From owner-freebsd-fs@FreeBSD.ORG Wed Mar 23 06:16:43 2011 Return-Path: Delivered-To: freebsd-fs@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 96FE510656A3 for ; Wed, 23 Mar 2011 06:16:43 +0000 (UTC) (envelope-from jdc@koitsu.dyndns.org) Received: from qmta02.emeryville.ca.mail.comcast.net (qmta02.emeryville.ca.mail.comcast.net [76.96.30.24]) by mx1.freebsd.org (Postfix) with ESMTP id 7CC768FC08 for ; Wed, 23 Mar 2011 06:16:43 +0000 (UTC) Received: from omta17.emeryville.ca.mail.comcast.net ([76.96.30.73]) by qmta02.emeryville.ca.mail.comcast.net with comcast id NWFl1g0011afHeLA2WGisa; Wed, 23 Mar 2011 06:16:42 +0000 Received: from koitsu.dyndns.org ([67.180.84.87]) by omta17.emeryville.ca.mail.comcast.net with comcast id NWGh1g00C1t3BNj8dWGh0D; Wed, 23 Mar 2011 06:16:42 +0000 Received: by icarus.home.lan (Postfix, from userid 1000) id 0E8FF9B422; Tue, 22 Mar 2011 23:16:41 -0700 (PDT) Date: Tue, 22 Mar 2011 23:16:41 -0700 From: Jeremy Chadwick To: Lawrence Stewart Message-ID: <20110323061641.GA74977@icarus.home.lan> References: <4D8989A5.1020203@swin.edu.au> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4D8989A5.1020203@swin.edu.au> User-Agent: Mutt/1.5.21 (2010-09-15) Cc: freebsd-fs@freebsd.org Subject: Re: mount -o union doesn't allow changes to sub directories? X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 23 Mar 2011 06:16:43 -0000 On Wed, Mar 23, 2011 at 04:48:21PM +1100, Lawrence Stewart wrote: > Hi again, > > If I run something like: > > mount -o union /dev/md0 /etc > > where md0 is a memory backed fs device, and /etc is fully populated but > mounted RO off a CD, I can touch a new file in /etc, but can't in any > subdir of etc (fails with "Read-only filesystem" reported). > > As far as I can tell this is a bug, but wanted to check if I'm > misunderstanding how the "-o union" mount option is supposed to work. Please see mount_unionfs(8), specifically the explanations of "lower" and "upper" layers, along with EROFS (errno 30, "Read-only filesystem"). -- | Jeremy Chadwick jdc@parodius.com | | Parodius Networking http://www.parodius.com/ | | UNIX Systems Administrator Mountain View, CA, USA | | Making life hard for others since 1977. PGP 4BD6C0CB |