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Linux/README

  1         Linux kernel release 2.4.xx
  2 
  3 These are the release notes for Linux version 2.4.  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 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 
 21 ON 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 
 27 DOCUMENTATION:
 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 
 49 INSTALLING 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-2.4.XX.tar.gz | tar xvf -
 56 
 57    Replace "XX" with the version number of the latest kernel.
 58 
 59    Do NOT use the /usr/src/linux area! This area has a (usually
 60    incomplete) set of kernel headers that are used by the library header
 61    files.  They should match the library, and not get messed up by
 62    whatever the kernel-du-jour happens to be.
 63 
 64  - You can also upgrade between 2.4.xx releases by patching.  Patches are
 65    distributed in the traditional gzip and the new bzip2 format.  To
 66    install by patching, get all the newer patch files, enter the
 67    top level directory of the kernel source (linux-2.4.xx) and execute:
 68 
 69                gzip -cd ../patch-2.4.xx.gz | patch -p1
 70 
 71    or
 72                bzip2 -dc ../patch-2.4.xx.bz2 | patch -p1
 73 
 74    (repeat xx for all versions bigger than the version of your current
 75    source tree, _in_order_) and you should be ok.  You may want to remove
 76    the backup files (xxx~ or xxx.orig), and make sure that there are no
 77    failed patches (xxx# or xxx.rej). If there are, either you or me has
 78    made a mistake.
 79 
 80    Alternatively, the script patch-kernel can be used to automate this
 81    process.  It determines the current kernel version and applies any
 82    patches found.
 83 
 84                 linux/scripts/patch-kernel linux
 85 
 86    The first argument in the command above is the location of the
 87    kernel source.  Patches are applied from the current directory, but
 88    an alternative directory can be specified as the second argument.
 89 
 90  - Make sure you have no stale .o files and dependencies lying around:
 91 
 92                 cd linux
 93                 make mrproper
 94 
 95    You should now have the sources correctly installed.
 96 
 97 SOFTWARE REQUIREMENTS
 98 
 99    Compiling and running the 2.4.xx kernels requires up-to-date
100    versions of various software packages.  Consult
101    ./Documentation/Changes for the minimum version numbers required
102    and how to get updates for these packages.  Beware that using
103    excessively old versions of these packages can cause indirect
104    errors that are very difficult to track down, so don't assume that
105    you can just update packages when obvious problems arise during
106    build or operation.
107 
108 CONFIGURING the kernel:
109 
110  - Do a "make config" to configure the basic kernel.  "make config" needs
111    bash to work: it will search for bash in $BASH, /bin/bash and /bin/sh
112    (in that order), so one of those must be correct for it to work. 
113 
114    Do not skip this step even if you are only upgrading one minor
115    version.  New configuration options are added in each release, and
116    odd problems will turn up if the configuration files are not set up
117    as expected.  If you want to carry your existing configuration to a
118    new version with minimal work, use "make oldconfig", which will
119    only ask you for the answers to new questions.
120 
121  - Alternate configuration commands are:
122         "make menuconfig"  Text based color menus, radiolists & dialogs.
123         "make xconfig"     X windows based configuration tool.
124         "make oldconfig"   Default all questions based on the contents of
125                            your existing ./.config file.
126    
127         NOTES on "make config":
128         - having unnecessary drivers will make the kernel bigger, and can
129           under some circumstances lead to problems: probing for a
130           nonexistent controller card may confuse your other controllers
131         - compiling the kernel with "Processor type" set higher than 386
132           will result in a kernel that does NOT work on a 386.  The
133           kernel will detect this on bootup, and give up.
134         - A kernel with math-emulation compiled in will still use the
135           coprocessor if one is present: the math emulation will just
136           never get used in that case.  The kernel will be slightly larger,
137           but will work on different machines regardless of whether they
138           have a math coprocessor or not. 
139         - the "kernel hacking" configuration details usually result in a
140           bigger or slower kernel (or both), and can even make the kernel
141           less stable by configuring some routines to actively try to
142           break bad code to find kernel problems (kmalloc()).  Thus you
143           should probably answer 'n' to the questions for
144           "development", "experimental", or "debugging" features.
145 
146  - Check the top Makefile for further site-dependent configuration
147    (default SVGA mode etc). 
148 
149  - Finally, do a "make dep" to set up all the dependencies correctly. 
150 
151 COMPILING the kernel:
152 
153  - Make sure you have gcc 2.95.3 available.  gcc 2.91.66 (egcs-1.1.2) may
154    also work but is not as safe, and *gcc 2.7.2.3 is no longer supported*.
155    gcc 4 is *not* supported.
156    Also remember to upgrade your binutils package (for as/ld/nm and company)
157    if necessary. For more information, refer to ./Documentation/Changes.
158 
159    Please note that you can still run a.out user programs with this kernel.
160 
161  - Do a "make bzImage" to create a compressed kernel image.  If you want
162    to make a boot disk (without root filesystem or LILO), insert a floppy
163    in your A: drive, and do a "make bzdisk".  It is also possible to do
164    "make install" if you have lilo installed to suit the kernel makefiles,
165    but you may want to check your particular lilo setup first. 
166 
167    To do the actual install you have to be root, but none of the normal
168    build should require that. Don't take the name of root in vain.
169 
170  - In the unlikely event that your system cannot boot bzImage kernels you
171    can still compile your kernel as zImage. However, since zImage support
172    will be removed at some point in the future in favor of bzImage we
173    encourage people having problems with booting bzImage kernels to report
174    these, with detailed hardware configuration information, to the
175    linux-kernel mailing list and to H. Peter Anvin <hpa+linux@zytor.com>.
176 
177  - If you configured any of the parts of the kernel as `modules', you
178    will have to do "make modules" followed by "make modules_install".
179    Read Documentation/modules.txt for more information.  For example,
180    an explanation of how to use the modules is included there.
181 
182  - Keep a backup kernel handy in case something goes wrong.  This is 
183    especially true for the development releases, since each new release
184    contains new code which has not been debugged.  Make sure you keep a
185    backup of the modules corresponding to that kernel, as well.  If you
186    are installing a new kernel with the same version number as your
187    working kernel, make a backup of your modules directory before you
188    do a "make modules_install".
189 
190  - In order to boot your new kernel, you'll need to copy the kernel
191    image (found in .../linux/arch/i386/boot/bzImage after compilation)
192    to the place where your regular bootable kernel is found. 
193 
194    For some, this is on a floppy disk, in which case you can copy the
195    kernel bzImage file to /dev/fd0 to make a bootable floppy.
196 
197    If you boot Linux from the hard drive, chances are you use LILO which
198    uses the kernel image as specified in the file /etc/lilo.conf.  The
199    kernel image file is usually /vmlinuz, /boot/vmlinuz, /bzImage or
200    /boot/bzImage.  To use the new kernel, save a copy of the old image
201    and copy the new image over the old one.  Then, you MUST RERUN LILO
202    to update the loading map!! If you don't, you won't be able to boot
203    the new kernel image.
204 
205    Reinstalling LILO is usually a matter of running /sbin/lilo. 
206    You may wish to edit /etc/lilo.conf to specify an entry for your
207    old kernel image (say, /vmlinux.old) in case the new one does not
208    work.  See the LILO docs for more information. 
209 
210    After reinstalling LILO, you should be all set.  Shutdown the system,
211    reboot, and enjoy!
212 
213    If you ever need to change the default root device, video mode,
214    ramdisk size, etc.  in the kernel image, use the 'rdev' program (or
215    alternatively the LILO boot options when appropriate).  No need to
216    recompile the kernel to change these parameters. 
217 
218  - Reboot with the new kernel and enjoy. 
219 
220 IF SOMETHING GOES WRONG:
221 
222  - If you have problems that seem to be due to kernel bugs, please check
223    the file MAINTAINERS to see if there is a particular person associated
224    with the part of the kernel that you are having trouble with. If there
225    isn't anyone listed there, then the second best thing is to mail
226    them to me (torvalds@transmeta.com), and possibly to any other
227    relevant mailing-list or to the newsgroup.  The mailing-lists are
228    useful especially for SCSI and networking problems, as I can't test
229    either of those personally anyway. 
230 
231  - In all bug-reports, *please* tell what kernel you are talking about,
232    how to duplicate the problem, and what your setup is (use your common
233    sense).  If the problem is new, tell me so, and if the problem is
234    old, please try to tell me when you first noticed it.
235 
236  - If the bug results in a message like
237 
238         unable to handle kernel paging request at address C0000010
239         Oops: 0002
240         EIP:   0010:XXXXXXXX
241         eax: xxxxxxxx   ebx: xxxxxxxx   ecx: xxxxxxxx   edx: xxxxxxxx
242         esi: xxxxxxxx   edi: xxxxxxxx   ebp: xxxxxxxx
243         ds: xxxx  es: xxxx  fs: xxxx  gs: xxxx
244         Pid: xx, process nr: xx
245         xx xx xx xx xx xx xx xx xx xx
246 
247    or similar kernel debugging information on your screen or in your
248    system log, please duplicate it *exactly*.  The dump may look
249    incomprehensible to you, but it does contain information that may
250    help debugging the problem.  The text above the dump is also
251    important: it tells something about why the kernel dumped code (in
252    the above example it's due to a bad kernel pointer). More information
253    on making sense of the dump is in Documentation/oops-tracing.txt
254 
255  - You can use the "ksymoops" program to make sense of the dump.  This
256    utility can be downloaded from
257    ftp://ftp.<country>.kernel.org/pub/linux/utils/kernel/ksymoops.
258    Alternately you can do the dump lookup by hand:
259 
260  - In debugging dumps like the above, it helps enormously if you can
261    look up what the EIP value means.  The hex value as such doesn't help
262    me or anybody else very much: it will depend on your particular
263    kernel setup.  What you should do is take the hex value from the EIP
264    line (ignore the "0010:"), and look it up in the kernel namelist to
265    see which kernel function contains the offending address.
266 
267    To find out the kernel function name, you'll need to find the system
268    binary associated with the kernel that exhibited the symptom.  This is
269    the file 'linux/vmlinux'.  To extract the namelist and match it against
270    the EIP from the kernel crash, do:
271 
272                 nm vmlinux | sort | less
273 
274    This will give you a list of kernel addresses sorted in ascending
275    order, from which it is simple to find the function that contains the
276    offending address.  Note that the address given by the kernel
277    debugging messages will not necessarily match exactly with the
278    function addresses (in fact, that is very unlikely), so you can't
279    just 'grep' the list: the list will, however, give you the starting
280    point of each kernel function, so by looking for the function that
281    has a starting address lower than the one you are searching for but
282    is followed by a function with a higher address you will find the one
283    you want.  In fact, it may be a good idea to include a bit of
284    "context" in your problem report, giving a few lines around the
285    interesting one. 
286 
287    If you for some reason cannot do the above (you have a pre-compiled
288    kernel image or similar), telling me as much about your setup as
289    possible will help. 
290 
291  - Alternately, you can use gdb on a running kernel. (read-only; i.e. you
292    cannot change values or set break points.) To do this, first compile the
293    kernel with -g; edit arch/i386/Makefile appropriately, then do a "make
294    clean". You'll also need to enable CONFIG_PROC_FS (via "make config").
295 
296    After you've rebooted with the new kernel, do "gdb vmlinux /proc/kcore".
297    You can now use all the usual gdb commands. The command to look up the
298    point where your system crashed is "l *0xXXXXXXXX". (Replace the XXXes
299    with the EIP value.)
300 
301    gdb'ing a non-running kernel currently fails because gdb (wrongly)
302    disregards the starting offset for which the kernel is compiled.
303 

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