linux-kernel - Re: Tux3 Report: Initial fsck has landed

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Message-Id: <201303200000.33356.Martin@lichtvoll.de>
Date:	Wed, 20 Mar 2013 00:00:32 +0100
From:	Martin Steigerwald <Martin@...htvoll.de>
To:	tux3@...nq.net
Cc:	Daniel Phillips <daniel.raymond.phillips@...il.com>,
	"Theodore Ts'o" <tytso@....edu>,
	"Darrick J. Wong" <darrick.wong@...cle.com>,
	David Lang <david@...g.hm>, linux-kernel@...r.kernel.org,
	tux3@...3.org, linux-fsdevel@...r.kernel.org
Subject: Re: Tux3 Report: Initial fsck has landed

Am Dienstag, 29. Januar 2013 schrieb Daniel Phillips:
> On Mon, Jan 28, 2013 at 5:40 PM, Theodore Ts'o <tytso@....edu> 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.

Thanks,
-- 
Martin 'Helios' Steigerwald - http://www.Lichtvoll.de
GPG: 03B0 0D6C 0040 0710 4AFA  B82F 991B EAAC A599 84C7
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