Re: grub-legacy fails with its root on raid1
On Wed, Dec 5, 2012 at 8:40 AM, Marcus Blumhagen
<marcus.blumhagen@web.de> wrote:
> Please CC me on reply, since I am not subscribed to the list.
I consider rude not to subscribe to a list asking for help - but
that's just me...
> just recently I was faced with a non-booting remote box running Debian 6.0
> (Squeeze). Lacking access to any kind of console, I was quite clueless why
> it wouldn´t come up after what should have been a routine reboot. I have
> access to a rescue system though, which, when requested from the provider,
> reboots the machine into a live system.
> Now I think I have found the problem in grub-legacy trying to boot of
> /dev/md0 which indeed is my boot partition:
>
> # Excerpt of grub´s menu.lst
>
> title Debian GNU/Linux, kernel 2.6.32-5-amd64
> root (md0) # software raid1 consisting of /dev/sd[ab]1
> kernel /vmlinuz-2.6.32-5-amd64 root=/dev/md1 ro
> initrd /initrd.img-2.6.32-5-amd64
>
> note that grub´s root is set to (md0) by update-grub. I am not entirely sure
> but I thought that wasn´t possible with grub-legacy. I might be wrong
> though.
> However changing the menu.lst manually to use (hd0,0) as root for grub
> finally fixed the machine to boot successfully again, after some very
> frustrating attempts to find the cause of the problem.
>
> Now, I honestly don´t know how it has worked before, not knowing if the
> menu.lst always pointed grub-legacy to (md0). I haven´t found a conclusive
> answer to whether grub-legacy is capable of using raid1 as root or not,
> since what documentation I have found online was either about grub2 or not
> clearly distinguishing between the two grub versions.
I've just skimmed through your message and I'll have to reread the
rest when I have more time to see if I can help but regarding the
above:
grub-legacy can boot from an mdraid "/boot" and/or "/".
The "root" of "root (md0)" is the device corresponding to "/boot". (I
wish that it'd been called "grubroot" in both grub1 and grub2. Too
much navel-gazing going on...)
The "root" of "kernel /vmlinuz-2.6.32-5-amd64 root=/dev/md1 ro" is the
device corresponding to "/".
The two "root" are of course the same, expressed differently, if "/"
and "/boot" are on the same partition.
Since you're using grub-legacy and might be using update-grub and the
"DEBIAN AUTOMAGIC KERNELS LIST" system, make sure that "groot" in
"/etc/boot/menu.lst" is set to the right value.
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