Re: The "uniqueness" of UUIDs

[Arno Lehmann <al@its-lehmann.de>]

Hi Roger,

Am 26.11.2024 um 08:51 schrieb Roger Price:
> On Tue, 26 Nov 2024, George at Clug wrote:
>
> > "$ lsblk -f" output is very nice !   Thanks.
>
> I tried this and noticed UUID duplication in the output.  Here is part 
> of what I saw:
>
> NAME    FSTYPE            FSVER LABEL          
> UUID                                 FSAVAIL FSUSE% MOUNTPOINT
> ...
> sdg
> ... ├─sdg6  linux_raid_member 1.0   10.218.0.100:3 
> f5e37a29-357a-e3f2-c731-e29eddce5e91 │ └─md3 ext4              
> 1.0                  39c24711-ab43-497c-bf3e-12b4032575ac  758.4G     7% 
> /mnt/home
> ...
> sdh
> ... ├─sdh6  linux_raid_member 1.0   10.218.0.100:3 
> f5e37a29-357a-e3f2-c731-e29eddce5e91 │ └─md3 ext4              
> 1.0                  39c24711-ab43-497c-bf3e-12b4032575ac  758.4G     7% 
> /mnt/home
>
> UUID sdg6 = UUID sdh6 !  If I wanted to retire /dev/sdg6 from the Raid 
> array, I would not be able to use the UUID, only the unique SDxn.
>
> Aren't UUIDs supposed to be unique?  Roger

The UUID reported might be the one of the file system. As the lsblk 
output is truncated I can not really guess the context of those lines; 
in all cases I checked here, non-unique UUIDs show up on components that 
are reported several times (i.e., file systems backed by several backed 
by several partitions that are members of one RAID array). If you want 
to have a list of all things with their UUIDs in a less ambigous view, 
try blkid.

Cheers,

Arno

--
Arno Lehmann

IT-Service Lehmann
Sandstr. 6, 49080 Osnabrück