add tool to take bounded, tagged zfs snapshots

zfssnap.sh

@@ -0,0 +1,83 @@
+#! /bin/sh
+
+tstamp=`date +%Y%m%d-%H%M%S`
+label_pfx="zbk-"
+usrlabel=$1
+maxnum=$2
+zpool="zroot"
+
+# names of the DATASETs to exclude (datasets, not mountpoints!)
+excludes="/usr/ports /usr/src /backups"
+
+usage () {
+    echo Usage:
+    echo "zfssnap [label [maxnum]]"
+    echo "default label: 'default'"
+    echo "default maxnum: infinite"
+    echo "Takes a ZFS snapshot with given custom label."
+    echo "If maxnum specified, keeps the so-many newest snaps only."
+    echo
+    echo "Optional envvars:"
+    echo "EXCLUDES  list of dataset paths to exclude from snaps. Overrides default."
+    echo "EXTRA_EXCLUDES  list of dataset paths to exclude from snaps. Extends default."
+    echo "default excluded DATASET paths:"
+    echo $excludes
+}
+
+# build list of dataset paths to exclude
+if [ "x$EXCLUDES" != x ]
+then
+    excludes=$EXCLUDES
+elif [ "x$EXTRA_EXCLUDES" != x ]
+then
+    excludes="$excludes $EXTRA_EXCLUDES"
+fi
+
+# label
+if [ "x$usrlabel" != "x" ]
+then
+    if echo "$usrlabel" | grep -qiE '^([a-z0-9]{1,10})$'
+    then
+        label_pfx="$label_pfx$usrlabel"
+    else
+        echo "Invalid label '$usrlabel'! Quitting."
+        usage
+        exit 1
+    fi
+else
+    label_pfx="${label_pfx}default"
+fi
+
+# maxnum
+if [ "x$maxnum" != "x" ]
+then
+    if ! echo "$maxnum" | grep -qE '^[0-9]+$'
+    then
+        echo "Invalid maxnum '$maxnum'! Terminating."
+        usage
+        exit 1
+    fi
+fi
+
+
+# add timestamp to label
+label="${label_pfx}-$tstamp"
+
+# take recursive snap
+zfs snapshot -r $zpool@$label || exit $?
+# exclude folders
+for xm in $excludes
+do
+    # let this fail, the ds might not exist
+    zfs destroy -r $zpool$xm@$label
+done
+
+# prune dbs if requested
+if [ "x$maxnum" != x ]
+then
+    ls /.zfs/snapshot/ | sort -rt- -k 3,4 | awk -v maxnum=$maxnum -v matchlabel=$label_pfx 'BEGIN {x=0} $0 ~ "^"matchlabel { x++; if (x>maxnum) print}' | while read snapname
+    do
+        zfs destroy -r $zpool@$snapname || exit $?
+    done
+fi
+