grub-install seg faults on partitionable raid1

[Peter Wienemann]

I am trying to install Ubuntu 12.04 amd64 automatically on a partitionable software RAID1 using the debian-installer and preseeding. The relevant preseeding settings are:

d-i partman/early_command string /bin/dd if=/dev/zero of=/dev/sda bs=512 count=1 && \
  /bin/dd if=/dev/zero of=/dev/sdb bs=512 count=1 && \
  /sbin/mdadm --create /dev/md0 --metadata=1.0 --auto=mdp \
  --raid-devices=2 --level=1 --bitmap=internal --homehost=xyz /dev/sd[ab]

d-i partman-auto/disk string /dev/md0

d-i grub-installer/only_debian boolean true
d-i grub-installer/with_other_os boolean true

Everything works smoothly until the grub installation step is reached. With these preseeding settings, d-i is supposed to install the boot loader into the MBR. Due to unknown reasons (a bug?), it tries to install grub to /dev/md0p1, i. e. the first partition on the RAID array. Moreover this attempt results in a grub-install segmentation fault. Even if I run

chroot /target grub-install /dev/md0

manually on a console, grub-install seg faults. If instead I run

chroot /target update-grub
chroot /target grub-install /dev/sda
chroot /target grub-install /dev/sdb

on a console, I get a bootable system on a partitionable raid (as desired).

In principle this workaround would probably be automisable by making use of

d-i grub-installer/bootdev string (hd0) (hd1)

but due to bug #1012629 (https://bugs.launchpad.net/ubuntu/+source/debian-installer/+bug/1012629) this does not work, either. :-(

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.