Re: BTRFS messes up snapshot LV with origin

[Phillip Susi <psusi@ubuntu.com>]

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On 11/18/2014 1:16 AM, Chris Murphy wrote:
> If fstab specifies rootfs as UUID, and there are two volumes with
> the same UUID, it’s now ambiguous which one at boot time is the
> intended rootfs. It’s no different than the days of /dev/sdXY where
> X would change designations between boots = ambiguity and why we
> went to UUID.

He already said he has NOT rebooted, so there is no way that the
snapshot has actually been mounted, even if it were UUID confusion.

> So we kinda need a way to distinguish derivative volumes. Maybe
> XFS and ext4 could easily change the volume UUID, but my vague 
> recollection is this is difficult on Btrfs? So that led me to the 
> idea of a way to create an on-the-fly (but consistent) “virtual 
> volume UUID” maybe based on a hash of both the LVM LV and fs
> volume UUID.

When using LVM, you should be referring to the volume by the LVM name
rather than UUID.  LVM names are stable, and don't have the duplicate
uuid problem.

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