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

zfs destroy will use -d for deferred destruction

Makefile

@@ -1,16 +1,18 @@
+PREFIX := /usr/local
+
 all:
 
 install:
-	install -d $(DESTDIR)$(PREFIX)/etc/cron.d
+	install -d $(DESTDIR)/etc/cron.d
-	install -d $(DESTDIR)$(PREFIX)/etc/cron.daily
+	install -d $(DESTDIR)/etc/cron.daily
-	install -d $(DESTDIR)$(PREFIX)/etc/cron.hourly
+	install -d $(DESTDIR)/etc/cron.hourly
-	install -d $(DESTDIR)$(PREFIX)/etc/cron.weekly
+	install -d $(DESTDIR)/etc/cron.weekly
-	install -d $(DESTDIR)$(PREFIX)/etc/cron.monthly
+	install -d $(DESTDIR)/etc/cron.monthly
-	install etc/zfs-auto-snapshot.cron.frequent $(DESTDIR)$(PREFIX)/etc/cron.d/zfs-auto-snapshot
+	install -m 0644 etc/zfs-auto-snapshot.cron.frequent $(DESTDIR)/etc/cron.d/zfs-auto-snapshot
-	install etc/zfs-auto-snapshot.cron.hourly   $(DESTDIR)$(PREFIX)/etc/cron.hourly/zfs-auto-snapshot
+	install etc/zfs-auto-snapshot.cron.hourly   $(DESTDIR)/etc/cron.hourly/zfs-auto-snapshot
-	install etc/zfs-auto-snapshot.cron.daily    $(DESTDIR)$(PREFIX)/etc/cron.daily/zfs-auto-snapshot
+	install etc/zfs-auto-snapshot.cron.daily    $(DESTDIR)/etc/cron.daily/zfs-auto-snapshot
-	install etc/zfs-auto-snapshot.cron.weekly   $(DESTDIR)$(PREFIX)/etc/cron.weekly/zfs-auto-snapshot
+	install etc/zfs-auto-snapshot.cron.weekly   $(DESTDIR)/etc/cron.weekly/zfs-auto-snapshot
-	install etc/zfs-auto-snapshot.cron.monthly  $(DESTDIR)$(PREFIX)/etc/cron.monthly/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

README

@@ -10,3 +10,12 @@ 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.daily

@@ -1,2 +1,5 @@
 #!/bin/sh
-exec zfs-auto-snapshot --quiet --syslog --label=daily --keep=31 //
+
+# 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

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

etc/zfs-auto-snapshot.cron.hourly

@@ -1,2 +1,5 @@
 #!/bin/sh
-exec zfs-auto-snapshot --quiet --syslog --label=hourly --keep=24 //
+
+# 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

@@ -1,2 +1,5 @@
 #!/bin/sh
-exec zfs-auto-snapshot --quiet --syslog --label=monthly --keep=12 //
+
+# 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

@@ -1,2 +1,5 @@
 #!/bin/sh
-exec zfs-auto-snapshot --quiet --syslog --label=weekly --keep=8 //
+
+# 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

@@ -64,6 +64,27 @@ Snapshot named filesystem and all descendants.
 \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

src/zfs-auto-snapshot.sh

@@ -39,6 +39,9 @@ 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'
@@ -69,6 +72,7 @@ print_usage ()
   -g, --syslog       Write messages into the system log.
   -r, --recursive    Snapshot named filesystem and all descendants.
   -v, --verbose      Print info messages.
+      --destroy-only Only destroy older snapshots, do not create new ones.
       name           Filesystem and volume names, or '//' for all ZFS datasets.
 " 
 }
@@ -148,6 +152,7 @@ do_snapshots () # properties, flags, snapname, oldglob, [targets...]
 	local GLOB="$4"
 	local TARGETS="$5"
 	local KEEP=''
+	local RUNSNAP=1
 
 	# global DESTRUCTION_COUNT
 	# global SNAPSHOT_COUNT
@@ -156,12 +161,20 @@ do_snapshots () # properties, flags, snapname, oldglob, [targets...]
 
 	for ii in $TARGETS
 	do
-		if do_run "zfs snapshot $PROPS $FLAGS '$ii@$NAME'" 
+		if [ -n "$opt_do_snapshots" ]
 		then
-			SNAPSHOT_COUNT=$(( $SNAPSHOT_COUNT + 1 ))
+			if [ "$opt_pre_snapshot" != "" ]
-		else
+			then
-			WARNING_COUNT=$(( $WARNING_COUNT + 1 ))
+				do_run "$opt_pre_snapshot $ii $NAME" || RUNSNAP=0
-			continue
+			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 $opt_keep number of old snapshots of this filesystem,
@@ -178,7 +191,7 @@ do_snapshots () # properties, flags, snapname, oldglob, [targets...]
 				KEEP=$(( $KEEP - 1 ))
 				if [ "$KEEP" -le '0' ]
 				then
-					if do_run "zfs destroy $FLAGS '$jj'" 
+					if do_run "zfs destroy -d $FLAGS '$jj'" 
 					then
 						DESTRUCTION_COUNT=$(( $DESTRUCTION_COUNT + 1 ))
 					else
@@ -198,6 +211,7 @@ GETOPT=$(getopt \
   --longoptions=default-exclude,dry-run,fast,skip-scrub,recursive \
   --longoptions=event:,keep:,label:,prefix:,sep: \
   --longoptions=debug,help,quiet,syslog,verbose \
+  --longoptions=pre-snapshot:,post-snapshot:,destroy-only \
   --options=dnshe:l:k:p:rs:qgv \
   -- "$@" ) \
   || exit 128
@@ -308,6 +322,18 @@ do
 			opt_verbose='1'
 			shift 1
 			;;
+		(--pre-snapshot)
+			opt_pre_snapshot="$2"
+			shift 2
+			;;
+		(--post-snapshot)
+			opt_post_snapshot="$2"
+			shift 2
+			;;
+		(--destroy-only)
+			opt_do_snapshots=''
+			shift 1
+			;;
 		(--)
 			shift 1
 			break
@@ -347,7 +373,11 @@ ZFS_LIST=$(env LC_ALL=C zfs list -H -t filesystem,volume -s name \
 
 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($0) )}') \
+	SNAPSHOTS_OLD=$(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) \
@@ -512,11 +542,28 @@ SNAPNAME="$opt_prefix${opt_label:+$opt_sep$opt_label}-$DATE"
 # The expression for matching old snapshots.  -YYYY-MM-DD-HHMM
 SNAPGLOB="$opt_prefix${opt_label:+?$opt_label}????????????????"
 
-test -n "$TARGETS_REGULAR" \
+if [ -n "$opt_do_snapshots" ]
-  && print_log info "Doing regular snapshots of $TARGETS_REGULAR"
+then
+	test -n "$TARGETS_REGULAR" \
+	  && print_log info "Doing regular snapshots of $TARGETS_REGULAR"
 
-test -n "$TARGETS_RECURSIVE" \
+	test -n "$TARGETS_RECURSIVE" \
-  && print_log info "Doing recursive snapshots of $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..."