Re: booting from a raid1

[lee]

On Sun, Oct 03, 2010 at 04:23:55PM -0400, Tom H wrote:
> 
> 1. I forgot to ask earlier, are you running "grub-install /dev/sdd"
> (and/or sdf)?

Yes, both --- it creates a /boot directory when I'm using another
partition for /boot, but no grub.cfg.

> 2. Differences with setups that I've used:
> 
> 2.a. I've never used the mdadm mdp option (I use md) or the fdisk da
> option (I use fd).

Hm, I don't know what these options are.

> 2.b. You're booted from sde1 and mount the md0p2 install's /tmp, /usr,
> /var, /home, and /opt over the sde1 install's equivalents before
> bind-mounting to the "/mnt/raid" mount of md0p2, and chrooting to it.
> I would've mounted them directly to "/mnt/raid".

sde1 is only the root partition, /tmp, /usr, /var and /opt are on
partitions of md0, and /home is on md126. md126 is not partitioned. On
/mnt/raid, the partition that needs to become the new root partition
is mounted. Then the other partitions are bind-mounted to respective
directories under /mnt/raid so that I can chroot to
/mnt/raid. Mounting them directly to /mnt/raid would require to mount
them twice.

> 2.c. I only bind-mount /dev and create "normal" mounts for /dev/shm,
> /proc, and /sys.
> 
> I'm not sure if any of the points in (2) are causing your
> "grub-install" failure but thought that I'd highlight them anyway.

I guess they shouldn't since they are only there to allow me to run
grub-install. From within chroot, /mnt/raid is the root
partition.

If I unmount everything except the old root partition and mount all
others directly to the new root partition, grub-install will probably
fail just the same way. I could try to manually make a grub.cfg which
could probably be read from a separate /boot partition, but since
there's no documentation, I don't know how to do that. It still won't
allow me to have /boot on the RAID1.

I'd also like to know before rebooting if it's going to work, but I've
no way to tell. Trial and error is very risky because you never know
if something happens when rebooting that overwrites your data.