On Mon, Jan 28, 2013 at 4:58 PM, Alessandro Pignotti
<alexpigna.dev@xxxxxxxxx> wrote:
> Hi everyone,
>
> the proposed patch would be useful in the following scenario
>
> 1) There is a large directory tree which needs to be fully read/write
> accessible from many different users, although in an isolated way (i.d.
> the changes made by Alice should not be visible to Bob)
> 2) All users expect to be owning the files. (i.d. that everything is
> private)
>
> With the proposed patch it is possible to store a single copy of the
> base directory tree and use it as the lowerdir. The upperdir is then set
> to a private user-writable directory. Each user as the illusion of a
> private fully-writable installation as required. Moreover, since all the
> changed files ends up in the upperdir it's easy to pack them for backup
> purposes.
Okay, makes sense.
One issue, though, is that stat("x") and fd=open("x"); fstat(fd) will
return different file stats (the fstat one will return the stats for
the original file). This may confuse some apps.
This is a something a "true" union filesystem can do better that
union-mounts or overlayfs.
Thanks,
Miklos
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