Re: Loopback (dir->dir) mounting (NOT -o loop)

From: Andries Brouwer (
Date: Fri Jun 02 2000 - 13:59:57 EST

On Thu, Jun 01, 2000 at 05:54:55PM -0400, Alexander Viro wrote:

> > > mount -t bind old new

> a) interface may change (-t is damn ugly way to do that)
> b) don't expect it in 2.2 - no backports possible.

Yes, -t is ugly - bind is not a filesystemtype at all.
What you do here is a certain manipulation of the name space structure,
for example like pivot_root. I think a new system call would be cleaner
than a wart on mount.

And it must require privileges. So many setups are based on the
physical separation of parts of the tree. What would happen with
"chown -R"? It really cannot be used anymore (without my --from option).
"rm -r"? Just the same - I create a 10 GB tree in /tmp, wait until
the sysadmin does the "rm -rf", and then quickly use bind to attach
some interesting stuff to this tree.
And it is so easy to create situations where umount fails
so that a clean shutdown is no longer possible.

In fact I think that the present implementation was a mistake.
We do not want a bind without privileges and with global effect.
We want the bind that one user does to affect only his own namespace.
Only root should be able to affect other people's namespace.


To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
Please read the FAQ at

This archive was generated by hypermail 2b29 : Wed Jun 07 2000 - 21:00:15 EST