Re: [PATCH] Fix prefix problem with LVM on RAID

[Michael Guntsche]

On Feb 23, 2008, at 21:54, Michael Guntsche wrote:

> Hello,
>
> While testing a soon to be deployed setup here I noticed that grub- 
> setup is setting the prefix wrong if you run
> LVM on Software RAID
>
> grub-setup -v /dev/md0
> ...
> grub-setup: info: dos partition is -2, bsd partition is -2, prefix  
> is (md0)(fatoftheland-main)/boot/grub
> ...

Some more information regarding the patch I submitted.

What is happening exactly.

grub-setup first checks if we are on a LVM, we are so it is ok to  
prepend the (vg-lv). The next step is to check if we are on RAID.  
Unfortunately we are on RAID too and (md0) gets prepended as well. In  
the end we end up with a prefix that looks like

(md0)(vg-lv)/boot/grub

which obviously won't work.
grub-setup calls "setup" on every disk that is part of the Raid. All  
the patch does is to pass "prefix" instead of "raid_prefix" if we are  
on LVM. Raid_prefix is only used for this setup call and freed later  
on, so I did not bother to if that out as well.

I can really test this setup next week, when the final hardware  
arrives (hopefully) but grub-emu is already doing the right thing and  
for grub it will be still a boot off a LVM device which already works.

Kind regards,
Michael

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