Question: How do I rewrite MBR with existing RAID config?

[William (Andy) Smith]

I didn't see mention of this in the FAQ, though I attempted to emulate
directions on installation.

What I have done is RAID1 on /dev/hde and /dev/hdg so I've a root raid and
raided swap.  It rebooted fine, so grub has no trouble with the existing
setup.  I did a COLD swap of /dev/hde, so the 'MBR' is offline.  I
rebooted with a boot floppy and I've properly recovered /dev/hde as
confirmed by /var/log/messages.  The new drive I've cold swapped out,
however, does NOT have the MBR written to it as RAID has nothing to do
with MBR.  It just happens that my 'otherwise perfectly functional grub
config' resides on the raided drive /dev/md0, and grub would function
properly (as it does with the prepared boot disk) if only the MBR knew
what to do.

# root (hd0,1)

...in the grub command line responds with 'Filesystem type unknown,
partition type 0xfd'

# install /boot/grub/stage1 d (hd0) /boot/grub/stage2 p /boot/grub/menu.lst
...in the grub command line responds with 'Error 17: Cannot mount selected
partition'

Anaconda's grub.conf has this info:

#boot=/dev/hde
default=0
timeout=10
splashimage=(hd0,0)/boot/grub/splash.xpm.gz
title Red Hat Linux (2.4.7-10)
        root (hd0,0)
        kernel /boot/vmlinuz-2.4.7-10 ro root=/dev/md1
        initrd /boot/initrd-2.4.7-10.imb

As I mentioned, the above works fine so long as I'm using the boot floppy.  
All I need is to restore the MBR for the 'virgin' /dev/hde, and I'll be
set.  Specific docs on grub are not part of the RedHat 7.2 install.

--Romaq