grub-install to /dev/vda (MBR!) suddenly fails

[Juha Kallio]

Hello!

I have migrated to grub2 from grub-legacy, and have had a working 
installation in a virtual machine for a while. Today I updated the 
Debian wheezy installation, and now grub-install to /dev/vda fails with 
the following error:

/usr/sbin/grub-setup: warn: Attempting to install GRUB to a disk with 
multiple partition labels or both partition label and filesystem.  This 
is not supported yet..
/usr/sbin/grub-setup: warn: Embedding is not possible.  GRUB can only be 
installed in this setup by using blocklists.  However, blocklists are 
UNRELIABLE and their use is discouraged..
/usr/sbin/grub-setup: error: will not proceed with blocklists.

This is a virtio disk from KVM, and should only have a basic partition 
table that was created on install. fdisk -l /dev/vda confirms that with 
the following information:

Disk /dev/vda: 6442 MB, 6442450944 bytes
16 heads, 63 sectors/track, 12483 cylinders, total 12582912 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x000d70a5

   Device Boot      Start         End      Blocks   Id  System
/dev/vda1   *        2048     8386559     4192256   83  Linux

I haven't tried to boot this virtual machine yet. I also haven't tried 
the --force flag, since I shouldn't be restricted to using blocklists. I 
can grub-install to another device, /dev/sda, but for some reason the 
actual boot device doesn't work anymore as a target for grub-install.

I'm sorry if this problem would be more suited to Debian mailing lists.

Regards,
Juha Kallio