Bug#542425: error: cannot find a device for /.

[Albin Stjerna]

At Mon, 31 Aug 2009 16:28:42 +0200,
Felix Zielcke wrote:
> 
> Am Sonntag, den 30.08.2009, 19:02 +0200 schrieb Albin Stjerna:
> > 
> > The output’s a bit over my head, but a point of interest seems to be:
> > 
> > + set /usr/sbin/grub-mkdevicemap dummy
> > + test -f /usr/sbin/grub-mkdevicemap
> > + :
> > + set /usr/sbin/grub-probe dummy
> > + test -f /usr/sbin/grub-probe
> > + :
> > + mkdir -p /boot/grub
> > + test -e /boot/grub/device.map
> > + :
> > ++ /usr/sbin/grub-probe --target=device /
> > grub-probe: error: cannot find a device for /.
> > 
> > Apparently, for some reason it’s running grub-probe on /, which, of course,
> > isn’t registered with GRUB. The only partition it’s supposed to know about is my
> > (unencrypted, plain) boot partition (/dev/hda1). Now, what I’m wondering is why
> > GRUB has forgotten this: I haven’t touched any of GRUB’s settings!
> 
> Oh right, I forgot that we use grub-probe even to find out the right
> device for the kernel root= parameter.
> Someone who has an encrypted LVM / had the same problem and just
> reported #544420
> This was also caused by a symlink instead of the device.
> So please check with `ls -l /dev/mapper/' if your / LVM is a symlink or
> device.
> If it's a symlink then try to run `echo change > /sys/block/dm-X/uevent'
> and replace X with the right number the symlink points to.
> If that doestn't fix it then I think `rm /dev/mapper/volume && cp -R /dev/dm-R /dev/mapper/volume'
> should do it.

Thanks, but something, I have no idea what, seems to have fixed it. grub-probe
now detects / to /dev/mapper/nyx-root as expected, and the setup of grub-pc
seems to run fine (I haven’t tried a reboot yet, though).