Peeking at the contents of a mount point

[Karl Auer]

On Wed, 2012-09-12 at 15:40 +1000, Basil Chupin wrote:
> On 12/09/12 12:25, Kevin O'Gorman wrote:
> > I recall some time ago seeing a command -- a variant or argument to
> > 'mount' I think -- which allowed you to see the real contents of a
> > mount point while something else was still mounted on it.
> > I've looked back through 2 years of postings and can't find it.
> > Anybody have a clue?
> 
> The "real mount point" is what you have mounted on it already. And I 
> don't know of any "fake" mount points :-) .

A mount point is a directory - like "/". A mount point can contain
files, just like any other directory. If a filesystem is mounted on a
directory that contains files, any files below the mount point are
hidden by the mounted filesystem. If you unmount the filesystem, the
files below the mount point become visible again.

Try it - put a file in (say) /mnt, then mount something on /mnt. The
file you created will "disappear" - to reappear unharmed when you
unmount the filesystem.

You can see the contents of the mountpoint under a mounted filesystem by
binding the mount point to another name:

   mount --bind /mnt /mnt_view

... then "ls /mnt_view" should show you the "hidden" files.

This is from memory, so do please test carefully.

Regards, K.

-- 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Karl Auer (kauer at biplane.com.au)
http://www.biplane.com.au/kauer
http://www.biplane.com.au/blog

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