mode of operation is now a job parameter [closes #5]

zfs-backup.cfg

@@ -1,14 +1,17 @@
 # required format:
-# SOURCE	TARGET					KEEPDAYS	ENABLED
-# dataset	[user@host:]dataset			number		Y or N
+# SOURCE	TARGET					KEEPDAYS	MODE		ENABLED
+# dataset	[user@host:]dataset			number		backup or sync	Y or N
 
 # we are securing this elsewhere; if we are using this method, we'll need to configure the target host
 # 'user' needs an authorized and restricted public key for SSH access and sudoer rights on 'remotehost' to execute the following as root:
 # /usr/sbin/zfs recv -Feuv datapool/backup, /usr/sbin/zfs destroy -r datapool/backup/*
-data/home	user@remotehost:datapool/backup		7		Y
+data/home	user@remotehost:datapool/backup		7		backup		Y
 
-# this goes to another pool on this host so no further configuration is necessary
-data/config	backup/data				5		Y
+# this goes to another pool on this host so no further configuration is	necessary
+data/config	backup/data				5		backup		Y
 
 # we no longer back this up
-data/volatile	backup/data				2		N
+data/volatile	backup/data				2		backup		N
+
+# we only sync this one
+data/replica	remote/dump				31		sync		Y

zfs-backup.sh

@@ -22,18 +22,18 @@ function snapuse() {
 function human() {
 	# found at http://unix.stackexchange.com/a/191787
 	nawk 'function human(x)	{
-							x[1]/=1024;
-							if (x[1]>=1000) { x[2]++; human(x); }
-							}
-							{a[1]=$1; a[2]=0; human(a); printf "%.2f%s\n",a[1],substr("KMGTEPYZ",a[2]+1,1)}' <<< $1
+					x[1]/=1024;
+					if (x[1]>=1000) { x[2]++; human(x); }
+				}
+				{a[1]=$1; a[2]=0; human(a); printf "%.2f%s\n",a[1],substr("KMGTEPYZ",a[2]+1,1)}' <<< $1
 }
 
 function backup() {
 	# check source
 	check_dataset ${DATASET} ||	{
-								logger -t $(basename ${0%.sh}) -p user.notice "source dataset \"${DATASET}\" in configuration entry #${COUNTER} does not exist; omitting"
-								continue 2
-								}
+						logger -t $(basename ${0%.sh}) -p user.notice "source dataset \"${DATASET}\" in configuration entry #${COUNTER} does not exist; omitting"
+						continue 2
+					}
 
 	# determine which local snapshots exist already
 	SNAPSHOTS=( $(zfs list -rt snapshot -d1 -Ho name -S creation ${DATASET} 2>/dev/null) )
@@ -69,21 +69,24 @@ function backup() {
 
 	# check target
 	check_dataset ${SAVETO} ||	{
-								logger -t $(basename ${0%.sh}) -p user.notice "target dataset \"${SAVETO}\" in configuration entry #${COUNTER} does not exist; omitting"
-								continue 2
-								}
+						logger -t $(basename ${0%.sh}) -p user.notice "target dataset \"${SAVETO}\" in configuration entry #${COUNTER} does not exist; omitting"
+						continue 2
+					}
 
 	R_SNAPSHOTS=( $(${R_RMOD} zfs list -rt snapshot -d1 -Ho name -S creation ${SAVETO}/$( basename ${DATASET}) 2>/dev/null) )
 	check_dataset ${SAVETO}/$( basename ${DATASET}) && R_USED_BEFORE=$(snapuse ${SAVETO}/$( basename ${DATASET}))
 
-	# determine current timestamp
-	DATE=$(date +%Y-%m-%d-%H%M)
+	if [ $MODE == "backup" ]
+		then
+			# determine current timestamp
+			DATE=$(date +%Y-%m-%d-%H%M)
 
-	# determine the name of the current snapshot to create
-	NEWSNAP="${DATASET}@${DATE}"
-	
-	# take a snapshot
-	zfs snapshot -r ${NEWSNAP}
+			# determine the name of the current snapshot to create
+			NEWSNAP="${DATASET}@${DATE}"
+
+			# take a snapshot
+			zfs snapshot -r ${NEWSNAP}
+	fi
 	
 	# check if source is encrypted
 	if [ $ENCRYPTION_FEATURE != "disabled" ]
@@ -103,40 +106,50 @@ function backup() {
 			# local snapshot(s) found
 			SNAPMODIFIER="i ${LASTSNAP}"
 			check_dataset ${SAVETO}/$(basename ${LASTSNAP}) ||	{
-																# last local snapshot is not available at the destination location
-																if [ ${#R_SNAPSHOTS[*]} -ge 1 ]
-																	then
-																		# remote snapshot(s) found
-																		R_SNAPMODIFIER="I $(dirname ${DATASET})/$(basename ${R_SNAPSHOTS[*]:(-1)})"
-																fi
-																# send any previous snapshots
-																zfs send -Rcv${RAW_MOD}${R_SNAPMODIFIER} ${LASTSNAP} | ${RMOD:-$R_RMOD} zfs recv -Feu${RESUME_MOD}v ${SAVETO} 2>&1 >> ${LOGFILE}
-																}
+											# last local snapshot is not available at the destination location
+											if [ ${#R_SNAPSHOTS[*]} -ge 1 ]
+												then
+													# remote snapshot(s) found
+													R_SNAPMODIFIER="I $(dirname ${DATASET})/$(basename ${R_SNAPSHOTS[0]})"
+											fi
+											# send any previous snapshots
+											zfs send -Rcv${RAW_MOD}${R_SNAPMODIFIER} ${LASTSNAP} | ${RMOD:-$R_RMOD} zfs recv -Feu${RESUME_MOD}v ${SAVETO} 2>&1 >> ${LOGFILE}
+											if [[ ${PIPESTATUS[*]} =~ [1-9]+ ]]
+												then
+													# replication failure
+													logger -t $(basename ${0%.sh}) -p user.notice "failed to replicate ${LASTSNAP} to ${TARGET:-local}:${SAVETO}"
+												else
+													let CHANGES++
+											fi
+										}
 		else
 			# ensure this does not remain in effect
 			unset SNAPMODIFIER R_SNAPMODIFIER
 	fi
 	
-	# send backup
-	zfs send -Rcv${RAW_MOD}${SNAPMODIFIER} ${NEWSNAP} | ${RMOD:-$R_RMOD} zfs recv -Feu${RESUME_MOD}v ${SAVETO} 2>&1 >> ${LOGFILE}
-	
-	# if replication is unsuccessful, omit the aging check so as to prevent data loss
-	if [ $? -eq 0 ]
+	if [ $MODE == "backup" ]
 		then
-			THRESHOLD=$(( $KEEP * 24 * 3600 ))
-			for SNAPSHOT in ${SNAPSHOTS[*]}
-				do
-					TIMESTAMP=$(zfs get -pHo value creation "${SNAPSHOT}")
-					AGE=$(( $NOW - $TIMESTAMP ))
-					if [ $AGE -ge $THRESHOLD ]
-						then
-							zfs destroy -r ${SNAPSHOT} 2>&1 >> ${LOGFILE}
-							${RMOD:-$R_RMOD} zfs destroy -r ${SAVETO}/$(basename ${SNAPSHOT}) 2>&1 >> ${LOGFILE}
-					fi
-				done
-		else
-			MY_EXIT_CODE=$?
-			logger -t $(basename ${0%.sh}) -p user.notice "failed to replicate ${NEWSNAP} (rc: $MY_EXIT_CODE) to ${TARGET:-local}:${SAVETO}, no aging"
+			# send backup
+			zfs send -Rcv${RAW_MOD}${SNAPMODIFIER} ${NEWSNAP} | ${RMOD:-$R_RMOD} zfs recv -Feu${RESUME_MOD}v ${SAVETO} 2>&1 >> ${LOGFILE}
+
+			# if replication is unsuccessful, omit the aging check so as to prevent data loss
+			if [[ ! ${PIPESTATUS[*]} =~ [1-9]+ ]]
+				then
+					let CHANGES++
+					THRESHOLD=$(( $KEEP * 24 * 3600 ))
+					for SNAPSHOT in ${SNAPSHOTS[*]}
+						do
+							TIMESTAMP=$(zfs get -pHo value creation "${SNAPSHOT}")
+							AGE=$(( $NOW - $TIMESTAMP ))
+							if [ $AGE -ge $THRESHOLD ]
+								then
+									zfs destroy -r ${SNAPSHOT} 2>&1 >> ${LOGFILE}
+									${RMOD:-$R_RMOD} zfs destroy -r ${SAVETO}/$(basename ${SNAPSHOT}) 2>&1 >> ${LOGFILE}
+							fi
+						done
+				else
+					logger -t $(basename ${0%.sh}) -p user.notice "failed to replicate ${NEWSNAP} to ${TARGET:-local}:${SAVETO}, no aging"
+			fi
 	fi
 
 	# re-evaluate snapshot data usage
@@ -148,34 +161,38 @@ function backup() {
 			R_RMOD="ssh ${USER}@${TARGET}"
 	fi
 			
-	R_USED_AFTER=$(snapuse ${SAVETO}/$( basename ${DATASET}))
-	L_DELTA=$(( $L_USED_AFTER - $L_USED_BEFORE ))
-	R_DELTA=$(( $R_USED_AFTER - ${R_USED_BEFORE:-0} ))
+	if [ ${CHANGES:-0} -gt 0 ]
+		then
+			# calculate data volume change
+			R_USED_AFTER=$(snapuse ${SAVETO}/$( basename ${DATASET}))
+			L_DELTA=$(( $L_USED_AFTER - $L_USED_BEFORE ))
+			R_DELTA=$(( $R_USED_AFTER - ${R_USED_BEFORE:-0} ))
 
-	for DELTA in L_DELTA R_DELTA
-		do
-			unset WHAT WHERE
-			eval _DELTA=\$$DELTA
+			for DELTA in L_DELTA R_DELTA
+				do
+					unset WHAT WHERE
+					eval _DELTA=\$$DELTA
 
-			if [ $_DELTA -lt 0 ]
-				then
-					_DELTA=$(( $_DELTA * -1 ))
-					WHAT="freed"
-			fi
+					if [ $_DELTA -lt 0 ]
+						then
+							_DELTA=$(( $_DELTA * -1 ))
+							WHAT="freed"
+					fi
 
-			if [[ $DELTA =~ ^L ]]
-				then
-					WHERE="$(dirname ${DATASET})"
-				else
-					WHERE="${SAVETO}"
-			fi
+					if [[ $DELTA =~ ^L ]]
+						then
+							WHERE="$(dirname ${DATASET})"
+						else
+							WHERE="${SAVETO}"
+					fi
 
-			if [ $_DELTA -ne 0 ]
-				then
-					_DELTA=$(human $_DELTA)
-					logger -t $(basename ${0%.sh}) -p user.notice "$_DELTA ${WHAT:-allocated} in \"${WHERE}\" by backing up \"${DATASET}\""
-			fi
-		done
+					if [ $_DELTA -ne 0 ]
+						then
+							_DELTA=$(human $_DELTA)
+							logger -t $(basename ${0%.sh}) -p user.notice "$_DELTA ${WHAT:-allocated} in \"${WHERE}\" by backing up \"${DATASET}\""
+					fi
+				done
+	fi
 
 	# reset remote configuration
 	unset R_RMOD RMOD RAW_MOD
@@ -274,12 +291,13 @@ LOGDIR="/var/log"
 # determine session logfile
 LOGFILE="${LOGDIR:-/tmp}/${ME}_${RUNDATE}.txt"
 
-while read -u 4 DATASET SAVETO KEEP ENABLED
+while read -u 4 DATASET SAVETO KEEP MODE ENABLED
 	# alternate file descriptor in use because SSH might be involved and we can not pass '-n' to it because we need stdin for 'zfs recv'
 	do
 		let COUNTER++
 		if [ ${ENABLED} == "Y" ]
 			then
+				# split this function -> snapshot(), sync(), age() ? -> a new backup() would call all three
 				backup
 		fi
 	done 4<<< "$(egrep -v '^(#|$)' "${CFGFILE}")" # graciously overlook any comments or blank lines