question about fstab in squeeze and uuid

[Paul E Condon <pecondon@mesanetworks.net>]

I'm working on a computer that I am trying to make dual-boot into both
Lenny and Squeeze. As some are already aware, squeeze rewrites
/etc/fstab to replace devices like /dev/hda2 with a UUID for the
device that is a long computer generated string.  I know very little
about UUIDs but I suppose they are intended to be 'unique'. But I
suppose that they are required to be persistent, i.e. they don't
change over time.

I experienced non-persistence today. While running Squeeze I noticed
that one of my partitions, in particular the one that contained the
Lenny installation, which I had put in the /dev/hda3, had been
re-identified with a different UUID on reboot of the compute so that
the entry in /etc/fstab could not be used to mount that partition
under Squeeze (which was installed in /dev/hda2). I edited /etc/fstab
to contain the new, diffenent UUID that I found by looking in
/dev/disk/by-uuid, and was able to mount the partition, but it was
hardly 'automatic'.

I'm looking for reliable information on how UUIDs are generated, and
how their uses is intended within Squeeze, so that I can puzzle out
what I might be doing wrong.
 
I think I know already that they are suppose to overcome some
difficulties in the traditional way SCSI devices are handled in the
Linux kernel.  The disks that I am working with are NOT SCSI. But the
fix for SCSI seems to be stepping on the traditional solution for ATA
that had been working nicely. Or, maybe I just did something stupid.

I need to read some more. Please make suggestions.

-- 
Paul E Condon           
pecondon@mesanetworks.net