Re: Tux3 Report: Initial fsck has landed

[David Lang]

On Wed, 20 Mar 2013, Martin Steigerwald wrote:

> Am Dienstag, 29. Januar 2013 schrieb Daniel Phillips:
> > On Mon, Jan 28, 2013 at 5:40 PM, Theodore Ts'o <tytso@xxxxxxx> wrote:
> > > On Mon, Jan 28, 2013 at 04:20:11PM -0800, Darrick J. Wong wrote:
> > > > On Mon, Jan 28, 2013 at 03:27:38PM -0800, David Lang wrote:
> > > > > The situation I'm thinking of is when dealing with VMs, you make a
> > > > > filesystem image once and clone it multiple times. Won't that end up
> > > > > with the same UUID in the superblock?
> > > >
> > > > Yes, but one ought to be able to change the UUID a la tune2fs
> > > > -U.  Even still... so long as the VM images have a different UUID
> > > > than the fs that they live on, it ought to be fine.
> > >
> > > ... and this is something most system administrators should be
> > > familiar with.  For example, it's one of those things that Norton
> > > Ghost when makes file system image copes (the equivalent of "tune2fs
> > > -U random /dev/XXX")
> >
> > Hmm, maybe I missed something but it does not seem like a good idea
> > to use the volume UID itself to generate unique-per-volume metadata
> > hashes, if users expect to be able to change it. All the metadata hashes
> > would need to be changed.
>
> I believe that is what BTRFS is doing.
>
> And yes, AFAIK there is no easy way to change the UUID of a BTRFS filesystems
> after it was created.

In a world where systems are cloned, and many VMs are started from one master 
copy of a filesystem, a UUID is about as far from unique as anything you can 
generate.

BTRFS may have this problem, but why should Tux3 copy the problem?

David Lang
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