NFS unmounts. We have to do this because networking is already down
by the time we get to the unmounting. It would be better to unmount
all remote file systems when an ip-down event occurs.
svn path=/nixos/trunk/; revision=7620
file systems can be unmounted).
* Remount all un-unmountable file systems as read-only.
* Explicitly call losetup to get rid of loopback devices to work
around a bug in mount.
svn path=/nixos/trunk/; revision=7454