====== Linux kernel ======






===== Compiling the debian way =====

**see:** [[http://kernel-handbook.alioth.debian.org/|Debian Linux Kernel Handbook]]


   bzip2 -dc /usr/src/patch.bz2 | patch -p1 --dry-run

   make-kpkg clean
   fakeroot make-kpkg --initrd --append-to-version=-custom kernel_image kernel_headers

After **''--append-to-version=''** you can write any string that helps you identify the kernel, but it must begin with a minus (-) and must not contain whitespace.

** SMP/DualCore compiling tip **
   # CONCURRENCY_LEVEL=4 make-kpkg --initrd --rootcmd=fakeroot --append-to-version=<version> kernel_image

==== Cross-compiling ====

see: http://michael-prokop.at/blog/2007/01/21/cross-compile-the-linux-kernel-on-debian/

Adjust $KERNELSOURCE/Makefile to:

   ARCH            = powerpc
   CROSS_COMPILE   = powerpc-linux-gnu-

   export ARCH=powerpc

   make-kpkg --arch powerpc ...




===== kernel lab =====

kernellab − manage kernel configs for many machines easily

  apt-get install kernellab


usage:	
   kernellab [options] <host> [<version>[−ac<patchlevel>] [<module>..]]

or more advance :)

   for a in router1 router2 router3 ...; do kernellab "$a"; done


=====  IO scheduler =====
    *  Completely Fair Queuing—elevator=cfq
    * Deadline—elevator=deadline
    * NOOP—elevator=noop
    * Anticipatory—elevator=as

   image = /boot/vmlinuz26113
   initrd = /boot/initrd.gz
   append = "elevator=deadline"
   root = /dev/hda1
   label = kernel_2.6.11.3
   read-only

   # cat /sys/block/hda/queue/scheduler
   noop [anticipatory] deadline cfq

how come deadline is not being chosen??

This works.
   # echo deadline > /sys/block/hda/queue/scheduler
   # cat /sys/block/hda/queue/scheduler
   noop anticipatory [deadline] cfq