RAID 1 error question - boot problem.

[Robin Laing]

Hello,

I am trying to help someone get a system to reboot after a system issue. 
    He is not the builder of the system and the person that knows the 
system is away for a few weeks.  Great timing.  :)

It is Fedora 10.

Two drives, two partitions each drive which one is a mirror.

/dev/sda is partitioned as /boot and / which is mirror 1.
/dev/sdb is partitioned as swap and /

The system wouldn't restart on the reboot and came up with an error 
after creating the raid arrays and then saying that it cannot find 
/dev/md0.  I don't have the exact error message right now.

Using an Ubuntu disk (persons personal preference) the system was booted 
into a live system and using gparted the partitions were shown to be as 
above with as I see it, one error.

/dev/sda1 ext3 boot
/dev/sda2 ext3 /   raid

/dev/sdb1 Swap
/dev/sdb2 Unknown  / raid

Running mdadm /dev/sdb2 --examine shows that the partition superblock is 
showing RAID 1 and that it is clean.

As this is a critical system, it is a priority and is being used as a 
virtual server.

With only the second drive installed, we tried to run fsck.ext3 on the 
/dev/sda2 (normally b2) with no success.  We also tried /dev/md0 as 
Ubuntu has created the /dev/md0 from the single drive.

The user has not tried to boot with only the one drive in yet.  He is 
making a copy of the drive on a different system.

Now, the question.  On booting from a mirror 1 array, if there is a 
problem with the raid system, how does the boot process read the 
mdadm.conf file when it is on the RAID array that needs to be created? 
Is there some data that is stored in the /boot or someplace else that 
has the necessary info to tell the system how to build the array?

Is it part of the /boot/grub/device.map or /boot/System.map* ?

Any suggestions to where to start?

Thank you.

-- 
Robin Laing