Re: 2.2.5:fs/super.c comment indicates stacked mounts possible?

Kurt Garloff (K.Garloff@ping.de)
Mon, 12 Apr 1999 23:01:17 +0200


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On Mon, Apr 12, 1999 at 02:31:27AM -0700, Michael Hasenstein wrote:
> This seems to indicate I can mount several filesystems under one mount
> point? (I didn't find any further comments/code for this)

Just try to do it ... you can't.
What you can do is mount a fs over non-empty subdirs of a mountpoint.

> I'm asking because I'm thinking about an overlay mount function, which
> means you can mount a filesystem on top of another one on the same
> mount point. Purpose: for example, I could overlay my minimal /usr
> installation with a big nfs-mounted /usr filesystem, and all the files
> that don't exist locally on the disk are taken (transparently) from the
> nfs filesystem. The question above has not much to do with this except
> that I'm curious now that I discovered that comment, but maybe some
> people who're familiar with the fs-implementation could comment on the id=
ea.

The old content disappears, if you another fs over an old one. There's no
way to get the sum.

--=20
Dipl.Phys. Kurt Garloff <kurt@garloff.de> [Wuppertal, FRG]
Plasma physics, high perf. computing [Linux-ix86,-axp, DUX]
PGP key: see mailheader / key servers [Linux SCSI driver: DC390]

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