Re: /usr mapped to /
On Fri, Jan 15, 1999 at 12:50:36AM -0500, John Tobey wrote:
> Wouldn't this mess about /bin:/usr/bin and /lib:/usr/lib be solved by
> a creative use of directory mapping (or whatever that Hurd feature is
> called)? How does it work?
Well, we already heard that this is a nice feature not implemented yet, but
I will take this chance and explain the real problem, which would not be
solved by shadowfs.
The real problem is, that we don't know what the problems are. However, it
is likely that we will get overlaps, that means, some package will contain
/file/which/is/called/foo, and some other (or even the same!) will contain
/usr/file/which/is/called/foo.
It should be easy to write a script which finds such overlaps. If you
are interested, the Debian ftp site contains a file "Contents.gz" in the
following format, which makes it very easy:
bin/ash shells/ash
bin/bash base/bash
bin/cat base/textutils
bin/chgrp base/fileutils
However, this is only half of the full story. Some packages _create_
additional files or symlinks in their installation scripts. For example,
/bin/vi is a script in the "ae" package, but every vi package (nvi, vim)
creates a symlink /usr/bin/vi via update-alternatives (which, btw, fails
because /bin/vi exists already). This leads to subtle
problems, for example, calling "vi" results in a loop which does not
terminate, because /bin/vi is calling /usr/bin/vi...
This problem can't be solved by shadowfs, obviously. The only solution is to
seperate /usr completely from /, or to find all such conflicts and solve
them in one way or another.
I have no idea how much of these problems exist. It can be just one, or some
dozens. Debian has over 2000 packages, auditing them all seems to ne
unpractical :)
Thanks,
Marcus
--
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