freebsd-snapshot is a set of convenience frontend tools to mount(8)
and mdconfig(8) for the management of UFS2 snapshots.  It is
also the under-lying tool used in the periodic snapshot
scheduler periodic-snapshot(8) and the mounting/unmouning
command in the amd(8) map /usr/local/etc/amd.map.snap. It
provides the making, expiring, visiting, mounting and
unmounting of filesystem snapshots.

WWW: http://people.freebsd.org/~rse/snapshot/