[sclug] UUIDs

[Jason Rivers]

On Mon, Jun 23, 2008 at 9:06 PM, Neil Haughton <haughtonomous at googlemail.com>
wrote:

>
> >
> > John Stumbles further wrote:
> >> Do memory cards (or memory card readers) have UUIDs too?
> >
> > Strictly speaking, I think not as it's filesystems, not devices,
> > which have UUIDs.  sdb1 in the above list is a FAT filesystem on
> > a Kingston memory stick.  It looks like the DOS disk-id or whatever
> > it's called is being used as the UUID.
> >
> > Ed.
> >
>
> IIRC it _is_ filesystems - from what I have learned on the topic the
> point (or at least, a point) of using UUIDs is that if you move the
> filesystem to another partition, or even to another device, the mount
> operation will still work - eg if you physically move /home from /sda1
> to /sda2, as long as it has retained the UUID it will still mount on
> next startup, because the startup mounting doesn't care about the
> underlying device. If you weren't using UUIDs your /etc/fstab would need
> to be edited before the startup mounting would work
>
> Regards,
>
> Neil Haughton
>
>

I think for the best part that is true, I'm pretty sure SD Cards (and the
like) do have UUID's, however, be aware that when you format a partition
it's UUID changes, (this is a problem that I ran into while creating new
backup scripts that format the partition before writing any data. You could
Label the filesystem, and mount from that too. this works equally well if
you have 2 drives that you want mounted in the same location (you might have
2 versions of /opt and have them on seperate disks, mounting the one you
require)

I'm not sure how you would move a filesystem to another partition and retain
the UUID's - or if it's even possible to do, might be nice to know though if
anyone knows?

Jay