building and installing a new kernel makes my system unbootable

[Robert P. J. Day]

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?

  it's clearly an LVM thing of some kind.

  it finally dawned on me that all of those earlier kernels i was
building and running without incident were on my earlier laptop, on
which i had installed ubuntu 10.04 with a single, honking big root
filesystem, as in:

  /dev/sda1 on / type ext4 (rw,errors=remount-ro)

and grub never had a problem booting my new kernel.  in fact, this is
that old system right now:

$ uname -a
Linux lynx 2.6.35-kwlug+ #1 SMP Mon Jun 7 13:13:50 EDT 2010 x86_64 GNU/Linux
$

  on my *new* system, though, well, i decided to get clever during the
installation:

$mount
/dev/mapper/lynx-root on / type ext4 (rw,errors=remount-ro)
... snip ...
/dev/sda1 on /boot type ext2 (rw)
... snip ...

and, unsurprisingly, the boot-time failure states that the kernel
can't open root device "mapper/lynx-root" so this tells me that,
somehow, i haven't built device mapper support into my initrd or
something like that.

  does this look familiar to anyone?  what probably trivial step have
i forgotten to do?  thanks.

rday

-- 

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Robert P. J. Day                               Waterloo, Ontario, CANADA

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