Date: Tue, 22 Mar 2011 23:16:41 -0700 From: Jeremy Chadwick <freebsd@jdc.parodius.com> To: Lawrence Stewart <lastewart@swin.edu.au> Cc: freebsd-fs@freebsd.org Subject: Re: mount -o union doesn't allow changes to sub directories? Message-ID: <20110323061641.GA74977@icarus.home.lan> In-Reply-To: <4D8989A5.1020203@swin.edu.au> References: <4D8989A5.1020203@swin.edu.au>
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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 |
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