In order to enable periodic snapshots you need
	to add these lines to your /etc/periodic.conf

	hourly_output="root"
	hourly_show_success="NO"
	hourly_show_info="YES"
	hourly_show_badconfig="NO"
	hourly_zfs_snapshot_enable="YES"
	hourly_zfs_snapshot_pools="tank"
	hourly_zfs_snapshot_keep=6
	daily_zfs_snapshot_enable="YES"
	daily_zfs_snapshot_pools="tank"
	daily_zfs_snapshot_keep=7
	weekly_zfs_snapshot_enable="YES"
	weekly_zfs_snapshot_pools="tank"
	weekly_zfs_snapshot_keep=5
	monthly_zfs_snapshot_enable="YES"
	monthly_zfs_scrub_enable="YES"
	monthly_zfs_scrub_pools="tank"
	monthly_zfs_snapshot_pools="tank"
	monthly_zfs_snapshot_keep=2