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Debian has its own method of recompiling the kernel and related modules. See also Debian and the kernel, Section 2.7.
The use of gcc, binutils, and
module-init-tools from Debian unstable may help when
compiling the latest Linux kernel. See
/usr/share/doc/kernel-package/README.gz, especially the bottom of
this, for the official information.
Since it is a moving target, kernel compilation is a difficult subject that may confuse even the most admired developer:
--initrd requires a Debian-only cramfs patch.
No it does not, all you have to do to use a filesystem other than CRAMFS is to
set MKIMAGE in /etc/mkinitrd/mkinitrd.conf.
Be careful and always rely on the
/usr/share/doc/kernel-package/README.gz by Manoj and Kent and
http://kernel-handbook.alioth.debian.org/.
Make sure to obtain the latest unstable version of the
kernel-package package if you are to compile the latest version of
the kernel.
initrd is not needed for a kernel compiled only for one machine.
I use it since I want my kernel to be almost the same as the one provided by
the kernel-image packages. If you use initrd, make sure to read
mkinitrd(8) and mkinitrd.conf(5).
Most "normal" programs don't need kernel headers and in fact may
break if you use them directly; instead they should be compiled against the
headers with which glibc was built, which are the
versions in /usr/include/linux and /usr/include/asm
of the Debian system.
So do not put symlinks to the directories in /usr/src/linux from
/usr/include/linux and /usr/include/asm, as suggested
by some outdated documents.
If you need particular kernel headers for some kernel-specific
application programs, alter the makefile(s) so that their include path points
to dir-of-particular-kernel-headers/include/linux and
dir-of-particular-kernel-headers/include/asm.
The behavior of the Linux kernel can be changed on the fly using the proc filesystem.
For basic information on changing kernel parameters through the
/proc filesystem, read Documentation/sysctl/* in the
Linux source.
See some examples of kernel parameter manipulations in
/etc/init.d/networking and Strange access problems with some websites,
Section 3.8.5.
See sysctl.conf(5) for how to set up the boot time kernel
configuration through /proc filesystem with
/etc/init.d/procps.sh script usually run from
/etc/rcS.d/S30procps.sh.
The Linux kernel may complain "Too many open files". This is due to the small default value (8096) for file-max. To fix this problem, run the following command as root:
# echo "65536" > /proc/sys/fs/file-max # for 2.2 and 2.4 kernel
# echo "131072" > /proc/sys/fs/inode-max # for 2.2 kernel only
or put the following into /etc/sysctl.conf for the permanent
change:
file-max=65536 # for 2.2 and 2.4 kernel
inode-max=131072 # for 2.2 kernel only
You can change disk flush intervals through the proc filesystem. The following will shorten its interval from the default five seconds to one second.
# echo "40 0 0 0 100 30000 60 0 0" > /proc/sys/vm/bdflush
This may negatively impact file I/O performance a little bit. But this secures file contents except for the last one second which is shorter than the default five seconds. This is true even for journaling filesystems.
For some old low memory systems, it may still be useful to enable over-commit of memory through the proc filesystem:
# echo 1 > /proc/sys/vm/overcommit_memory
The udev is a dynamic replacement for /dev/. Device names can be
chosen to be very short ones. The devfs used in the 2.4 kernel is now
obsolete.
Installing the new Debian 2.6 kernel provided by
kernel-image-2.6.NN with udev package will
enable this.
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