linux-kernel.html

Linus guide, Linus guide, Linus guide,

module dependencies for these, see the <A
HREF="compile-notes-modules">Note on modules</A>.</P>

<H4><A NAME="10"><A NAME="compile-notes">Notes on Compilation</A></A></H4>

<P><A NAME="compile-notes-sig11"><B>Note on sig11:</B></A><br> A
<tt>signal 11</tt> error during kernel compilation means that <tt>gcc</tt>
found an error in one of the files while compiling. <TT>sig11</TT>s, as
they are commonly referred to, are typically caused by bad hardware.  In
my (jbm) experience, they have been caused by bad processors, bad memory,
and overclocked memory. With the popularity of 100MHz bus clock systems
(ie: k6-2/3 and pII/pIII), there is an increasing number of people
overclocking RAM. I know, I do it myself. I often get <TT>sig11</TT>
messages during compiles, when the computer is getting hot.  My general
strategy for dealing with these is to lower system load (close x, stop
listening to MP3s, etc), and recompile the whole kernel. Because this is a
kernel-level file, do not simply remove the .o file and move on. This
could lead to system damage.

<H4><A NAME="11">Where to Copy the Kernel</A></H4>

<P>When you're copying the kernel to where it's supposed to be, that may
change from system to system. You can use what I have up there if you're
on a standard Red Hat system; if you're using Slackware, it's not in
<TT>/boot</TT>--it's in <TT>/</TT>. So instead of
<TT>/boot/vmlinuz-2.2.zz-new</TT>, it's <TT>/vmlinuz-2.2.zz-new</TT>.</P>

<P>We use the vmlinuz-2.2.zz-new for safety's sake. If you forgot
something essential in your kernel, your computer wouldn't be able to boot
with the new kernel. Unfortunately, this makes life a little more
complicated now, but it's not so bad. All you have to do is edit
<TT>/etc/lilo.conf</TT> (a somewhat daunting task, but really pretty
simple).</P>

<H4><A NAME="12">Editing <TT>/etc/lilo.conf</TT></A></H4>

<P><TT>/etc/lilo.conf</TT> is the settings file for <B>lilo</B>, the LInux
LOader. Editing this file can be hazardous to the health of your computer.  
Before you edit it, make a backup copy of it (<TT>cp /etc/lilo.conf
/etc/lilo.conf.backup-foo</TT>, or some other name you can remember.).  
This backup is in case you accidentally delete a line in the file. If you
need to restore your old lilo.conf, just do <TT>cp 
/etc/lilo.conf.backup-foo /etc/lilo.conf</TT> and start anew. Now then -
to the real work with lilo.conf</P>

<P>Open up <TT>/etc/lilo.conf</TT> in your favorite text editor. The file
should look something like this:

<PRE>
# LILO configuration file
# generated by 'liloconfig'
#
# Start LILO global section
boot = /dev/hda
#compact        # faster, but won't work on all systems.
delay = 50
vga = normal    # force sane state
# ramdisk = 0     # paranoia setting
# End LILO global section
# Linux bootable partition config begins
image = /vmlinuz
  root = /dev/hda2
  label = Linux
  append = &quot;ether=9,0x310,eth0 mem=64M&quot;
# Linux bootable partition config ends
# DOS bootable partition config begins
other = /dev/hda1
  label = DOS
  table = /dev/hda
# DOS bootable partition config ends
</PRE>

<P>What you want to do is this: copy the section from &quot;image =
vmlinuz&quot; through to the &quot;# Linux bootable partition config
ends&quot;(or the next &quot;image =&quot; line, if you have one) letter
for letter right below where it currently is, like so:</P>

<PRE>
# LILO configuration file
# generated by 'liloconfig'
#
# Start LILO global section
boot = /dev/hda
#compact        # faster, but won't work on all systems.
delay = 50
vga = normal    # force sane state
# ramdisk = 0     # paranoia setting
# End LILO global section
# Linux bootable partition config begins
image = /vmlinuz
  root = /dev/hda2
  label = Linux
  append = &quot;ether=9,0x310,eth0 mem=64M&quot;
image = /vmlinuz
  root = /dev/hda2
  label = Linux
  append = &quot;ether=9,0x310,eth0 mem=64M&quot;
# Linux bootable partition config ends
# DOS bootable partition config begins
other = /dev/hda1
  label = DOS
  table = /dev/hda
# DOS bootable partition config ends
</PRE>

<P>If you don't have a &quot;delay = xx&quot; line, or if xx is equal to
0, change it to &quot;delay = 50&quot; (without the quotes). By adding
this line, you instruct LILO to wait 5 seconds for you to enter in a
kernel image to load before it automatically boots the first one in the
list (in this case Linux). Now change the second &quot;image =
/vmlinuz&quot; (or &quot;image = /boot/vmlinuz&quot;) line to &quot;image
= /vmlinuz-2.2.zz-new&quot; (xx is the version number, like 2.2.4).  Also
change the second &quot;label = Linux&quot; line to &quot;label =
New&quot;. This section of the file now looks like this:</P>

<PRE>
image = /vmlinuz
  root = /dev/hda2
  label = Linux
  append = &quot;ether=9,0x310,eth0 mem=64M&quot;
image = /vmlinuz-2.2.zz-new
  root = /dev/hda2
  label = New
  append = &quot;ether=9,0x310,eth0 mem=64M&quot;
</PRE>

<P>Save the file to lilo.conf. Now type in <TT>lilo</TT> at the command
prompt. It should give you output similiar to this:</P>

<PRE>
Added Linux *
Added New
Added DOS
</PRE>

<P>If you encounter any error when you type <TT><B>lilo</B></TT> then
there the kernel is probably in a differnt locataion than the image = line
says. Check that, and look for capitialization problems.</P>

<P>Reboot, and when the LILO: comes up, hit left-shift (or any other key
that happens to please you), and then type in &quot;new&quot; (without
quotes, again). This will boot the image labeled new -
/vmlinuz-2.2.zz-new. If this boots and works well, just do <TT>cp /vmlinuz
/vmlinuz-backup</TT> and <TT>cp /vmlinuz-2.2.zz-new /vmlinuz</TT>. Open up
<TT>/etc/lilo.conf</TT> again and change the New section to be name =
backup, with the image being /vmlinuz-backup. If you don't want the LILO
boot prompt, comment out the delay = 50 line (stick a # in front of it).  
Now type <TT>lilo</TT> at a prompt and if lilo installs well, try
rebooting to make sure both your new kernel and your backup kernel
work.</P>

<H4><A NAME="13">PPP Support in the Kernel</A></H4>

<P>Before compiling, make sure you enable PPP support during <TT>make
config</TT> or <TT>make menuconfig</TT>. It's left to be NOT supported on
most of the kernels I've compiled so far (maybe because the kernel
developers have high-speed digital connections), but if you connect to
your ISP through PPP, you better enable this or else you'll have to
recompile later on to connect to the Internet.</P>

<H4><A NAME="14">Math Coprocessor/FPU</A></H4>

<P>If you don't have a math coprocessor (if your CPU is a 386DX or 486SX
without a math coprocessor), make sure you say <B>YES</B> on <B>kernel
math emulation</B>. This is what stopped me the first two times; I forgot
about the <B>EMULATION</B> part. If you have a tape drive, SCSI interface,
or any other weird or expensive stuff then go through <B><TT>make
config</TT></B> very carefully to optimize your system. If you have a
486DX, Pentium, or higher processor with normal system specs, then just
browse through configuration a bit and be careful. This may get boring
(especially if you have to do it three times to get it right), but still
read through it before jumping to compilation. Eventually you'll know
what's there to configure and you'll just zoom past it.</P>

<H4><A NAME="15">Unresolved Modules?</A></H4>

<P>You might see some errors/complaints about &quot;unresolved
modules&quot; when you're booting the new kernel. Whatever the cause is,
try moving your old module directory in <TT>/lib/modules</TT> (or wherever
your kernel module directory is) to <TT>/lib/oldmodules/</TT>.  For
example, when I boot up and some errors pop up about my 2.2.4 modules
being unresolved, I might go into <TT>/lib/modules/2.2.4</TT> and move the
modules that are being complained about. To avoid these errors, do <TT>cp
-r /lib/modules/2.2.yy /lib/oldmodules/; rm -rf /lib/modules/2.2.yy</TT>
before you do <TT>make modules</TT> and <TT>make modules_install</TT>.
(For example, if I were recompiling Linux 2.2.4 and I already had modules
for 2.2.4 installed, I would type <TT>cp -r /lib/modules/2.2.4
/lib/oldmodules/; rm -rf /lib/modules/2.2.4</TT> before I went and
compiled the modules). The unresolved modules error is quite common for
the first few times you complie the kernel and has stumped Linux newbies
worldwide. Of course, you could just delete the old modules directory
(<TT>rm -rf /lib/modules/2.2.4</TT> for example), but it is generally a
bad idea to delete things you might wind up needing if the compile doesn't
go quite right (also a common problem for your first few compiles ;^) ).
So just move things around.</P>

<P>I've had a problem while compiling development kernels (those starting
with 2.1) that complains about unresolved modules; I thought I needed to
update a few programs, and I was right. I found the page at <A
HREF="http://www.linuxhq.com/pgmup21.html"
TARGET="_top">http://www.linuxhq.com/pgmup21.html</A>.</P>

<H3><A NAME="16">Comments</A></H3>

<P>
<!-- Simon's comments -->
<tt>You might wish to add that when you use an <b>RPM</b> kernel version, it
appears to come in separate kernel-source and kernel-headers files.
<br>
<a href="[e-mail]">Simon Hampton
  &lt;[e-mail]&gt;</a>
<!-- /simon's comments -->
</tt>

<P>(The bold is my own, to stress the importance of <font
size="+1"><b>RPM</b></font> here. This particular problem is due to a
broken-by-design strategy on the part of the RPM package maintainers. I
guess it keeps package size down, at a large convenience/stability cost.
-jbm)</P>

<H3><A NAME="17">Authors' Notes</A></H3>

<!-- Include information here about sig11 messages -->

<P>Some people using SCSI on their Linux box <I>may</I> have problems
compiling the kernel. Since I don't have SCSI installed on my system, I
don't know what to do. However, Jeffrey here seems to know. If any of you
SCSI users have been having the same problem, please verify this
information with me so that I'll sound more confident. :)</P>

<PRE>
Here's a list of my in's and out's of getting the SCSI modules to boot
with your new kernel.

* After you have made the kerenel and modules i.e. &quot;make zImage&quot;
  and &quot;make modules&quot; make sure that your loopback device is
  available try &quot;insmod loop&quot; OR maybe it isn't a module or just
  complied in straight then you don't have RHL installed and this isn't for
  you!, This is default as a module with RHL along with everything else

* Another trap that I found is that with comfiguring the Kerenel with
  &quot;make xconfig&quot; at a res of 640x480 the two buttons at the bottom
  are cut off and I kept on going to just close the window and wonder why
  the kerenel wouldn't compile! 

* After you have inseted the loopback device, do a &quot;make
  modules_install&quot; to install the new modules (including you brand new
  SCSI drivers!) (Don't forget to back up the old set of modules in case you
  stuffed on the &quot;insmod loop&quot; and need to reinsert it later! 

* Now just type &quot;mkinitrd /boot/initrd 2.2.3&quot; where the
  filename points to the image file in the lilo.conf and the version of your
  new kerenel is there and present! The program mkinitrd works off your
  /etc/config.modules file! 

* FEW THINGS TO REMEMBER! - Don't forget to back up your old kernels and
  old initrd image file!, you never know this MAY not work successfully! (I
  know I have stuffed it up completely about 10 times!) :( anyway this
  booted for me on both options the old and linux in LILO then copy your new
  kerenel into it's final home and RUN LILO! 

Jeffrey Borg
<A HREF="mailto:[e-mail]">[e-mail]</A>
</PRE>

<HR>

<P>Comments, questions, suggestions, corrections?  Send them to <A
HREF="mailto:[e-mail]">[e-mail]</A> - if they're my mistake
I'll reply, if not I'll forward them on to Joshua.</P>

<HR>

<P><B><FONT SIZE="-1">Copyright &copy; 1997-1999 <A
HREF="mailto:[e-mail]">Joshua Go ([e-mail])</A>.
All rights reserved. Permission to use, distribute, and copy this document
is hereby granted.  You may modify this document as long as credit to me
is given.</FONT></B></P>

<P><B><FONT SIZE="-1">jbm hereby grants all copyright permissions he
has to Joshua Go. In other words - it's still Joshua's property, although
I'd like a little credit if you use this document.</FONT></B></P>

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