Re: Symlink indirection

From: John Bradford (
Date: Sun Dec 15 2002 - 07:58:14 EST

> > "AW" == Andrew Walrond <> gives an example of
> > a/{x,y,z}, b/{y,z}, c/z mounted on d/. in that order, later
> > mounts covering the earlier ones.
> >
> > AW> echo "d/w" > d/w would create a new file in directory a.

I disagree. It should create it in directory d, even though that is
the mount point.

A union mount should include files from another directory, but writes
should go to the actual named directory.

> > Back to your example; what do you wish to happen when we do
> > this?
> >
> > $ mv d/z d/zz && test -f d/z && cat d/z
> >
> > Here we rename d/z (which is really c/z) to zz. Does this
> > reveal z that used to be hidden by that, namely b/z, and "cat
> > d/z" now shows "b/z"?
> Yes - exactly

Union mounts should be read only.

If read-write union mounts are needed, I don't think that we should
implement them significantly differently to the way they work in BSD.

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