Sharing among jails

[The Hermit Hacker]

On Sat, 26 Jul 2003, BSD wrote:

> IMHO, the best way would be to use mount_union or mount_null (I still
> can't figure out what's the difference between them...) of the ports
> directory. However, that said, I tried that myself about a year back,
> and accesses in the jail caused my FreeBSD machine to lock up solid. So
> I guess the warnings in the BUGS section of the mount_union and
> mount_null man pages are still in full effect.

*Alot* has changed in a year ... I use UNIONFS to share between 60 jails
on one server right now, and the server has been purring *knock on wood*

		up  19+08:28,     0 users,  load 10.66, 11.52, 10.17

As for the difference between UNION and NULL ... and someone more
knowledge will hopefully correct me, but based on my experience ...

If you UNIONfs a file system over top of another, you can use NULLfs to
"seperate" the two ... as an example, if you UNIONFS /usr/ports under
/jail/usr/ports and do a du of /jail/usr/ports, you will get everything
... if you NULLFS mount /jail/usr/ports to /null/usr/ports, and do
/null/usr/ports, you will get only those files that are *on*
/jail/usr/ports ...

Basically, NULLFS gives the same result as if you unmounted the UNIONFS
and looked at /jail/usr/ports ...