From mboxrd@z Thu Jan 1 00:00:00 1970 From: C Anthony Risinger Subject: Re: What to do about subvolumes? Date: Wed, 1 Dec 2010 12:48:19 -0600 Message-ID: References: <20101201142136.GD427@dhcp231-156.rdu.redhat.com> <201012011933.40169.kreijack@libero.it> <20101201183656.GD7021@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Goffredo Baroncelli , ssorce@redhat.com, linux-btrfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, chris.mason@oracle.com To: Josef Bacik Return-path: Received: from mail-gx0-f174.google.com ([209.85.161.174]:57467 "EHLO mail-gx0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756186Ab0LASsT convert rfc822-to-8bit (ORCPT ); Wed, 1 Dec 2010 13:48:19 -0500 In-Reply-To: <20101201183656.GD7021@localhost.localdomain> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Wed, Dec 1, 2010 at 12:36 PM, Josef Bacik wrote: > On Wed, Dec 01, 2010 at 07:33:39PM +0100, Goffredo Baroncelli wrote: > >> Another point that I want like to discuss is how manage the "pivotin= g" between >> the subvolumes. One of the most beautiful feature of btrfs is the sn= apshot >> capability. In fact it is possible to make a snapshot of the root of= the >> filesystem and to mount it in a subsequent reboot. >> But is very complicated to manage the pivoting of a snapshot of a ro= ot >> filesystem, because I cannot delete the "old root" due to the fact t= hat the >> "new root" is placed in the "old root". >> >> A possible solution is not to put the root of the filesystem (where = are placed >> /usr, /etc....) in the root of the btrfs filesystem; but it should b= e accepted >> from the beginning the idea that the root of a filesystem should be = placed in >> a subvolume which int turn is placed in the root of a btrfs filesyst= em... >> >> I am open to other opinions. >> > > Agreed, one of the things that Chris and I have discussed is the poss= iblity of > just having dangling roots, since really the directories are just an = easy way to > get to the subvolumes. =A0This would let you delete the original volu= me and use > the snapshot from then on out. =A0Something to do in the future for s= ure. i would really like to see a solution to this particular issue. i may be missing something, but the dangling subvol roots doesn't seem to address the management of the root volume itself. for example... most people will install their whole system into the real root (id=3D5), but this renders the system unmanageable, because there is no way to ever empty it without manually issuing an `rm -rf`. i'm having a really hard time controlling this with the initramfs hook i provide for archlinux users. the hook requires a specific structure "underneath" what the user perceives as /, but i can only accomplish this for new installs -- for existing installs i can setup the proper "subroot" structure, and snapshot their current root... but i cannot remove the stagnant files in the real root (id=3D5) that well never, ever be accessed again. =2E.. or does dangling roots address this? C Anthony -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel= " in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html