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

[Felix Zielcke]

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.


-- 
Felix Zielcke
Proud Debian Maintainer