed for 386/486-based PCs. These days it also
27 runs on ARMs, DEC Alphas, SUN Sparcs, M68000 machines (like Atari and
28 Amiga), MIPS and PowerPC, and others.
30 DOCUMENTATION:
32 - There is a lot of documentation available both in electronic form on
33 the Internet and in books, both Linux-specific and pertaining to
34 general UNIX questions. I'd recommend looking into the documentation
35 subdirectories on any Linux FTP site for the LDP (Linux Documentation
36 Project) books. This README is not meant to be documentation on the
37 system: there are much better sources available.
39 - There are various README files in the Documentation/ subdirectory:
40 these typically contain kernel-specific installation notes for some
41 drivers for example. See ./Documentation/00-INDEX for a list of what
42 is contained in each file. Please read the Changes file, as it
43 contains information about the problems, which may result by upgrading
44 your kernel.
46 - The Documentation/DocBook/ subdirectory contains several guides for
47 kernel developers and users. These guides can be rendered in a
48 number of formats: PostScript (.ps), PDF, and HTML, among others.
49 After installation, "make psdocs", "make pdfdocs", or "make htmldocs"
50 will render the documentation in the requested format.
52 INSTALLING the kernel:
54 - If you install the full sources, put the kernel tarball in a
55 directory where you have permissions (eg. your home directory) and
56 unpack it:
58 gzip -cd linux-2.5.XX.tar.gz | tar xvf -
60 Replace "XX" with the version number of the latest kernel.
62 Do NOT use the /usr/src/linux area! This area has a (usually
63 incomplete) set of kernel headers that are used by the library header
64 files. They should match the library, and not get messed up by
65 whatever the kernel-du-jour happens to be.
67 - You can also upgrade between 2.5.xx releases by patching. Patches are
68 distributed in the traditional gzip and the new bzip2 format. To
69 install by patching, get all the newer patch files, enter the
70 top level directory of the kernel source (linux-2.5.xx) and execute:
72 gzip -cd ../patch-2.5.xx.gz | patch -p1
74 or
75 bzip2 -dc ../patch-2.5.xx.bz2 | patch -p1
77 (repeat xx for all versions bigger than the version of your current
78 source tree, _in_order_) and you should be ok. You may want to remove
79 the backup files (xxx~ or xxx.orig), and make sure that there are no
80 failed patches (xxx# or xxx.rej). If there are, either you or me has
81 made a mistake.
83 Alternatively, the script patch-kernel can be used to automate this
84 process. It determines the current kernel version and applies any
85 patches found.
87 linux/scripts/patch-kernel linux
89 The first argument in the command above is the location of the
90 kernel source. Patches are applied from the current directory, but
91 an alternative directory can be specified as the second argument.
93 - Make sure you have no stale .o files and dependencies lying around:
95 cd linux
96 make mrproper
98 You should now have the sources correctly installed.
100 SOFTWARE REQUIREMENTS
102 Compiling and running the 2.5.xx kernels requires up-to-date
103 versions of various software packages. Consult
104 ./Documentation/Changes for the minimum version numbers required
105 and how to get updates for these packages. Beware that using
106 excessively old versions of these packages can cause indirect
107 errors that are very difficult to track down, so don't assume that
108 you can just update packages when obvious problems arise during
109 build or operation.
111 CONFIGURING the kernel:
113 - Do a "make config" to configure the basic kernel. "make config" needs
114 bash to work: it will search for bash in $BASH, /bin/bash and /bin/sh
115 (in that order), so one of those must be correct for it to work.
117 Do not skip this step even if you are only upgrading one minor
118 version. New configuration options are added in each release, and
119 odd problems will turn up if the configuration files are not set up
120 as expected. If you want to carry your existing configuration to a
121 new version with minimal work, use "make oldconfig", which will
122 only ask you for the answers to new questions.
124 - Alternate configuration commands are:
125 "make menuconfig" Text based color menus, radiolists & dialogs.
126 "make xconfig" X windows based configuration tool.
127 "make oldconfig" Default all questions based on the contents of
128 your existing ./.config file.
130 NOTES on "make config":
131 - having unnecessary drivers will make the kernel bigger, and can
132 under some circumstances lead to problems: probing for a
133 nonexistent controller card may confuse your other controllers
134 - compiling the kernel with "Processor type" set higher than 386
135 will result in a kernel that does NOT work on a 386. The
136 kernel will detect this on bootup, and give up.
137 - A kernel with math-emulation compiled in will still use the
138 coprocessor if one is present: the math emulation will just
139 never get used in that case. The kernel will be slightly larger,
140 but will work on different machines regardless of whether they
141 have a math coprocessor or not.
142 - the "kernel hacking" configuration details usually result in a
143 bigger or slower kernel (or both), and can even make the kernel
144 less stable by configuring some routines to actively try to
145 break bad code to find kernel problems (kmalloc()). Thus you
146 should probably answer 'n' to the questions for
147 "development", "experimental", or "debugging" features.
149 - Check the top Makefile for further site-dependent configuration
150 (default SVGA mode etc).
152 COMPILING the kernel:
154 - Make sure you have gcc 2.95.3 available.
155 gcc 2.91.66 (egcs-1.1.2), and gcc 2.7.2.3 are known to miscompile
156 some parts of the kernel, and are *no longer supported*.
157 Also remember to upgrade your binutils package (for as/ld/nm and company)
158 if necessary. For more information, refer to ./Documentation/Changes.
160 Please note that you can still run a.out user programs with this kernel.
162 - Do a "make bzImage" to create a compressed kernel image. If you want
163 to make a boot disk (without root filesystem or LILO), insert a floppy
164 in your A: drive, and do a "make bzdisk". It is also possible to do
165 "make install" if you have lilo installed to suit the kernel makefiles,
166 but you may want to check your particular lilo setup first.
168 To do the actual install you have to be root, but none of the normal
169 build should require that. Don't take the name of root in vain.
171 - In the unlikely event that your system cannot boot bzImage kernels you
172 can still compile your kernel as zImage. However, since zImage support
173 will be removed at some point in the future in favor of bzImage we
174 encourage people having problems with booting bzImage kernels to report
175 these, with detailed hardware configuration information, to the
176 linux-kernel mailing list and to H. Peter Anvin <hpa+linux@zytor.com>.
178 - If you configured any of the parts of the kernel as `modules', you
179 will have to do "make modules" followed by "make modules_install".
180 Read Documentation/modules.txt for more information. For example,
181 an explanation of how to use the modules is included there.
183 - Keep a backup kernel handy in case something goes wrong. This is
184 especially true for the development releases, since each new release
185 contains new code which has not been debugged. Make sure you keep a
186 backup of the modules corresponding to that kernel, as well. If you
187 are installing a new kernel with the same version number as your
188 working kernel, make a backup of your modules directory before you
189 do a "make modules_install".
191 - In order to boot your new kernel, you'll need to copy the kernel
192 image (found in .../linux/arch/i386/boot/bzImage after compilation)
193 to the place where your regular bootable kernel is found.
195 For some, this is on a floppy disk, in which case you can copy the
196 kernel bzImage file to /dev/fd0 to make a bootable floppy.
198 If you boot Linux from the hard drive, chances are you use LILO which
199 uses the kernel image as specified in the file /etc/lilo.conf. The
200 kernel image file is usually /vmlinuz, /boot/vmlinuz, /bzImage or
201 /boot/bzImage. To use the new kernel, save a copy of the old image
202 and copy the new image over the old one. Then, you MUST RERUN LILO
203 to update the loading map!! If you don't, you won't be able to boot
204 the new kernel image.
206 Reinstalling LILO is usually a matter of running /sbin/lilo.
207 You may wish to edit /etc/lilo.conf to specify an entry for your
208 old kernel image (say, /vmlinux.old) in case the new one does not
209 work. See the LILO docs for more information.
211 After reinstalling LILO, you should be all set. Shutdown the system,
212 reboot, and enjoy!
214 If you ever need to change the default root device, video mode,
215 ramdisk size, etc. in the kernel image, use the 'rdev' program (or
216 alternatively the LILO boot options when appropriate). No need to
217 recompile the kernel to change these parameters.
219 - Reboot with the new kernel and enjoy.
221 IF SOMETHING GOES WRONG:
223 - If you have problems that seem to be due to kernel bugs, please check
224 the file MAINTAINERS to see if there is a particular person associated
225 with the part of the kernel that you are having trouble with. If there
226 isn't anyone listed there, then the second best thing is to mail
227 them to me (torvalds@transmeta.com), and possibly to any other
228 relevant mailing-list or to the newsgroup. The mailing-lists are
229 useful especially for SCSI and networking problems, as I can't test
230 either of those personally anyway.
232 - In all bug-reports, *please* tell what kernel you are talking about,
233 how to duplicate the problem, and what your setup is (use your common
234 sense). If the problem is new, tell me so, and if the problem is
235 old, please try to tell me when you first noticed it.
237 - If the bug results in a message like
239 unable to handle kernel paging request at address C0000010
240 Oops: 0002
241 EIP: 0010:XXXXXXXX
242 eax: xxxxxxxx ebx: xxxxxxxx ecx: xxxxxxxx edx: xxxxxxxx
243 esi: xxxxxxxx edi: xxxxxxxx ebp: xxxxxxxx
244 ds: xxxx es: xxxx fs: xxxx gs: xxxx
245 Pid: xx, process nr: xx
246 xx xx xx xx xx xx xx xx xx xx
248 or similar kernel debugging information on your screen or in your
249 system log, please duplicate it *exactly*. The dump may look
250 incomprehensible to you, but it does contain information that may
251 help debugging the problem. The text above the dump is also
252 important: it tells something about why the kernel dumped code (in
253 the above example it's due to a bad kernel pointer). More information
254 on making sense of the dump is in Documentation/oops-tracing.txt
256 - You can use the "ksymoops" program to make sense of the dump. This
257 utility can be downloaded from
258 ftp://ftp.<country>.kernel.org/pub/linux/utils/kernel/ksymoops.
259 Alternately you can do the dump lookup by hand:
261 - In debugging dumps like the above, it helps enormously if you can
262 look up what the EIP value means. The hex value as such doesn't help
263 me or anybody else very much: it will depend on your particular
264 kernel setup. What you should do is take the hex value from the EIP
265 line (ignore the "0010:"), and look it up in the kernel namelist to
266 see which kernel function contains the offending address.
268 To find out the kernel function name, you'll need to find the system
269 binary associated with the kernel that exhibited the symptom. This is
270 the file 'linux/vmlinux'. To extract the namelist and match it against
271 the EIP from the kernel crash, do:
273 nm vmlinux | sort | less
275 This will give you a list of kernel addresses sorted in ascending
276 order, from which it is simple to find the function that contains the
277 offending address. Note that the address given by the kernel
278 debugging messages will not necessarily match exactly with the
279 function addresses (in fact, that is very unlikely), so you can't
280 just 'grep' the list: the list will, however, give you the starting
281 point of each kernel function, so by looking for the function that
282 has a starting address lower than the one you are searching for but
283 is followed by a function with a higher address you will find the one
284 you want. In fact, it may be a good idea to include a bit of
285 "context" in your problem report, giving a few lines around the
286 interesting one.
288 If you for some reason cannot do the above (you have a pre-compiled
289 kernel image or similar), telling me as much about your setup as
290 possible will help.
292 - Alternately, you can use gdb on a running kernel. (read-only; i.e. you
293 cannot change values or set break points.) To do this, first compile the
294 kernel with -g; edit arch/i386/Makefile appropriately, then do a "make
295 clean". You'll also need to enable CONFIG_PROC_FS (via "make config").
297 After you've rebooted with the new kernel, do "gdb vmlinux /proc/kcore".
298 You can now use all the usual gdb commands. The command to look up the
299 point where your system crashed is "l *0xXXXXXXXX". (Replace the XXXes
300 with the EIP value.)
302 gdb'ing a non-running kernel currently fails because gdb (wrongly)
303 disregards the starting offset for which the kernel is compiled.