Quoting Jerry Geis (geisj@pagestation.com):

I have a system that is RAID -1 configured as

/dev/md0 is /dev/hda1 /dev/hdb1 /dev/md1 is /dev/hdb3 /dev/hdb3

it seems as though /dev/hda has failed....

I have another disk (identical model) that I can replace hda with.

I know about the commands fdisk to repartion and raidhotadd /dev/md0 /dev/hda1 and raidhotadd /dev/md1 /dev/hda3 (to be ran after the system boots).

BUT... how do I now get the system to boot since hda is not there to boot... I can certainly execute the fdisk and raidhotadd after it boots... How do I get it to boot.

The hardware is a D865 intel motherboard with 2 seagate 120G drives.

Assuming the machine is still running, you need to install grub on the second disk. From memory, this goes something like:

# grub grub> root (hd1,0) grub> setup (hd1) grub> quit

You *should* then be able to boot from the second drive with the first drive replaced. It's possible your BIOS may need tweaking to allow that though.

The alternative is to replace the first drive and then boot off the install CD using

linux rescue

then rebuild the mirrors and re-install grub on each once the /boot filesystem is fully synchronised:

# grub grub> root (hd0,0) grub> setup (hd0) grub> root (hd1,0) grub> setup (hd1) grub> quit

and the machine should in theory now boot from either disk.

As I said, this is from memory -- I installed a kernel update the other night that somehow caused the machine not to boot from the (mirrored) /boot parition any more and I recovered it by doing something very similar.

James