Re: Grub2 reinstall on raid1 system.

[Henrique de Moraes Holschuh <hmh@debian.org>]

On Sat, 15 Jan 2011, Tom H wrote:
> On Sat, Jan 15, 2011 at 9:06 AM, Henrique de Moraes Holschuh
> <hmh@debian.org> wrote:
> > On Sat, 15 Jan 2011, Jack Schneider wrote:
> >> > >> You might want to try configuring grub and fstab to use UUID's
> >> > >> instead of /dev/mdX.  That removes the possibility that the kernel
> >> > >> will change the mdX designations.
> >> > >>
> >> > >> Use blkid to find out the UUID's of your partitions.
> >
> > Whatever you do, NEVER use the UUIDs of partitions, use the UUID of the
> > md devices.  The worst failure scenario involving MD and idiotic tools
> > is for a tool to cause a component device to be mounted instead of the
> > MD array.
> >
> > This is one of the reasons why the new MD formats that offset the data
> > inside the component devices exists.
> 
> If you want to use an md device's UUID in grub.cfg, you're going to
> have to edit it by hand or edit the grub2 scripts. AFAIK, they'll only
> use the md device names because they're unique (through their UUIDs).

You must either use /dev/md* or the MD device UUID.  Anything else is going
to bite you back, hard.

There really isn't a reason to use UUIDs with MD.  The md devices will _not_
move around, especially not when kernel autostart is non-operational (and it
is not operational in any Debian kernel).  But some initrd scripts will keep
pestering you until you do switch to UUIDs everywhere.  Annoying, that.

OTOH, you will learn very fast to never ever forget to update
/etc/mdadm/mdadm.conf AND the initrds when you touch the md arrays...

-- 
  "One disk to rule them all, One disk to find them. One disk to bring
  them all and in the darkness grind them. In the Land of Redmond
  where the shadows lie." -- The Silicon Valley Tarot
  Henrique Holschuh