mount_unionfs for jails

Nejc S(koberne nejc at
Thu Sep 25 23:12:40 UTC 2008


> 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.


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