[CentOS] Problem with dual-booting soft-RAID

[Les Mikesell]

On Fri, 2006-06-09 at 18:31 +0200, Kai Schaetzl wrote:

>   IDE, on the other hand 
> > does not shift the bios view of the drives so some of the HOWTO 
> > instructions you'll find for hand-installing grub take this into 
> > account.

> It still seems to boot the same OS from the grub.conf, though. No matter which 
> of the two disks is powered down. It always boot my default and not the fallback 
> which it should boot theoretically once the first disk is gone.

If you followed the HOWTO you may have accounted for the different drive
in the grub setup.  

>   However, most of the ways that IDE drives fail will make 
> > the machine unbootable until you open the case and unplug it.
> 
> Yes, I feared this. It's a bit hard to establish such a situation for testing, 
> though ;-) How to maske a disk fail without damaging it? How can I nuke the grub 
> on the first disk to see what happens?

Power down and pull the cable from the drive.  

>   Then 
> > you may have to adjust the bios settings to boot from the other 
> > position - but while you have the case open it is probably easier 
> > to shift the jumper or cable position so the working drive is the 
> > primary.  Then if you followed one of the sets of instructions, grub 
> > will load but will be looking for the now-missing 2nd drive for the 
> > /boot partition to load the kernel.  SATA probably has it's own way 
> > of doing things too. 
> 
> Didn't have these problems here. 

You can't emulate that problem without a broken drive. Some failure
modes just hang forever and the machine will never go on to the
next one as long as the bad one is connected.

> > Maybe... It's not that hard to do it by hand.  Do an fdisk -l on the 
> > existing drive, then an interactive fdisk of the new mate, creating 
> > the same sized partitions with type FD. 
> 
> I hate to use fdisk, haven't done this for a long time. If there are GUI ways I 
> much prefer them in a few cases over command line :-)

And I hate to use things where I can't look at the results before the
final save.  

-- 
  Les Mikesell
   lesmikesell at gmail.com