Re: Problem booting RAID1/mdadm system when one disk is unplugged

[James Brown <jbrown@orange.net>]

Justin Piszcz wrote:
> On Fri, 1 Sep 2006, James Brown wrote:
>
> > All,
> >
> > I have already posted this question to gmane.linux.raid, but would 
> > really appreciate some help from a Debian perspective please...
> >
> > My System has 2x120GB IDE disks with the an up-to-date Sarge install, 
> > running kernel 2.6.8-3 and configured for mirroring.
> >
> > When I tested booting my system, I found:
> >
> > a) A kernel panic unless both disks are plugged in.
> > b) One disk removes from the array each reboot.
> >
> > The relevant logs are on this thread:
> > http://article.gmane.org/gmane.linux.raid/13033/match=newbie+kernel+panic+raid1 
> >
> >
> > I was advised this was a problem with my initrd because it didn't 
> > contain a mdadm.conf file and presumably that I should make a new one.
> >
> > Unfortunately, some friends of mine do not agree that my initrd is the 
> > problem because they point out that I can still boot when two disks 
> > are present. What do people here think?
> >
> > Thanks in advance
> >
> > James.
> >
> >
> > --
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>
> 1) You do not need an initrd at all.

I'm actually a newbie and using GRUB as it was installed by default.

Will deleting the /boot/initrd.img-2.6.8-3-386 file and initrd 
instruction within menu.lst be sufficient?

> 2) I would make sure you are booting from the /dev/md* partition.

I *think* I am booting from the /dev/md0 partition:

# cat /boot/grub/menu.lst
[...]
# groot=(hd0,5)
[...]
title           Debian GNU/Linux, kernel 2.6.8-3-386
root            (hd0,5)
kernel          /boot/vmlinuz-2.6.8-3-386 root=/dev/md0 ro
initrd          /boot/initrd.img-2.6.8-3-386
savedefault
boot
[...]

I understand this means the system will load the BootLoader from the 
first disk BIOS presents, and partition number 6 on that disk (in my 
case, hda6 or hdc6). It will then try to boot the kernel from /dev/md0, 
which it should manage:

# cat /etc/fstab
proc            /proc           proc    defaults        0       0
/dev/md0        /               ext3    defaults,errors=remount-ro 0       1
/dev/md1        /var/mail       ext3    defaults        0       2
/dev/hda5       none            swap    sw              0       0
/dev/hdc5       none            swap    sw              0       0
/dev/hdd        /media/cdrom0   iso9660 ro,user,noauto  0       0

I don't see a problem here, but please correct me if I've said somthing 
wrong.

> 3) You must have a /boot on a /dev/md partition.

From looking at the above, /boot would fall under /dev/md0 (I think)?

> 4) You need LILO installed with the special raid option in the config.

Maybe I should ditch GRUB and learn/install LILO.

> 5) I have done this and tested by pulling each HDD out and it working
>    successfully with Debian + 2x74GB raptors.
>
> Justin.

Thanks very much for your time.