# mount --bind / /mnt/tmp
Is safe. The kernel knows that it's the same filesystem.
Brilliant! I just moved things from /mnt/tmp/usr: Filesystem 1k-blocks Used Available Use% Mounted on /dev/md0 365492 85809 260813 25% /
PS: I just noticed that this will create loops in the directory structure; something is bound to get confused by that...Many tools traversing filesystems have a 'don't cross filesystem boundaries' that comes in handy in these cases.
I don't think this is an issue because these mount points are just directories until you mount something on top of them. So if you mount the original filesystem you get it with those directories.
Erik /--------------------------------------------------------------------\ | Erik Erskine | | Sundayta Ltd | \--------------------------------------------------------------------/