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To: linux-kernel@vger.kernel.org
From: "H. Peter Anvin" <hpa@zytor.com>
Subject: Re: automount doesn't "follow" bind mounts
Date: 20 Aug 2002 14:35:26 -0700
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References: <Pine.LNX.4.44.0208201752430.23681-100000@r2-pc.dcs.qmul.ac.uk> <ajuahu$hf$1@cesium.transmeta.com>
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Followup to:  <ajuahu$hf$1@cesium.transmeta.com>
By author:    "H. Peter Anvin" <hpa@zytor.com>
In newsgroup: linux.dev.kernel
>
> Followup to:  <Pine.LNX.4.44.0208201752430.23681-100000@r2-pc.dcs.qmul.ac.uk>
> By author:    Matt Bernstein <mb/lkml@dcs.qmul.ac.uk>
> In newsgroup: linux.dev.kernel
> >
> > I tried to subscribe to the autofs list, but majordomo isn't replying to 
> > me! I think this is a problem in the automount daemon rather than the 
> > kernel autofs code itself.
> > 
> > I'm trying to automount our home dirs as
> > 	/homes/$USERNAME
> > which should bind mount to
> > 	:/home/$SERVER/$HOMENAME/$USERNAME
> > which should bind mount to
> > 	:/home/$SERVER/$VOLUME/$PATH/$USERNAME
> > which (phew!) will be an NFS mount to
> > 	$SERVER:/$VOLUME/$PATH/$USERNAME
> > 
> > The idea is that:
> > 	(1) `/bin/pwd` = "/homes/$USERNAME"
> > 	(2) when you run "quota" it'll only report for $SERVER:/$VOLUME
> > 
> > Now.. this all works perfectly if before looking at /homes/$USERNAME you
> > look at firstly /home/$SERVER/$VOLUME/$PATH/$USERNAME and then secondly
> > /home/$SERVER/$HOMENAME/$USERNAME, because the bind mounts have something
> > to bind to. Of course you shouldn't need to know the middle bits, but you
> > could look them up. Currently the binds mount fail and automount drops in
> > symlinks; this satisfies (2)  above, but unfortunately not (1).
> > 
> > I hope someone can make sense of this. Is it different in autofs4?
> > 
> 
> This is unfortunately nearly impossible to solve.  It's a known bug,
> but it's questionable if anything can be done about it.
> 
> For right now, autofs cannot bind-mount to a mount from the same
> automount point (the problem is with the double-use of /home/$SERVER
> in your case.)
> 

Actually, if you're using autofs v3, which it sounds like you're
doing, it's even more broken, since autofs v3 doesn't support
multilevel mounts.

	-hpa
-- 
<hpa@transmeta.com> at work, <hpa@zytor.com> in private!
"Unix gives you enough rope to shoot yourself in the foot."
http://www.zytor.com/~hpa/puzzle.txt	<amsp@zytor.com>
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