Re: Understanding LVM UUIDS
On 20100623_054331, Ron Johnson wrote:
> On 06/23/2010 05:20 AM, Javier Barroso wrote:
> >On Wed, Jun 23, 2010 at 10:40 AM, Alan Chandler
> ><alan@chandlerfamily.org.uk>wrote:
> >
> >>I feel I should move my entire /etc/fstab over to using uuids
> >>
> [snip]
> >>
> >>Which do I use, and what does the other one mean?
> >>
> >
> >Get your uuid from dumpe2fs -h /dev/vg/lv | grep UUID
> >
> >But /dev/vg/lv is a persistent name, so no sense changing it to uuid, or
> >maybe I'm missing something ?
> >
>
> Or use labels.
In squeeze, a recent revision in pata support seemed to introduce rewriting
/etc/fstab to reference all file systems via UUID.
Before that, I had constructed a system using labels which was totally
clobbered by the pata upgrade (which also suppressed all mention of
/dev/hd[ab][123] )
I don't use LVM. Perhaps using LVM protects you from 'upgrades' from
ata to pata. Or from future upgrades in pata support. But I'm inclined
to believe that we are in for a spate of instability as pata is worked
out in all its unintended ramifications.
FYI, the UUID is just a 128 bit number that is stored in a 16 byte
space in the superblock of the ext[234] file system. Mostly it is set
to a random value by mke2fs when the fs is originally created. But it
can also be set to a user designated (non-random?) value by
tune2fs -U <UUID> device.
--
Paul E Condon
pecondon@mesanetworks.net
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