2006-05-06
Using a stock kernel.org kernel on Fedora Core 5
If you like initrds, the stock Linux kernels from kernel.org should just compile and work. Install the
kernel-devel
RPM, copy the .config
from /usr/src/kernels/<ver>
to your source tree to duplicate the normal Fedora Core kernel
configuration, make oldconfig
, and go.
I don't like initrds, though. So one of the usual benefits of compiling
my own kernel is not needing one, so there's one fewer moving part in
my system environment. Unfortunately, Fedora Core 5 uses udev, which
introduces a problem: the normal initrd is what creates /dev
. No
initrd, no /dev/console
, and your kernel reports:
Warning: unable to open an initial console.
Usually things blow up shortly afterward. (You're also missing
/dev/zero
and /dev/null
, which doesn't help.)
One way around this is to populate a basic /dev
on the root
filesystem. To get around the chicken and egg problem that FC5 boots
with something mounted on top of /dev
, you can use the NFS trick
I mentioned yesterday.
The simpler way out is just to make an initrd anyways, despite
theoretically not needing one. mkinitrd
is happy to set you up with
a basic initrd that just does the necessary magic to create /dev
and
switch into the real root filesystem and so on. As a bonus, this initrd
is kernel agnostic: you can use it for any kernel version (making it
slightly more palatable).
It looks somewhat like the resulting 'generic' initrd does know what
your root filesystem is. Unfortunately the nash
manual page and the
actual init script buried in the initrd disagree with each other, so I'm
not entirely sure.
Since I was in a rush yesterday, I opted to hold my nose a bit and use
the initrd approach. Thus, unfortunately, I have no idea what additional
steps making a real /dev
may require; caveat emptor.
Sidebar: inspecting initrds
Fedora Core 5 initrds are gzip'd cpio archives. cpio -tv
will
list the contents; cpio -id
will extract them (into the current
directory). /init
is the magic script that does all the work.
I will reluctantly concede that this is more convenient than the old approach of gziped filesystem images.