Check whether we have zfs-auto-snapshot before running it

zfs destroy will use -d for deferred destruction

Makefile

@@ -1,7 +1,19 @@
+PREFIX := /usr/local
+
 all:
 
 install:
-	install -d $(DESTDIR)$(PREFIX)/etc/cron.d
-	install etc/zfs-auto-snapshot.cron $(DESTDIR)$(PREFIX)/etc/cron.d/zfs-auto-snapshot
+	install -d $(DESTDIR)/etc/cron.d
+	install -d $(DESTDIR)/etc/cron.daily
+	install -d $(DESTDIR)/etc/cron.hourly
+	install -d $(DESTDIR)/etc/cron.weekly
+	install -d $(DESTDIR)/etc/cron.monthly
+	install -m 0644 etc/zfs-auto-snapshot.cron.frequent $(DESTDIR)/etc/cron.d/zfs-auto-snapshot
+	install etc/zfs-auto-snapshot.cron.hourly   $(DESTDIR)/etc/cron.hourly/zfs-auto-snapshot
+	install etc/zfs-auto-snapshot.cron.daily    $(DESTDIR)/etc/cron.daily/zfs-auto-snapshot
+	install etc/zfs-auto-snapshot.cron.weekly   $(DESTDIR)/etc/cron.weekly/zfs-auto-snapshot
+	install etc/zfs-auto-snapshot.cron.monthly  $(DESTDIR)/etc/cron.monthly/zfs-auto-snapshot
+	install -d $(DESTDIR)$(PREFIX)/share/man/man8
+	install src/zfs-auto-snapshot.8 $(DESTDIR)$(PREFIX)/share/man/man8/zfs-auto-snapshot.8
 	install -d $(DESTDIR)$(PREFIX)/sbin
 	install src/zfs-auto-snapshot.sh $(DESTDIR)$(PREFIX)/sbin/zfs-auto-snapshot

README

@@ -1,4 +1,21 @@
-An alternative implementation of the zfs-auto-snapshot service for Linux.
+zfs-auto-snapshot:
+
+An alternative implementation of the zfs-auto-snapshot service for Linux
+that is compatible with zfs-linux and zfs-fuse.
+
+Automatically create, rotate, and destroy periodic ZFS snapshots. This is
+the utility that creates the @zfs-auto-snap_frequent, @zfs-auto-snap_hourly,
+@zfs-auto-snap_daily, @zfs-auto-snap_weekly, and @zfs-auto-snap_monthly
+snapshots if it is installed.
 
 This program is a posixly correct bourne shell script.  It depends only on
 the zfs utilities and cron, and can run in the dash shell.
+
+
+Installation:
+-------------
+
+wget https://github.com/zfsonlinux/zfs-auto-snapshot/archive/master.zip
+unzip master.zip
+cd zfs-auto-snapshot-master
+make install

etc/zfs-auto-snapshot.cron

@@ -1,7 +0,0 @@
-PATH="/usr/bin:/bin:/usr/sbin:/sbin"
-
-*/15 * * * * root zfs-auto-snapshot -q -g --label=frequent --keep=4  //
-@hourly      root zfs-auto-snapshot -q -g --label=hourly   --keep=24 //
-@daily       root zfs-auto-snapshot -q -g --label=daily    --keep=31 //
-@weekly      root zfs-auto-snapshot -q -g --label=weekly   --keep=4  //
-@monthly     root zfs-auto-snapshot -q -g --label=monthly  --keep=12 //

etc/zfs-auto-snapshot.cron.daily

@@ -0,0 +1,5 @@
+#!/bin/sh
+
+# Only call zfs-auto-snapshot if it's available
+exec which zfs-auto-snapshot > /dev/null && \
+     zfs-auto-snapshot --quiet --syslog --label=daily --keep=31 //

etc/zfs-auto-snapshot.cron.frequent

@@ -0,0 +1,3 @@
+PATH="/usr/bin:/bin:/usr/local/sbin:/usr/sbin:/sbin"
+
+*/15 * * * * root which zfs-auto-snapshot > /dev/null && zfs-auto-snapshot --quiet --syslog --label=frequent --keep=4  //

etc/zfs-auto-snapshot.cron.hourly

@@ -0,0 +1,5 @@
+#!/bin/sh
+
+# Only call zfs-auto-snapshot if it's available
+exec which zfs-auto-snapshot > /dev/null && \
+     zfs-auto-snapshot --quiet --syslog --label=hourly --keep=24 //

etc/zfs-auto-snapshot.cron.monthly

@@ -0,0 +1,5 @@
+#!/bin/sh
+
+# Only call zfs-auto-snapshot if it's available
+exec which zfs-auto-snapshot > /dev/null && \
+     zfs-auto-snapshot --quiet --syslog --label=monthly --keep=12 //

etc/zfs-auto-snapshot.cron.weekly

@@ -0,0 +1,5 @@
+#!/bin/sh
+
+# Only call zfs-auto-snapshot if it's available
+exec which zfs-auto-snapshot > /dev/null && \
+     zfs-auto-snapshot --quiet --syslog --label=weekly --keep=8 //

src/zfs-auto-snapshot.8

@@ -0,0 +1,91 @@
+.TH ZFS-AUTO-SNAPSHOT "8" "June 16, 2013" "zfs-auto-snapshot.sh" "System Administration Commands"
+.SH NAME
+zfs-auto-snapshot \- take regular ZFS snapshots
+.SH SYNOPSIS
+.B zfs-auto-snapshot
+[\fIoptions\fR] [\fI-l label\fR] \fI<'//' | name \fR[\fIname\fR...]\fI>\fR
+.SH DESCRIPTION
+.B zfs-auto-snapshot
+automatically creates, rotates, and destroys snapshots for all your
+ZFS datasets, and is compatible with both zfsonlinux and zfs-fuse.
+.SH OPTIONS
+.TP
+\fB\-\-default\-exclude\fR
+By default \fBzfs-auto-snapshot\fR will snapshot all datasets except
+for those in which the user-property \fBcom.sun:auto-snapshot\fR is
+set to \fBfalse\fR.  This option reverses the behavior and requires
+\fBcom.sun:auto-snapshot\fR to be set to \fBtrue\fR.
+.TP
+\fB\-d\fR, \fB\-\-debug\fR
+Print debugging messages.
+.TP
+\fB\-e\fR, \fB\-\-event\fR=\fIEVENT\fR
+Set the com.sun:auto\-snapshot\-desc property to EVENT.
+.TP
+\fB\-\-fast\fR
+Use a faster zfs list invocation.
+.TP
+\fB\-n\fR, \fB\-\-dry\-run\fR
+Print actions without actually doing anything.
+.TP
+\fB\-s\fR, \fB\-\-skip\-scrub\fR
+Do not snapshot filesystems in scrubbing pools.
+.TP
+\fB\-h\fR, \fB\-\-help\fR
+Print the usage message.
+.TP
+\fB\-k\fR, \fB\-\-keep\fR=\fINUM\fR
+Keep NUM recent snapshots and destroy older snapshots.
+.TP
+\fB\-l\fR, \fB\-\-label\fR=\fILAB\fR
+LAB is usually 'hourly', 'daily', or 'monthly'.
+.TP
+\fB\-p\fR, \fB\-\-prefix\fR=\fIPRE\fR
+PRE is 'zfs\-auto\-snap' by default.
+.TP
+\fB\-q\fR, \fB\-\-quiet\fR
+Suppress warnings and notices at the console.
+.TP
+\fB\-\-send\-full\fR=\fIF\fR
+Send zfs full backup. Unimplemented.
+.TP
+\fB\-\-send\-incr\fR=\fIF\fR
+Send zfs incremental backup. Unimplemented.
+.TP
+\fB\-\-sep\fR=\fICHAR\fR
+Use CHAR to separate date stamps in snapshot names.
+.TP
+\fB\-g\fR, \fB\-\-syslog\fR
+Write messages into the system log.
+.TP
+\fB\-r\fR, \fB\-\-recursive\fR
+Snapshot named filesystem and all descendants.
+.TP
+\fB\-v\fR, \fB\-\-verbose\fR
+Print info messages.
+.TP
+\fB\-\-pre-snapshot\fR=\fICOMMAND\fR
+Command to run before each dataset is snapshotted. 
+It is passed the dataset and snapshot name. If it
+returns non-zero, snapshotting this dataset is 
+aborted.
+.TP
+\fB\-\-post-snapshot\fR=\fICOMMAND\fR
+Command to run after each dataset is snapshotted. 
+It is passed the dataset and snapshot name.
+.TP
+\fB\-\-destroy-only\fR
+Do not create new snapshots, but do destroy older 
+snapshots. Has no effect unless used with \fB\-k\fR.
+.IP
+A non-obvious use may be constructon of cron jobs or
+scripts that run pre-snapshot command(s), then run 
+zfs-auto-snapshot (without \fB\-k\fR) to quickly
+snapshot all datasets, then run post-snapshot
+command(s) and clean up with zfs-auto-snapshot
+\fB\-\-destroy-only\fR.
+.TP
+name
+Filesystem and volume names, or '//' for all ZFS datasets.
+.SH SEE ALSO
+.BR zfs (8)

src/zfs-auto-snapshot.sh

@@ -28,6 +28,8 @@ opt_backup_full=''
 opt_backup_incremental=''
 opt_default_exclude=''
 opt_dry_run=''
+opt_event='-'
+opt_fast_zfs_list=''
 opt_keep=''
 opt_label=''
 opt_prefix='zfs-auto-snap'
@@ -37,13 +39,26 @@ opt_setauto=''
 opt_syslog=''
 opt_skip_scrub=''
 opt_verbose=''
+opt_pre_snapshot=''
+opt_post_snapshot=''
+opt_do_snapshots=1
+
+# Global summary statistics.
+DESTRUCTION_COUNT='0'
+SNAPSHOT_COUNT='0'
+WARNING_COUNT='0'
+
+# Other global variables.
+SNAPSHOTS_OLD=''
 
 
 print_usage ()
 {
 	echo "Usage: $0 [options] [-l label] <'//' | name [name...]>
-  --default-exclude  Exclude objects if com.sun:auto-snapshot is unset.
+  --default-exclude  Exclude datasets if com.sun:auto-snapshot is unset.
   -d, --debug        Print debugging messages.
+  -e, --event=EVENT  Set the com.sun:auto-snapshot-desc property to EVENT.
+      --fast         Use a faster zfs list invocation.
   -n, --dry-run      Print actions without actually doing anything.
   -s, --skip-scrub   Do not snapshot filesystems in scrubbing pools.
   -h, --help         Print this usage message.
@@ -57,7 +72,8 @@ print_usage ()
   -g, --syslog       Write messages into the system log.
   -r, --recursive    Snapshot named filesystem and all descendants.
   -v, --verbose      Print info messages.
-      name           Filesystem and volume names, or '//' for all ZFS objects.
+      --destroy-only Only destroy older snapshots, do not create new ones.
+      name           Filesystem and volume names, or '//' for all ZFS datasets.
 " 
 }
 
@@ -108,7 +124,7 @@ print_log () # level, message, ...
 }
 
 
-do_run ()
+do_run () # [argv]
 {
 	if [ -n "$opt_dry_run" ]
 	then
@@ -117,7 +133,7 @@ do_run ()
 	else
 		eval $*
 		RC="$?"
-		if [ "$RC" -eq 0 ]
+		if [ "$RC" -eq '0' ]
 		then
 			print_log debug "$*"
 		else
@@ -127,40 +143,115 @@ do_run ()
 	return "$RC"
 }
 
+
+do_snapshots () # properties, flags, snapname, oldglob, [targets...]
+{
+	local PROPS="$1"
+	local FLAGS="$2"
+	local NAME="$3"
+	local GLOB="$4"
+	local TARGETS="$5"
+	local KEEP=''
+	local RUNSNAP=1
+
+	# global DESTRUCTION_COUNT
+	# global SNAPSHOT_COUNT
+	# global WARNING_COUNT
+	# global SNAPSHOTS_OLD
+
+	for ii in $TARGETS
+	do
+		if [ -n "$opt_do_snapshots" ]
+		then
+			if [ "$opt_pre_snapshot" != "" ]
+			then
+				do_run "$opt_pre_snapshot $ii $NAME" || RUNSNAP=0
+			fi
+			if [ $RUNSNAP -eq 1 ] && do_run "zfs snapshot $PROPS $FLAGS '$ii@$NAME'"
+			then
+				[ "$opt_post_snapshot" != "" ] && do_run "$opt_post_snapshot $ii $NAME"
+				SNAPSHOT_COUNT=$(( $SNAPSHOT_COUNT + 1 ))
+			else
+				WARNING_COUNT=$(( $WARNING_COUNT + 1 ))
+				continue
+			fi 
+		fi
+
+		# Retain at most $opt_keep number of old snapshots of this filesystem,
+		# including the one that was just recently created.
+		test -z "$opt_keep" && continue
+		KEEP="$opt_keep"
+
+		# ASSERT: The old snapshot list is sorted by increasing age.
+		for jj in $SNAPSHOTS_OLD
+		do
+			# Check whether this is an old snapshot of the filesystem.
+			if [ -z "${jj#$ii@$GLOB}" ]
+			then
+				KEEP=$(( $KEEP - 1 ))
+				if [ "$KEEP" -le '0' ]
+				then
+					if do_run "zfs destroy -d $FLAGS '$jj'" 
+					then
+						DESTRUCTION_COUNT=$(( $DESTRUCTION_COUNT + 1 ))
+					else
+						WARNING_COUNT=$(( $WARNING_COUNT + 1 ))
+					fi
+				fi
+			fi
+		done
+	done
+}
+
+
 # main ()
 # {
 
-DATE=$(date +%F-%H%M)
-
 GETOPT=$(getopt \
-  --longoptions=default-exclude,dry-run,skip-scrub,recursive \
-  --longoptions=keep:,label:,prefix:,sep: \
+  --longoptions=default-exclude,dry-run,fast,skip-scrub,recursive \
+  --longoptions=event:,keep:,label:,prefix:,sep: \
   --longoptions=debug,help,quiet,syslog,verbose \
-  --options=dnshl:k:rs:gv \
+  --longoptions=pre-snapshot:,post-snapshot:,destroy-only \
+  --options=dnshe:l:k:p:rs:qgv \
   -- "$@" ) \
-  || exit 1
+  || exit 128
 
 eval set -- "$GETOPT"
 
-while [ "$#" -gt 0 ]
+while [ "$#" -gt '0' ]
 do
 	case "$1" in
 		(-d|--debug)
-			opt_debug=1
+			opt_debug='1'
 			opt_quiet=''
-			opt_verbose=1
+			opt_verbose='1'
 			shift 1
 			;;
 		(--default-exclude)
 			opt_default_exclude='1'
 			shift 1
 			;;
+		(-e|--event)
+			if [ "${#2}" -gt '1024' ]
+			then
+				print_log error "The $1 parameter must be less than 1025 characters."
+				exit 139
+			elif [ "${#2}" -gt '0' ]
+			then
+				opt_event="$2"
+			fi
+			shift 2
+			;;
+		(--fast)
+			opt_fast_zfs_list='1'
+			shift 1
+			;;
 		(-n|--dry-run)
 			opt_dry_run='1'
 			shift 1
 			;;
 		(-s|--skip-scrub)
-			opt_skip_scrub=1
+			opt_skip_scrub='1'
 			shift 1
 			;;
 		(-h|--help)
@@ -168,10 +259,10 @@ do
 			exit 0
 			;;
 		(-k|--keep)
-			if ! test "$2" -gt 0 2>/dev/null
+			if ! test "$2" -gt '0' 2>/dev/null
 			then
 				print_log error "The $1 parameter must be a positive integer."
-				exit 2
+				exit 129
 			fi
 			opt_keep="$2"
 			shift 2
@@ -181,8 +272,19 @@ do
 			shift 2
 			;;
 		(-p|--prefix)
-			# @TODO: Parameter validation. See --sep below for the regex.
 			opt_prefix="$2"
+			while test "${#opt_prefix}" -gt '0'
+			do
+				case $opt_prefix in
+					([![:alnum:]_.:\ -]*)
+						print_log error "The $1 parameter must be alphanumeric."
+						exit 130
+						;;
+				esac
+				opt_prefix="${opt_prefix#?}"
+			done
+			opt_prefix="$2"
+			shift 2
 			;;
 		(-q|--quiet)
 			opt_debug=''
@@ -191,33 +293,45 @@ do
 			shift 1
 			;;
 		(-r|--recursive)
-			opt_recursive=1
+			opt_recursive='1'
 			shift 1
 			;;
 		(--sep)
 			case "$2" in 
-				([[:alnum:]_-.:\ ])
+				([[:alnum:]_.:\ -])
 					:
 					;;
 				('')
 					print_log error "The $1 parameter must be non-empty."
-					exit 3
+					exit 131
 					;;
 				(*)
 					print_log error "The $1 parameter must be one alphanumeric character."
-					exit 4
-				;;
+					exit 132
+					;;
 			esac
 			opt_sep="$2"
 			shift 2
 			;;
 		(-g|--syslog)
-			opt_syslog=1
+			opt_syslog='1'
 			shift 1
 			;;
 		(-v|--verbose)
 			opt_quiet=''
-			opt_verbose=1
+			opt_verbose='1'
+			shift 1
+			;;
+		(--pre-snapshot)
+			opt_pre_snapshot="$2"
+			shift 2
+			;;
+		(--post-snapshot)
+			opt_post_snapshot="$2"
+			shift 2
+			;;
+		(--destroy-only)
+			opt_do_snapshots=''
 			shift 1
 			;;
 		(--)
@@ -227,10 +341,10 @@ do
 	esac
 done
 
-if [ "$#" -eq 0 ]
+if [ "$#" -eq '0' ]
 then
 	print_log error "The filesystem argument list is empty."
-	exit 5
+	exit 133
 fi 
 
 # Count the number of times '//' appears on the command line.
@@ -240,10 +354,10 @@ do
 	test "$ii" = '//' && SLASHIES=$(( $SLASHIES + 1 ))
 done
 
-if [ "$#" -gt 1 -a "$SLASHIES" -gt 0 ]
+if [ "$#" -gt '1' -a "$SLASHIES" -gt '0' ]
 then
 	print_log error "The // must be the only argument if it is given."
-	exit 6
+	exit 134
 fi
 
 # These are the only times that `zpool status` or `zfs list` are invoked, so
@@ -251,15 +365,24 @@ fi
 # Solaris implementation.
 
 ZPOOL_STATUS=$(env LC_ALL=C zpool status 2>&1 ) \
-  || { print_log error "zpool status $?: $ZPOOL_STATUS"; exit 7; }
+  || { print_log error "zpool status $?: $ZPOOL_STATUS"; exit 135; }
 
 ZFS_LIST=$(env LC_ALL=C zfs list -H -t filesystem,volume -s name \
   -o name,com.sun:auto-snapshot,com.sun:auto-snapshot:"$opt_label") \
-  || { print_log error "zfs list $?: $ZFS_LIST"; exit 8; }
-
-SNAPSHOTS_OLD=$(env LC_ALL=C zfs list -H -t snapshot -S creation -o name) \
-  || { print_log error "zfs list $?: $SNAPSHOTS_OLD"; exit 9; }
+  || { print_log error "zfs list $?: $ZFS_LIST"; exit 136; }
 
+if [ -n "$opt_fast_zfs_list" ]
+then
+	SNAPSHOTS_OLD=$(env LC_ALL=C zfs list -H -t snapshot -o name -s name | \
+		grep $opt_prefix | \
+		awk '{ print substr( $0, length($0) - 14, length($0) ) " " $0}' | \
+		sort -r -k1,1 -k2,2 | \
+		awk '{ print substr( $0, 17, length($0) )}') \
+	  || { print_log error "zfs list $?: $SNAPSHOTS_OLD"; exit 137; }
+else
+	SNAPSHOTS_OLD=$(env LC_ALL=C zfs list -H -t snapshot -S creation -o name) \
+	  || { print_log error "zfs list $?: $SNAPSHOTS_OLD"; exit 137; }
+fi
 
 # Verify that each argument is a filesystem or volume.
 for ii in "$@"
@@ -272,30 +395,30 @@ do
 	$ZFS_LIST
 	HERE
 	print_log error "$ii is not a ZFS filesystem or volume."
-	exit 10
+	exit 138
 done
 
 # Get a list of pools that are being scrubbed.
-ZPOOLS_SCRUBBING=$(echo "$ZFS_STATUS" | awk -F ': ' \
+ZPOOLS_SCRUBBING=$(echo "$ZPOOL_STATUS" | awk -F ': ' \
   '$1 ~ /^ *pool$/ { pool = $2 } ; \
    $1 ~ /^ *scan$/ && $2 ~ /scrub in progress/ { print pool }' \
   | sort ) 
 
 # Get a list of pools that cannot do a snapshot.
-ZPOOLS_NOTREADY=$(echo "$ZFS_STATUS" | awk -F ': ' \
+ZPOOLS_NOTREADY=$(echo "$ZPOOL_STATUS" | awk -F ': ' \
   '$1 ~ /^ *pool$/ { pool = $2 } ; \
    $1 ~ /^ *state$/ && $2 !~ /ONLINE|DEGRADED/ { print pool } ' \
   | sort)
 
-# Get a list of objects for which snapshots are explicitly disabled.
+# Get a list of datasets for which snapshots are explicitly disabled.
 NOAUTO=$(echo "$ZFS_LIST" | awk -F '\t' \
   'tolower($2) ~ /false/ || tolower($3) ~ /false/ {print $1}')
 
-# If the --default-exclude flag is set, then exclude all objects that lack
+# If the --default-exclude flag is set, then exclude all datasets that lack
 # an explicit com.sun:auto-snapshot* property. Otherwise, include them.
 if [ -n "$opt_default_exclude" ]
 then
-	# Get a list of objects for which snapshots are explicitly enabled.
+	# Get a list of datasets for which snapshots are explicitly enabled.
 	CANDIDATES=$(echo "$ZFS_LIST" | awk -F '\t' \
 	  'tolower($2) ~ /true/ || tolower($3) ~ /true/ {print $1}')
 else
@@ -304,20 +427,20 @@ else
 	  'tolower($2) !~ /false/ && tolower($3) !~ /false/ {print $1}')
 fi
 
-# Initialize the list of objects that will get a recursive snapshot.
+# Initialize the list of datasets that will get a recursive snapshot.
 TARGETS_RECURSIVE=''
 
-# Initialize the list of objects that will get a non-recursive snapshot.
+# Initialize the list of datasets that will get a non-recursive snapshot.
 TARGETS_REGULAR=''
 
 for ii in $CANDIDATES
 do
-	# Qualify object names so variable globbing works properly.
+	# Qualify dataset names so variable globbing works properly.
 	# Suppose ii=tanker/foo and jj=tank sometime during the loop.
 	# Just testing "$ii" != ${ii#$jj} would incorrectly match.
 	iii="$ii/"
 
-	# Exclude objects that are not named on the command line.
+	# Exclude datasets that are not named on the command line.
 	IN_ARGS='0'
 	for jj in "$@"
 	do
@@ -331,13 +454,13 @@ do
 		continue
 	fi
 
-	# Exclude objects in pools that cannot do a snapshot.
+	# Exclude datasets in pools that cannot do a snapshot.
 	for jj in $ZPOOLS_NOTREADY
 	do
 		# Ibid regarding iii.
 		jjj="$jj/"
 
-		# Check whether the pool name is a prefix of the object name.
+		# Check whether the pool name is a prefix of the dataset name.
 		if [ "$iii" != "${iii#$jjj}" ]
 		then
 			print_log info "Excluding $ii because pool $jj is not ready."
@@ -345,13 +468,13 @@ do
 		fi
 	done
 
-	# Exclude objects in scrubbing pools if the --skip-scrub flag is set.
-	test -z "$opt_skip_scrub" && for jj in $ZPOOLS_SCRUBBING
+	# Exclude datasets in scrubbing pools if the --skip-scrub flag is set.
+	test -n "$opt_skip_scrub" && for jj in $ZPOOLS_SCRUBBING
 	do
 		# Ibid regarding iii.
 		jjj="$jj/"
 
-		# Check whether the pool name is a prefix of the object name.
+		# Check whether the pool name is a prefix of the dataset name.
 		if [ "$iii" != "${iii#$jjj}" ]
 		then
 			print_log info "Excluding $ii because pool $jj is scrubbing."
@@ -364,17 +487,17 @@ do
 		# Ibid regarding iii.
 		jjj="$jj/"
 
-		# The --recusive switch only matters for non-wild arguments.
+		# The --recursive switch only matters for non-wild arguments.
 		if [ -z "$opt_recursive" -a "$1" != '//' ]
 		then
-			# Snapshot this object non-recursively.
+			# Snapshot this dataset non-recursively.
 			print_log debug "Including $ii for regular snapshot."
 			TARGETS_REGULAR="${TARGETS_REGULAR:+$TARGETS_REGULAR	}$ii" # nb: \t
 			continue 2
-		# Check whether the candidate name is a prefix of any excluded object name.
+		# Check whether the candidate name is a prefix of any excluded dataset name.
 		elif [ "$jjj" != "${jjj#$iii}" ]
 		then
-			# Snapshot this object non-recursively.
+			# Snapshot this dataset non-recursively.
 			print_log debug "Including $ii for regular snapshot."
 			TARGETS_REGULAR="${TARGETS_REGULAR:+$TARGETS_REGULAR	}$ii" # nb: \t
 			continue 2
@@ -386,7 +509,7 @@ do
 		# Ibid regarding iii.
 		jjj="$jj/"
 
-		# Check whether any included object is a prefix of the candidate name.
+		# Check whether any included dataset is a prefix of the candidate name.
 		if [ "$iii" != "${iii#$jjj}" ]
 		then
 			print_log debug "Excluding $ii because $jj includes it recursively."
@@ -405,107 +528,53 @@ do
 	TARGETS_RECURSIVE="${TARGETS_RECURSIVE:+$TARGETS_RECURSIVE	}$ii" # nb: \t
 done
 
-# Summary statistics.
-DESTRUCTION_COUNT='0'
-SNAPSHOT_COUNT='0'
-WARNING_COUNT='0'
+# Linux lacks SMF and the notion of an FMRI event, but always set this property
+# because the SUNW program does. The dash character is the default.
+SNAPPROP="-o com.sun:auto-snapshot-desc='$opt_event'"
 
-# Linux lacks SMF and the notion of an FMRI event.
-FMRI_EVENT='-'
+# ISO style date; fifteen characters: YYYY-MM-DD-HHMM
+# On Solaris %H%M expands to 12h34.
+DATE=$(date --utc +%F-%H%M)
 
-# Create the snapshot using these arguments.
-SNAPSHOT_PROPERTIES="-o com.sun:auto-snapshot-desc='$FMRI_EVENT'"
-SNAPSHOT_NAME="$opt_prefix${opt_label:+$opt_sep$opt_label-$DATE}"
+# The snapshot name after the @ symbol.
+SNAPNAME="$opt_prefix${opt_label:+$opt_sep$opt_label}-$DATE"
 
-# The expression for old snapshots.                 -YYYY-MM-DD-HHMM
-SNAPSHOT_MATCH="$opt_prefix${opt_label:+?$opt_label}????????????????"
+# The expression for matching old snapshots.  -YYYY-MM-DD-HHMM
+SNAPGLOB="$opt_prefix${opt_label:+?$opt_label}????????????????"
 
-test -n "$TARGETS_REGULAR" \
-  && print_log info "Doing regular snapshots of $TARGETS_REGULAR"
+if [ -n "$opt_do_snapshots" ]
+then
+	test -n "$TARGETS_REGULAR" \
+	  && print_log info "Doing regular snapshots of $TARGETS_REGULAR"
 
-test -n "$TARGETS_RECURSIVE" \
-  && print_log info "Doing recursive snapshots of $TARGETS_RECURSIVE"
+	test -n "$TARGETS_RECURSIVE" \
+	  && print_log info "Doing recursive snapshots of $TARGETS_RECURSIVE"
+
+	if test -n "$opt_keep" && [ "$opt_keep" -ge "1" ]
+	then
+		print_log info "Destroying all but the newest $opt_keep snapshots of each dataset."
+	fi
+elif test -n "$opt_keep" && [ "$opt_keep" -ge "1" ]
+then
+	test -n "$TARGETS_REGULAR" \
+	  && print_log info "Destroying all but the newest $opt_keep snapshots of $TARGETS_REGULAR"
+
+	test -n "$TARGETS_RECURSIVE" \
+	  && print_log info "Recursively destroying all but the newest $opt_keep snapshots of $TARGETS_RECURSIVE"
+else
+	print_log notice "Only destroying snapshots, but count of snapshots to preserve not given. Nothing to do."
+fi
 
 test -n "$opt_dry_run" \
   && print_log info "Doing a dry run. Not running these commands..."
 
+do_snapshots "$SNAPPROP" ""   "$SNAPNAME" "$SNAPGLOB" "$TARGETS_REGULAR"
+do_snapshots "$SNAPPROP" "-r" "$SNAPNAME" "$SNAPGLOB" "$TARGETS_RECURSIVE"
 
-for ii in $TARGETS_REGULAR
-do
-	if do_run "zfs snapshot $SNAPSHOT_PROPERTIES '$ii@$SNAPSHOT_NAME'"
-	then
-		SNAPSHOT_COUNT=$(( $SNAPSHOT_COUNT +1 ))
-	else
-		WARNING_COUNT=$(( $WARNING_COUNT +1 ))
-		continue
-	fi
-
-	# Retain at most $opt_keep number of old snapshots of this filesystem,
-	# including the one that was just recently created.
-	if [ -z "$opt_keep" ]
-	then
-		continue
-	fi
-	KEEP="$opt_keep"
-
-	for jj in $SNAPSHOTS_OLD
-	do
-		# Check whether this is an old snapshot of the filesystem.
-		if [ -z "${jj#$ii@$SNAPSHOT_MATCH}" ]
-		then
-			KEEP=$(( $KEEP - 1 ))
-			if [ "$KEEP" -le 0 ]
-			then
-				if do_run "zfs destroy '$jj'"
-				then
-					DESTRUCTION_COUNT=$(( $DESTRUCTION_COUNT +1 ))
-				else
-					WARNING_COUNT=$(( $WARNING_COUNT + 1 ))
-				fi
-			fi
-		fi
-	done
-done
-
-for ii in $TARGETS_RECURSIVE
-do
-	if do_run "zfs snapshot $SNAPSHOT_PROPERTIES -r '$ii@$SNAPSHOT_NAME'" 
-	then
-		SNAPSHOT_COUNT=$(( $SNAPSHOT_COUNT +1 ))
-	else
-		WARNING_COUNT=$(( $WARNING_COUNT +1 ))
-		continue
-	fi 
-
-	# Retain at most $opt_keep number of old snapshots of this filesystem,
-	# including the one that was just recently created.
-	if [ -z "$opt_keep" ]
-	then
-		continue
-	fi
-	KEEP="$opt_keep"
-
-	# ASSERT: The old snapshot list is sorted by increasing age.
-	for jj in $SNAPSHOTS_OLD
-	do
-		# Check whether this is an old snapshot of the filesystem.
-		if [ -z "${jj#$ii@$SNAPSHOT_MATCH}" ]
-		then
-			KEEP=$(( $KEEP - 1 ))
-			if [ "$KEEP" -le 0 ]
-			then
-				if do_run "zfs destroy -r '$jj'" 
-				then
-					DESTRUCTION_COUNT=$(( $DESTRUCTION_COUNT +1 ))
-				else
-					WARNING_COUNT=$(( $WARNING_COUNT + 1 ))
-				fi
-			fi
-		fi
-	done
-done
-
-print_log notice "@$SNAPSHOT_NAME, \
-$SNAPSHOT_COUNT created, $DESTRUCTION_COUNT destroyed, $WARNING_COUNT warnings."
+print_log notice "@$SNAPNAME," \
+  "$SNAPSHOT_COUNT created," \
+  "$DESTRUCTION_COUNT destroyed," \
+  "$WARNING_COUNT warnings."
 
+exit 0
 # }