From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754756Ab0JKNwD (ORCPT ); Mon, 11 Oct 2010 09:52:03 -0400 Received: from adelie.canonical.com ([91.189.90.139]:33811 "EHLO adelie.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754211Ab0JKNwB (ORCPT ); Mon, 11 Oct 2010 09:52:01 -0400 Message-ID: <4CB3166B.8080008@ubuntu.com> Date: Mon, 11 Oct 2010 14:51:39 +0100 From: Scott James Remnant User-Agent: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.6; en-US; rv:1.9.2.9) Gecko/20100915 Thunderbird/3.1.4 MIME-Version: 1.0 To: Valerie Aurora CC: Andreas Gruenbacher , Michal Suchanek , Andy Whitcroft , Scott James Remnant , Vladimir Dronnikov , Felix Fietkau , Miklos Szeredi , linuxram@us.ibm.com, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, neilb@suse.de, viro@zeniv.linux.org.uk Subject: Re: [PATCH 6/7 v3] overlay: hybrid overlay filesystem prototype References: <20100920180404.939991832@szeredi.hu> <201009281025.00727.agruen@suse.de> <20100930215114.GD490@shell> <201010011134.57594.agruen@suse.de> <20101006173141.GB18479@shell> In-Reply-To: <20101006173141.GB18479@shell> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/10/2010 18:31, Valerie Aurora wrote: > On Fri, Oct 01, 2010 at 11:34:57AM +0200, Andreas Gruenbacher wrote: >> On Thursday 30 September 2010 23:51:15 Valerie Aurora wrote: >>> Hm, this was a pretty basic assumption for me - that you'd want to >>> construct a topmost image offline that would be "merged" with the >>> lower layers. So, for example: >>> >>> Topmost layer contains: >>> >>> /etc/hostname >>> >>> Lower layers contain everything else in /etc/. So /etc/ would exist >>> on the topmost layer at the time of union mount, but we would want it >>> to be transparent. But if we created a new dir *during* the union >>> mount, it would be opaque. >>> >>> What was your model? >> The prevalent use case probably is to start out with an empty topmost layer on >> top of an existing file system. When things are modified, changes obviously >> go into the topmost layer. Additional layers can later be stacked on top of >> that, turning the previous topmost layer into a read-only lower layer. >> >> Overlaying preexisting file systems doesn't seem that important; users >> commonly should be able to start out with an empty topmost layer instead. To > Okay, that surprises me. Let me check my assumptions. I cc'd several > people who seem to be actively using unionfs or aufs in ways that we > want union mounts to replace. Do you start out with an empty topmost > file system in most cases? Or do you prepopulate with some files in > dirs you want to be transparent? > Our use would be for the Live CD and for Update testing - in both of these scenarios I imagine that the top-most layer would start empty, yes. Scott