added take_snapshot.sh

take_snapshot.sh

@@ -0,0 +1,54 @@
+#!/bin/bash
+
+# this will take read-only btrfs snapshots and make it available in /srv/snapshots
+
+# variables
+SUBVOLUMES="/"
+DESTINATION_ROOT=/srv/snapshots
+TIMESTAMP=$(date +%Y%m%d%H%M) #add %S if you want sub-minute snapshots
+PREFIX="snapshot-"
+NAME="$PREFIX$TIMESTAMP"
+MAX_SNAPSHOTS=28 #how many snapshots should be kept?
+
+# preflight checks
+if [ $(whoami) != "root" ]; then
+    echo "error: you need to be root"
+    exit 1
+fi
+
+# take the snapshots
+for SUBVOLUME in $SUBVOLUMES; do
+    if [ -z ${SUBVOLUME#/} ]; then
+        SNAPSHOT_PATH="$DESTINATION_ROOT"
+    else
+	PATH="$DESTINATION_ROOT/${SUBVOLUME#/}"
+    fi
+    if [ ! -d $SNAPSHOT_PATH ]; then
+        echo "warning: snapshot path ($SNAPSHOT_PATH) does not yet exist. creating."
+        mkdir -p $SNAPSHOT_PATH
+    fi
+    if [ -d $SNAPSHOT_PATH/$NAME ]; then
+        echo "warning: snapshots with same name already exists. skipping."
+    else
+	#TODO: handle failed snapshots and failed link creations
+        btrfs -q subvolume snapshot -r $SUBVOLUME $SNAPSHOT_PATH/$NAME
+	if [ -h $SNAPSHOT_PATH/latest ]; then
+	    rm $SNAPSHOT_PATH/latest
+	fi
+        ln -sf $SNAPSHOT_PATH/$NAME $SNAPSHOT_PATH/latest
+    fi
+done
+
+# prune old snapshots
+SNAPSHOTS=$(ls -r $SNAPSHOT_PATH | grep $PREFIX)
+i=0
+for SNAPSHOT in $SNAPSHOTS; do
+    if [ $i -ge $MAX_SNAPSHOTS ]; then
+	#TODO: handle failed snapshot deletions
+	btrfs -q subvolume delete $SNAPSHOT_PATH/$SNAPSHOT
+    fi
+    i=$((i+1))
+done
+
+# end script successfully
+exit 0