Messages in this thread | | | Date | Tue, 6 Jul 1999 21:14:15 +0200 | From | Jens Benecke <> | Subject | Re: FS union |
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On Wed, Jun 16, 1999 at 08:32:57AM -0400, Lou Grinzo wrote:
> One possibility that I don't think anyone has mentioned is > giving the user or programmer finer-grained control over the > name space for the unioned FS's. In other words, there could > easily be times when you would want to make just certain files > in the underlying FS take precedence in the name space.
One thing that sort of disturbs me ist that you'd really have a whole filesystem that you'd have to mount and umount every time. I don't know about POSIX standards etc, but to the layman (me ;) perhaps a kind of 'extended symlink' would look easier (to use, not necessarily to implement...)
Take two directories, say /dir1 and /dir2, create an empty 'union mount point' (mkdir /union) and join them:
ln -U /dir1 /dir2 /union
or perhaps with a different command:
union /dir1 /dir2 /union
Then all acesses to /union would get redirected to /dir1, if nothing was found there, /dir2 would be searched. Write access would go to /dir1 (or perhaps to somewhere else, whatever). You can, for static content, do this now with a symlinking script. But not for dynamic content.
You wouldn't have any mount/umount nightmares, wouldn't have to care about on what physical partitions your data is to 'unimount' them, it would be a user space issue (at least, it looks like it ;) and all users could use this feature, even if they did not have the possibility to mount/umount things on a machine. It would not be an admin issue.
To me, this sounds like a Good Thing. I'd like to hear what you think, especially concerning implementation.
-- _ciao, Jens_______________________________ http://www.pinguin.conetix.de
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