Merge pull request #109 from mergwyn/master

Correct incorrect sh syntax

CHANGELOG

@@ -0,0 +1,9 @@
+[ 1.2.5 (Unreleased) ]
+
+ * Start a changelog
+ * Accept PR#94 from aimileus/macos
+   - Replace --utc longform option with -u for macos compatibility
+ * Accept PR#107 from ArakniD/master
+   - Add optional label for snap removals
+
+ -- Jonathan Carter 2019-09-25, 15:24 SAST

Makefile

@@ -1,7 +1,28 @@
+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 -m 0644 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
+
+uninstall:
+	rm $(DESTDIR)/etc/cron.d/zfs-auto-snapshot
+	rm $(DESTDIR)/etc/cron.hourly/zfs-auto-snapshot
+	rm $(DESTDIR)/etc/cron.daily/zfs-auto-snapshot
+	rm $(DESTDIR)/etc/cron.weekly/zfs-auto-snapshot
+	rm $(DESTDIR)/etc/cron.monthly/zfs-auto-snapshot
+	rm $(DESTDIR)$(PREFIX)/share/man/man8/zfs-auto-snapshot.8
+	rm $(DESTDIR)$(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/upstream/1.2.4.tar.gz
+tar -xzf 1.2.4.tar.gz
+cd zfs-auto-snapshot-upstream-1.2.4
+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 +1,6 @@
+#!/bin/sh
+
+# Only call zfs-auto-snapshot if it's available
+which zfs-auto-snapshot > /dev/null || exit 0
+
+exec 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 || exit 0 ; zfs-auto-snapshot --quiet --syslog --label=frequent --keep=4 //

etc/zfs-auto-snapshot.cron.hourly

@@ -0,0 +1,6 @@
+#!/bin/sh
+
+# Only call zfs-auto-snapshot if it's available
+which zfs-auto-snapshot > /dev/null || exit 0
+
+exec zfs-auto-snapshot --quiet --syslog --label=hourly --keep=24 //

etc/zfs-auto-snapshot.cron.monthly

@@ -0,0 +1,6 @@
+#!/bin/sh
+
+# Only call zfs-auto-snapshot if it's available
+which zfs-auto-snapshot > /dev/null || exit 0
+
+exec zfs-auto-snapshot --quiet --syslog --label=monthly --keep=12 //

etc/zfs-auto-snapshot.cron.weekly

@@ -0,0 +1,6 @@
+#!/bin/sh
+
+# Only call zfs-auto-snapshot if it's available
+which zfs-auto-snapshot > /dev/null || exit 0
+
+exec 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 construction 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

@@ -29,6 +29,7 @@ opt_backup_incremental=''
 opt_default_exclude=''
 opt_dry_run=''
 opt_event='-'
+opt_fast_zfs_list=''
 opt_keep=''
 opt_label=''
 opt_prefix='zfs-auto-snap'
@@ -38,6 +39,10 @@ opt_setauto=''
 opt_syslog=''
 opt_skip_scrub=''
 opt_verbose=''
+opt_pre_snapshot=''
+opt_post_snapshot=''
+opt_do_snapshots=1
+opt_min_size=0
 
 # Global summary statistics.
 DESTRUCTION_COUNT='0'
@@ -51,9 +56,10 @@ 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.
@@ -67,7 +73,8 @@ 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.
 " 
 }
 
@@ -104,7 +111,7 @@ print_log () # level, message, ...
 			;;
 		(inf*)
 			# test -n "$opt_syslog" && logger -t "$opt_prefix" -p daemon.info $*
-			test -n "$opt_verbose" && echo $*
+			test -z "$opt_quiet" && test -n "$opt_verbose" && echo $*
 			;;
 		(deb*)
 			# test -n "$opt_syslog" && logger -t "$opt_prefix" -p daemon.debug $*
@@ -146,6 +153,7 @@ do_snapshots () # properties, flags, snapname, oldglob, [targets...]
 	local GLOB="$4"
 	local TARGETS="$5"
 	local KEEP=''
+	local RUNSNAP=1
 
 	# global DESTRUCTION_COUNT
 	# global SNAPSHOT_COUNT
@@ -154,13 +162,37 @@ do_snapshots () # properties, flags, snapname, oldglob, [targets...]
 
 	for ii in $TARGETS
 	do
-		if do_run "zfs snapshot $PROPS $FLAGS '$ii@$NAME'" 
+                # Check if size check is > 0
+                size_check_skip=0
+                if [ "$opt_min_size" -gt 0 ]
+                then
+                        bytes_written=`zfs get -Hp -o value written $ii`
+                        kb_written=$(( $bytes_written / 1024 ))
+                        if [ "$kb_written" -lt "$opt_min_size" ]
+                        then
+                                size_check_skip=1
+                                if [ $opt_verbose -gt 0 ]
+                                then
+                                        echo "Skipping target $ii, only $kb_written kB written since last snap. opt_min_size is $opt_min_size"
+                                fi
+                        fi
+                fi
+
+                if [ -n "$opt_do_snapshots" -a "$size_check_skip" -eq 0 ]
 		then
-			SNAPSHOT_COUNT=$(( $SNAPSHOT_COUNT + 1 ))
-		else
-			WARNING_COUNT=$(( $WARNING_COUNT + 1 ))
-			continue
-		fi 
+			if [ "$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 $opt_keep number of old snapshots of this filesystem,
 		# including the one that was just recently created.
@@ -176,7 +208,7 @@ do_snapshots () # properties, flags, snapname, oldglob, [targets...]
 				KEEP=$(( $KEEP - 1 ))
 				if [ "$KEEP" -le '0' ]
 				then
-					if do_run "zfs destroy $FLAGS '$jj'" 
+					if do_run "zfs destroy -d $FLAGS '$jj'"
 					then
 						DESTRUCTION_COUNT=$(( $DESTRUCTION_COUNT + 1 ))
 					else
@@ -192,11 +224,19 @@ do_snapshots () # properties, flags, snapname, oldglob, [targets...]
 # main ()
 # {
 
-GETOPT=$(getopt \
-  --longoptions=default-exclude,dry-run,skip-scrub,recursive \
+if [ "$(uname)" = "Darwin" ]; then
+  GETOPT_BIN="$(brew --prefix gnu-getopt 2> /dev/null || echo /usr/local)/bin/getopt"
+else
+  GETOPT_BIN="getopt"
+fi
+
+GETOPT=$($GETOPT_BIN \
+  --longoptions=default-exclude,dry-run,fast,skip-scrub,recursive \
   --longoptions=event:,keep:,label:,prefix:,sep: \
   --longoptions=debug,help,quiet,syslog,verbose \
-  --options=dnshe:l:k:p:rs:qgv \
+  --longoptions=pre-snapshot:,post-snapshot:,destroy-only \
+  --longoptions=min-size: \
+  --options=dnshe:l:k:p:rs:qgvm: \
   -- "$@" ) \
   || exit 128
 
@@ -226,6 +266,10 @@ do
 			fi
 			shift 2
 			;;
+		(--fast)
+			opt_fast_zfs_list='1'
+			shift 1
+			;;
 		(-n|--dry-run)
 			opt_dry_run='1'
 			shift 1
@@ -251,12 +295,16 @@ do
 			opt_label="$2"
 			shift 2
 			;;
+		(-m|--min-size)
+			opt_min_size="$2"
+			shift 2
+			;;
 		(-p|--prefix)
 			opt_prefix="$2"
 			while test "${#opt_prefix}" -gt '0'
 			do
 				case $opt_prefix in
-					([![:alnum:]_-.:\ ]*)
+					([![:alnum:]_.:\ -]*)
 						print_log error "The $1 parameter must be alphanumeric."
 						exit 130
 						;;
@@ -277,8 +325,8 @@ do
 			shift 1
 			;;
 		(--sep)
-			case "$2" in 
-				([[:alnum:]_-.:\ ])
+			case "$2" in
+				([[:alnum:]_.:\ -])
 					:
 					;;
 				('')
@@ -302,6 +350,18 @@ do
 			opt_verbose='1'
 			shift 1
 			;;
+		(--pre-snapshot)
+			opt_pre_snapshot="$2"
+			shift 2
+			;;
+		(--post-snapshot)
+			opt_post_snapshot="$2"
+			shift 2
+			;;
+		(--destroy-only)
+			opt_do_snapshots=''
+			shift 1
+			;;
 		(--)
 			shift 1
 			break
@@ -313,7 +373,7 @@ if [ "$#" -eq '0' ]
 then
 	print_log error "The filesystem argument list is empty."
 	exit 133
-fi 
+fi
 
 # Count the number of times '//' appears on the command line.
 SLASHIES='0'
@@ -335,13 +395,35 @@ fi
 ZPOOL_STATUS=$(env LC_ALL=C zpool status 2>&1 ) \
   || { 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 136; }
 
-SNAPSHOTS_OLD=$(env LC_ALL=C zfs list -H -t snapshot -S creation -o name) \
-  || { print_log error "zfs list $?: $SNAPSHOTS_OLD"; exit 137; }
-
+if [ -n "$opt_fast_zfs_list" ]
+then
+	# Check if a snapshot label is being used, in which case restrict the old
+	# snapshot removal to only snapshots with the same label format
+	if [ -n "$opt_label" ]
+	then
+		SNAPSHOTS_OLD=$(env LC_ALL=C zfs list -H -t snapshot -o name -s name | \
+			grep "$opt_prefix"_"$opt_label" | \
+			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 -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 $?: $SNAPSHOTS_OLD"; exit 137; }
+	fi
+else
+        SNAPSHOTS_OLD=$(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 "$@"
@@ -358,26 +440,26 @@ do
 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
@@ -386,24 +468,33 @@ 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 or
+	# * those whose prefix is not on the command line (if --recursive flag is set)
 	IN_ARGS='0'
 	for jj in "$@"
 	do
+		# Ibid regarding iii.
+		jjj="$jj/"
+
 		if [ "$jj" = '//' -o "$jj" = "$ii" ]
+		then
+			IN_ARGS=$(( $IN_ARGS + 1 ))
+		elif [ -n "$opt_recursive" -a "$iii" != "${iii#$jjj}" ]
 		then
 			IN_ARGS=$(( $IN_ARGS + 1 ))
 		fi
@@ -413,13 +504,13 @@ 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."
@@ -427,13 +518,13 @@ do
 		fi
 	done
 
-	# Exclude objects in scrubbing pools if the --skip-scrub flag is set.
+	# 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 $jj is scrubbing."
@@ -446,17 +537,17 @@ do
 		# Ibid regarding iii.
 		jjj="$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
@@ -468,7 +559,7 @@ 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 $jj includes it recursively."
@@ -493,19 +584,37 @@ SNAPPROP="-o com.sun:auto-snapshot-desc='$opt_event'"
 
 # ISO style date; fifteen characters: YYYY-MM-DD-HHMM
 # On Solaris %H%M expands to 12h34.
-DATE=$(date +%F-%H%M)
+# We use the shortfirm -u here because --utc is not supported on macos.
+DATE=$(date -u +%F-%H%M)
 
 # The snapshot name after the @ symbol.
-SNAPNAME="$opt_prefix${opt_label:+$opt_sep$opt_label-$DATE}"
+SNAPNAME="${opt_prefix:+$opt_prefix$opt_sep}${opt_label:+$opt_label}-$DATE"
 
 # The expression for matching old snapshots.  -YYYY-MM-DD-HHMM
-SNAPGLOB="$opt_prefix${opt_label:+?$opt_label}????????????????"
+SNAPGLOB="${opt_prefix:+$opt_prefix$opt_sep}${opt_label:+$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..."