Restore UFS snapshot

[Lars Kristiansen]

> 
> # umount
> # snap_rollback
> *wait 10 seconds*
> # mount
> 
> .. and I'm set.
> 
> I believe it should be possible. And if nothing like that exists, it
> should be made. I could look into it, but I would have to learn a
> lot more about the inner workings of the file system first.

related:
afaik, zfs rollback is working and is planned for freebsd 7.0.