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Re: [PATCH 0/5] hybrid union filesystem prototype

From:  Valerie Aurora <>
To:  Miklos Szeredi <>
Subject:  Re: [PATCH 0/5] hybrid union filesystem prototype
Date:  Tue, 31 Aug 2010 15:29:19 -0400
Message-ID:  <20100831192919.GB5759@shell>
Cc:  Neil Brown <>,,,,,
Archive-link:  Article

On Mon, Aug 30, 2010 at 12:18:11PM +0200, Miklos Szeredi wrote:
> On Sun, 29 Aug 2010, Neil Brown wrote:
> > My comment about set-theory unions being commutative set me thinking.  I
> > really don't think "union" is the right name for this thing.  There is
> > nothing about it which really fits that proper definition of a union.
> > whiteouts mean that even the list of names in a directory is not the union of
> > the lists of names in the upper and lower directories.
> > "overlay" is a much more accurate name.  But union seems to be the name
> > that is most used.  I wonder if it is too late to change that.
> We could call it overlayfs.  People learn new names quickly :)

Union mounts was named "writable overlays" for one release in an
attempt to get away from the "arbitrary union of file systems" idea.
I think it helped, but went back to union mounts since it was more
familiar and made prettier function names.

The config option for union mounts says:

Union mounts allow you to mount a transparent writable layer over a
read-only file system, for example, an ext3 partition on a hard drive
over a CD-ROM root file system image.


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