mount -o union doesn't allow changes to sub directories?
freebsd at jdc.parodius.com
Wed Mar 23 06:16:43 UTC 2011
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 at 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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