ZFS automatic snapshot service

 Automatically create, rotate, and destroy periodic ZFS snapshots. This is
 the utility that creates the @zfs-auto-snap_frequent, @zfs-auto-snap_hourly,
 @zfs-auto-snap_daily, @zfs-auto-snap_weekly, and @zfs-auto-snap_monthly
 snapshots if it is installed.
 .
 This program is a posixly correct bourne shell script. It depends only on
 the zfs utilities and cron, and can run in the dash shell.