[gentoo-user] kerninst (was Optional /usr merge in Gentoo)

["Canek Peláez Valdés" <caneko@gmail.com>]

I am following vanilla-sources in all my machines, which is what
people like Greg Kroah-Hartman actually recommends [1][2]. Since they
are now never stabilized [3], this means that I need to update them
pretty regularly to keep them safe.

This implies that I have to change the /usr/src/linux symbolic link,
configure the kernel using make oldconfig, compile it, install it,
install its modules, reemerge any package that provides kernel modules
(if any), regenerate its initramfs, regenerate the GRUB2 config file
OR adding a new entry in GRUB.

None of this steps are particularly difficult, but any mistake in one
of them can result in an unbootable system. So I wrote a little script
that takes care of each of this steps automagically:

https://github.com/canek-pelaez/kerninst

So now everytime I need to use a new kernel version, I only do:

# eselect kernel set <new-kernel>
# kerninst

Everything is done by the script.

The script is 167 lines of Bash, and I think is pretty easy to follow
what it does. Any of the steps can be called individually, and I have
been using it in all of my machines without any problem. It works with
both GRUB and GRUB2, generating a very simple GRUB config file for
every image available in /boot, with corresponding inird line if
availabe.

WARNINGS

• If /usr/src/linux points to /usr/src/linux-3.10.10, then the script
deletes /boot vmlinuz-3.10.10, /boot/initrd-3.10.10 *and*
/lib/modules/3.10.10.
• The script *WILL* overwrite your GRUB/GRUB2 configuration file, so
make a copy before trying it.
• The script requires a valid kernel .config file which will be copied
into /usrc/src/linux, and then used to configure the kernel with:

      yes "" | make oldconfig

   Some people recommend not doing this, and it can stall if a new
option for the kernel requires an answer with no default value.
• The script only supports dracut, but adding genkernel (or any other
initramfs maker) should be easy. Patches accepted. Dracut should be
already configured.
• I have only tested it with vanilla-sources, but probably will work
with other *-sources packages.

I have been using it in all of my machines for some days now, and it
works for me; but I take no responsibility if it breaks your machine,
or if it kills your dog.

Regards.

[1] http://article.gmane.org/gmane.linux.gentoo.devel/86496
[2] http://article.gmane.org/gmane.linux.gentoo.devel/86506
[3] http://article.gmane.org/gmane.linux.gentoo.devel/87015
-- 
Canek Peláez Valdés
Posgrado en Ciencia e Ingeniería de la Computación
Universidad Nacional Autónoma de México