building and installing a new kernel makes my system unbootable

Robert P. J. Day rpjday at
Tue Jul 6 11:18:39 UTC 2010

On Tue, 6 Jul 2010, Markus Schönhaber wrote:

> 05.07.2010 20:01, Robert P. J. Day:
> > $ sudo make modules_install
> > $ sudo make install
> > $ sudo update-initramfs -c -k 2.6.35-crash+
> > $ sudo update-grub
> >
> >   that's worked fine until now, but with this kernel tree, if i do the
> > above and reboot, i not only can't stop in GRUB, but the boot fails as
> > the kernel panics, claiming it can't mount a root file system.
> >
> >   i recovered by booting off the CD into rescue mode, mounting
> > /dev/sda1 (/boot), then literally editing grub/grub.cfg and deleting
> > the entries for that new kernel.  nothing else would allow me to boot.
> If GRUB doesn't work with the entries for your self-built kernel but
> does without them, it seems that exactly these entries makes GRUB
> choke. WAG: Does it get better if you rename your kernel and initrd
> files to something that doesn't end with a '+' character?

  ok, for reasons i can't explain, SHIFT is now back to giving me a
GRUB menu so i can boot my new kernel, watch it explode, and reboot to
a working kernel (as i just did), and now i have some clues.

  booting the regular new kernel gave me:

Kernel panic - not syncing: VFS: Unable to mount root fs on

  hmmm ... so boot new kernel in recovery mode and see:

md: ... autorun DONE
VFS:  cannot open root device "mapper/lynx-root" on unknown-block(0,0)

  ah, so the kernel can't use LVM to mount the root filesystem in that
logical volume.  on the older kernel (and the one i'm running under
right now), that mount works just fine:

$ mount
/dev/mapper/lynx-root on / type ext4 (rw,errors=remount-ro)
... snip ...

  so the kernel can't mount the root filesystem?  why not?  normally,
i'd assume it's because i don't have either LVM or ext4 support.  hmmm
... i wonder if support for that is in my initrd ...



Robert P. J. Day                               Waterloo, Ontario, CANADA

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