Re: Confusion on GPT wedges

[mlelstv%serpens.de@localhost (Michael van Elst)]

rnestor%mac.com@localhost (Robert Nestor) writes:

>So a bit further digging and I discover that one can replace the actual wedge name with the unique UUID (actually the wedge GUID value).  That works on a system that has already been booted, but fails during boot.  Apparently the utilities used during boot haven?t been modified to use either wedge by name or wedge by UUID.  Is this a bug or oversight in wedge processing by the components used for booting?

A wedge only has a single name. Wedges are automatically configured from
a GPT, a wedge names is taken from the partition label or if that
isn't that or already exists, from the partition GUID. If the GUID
also conflicts, the wedge isn't configured.

So in your situation with two disks using the same partition labels, you get
wedges named after the partitions on the first disk and wedges named after
the GUID on the second disk. "First" and "Second" refer to attachment order
which is well-defined on e.g. a single ATA or SCSI bus, but not necessarily
on different busses or busses that support hot-plugging (e.g. USB).

It's probably a good idea to find a good naming convention from disk labels.
System partitions could be named like $HOST-root or $HOST-$INSTANCE-root
if you use multiple installations. Data partitions could refer to the
specific data set. Not using labels at all and relying on GUIDs is
possible to, but not as readable.

N.B. wedges can also be used for non-GPT disks, but then you get other
naming rules.

-- 
-- 
                                Michael van Elst
Internet: mlelstv%serpens.de@localhost
                                "A potential Snark may lurk in every tree."