zfs-snap periodically creates and deletes ZFS snapshots on a FreeBSD machine.
At least, add the following lines to /etc/periodic.conf:
zfs_snap_enable="YES" zfs_snap_filesystems="zroot/usr zroot/home:3m"Every time zfs-snap is executed, it'll create a snapshot of zroot/usr and zroot/home. Snapshots are named like zroot/usr@zs20161227-123242, i.e. current date and time. Snapshots created by zfs-snap will be kept for 1 month (the default) on zroot/usr, but will be kept for 3 months on zroot/home. You can specify any time adjustment which is accepted by date (see option -v). To override the default time period for which snapshots are kept, add this to /etc/periodic.conf:
zfs_snap_keep="6w"Every snapshot will be kept for 6 weeks unless overridden by some entry within zfs_snap_filesystems.