grub-pc misdetects md RAID layout and fails to initialize [was Re: grub-pc jumps straight to rescue and prints error: no such disk / file not found]

[Josip Rodin]

On Sun, Jan 03, 2010 at 01:14:47PM +0100, Josip Rodin wrote:
> On Sat, Jan 02, 2010 at 03:00:39PM +0100, Josip Rodin wrote:
> > On Sat, Jan 02, 2010 at 02:29:36PM +0100, Josip Rodin wrote:
> > > I've got two disks and a software RAID setup on the partition that holds
> > > the /boot directory. I have several Linux software RAID partitions, based
> > > on this scheme:
> > > 
> > > sda2+sdb2 -> Linux amd64 /
> > > sda3+sdb3 -> Linux i386 /
> > > 
> > > The first two become md0, differentiated by old GRUB menu entries -
> > > Linux parameters raid=noautodetect and md0=first,second ... settings.
> > 
> > So I then set root=(md3), and set prefix to use one as well, and am able
> > to get to my menu by running insmod normal, insmod configfile, configfile
> > /boot/grub/grub.cfg. Yay!
> 
> I also can't seem to get rid of the need to change md0 to md3 early on.
> I tried running:
> 
> grub-setup -r '(md3)' /dev/sda
> grub-setup -r '(md3)' /dev/sdb
> 
> These commands seemed to work, but there was no change in behaviour...?!
> This is how -v output looks:
> 
> grub-setup: info: setting the root device to `md3'
> grub-setup: info: dos partition is -2, bsd partition is -2
> grub-setup: info: the core image will be embedded at sector 0x1

Oddly enough, I was able to get it to work with a sequence of manual
commands, and I'm not actually sure what was the winning combination was.
This is what I gathered from the shell history of the winning session :)

sudo grub-mkimage --verbose --output=/boot/grub/core.img 
--prefix='(md3)'/boot/grub biosdisk ext2 part_msdos part_msdos raid mdraid
sudo grub-setup -v --skip-fs-probe -r '(md3)' /dev/sda
sudo grub-setup -v --skip-fs-probe -r '(md3)' /dev/sdb

Obviously the problem isn't solved, but it's worked around.

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