Here’s a nifty little submission from Ralf Ramge. It will do a ZFS snapshot backup to a local directory, a remote machine and also clone and promote the filesystem on the remote machine. It keeps the last 7 backups around. Take a look:

#!/bin/bash
# backup_zfssnap.sh, (c) 2007 ralf [dot] ramge [at] webde [dot] de

BACKUPDIR="/export/backup/snapshots"
DSTAMP=`date '+%y%m%d-%H%M%S'`
FILESYS=$1
DEST=$2
REPLICA=$3
BACKUPNAME=`echo $FILESYS | sed 's/\//_/g'`
BACKUPFILE=$BACKUPNAME"-"$DSTAMP".zfs"
SNAPSHOT=$FILESYS"@backup-"$DSTAMP

if [ ! -d $BACKUPDIR ]; then
echo "Backup Directory doesn't exist"
exit 1
fi

cd $BACKUPDIR

# Check here if we have 7 backup files, create them if we don't
COUNT_FILES=`ls -1 $BACKUPNAME* | wc -l`
if [ $COUNT_FILES -le 1 ]; then
for COUNT in 1 2 3 4 5 6 7
do
if [ ! -f $BACKUPNAME"-000000-00000"$COUNT".zfs" ]; then
touch $BACKUPNAME"-000000-00000"$COUNT".zfs"
sleep 1
fi
done
fi

# Check here that we have less than 8 backup files
COUNT_FILES=`ls -1 $BACKUPNAME* | wc -l`
if [ $COUNT_FILES -gt 7 ]; then
# echo "More than 7 backup files exist"
# exit 1
while [ $COUNT_FILES -gt 7 ]
do
OLDEST_BACKUP_FILE=`ls -rt1 $BACKUPNAME* | head -1`
rm $OLDEST_BACKUP_FILE
let COUNT_FILES=COUNT_FILES-1
done
fi

# Find the oldest backup file to delete
OLDEST_BACKUP_FILE=`ls -rt1 $BACKUPNAME* | head -1`

# Create the snapshot
zfs snapshot $SNAPSHOT

# Create a filesystem image in the local backup directory
zfs send $SNAPSHOT > $BACKUPDIR"/"$BACKUPFILE

# Check for $2 and, if exists, create a second copy on a remote host for tape archival
if [ ! -z $2 ]; then
`zfs send $SNAPSHOT | ssh root@$2 "cat >$BACKUPDIR/$BACKUPFILE"`
fi

# Check for $3 and, if exists, mirror the filesystem on the remote host
if [ ! -z $3 ]; then
`ssh root@$2 "zfs receive $3 < $BACKUPDIR/$BACKUPFILE"`
fi

# Check for $4 and, if exists, clone and promote the filesystem on the remote host
if [ ! -z $4 ]; then
`ssh root@$2 "zfs clone $SNAPSHOT $4; sleep 30; zfs promote $4"`
fi

# Get the trash out of the house
rm $OLDEST_BACKUP_FILE
if [ ! -z $2 ]; then
ssh root@$2 "rm $BACKUPDIR/$OLDEST_BACKUP_FILE"
fi

SNAPLIST=`zfs list -H | grep $FILESYS | grep @backup | cut -f1`
for i in $SNAPLIST; do
zfs destroy $i
done

# Exit cleanly
exit 0

Thanks for the submission Ralf! (I changed your email address in the script comments so you wouldn’t get spam)