Re: "grub-probe -t partmap" doesn't work with software RAID

[Robert Millan <rmh@aybabtu.com>]

On Sun, May 13, 2007 at 12:02:26PM +0100, Sam Morris wrote:
> On Sat, 2007-05-12 at 22:16 +0100, Sam Morris wrote:
> > On Wed, 2007-05-09 at 18:13 +0200, Robert Millan wrote:
> > > I'm forwarding you a bug report from Debian.  It seems that the grub-probe
> > > -t partmap feature I just added doesn't play nice with RAID.  Unfortunately,
> > > I have no idea how software RAID is implemented.  Is it okay to just exit
> > > succesfuly and install core.img without any partmap module?

... so apparently it isn't.  We still need to detect this somehow, or maybe we
could just print "pc gpt".. anyone can cast some light on this?

> I experimented some more. At the command prompt I entered 'insmod raid'
> and got the message 'error: out of disk'. I assume that is because the
> partition containing my RAID1 array extends past the area readably by
> BIOS functions. However, I was able to ignore the message: if I then ran
> 'ls', '(md0)' showed up in the list of devices just fine!

How strange.  If you can't access the disk, you wouldn't be able to insmod
anything.  Can you check the following (before running 'insmod raid'):

  - That raid is not already loaded (with lsmod).
  - The 'prefix' variable (with set).
  - Whether you can access (ls) the directory pointed to by 'prefix'.

> I had to do one more thing to boot up correctly: edit the command line.
> It had 'root=md0' but it needed 'root=/dev/md0'. It appears that
> 'grub-probe -t device /boot/grub' outputs 'md0' when it should be
> outputting '/dev/md0' (just as it outputs e.g., '/dev/hde1' instead of
> 'hde1' for 'grub-probe -t device /mnt'). Shall I file a separate bug for
> that?

Please do.

> BTW, it would be convenient if I could override the detected GRUB_DEVICE
> by editing /etc/default/grub; however it seems that update-grub ignores
> the environment variable and always overrides it with the value output
> by grub-probe. It might be useful to allow the user to specify the grub
> device manually in this manner.

Another bug please? :-)

-- 
Robert Millan

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