Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751691Ab3CTEST (ORCPT ); Wed, 20 Mar 2013 00:18:19 -0400 Received: from mail.lang.hm ([64.81.33.126]:53820 "EHLO bifrost.lang.hm" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751290Ab3CTESS (ORCPT ); Wed, 20 Mar 2013 00:18:18 -0400 X-Greylist: delayed 725 seconds by postgrey-1.27 at vger.kernel.org; Wed, 20 Mar 2013 00:18:13 EDT Date: Tue, 19 Mar 2013 21:04:15 -0700 (PDT) From: David Lang X-X-Sender: dlang@asgard.lang.hm To: Martin Steigerwald cc: tux3@phunq.net, Daniel Phillips , "Theodore Ts'o" , "Darrick J. Wong" , linux-kernel@vger.kernel.org, tux3@tux3.org, linux-fsdevel@vger.kernel.org Subject: Re: Tux3 Report: Initial fsck has landed In-Reply-To: <201303200000.33356.Martin@lichtvoll.de> Message-ID: References: <20130129014000.GA7003@thunk.org> (sfid-20130129_203331_599683_707322ED) <201303200000.33356.Martin@lichtvoll.de> User-Agent: Alpine 2.02 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1834 Lines: 41 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 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/