bind vs pwd

[Philip Guenther guenther@stolaf.edu]

>Given bind -c /usr/$user/tmp /tmp
>if I cd to /usr/$user/tmp and then cd .., pwd says that I'm now in /.
>I expected to be in /usr/$user.  Is that how it's supposed to work,
>or am I all confused about something?

bind is not like ln -s.  The bind command shown above makes /tmp into
a union directory, containing the union of the previous contents of /tmp
(probably nothing in this case), and the contents of /usr/$user/tmp.
In addition, the -c flag specifies that files created in /tmp should
*really* be created in /usr/$user/tmp.  This is critical here as /tmp
is unwritable previous to this.

However, /tmp is still /tmp.  It's contents are really somewhere else,
but as far as the shell is concerned, nothing has happened.  The kernel
may catch readdir() a lie a little, but cd is unaffected.

I think you may be able to "trick" it with something like:

	bind -c /usr/tor/tmp /tmp
	mkdir /tmp/foo
	cd /tmp/foo
	cd ..

I think that will leave you in /usr/tor, as the cd takes you to
/usr/tor/tmp/foo.  At least that's what it appears to me...

Philip Guenther

guenther@stolaf.edu (Philip Guenther) St Olaf College, Northfield, MN 55057
(defun sig-hook () (insert-disclaimer 'my-opinion-only 'powerless-student))
"To go outside the mythos is to become insane..." -Robert Pirsig