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Date:      Thu, 18 Nov 1999 19:16:24 -0800
From:      Dann Lunsford <dann@greycat.com>
To:        Richard Tobin <richard@cogsci.ed.ac.uk>
Cc:        questions@freebsd.org
Subject:   Re: "whiteouts" in rm manpage
Message-ID:  <19991118191624.B11031@greycat.com>
In-Reply-To: <199911181650.QAA27745@rhymer.cogsci.ed.ac.uk>
References:  <199911181650.QAA27745@rhymer.cogsci.ed.ac.uk>

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On Thu, Nov 18, 1999 at 04:50:54PM +0000, Richard Tobin wrote:
> > WHITEOUTS???  What is this?
> 
> IIRC, whiteouts are (would be?) used for the union filesystem (similar
> to Sun's "translucent" filesystem).  The union filesystem allows one
> filesystem to be mounted "over" another, where you see files in both
> filesystems with those in the "upper" filesystem overriding those in
> the (typically read-only) "lower".  A whiteout in the upper filesystem
> hides one in the lower, allowing you to delete files from the union.
> Undeleting such a whited-out file would just be a question of removing
> the whiteout to expose the original again.

Hmmm.   Sounds a little like CMS mini-disks.  You can specify a 
search order that does the same sort of thing.  So, what would 
you do to "white out" a file ?  Create an empty file with the same
name?  Or is there some special attribute you give files on 
a union fs?  Guess it's hit-the-code time.

Thanks!

-- 
Dann Lunsford       The only thing necessary for the triumph of evil
dann@greycat.com    is that men of good will do nothing.  --  Cicero


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