Re: Linux not adhering to BIOS Drive boot order?

[Andreas Dilger]

Kelsey Hudson writes:
> however, this brings up an interesting question: what happens if two disks
> (presumably from two different machines) have the same disk label? what
> happens then? for instance, i have several linux machines both at my
> workplace and my home. if for some reason one of these machines dies due
> to hardware failure and i want to get stuff off the drives, i put the disk
> containing the /home partition on the failed machine into a working
> machine and reboot. What /home gets mounted then? the original /home or
> the new one from the dead machine? (and don't say end users wouldn't
> possibly do that... if they are adding hardware into their systems this is
> by no means beyond their capabilities)

Don't do that (tm).  You may still have that problem (or even all filesystems
being mounted wrong) if you add a new drive to a SCSI chain.  Likewise if
you add an IDE controller, the controllers may be numbered differently...

> at least with physical device nodes i can say 'computer, you will mount
> this partition on this mountpoint!' and be done with it.

If you use a UUID, you will never have conflicts (unless you do drive
imaging, which is bad).  The label is just a lot more convenient to use
than the UUID.

> so tell me then, how would one discern between two partitions with the
> same label?

It will pick the first one found, I guess.  However, this still reduces
the problem of drive renaming by 99%.  It goes from "each time drives
are added/moved/removed my system may be broken" to "if I insert two
drives with the same label 50% chance my system is broken".  I'll take
the latter any day.

Cheers, Andreas
-- 
Andreas Dilger  \ "If a man ate a pound of pasta and a pound of antipasto,
                 \  would they cancel out, leaving him still hungry?"
http://www-mddsp.enel.ucalgary.ca/People/adilger/               -- Dogbert