FC5 RAID 1 - booting off either drive

[Craig White]

On Mon, 2006-03-27 at 21:43 -0600, Laurence Vanek wrote:
> Greetings -
> 
> To my surprise, fresh install of FC5 with RAID 1 configured at install 
> time went without a hitch.  I have /dev/md0 defined on /boot 
> partitions.  It boots fine with this setup.
> 
> I had my FC4 system setup this exact way except I found that I had to 
> manually install grub on one of the disks to permit booting off either 
> one if the other is down.
> 
> Does anyone know of a way to check for the presence of grub on each 
> drive (obviously its on hda since it boots presently) to see if this 
> needs to be done for FC5 also without powering down each drive in turn & 
> attempting to boot?
----
thought I should post against the right thread

just an untested thought...

bb if=/dev/sda of=/tmp/sda-bootblock.bin bs=512 count=1
bb if=/dev/sdb of=/tmp/sdb-bootblock.bin bs=512 count=1

diff /tmp/sda-bootblock.bin /tmp/sdb-bootblock.bin

Thinking...

- substitute different values for sda/sdb as fits
- the first 512 bytes on each drive are the boot (perhaps less, someone
will surely correct me...it might just be the first 256 or 384 bytes)
- if they are the same (i.e. grub has been installed on both), there
will be no diff

otherwise...

grub-install /dev/sdb

Of course, the only way that you'll ever KNOW for sure that it's going
to work is to do a real simulation, i.e. disconnecting one drive, then
the other drive...

Craig