Bug#686955: grub-installer: Grub fails to install on dm-crypt on LVM on SATA RAID 0

[Conrad Hughes <debbugs@xrad.org>]

Dear Lennart,

Thanks very much for such a fast response --- I'm well aware that dmraid
is "not recommended", but it would be really handy if I could keep it
for the Windows dual boot.  Your suggestion that mdadm supports Intel
RST sounds really interesting --- but I can't see anything that
documents how you activate/use it in the Debian installer.

It does appear possibly to just be enabled by default, in that if I run
through the wheezy installer *without* adding the dmraid=true kernel
boot parameter, then it recognises a "Linux Software Raid" array on
/dev/md126; with some false starts I've managed to partition this as
before (small /boot, then a large dm-crypt partition on which I put LVM,
then splitting the LVM into swap and root partitions).  Again, grub
tries to install to /dev/hda1 and fails, but this time when I reboot to
the wheezy rescue mode, things are much more complicated.  During disk
discovery, it doesn't recognise the RAID array until I tell the
installer to look for it, at which point it recognises /dev/md126 but
doesn't do anything with it.  I had to manually start a shell and invoke

  cryptsetup luksOpen /dev/md126p7 dm-6_crypt

then restart the disk discovery process, finally being given an option
to use /dev/mapper/waif-root for my root partition.  Then, however, I
ran into trouble with grub: update-grub complained of file not found
repeatedly, and grub-install failed to install because it "couldn't
find" my LVM root volume.  /boot/grub/device.map at this point contains
just three drives, my USB install disk, and the base hard drives of the
machine's RAID array (as hd0, hd1, hd2 respectively).  If I add a bogus
(hd3) entry pointing at the raid drive, /dev/md126, then update-grub
stops complaining "file not found", and even successfully finds the
Windows partition.  If I then add a bogus (hd4) entry pointing at the
dm-crypt partition I mounted, /dev/mapper/dm-6_crypt, then grub-install
stops complaining about not finding /dev/mapper/waif-root and claims to
have successfully executed.

The net result though, is exactly the same --- on reboot I get

  Welcome to GRUB!

  error: no such disk.
  Entering rescue mode...
  grub rescue>

I'm assuming I need some additional magic to make grub assemble the raid
array, find the boot partition, decrypt the dm-crypt partition, and open
the root volume...

Conrad