On this page is described an easy way to debug kernel issues, by using "git-bisect". The idea of this tool is to track down a particular issue (or regression) by selecting the faulty revision.
- Hibernation works under 2.6.25-rc6 but not anymore under 2.6.25-rc7 and I would like to know wich revision caused the regression.
For these regression tests, you will need the following packages (to install with your favorite package manager) :
git-core gitk kernel-package fakeroot
Getting the Linux git source
In this step, we will get a local copy of the whole Linux kernel source code by using Linux's distributed version control system : git.
Move to your source directory
$ cd ~/src
Clone Linus's version (HEAD)
This will download about 170 MiB and thus need some time. Go take yourself a coffee !
$ git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6.git
Separate the wheat from the chaff
In that step, we will mark the versions good or bad.
Start the git-bisect process
$ git bisect start
Mark the ''good'' version
$ git bisect good v2.6.25-rc6
Mark the ''bad'' version
$ git bisect bad v2.6.25-rc7
At this point, this command should answer you something like that :
Bisecting: 182 revisions left to test after this [2c7871982cf27caaddbaeb7e2121ce1374b520ff] Merge git://git.kernel.org/pub/scm/linux/kernel/git/lethal/sh-2.6.25
The interesting part is the number (in our case, 182) which is the number of kernel revisions that lay between your good and your bad.
Build your kernel
In this step, we will configure the future kernel according to the actual configuration and then compile the new kernel.
Copy a valid configuration
$ cp /boot/config-$(uname -r) .config
Configure the kernel
$ make oldconfig
Simply press Enter at each question.
Build the kernel
This will take a lot of time and computation power too. Get yourself a pause and get your laptop off your legs.
$ fakeroot make deb-pkg
Install the newly created kernel
(According to the name lastly pointed by latest command.
# dpkg -i ../linux-2.6.25-rc6_2.6.25-rc6-2_amd64.deb
Update the initramfs
The version is probably the good one (new version of it)
# update-initramfs -c -k 2.6.25-rc6
Update the boot loader
This is for all versions of Grub. Anyone for LILO ?
Reboot under newly built kernel