>>>Will there be an NFS implementation?

   >>Too bad--being able to do a read-only NFS mount of a source tree and then
   >>apply a magnetic layer would be very nice.

   >You can already do that, if the upper layer is in one of the UFS file
   >systems.

   Oh, so you can't overlay an NFS layer onto a UFS one.
   But you can overlay a UFS one over an NFS one.

No, that's not right either.  Did you read what I originally wrote?

You can overlay any two file systems, but whiteouts only work if the
upper layer is one of the UFS family file systems.