From c248cb851182c868b0a5ef89d02f65ece4bf1ad3 Mon Sep 17 00:00:00 2001
From: Steffen Vogel <post@steffenvogel.de>
Date: Fri, 1 Nov 2013 03:56:46 +0100
Subject: [PATCH] added a first version of my Btrfs snapshot backup script

For usage details please consult the file header and https://btrfs.wiki.kernel.org/index.php/Incremental_Backup
---
 bash/backup-btrfs.sh | 93 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 93 insertions(+)
 create mode 100644 bash/backup-btrfs.sh

diff --git a/bash/backup-btrfs.sh b/bash/backup-btrfs.sh
new file mode 100644
index 0000000..48fc98a
--- /dev/null
+++ b/bash/backup-btrfs.sh
@@ -0,0 +1,93 @@
+#!/bin/bash
+##
+ # Incremental backups with Btrfs snapshots
+ #
+ # This script does incremental backups of Btrfs subvolumes
+ # across filesystem boundaries as proposed in the Btrfs wiki:
+ #  https://btrfs.wiki.kernel.org/index.php/Incremental_Backup
+ #
+ # It uses the 'btrfs send' and 'btrfs receive' commands.
+ # Its not intended for simple snapshots in a single filesystem enviroment.
+ #
+ # @copyright   2013 Steffen Vogel
+ # @license     http://www.gnu.org/licenses/gpl.txt GNU Public License
+ # @author      Steffen Vogel <info@steffenvogel.de>
+ # @link        http://www.steffenvogel.de
+ ##
+##
+ # This script is free software: you can redistribute it and/or modify
+ # it under the terms of the GNU General Public License as published by
+ # the Free Software Foundation, either version 3 of the License, or
+ # any later version.
+ #
+ # This script is distributed in the hope that it will be useful,
+ # but WITHOUT ANY WARRANTY; without even the implied warranty of
+ # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ # GNU General Public License for more details.
+ #
+ # You should have received a copy of the GNU General Public License
+ # along with this script. If not, see <http://www.gnu.org/licenses/>.
+ ##
+
+# TODO: delete old snapshots in destination fs
+# TODO: print statistics of send | receive pipe (speed & size)
+
+function usage {
+	echo "Usage: $(basename $0) SOURCE [DEST]"
+	echo
+	echo "   SOURCE  a path to the subvolume to backup"
+	echo "   DEST    an optional path to the backup destination"
+	echo "             only required for initialization"
+	exit 1
+}
+
+set -e
+
+if [ $# -lt 1 ]; then
+	echo -e "missing source"
+	echo
+	usage
+fi
+
+SRC=$(readlink -f "$1")
+
+if [ -h "$SRC/.backup/destination" ]; then
+	DEST=$(readlink -f "$SRC/.backup/destination")
+elif [ $# -ne 2 ] ; then
+	echo -e "missing destination"
+	echo
+	usage
+else
+	DEST=$(readlink -f $2)
+
+	mkdir -p "$SRC/.backup/"
+	mkdir -p "$DEST"
+
+	ln -sf "$DEST" "$SRC/.backup/destination"
+	ln -sf "$SRC" "$DEST/source"
+fi
+
+# name for the new snapshot
+SNAPSHOT=$(date +%F_%H-%M-%S)
+LATEST="$SRC/.backup/$SNAPSHOT"
+
+# snapshot the current state
+btrfs subvolume snapshot -r "$SRC" "$LATEST"
+
+# send changes
+if [ -h "$DEST/latest-source" ]; then
+	PREVIOUS=$(readlink -f "$DEST/latest-source")
+	btrfs send -p "$PREVIOUS" "$LATEST" | btrfs receive "$DEST"
+else
+	btrfs send "$LATEST" | btrfs receive "$DEST"
+fi
+
+# delete old snapshot in source fs
+if [ -n "$PREVIOUS" ]; then
+	btrfs subvolume delete "$PREVIOUS"
+fi
+
+# update links to last backup
+ln -rsfT "$DEST/$SNAPSHOT" "$DEST/latest"
+ln -sfT "$LATEST" "$DEST/latest-source"
+