Bug#491977: grub-probe fails with "Cannot find a GRUB drive for /dev/dm-N."

[Robert Millan]

On Mon, Jul 28, 2008 at 10:36:02PM +0200, Moritz Naumann wrote:
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> Robert Millan wrote:
> > Please try:
> > 
> >   mdadm -D -b /dev/md0
> >   mdadm -D /dev/md0
> 
> > debby:~# mdadm -D -b /dev/md0
> > ARRAY /dev/md0 level=raid1 num-devices=1 spares=1 UUID=b36bed37:7b1ca284:5f985e7d:0ec83b51
> 
> > debby:~# mdadm -D /dev/md0
> > /dev/md0:
> >         Version : 00.90.03
> >   Creation Time : Thu Jun 16 19:10:19 2005
> >      Raid Level : raid1
> >      Array Size : 192640 (188.16 MiB 197.26 MB)
> >   Used Dev Size : 192640 (188.16 MiB 197.26 MB)
> >    Raid Devices : 1
> >   Total Devices : 2
> > Preferred Minor : 0
> >     Persistence : Superblock is persistent
> > 
> >     Update Time : Mon Jul 28 22:24:03 2008
> >           State : clean
> >  Active Devices : 1
> > Working Devices : 2
> >  Failed Devices : 0
> >   Spare Devices : 1
> > 
> >            UUID : b36bed37:7b1ca284:5f985e7d:0ec83b51
> >          Events : 0.12672
> > 
> >     Number   Major   Minor   RaidDevice State
> >        0     254        5        0      active sync   /dev/dm-5
> > 
> >        1     254        2        -      spare   /dev/dm-2
> > debby:~# 
> 
> I'm aware this is a silly configuration, 1 active device 1 spare with a
> total of two devices. So, while this configuration neither gives me
> redundancy nor speedy access it is still a perfectly legal configuration
> as per mdraid. I didn't think of wheter or not this could be the cause
> of the grub problems until now.

I think the usual thing to find in that output are physical devices instead
of /dev/dm-X.

What other special things are in your setup that we should know about?  Are
you using LVM / EVMS or something like that?

-- 
Robert Millan

  The DRM opt-in fallacy: "Your data belongs to us. We will decide when (and
  how) you may access your data; but nobody's threatening your freedom: we
  still allow you to remove your data and not access it at all."