Bug#668920: grub-pc: grub 1.99-21 fails to detect mdraid partitions

[Colin Watson]

On Mon, Apr 16, 2012 at 12:17:59AM +0800, Arne Goetje wrote:
> Upgrading from 1.99-17 to 1.99-21 on wheezy today renders the system
> unbootable.
> Grub cannot detect any mdraid partition and is therefor unable to load
> the kernel.

Does it emit any error messages that might be useful to help us track
this down?

> Downgrading to 1.99-17 solves the problem.
[...]
> *********************** BEGIN /proc/mdstat
> Personalities : [raid1] md1 : active raid1 sdc[0] sdd[1]
>       488386496 blocks [2/2] [UU]
>       md127 : active raid1 sda[0] sdb[1]
>       488386496 blocks [2/2] [UU]
>       unused devices: <none>
> *********************** END /proc/mdstat
[...]
> * grub-pc/install_devices: /dev/sdc

This jumped out at me.  Are you quite sure that your BIOS is actually
booting from /dev/sdc?  It's possible that it's attempting to boot from
an old copy of the GRUB core image installed to a different disk, which
then gets confused by the newer modules in /boot/grub/.  In this theory,
downgrading to 1.99-17 would help because perhaps that core image is
ABI-compatible with those modules; the support for non-512-byte sectors
in 1.99-19 was probably a core/modules ABI break so this is plausible
enough.

My standard advice is to install GRUB to all fixed disks
('dpkg-reconfigure grub-pc') unless you have a good reason not to.

Cheers,

-- 
Colin Watson                                       [cjwatson at debian.org]