[Ma-linux] SCSI drive assignments; how to set order?

[Michael Henry]

On 09/04/2009 03:07 PM, Nick Danger wrote:
>  David wrote:
> >
> > SPARC Linux
> >
> > So I'm trying to add more SCSI drives to Tux's SPARC Linux box.
> >
> > Here is the hassle. When I add more drives, on an added
> > controller; they are detected at boot. But Linux assigns the
> > drive names (/dev/sda, /dev/sdb, etc) in some manner of its
> > own choosing.

>  Is this a newer distro that supports UIDs in the /etc/fstab?

I'm using UUIDs (note: UID was a typo) on my Fedora 11 systems,
and it works nicely.  UUIDs are Universally Unique IDs
(Identifiers), and they are basically large random numbers
constructed in such a way that they are almost certain to be
unique in the world.  An example UUID from the manpage (man
fstab) is:

   UUID=3e6be9de-8139-11d1-9106-a43f08d823a6

Instead of mounting by device node something like this:

   /dev/sda1  / ext3 defaults 1 1

You mount by UUID like this:

   UUID=3e6be9de-8139-11d1-9106-a43f08d823a6  / ext3 defaults 1 1

You can enumerate the UUIDs on your system via the blk_id
command:

   $ blkid
   /dev/sda1: UUID="3e6be9de-8139-11d1-9106-a43f08d823a6" TYPE="ext3"

I'm not sure how recently support for identifying partitions by
UUID came about.  A similar but inferior method involves
labeling a partition with an identifier, and locating the
partition based on this identifier.  I think this was around
before the UUID support, so if your system is too old for UUIDs,
perhaps labels would still work.  One downside of the
label-based system is how labels were often chosen.  The
installer chose names such as "HOME" or "ROOT".  This is fine
until you bring over a disk from another system and now have two
partitions labeled "HOME".  In any event, you can try using
labels by assigning a label to a partition:

   $ e2label /dev/sda1 MY_ROOT_LABEL

Then you can mount by label in /etc/fstab:

   LABEL=MY_ROOT_LABEL  / ext3 defaults 1 1

You can of course make your labels be arbitrarily unique within
the 16-character limit imposed by the e2label command.

Michael Henry

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