This is a script to take daily snapshots of a ZFS filesystem (and prune older snapshots).

daily_zfs_snapshot.sh

#!/bin/bash
# 
# This will by default take snapshots of all zfs filesystems, 
# but could be adapted to only pull specific ones. This script 
# will also rotate snapshots, removing those that are older 
# than 2 weeks.
#

CURDATE=$(date +%Y%m%d)
TWOWEEKSAGO=$(date -d'2 weeks ago' +%Y%m%d)

create_snapshot() {
    if [ "$(/sbin/zfs list -tsnapshot | grep $1@$CURDATE)" = "" ]; then
    	/sbin/zfs snapshot $1@$CURDATE
    fi
}

prune_old () {
    if [ "$(/sbin/zfs list -tsnapshot | grep "$1@")" != "" ]; then
    	for f in $(/sbin/zfs list -tsnapshot | grep "$1@" | awk '{print $1}'); do
        	echo ">>> $f"
		SNAPDATE=$(echo $f | sed -e 's/@/ /' | awk '{print $2}')
		if [ $SNAPDATE -lt $TWOWEEKSAGO ]; then
			# echo "destroying snapshot $f"
			/sbin/zfs destroy $f
		fi
	done
    fi
}

FS=$(/sbin/zfs list  | awk '{print $1}' | tail -n+2)

for f in $FS; do
    create_snapshot $f
    prune_old $f 2>/dev/null
done