mount_unionfs for jails

David Polak me at
Thu Sep 25 23:43:43 UTC 2008

> -----Original Message-----
> From: owner-freebsd-questions at [mailto:owner-freebsd-
> questions at] On Behalf Of Nejc S(koberne
> Sent: Thursday, September 25, 2008 6:13 PM
> To: David Polak
> Cc: freebsd-questions at
> Subject: Re: mount_unionfs for jails
> Hello,
> > Well, it turns out that my problem was due to a typo in my host
> systems
> > rc.conf.
> Thought so.
> > Do you know if there is a way to "reset" the unionfs? I did notice
> this:
> It is called "whiteout". When you delete the file which is on lower
> layer
> in unionfs, you actually create a file of type "whiteout" on the upper
> layer,
> which tells you that the file is not there. So it is a mark for a
> deleted file.
> To "reset" it, you just need to delete the whiteout. You can do this
> via
> "rm -W". Actually whiteouts seem to be a nice solution but sometimes
> you'll
> run into interesting problems. When you try to upgrade jails, for
> example.
> Also, the problem is, because very few programs "support" whiteouts,
> for
> example "find" utility doesn't know about them, so you have to
> reimplement
> it (we made a shell script).
> We have created a lot of scripts which can do a lot of stuff with jails
> and
> unionfs on our server. If you are interested, let me know.
> HTH,
> Nejc

It would be much appreciated, thank you.

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