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Re: deprecating /usr as a standalone filesystem?

On Tue, May 05, 2009 at 06:50:47PM +0200, Giacomo Catenazzi wrote:
> Roger Leigh wrote:
> > On Tue, May 05, 2009 at 05:41:06PM +0200, Stéphane Glondu wrote:
> >> Marco d'Itri a écrit :
> >>> I know that Debian supports this, but I also know that maintaning
> >>> forever large changes to packages for no real gain sucks.
> >>> A partial list of invalid reasons is: [...]
> >> How about: "my /usr is shared by many machines over NFS"?
> > 
> > That might have been a "traditional" reason for a shared /usr.
> > However, the package manager can't cope with this setup since
> > you have some components of a package installed locally and
> > some remotely for all systems using the "shared" part.  It's
> > an impossible situation to actually cater for in real life.
> > Has anyone ever actually *done* this?
> So why we created /usr/share (and moved documentation) ?

Good question.  While it's nice to keep arch-indep and arch-dep
files separated, I have never seen any cases where the arch-indep
information is actually shared amongst architectures (except for
at the arch:all package level, of course).

> But also I don't think it is a problem sharing usr
> on multiple system with multiple configurations.

Keeping such as configuration updated would be hard, since
each system would have an independent dpkg state in /var
and different conffile state in /etc.  If you removed a
package on one system, it might purge files in use on
another, and if you install a package on one the conffiles
won't be installed on the others, etc..

> On non public working stations, one doesn't run randomly
> programs. If I installed mysql-server on a system,
> it will work on such system, but if I install on
> an other system, it work also on the other system,
> occupying only one instance.
> I don't see problem from package management
> (also because we have a nullpotent dpkg), so
> we can upgrade from multiple system without problems.

I'm not sure I see how this would work; I'd like to see
some examples, especially WRT the simple problems I
outlined above.

> > Looking at GNU/Hurd, /usr is a symlink to /.  If we were to make
> > /usr non-separable, maybe this would be the way to go.
> or plan9, which bind mount all /*/bin into the main /bin.
> I can live with such solution, but please allow us to use /usr
> in a different (maybe shared) partition.

The plan9 situation is truly wonderful, and one can only hope
that Linux can do this at some point in the future.  I know
we have unionfs and aufs, but I wouldn't trust them for this
just yet!


  .''`.  Roger Leigh
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