Here’s a nice script found on thinking sysadmin. I slightly modified it to use the real mount point instead of assuming “/”, my changes are highlighted below:
#!/usr/local/bin/bash
# FROM: http://andyleonard.com/2010/04/07/automatic-zfs-snapshot-rotation-on-freebsd/
# Path to ZFS executable:
ZFS=/sbin/zfs
# Parse arguments:
TARGET=$1
SNAP=$2
COUNT=$3
# Function to display usage:
usage() {
scriptname=`/usr/bin/basename $0`
echo "$scriptname: Take and rotate snapshots on a ZFS file system"
echo
echo " Usage:"
echo " $scriptname target snap_name count"
echo
echo " target: ZFS file system to act on"
echo " snap_name: Base name for snapshots, to be followed by a '.' and"
echo " an integer indicating relative age of the snapshot"
echo " count: Number of snapshots in the snap_name.number format to"
echo " keep at one time. Newest snapshot ends in '.0'."
echo
exit
}
# Basic argument checks:
if [ -z $COUNT ] ; then
usage
fi
if [ ! -z $4 ] ; then
usage
fi
# Get the TARGET mountpoint
TARGET_MOUNT=$($ZFS get -H -o value mountpoint $TARGET)
# Snapshots are number starting at 0; $max_snap is the highest numbered
# snapshot that will be kept.
max_snap=$(($COUNT -1))
# Clean up oldest snapshot:
if [ -d ${TARGET_MOUNT}/.zfs/snapshot/${SNAP}.${max_snap} ] ; then
$ZFS destroy -r ${TARGET}@${SNAP}.${max_snap}
fi
# Rename existing snapshots:
dest=$max_snap
while [ $dest -gt 0 ] ; do
src=$(($dest - 1))
if [ -d ${TARGET_MOUNT}/.zfs/snapshot/${SNAP}.${src} ] ; then
$ZFS rename -r ${TARGET}@${SNAP}.${src} ${TARGET}@${SNAP}.${dest}
fi
dest=$(($dest - 1))
done
# Create new snapshot:
$ZFS snapshot -r ${TARGET}@${SNAP}.0
Thanks Andy!