82 lines
2 KiB
Bash
Executable file
82 lines
2 KiB
Bash
Executable file
#!/bin/bash
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##
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# Incremental backups with Btrfs snapshots
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#
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# This script does incremental backups of Btrfs subvolumes
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# across filesystem boundaries as proposed in the Btrfs wiki:
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# https://btrfs.wiki.kernel.org/index.php/Incremental_Backup
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#
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# It uses the 'btrfs send' and 'btrfs receive' commands.
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# Its not intended for simple snapshots in a single filesystem enviroment.
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#
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# @copyright 2021, Steffen Vogel
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# @license http://www.gnu.org/licenses/gpl.txt GNU Public License
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# @author Steffen Vogel <post@steffenvogel.de>
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# @link https://www.steffenvogel.de
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##
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# TODO: delete old snapshots in source and destination fs
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set -e
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function usage {
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echo "Usage: $(basename $0) SOURCE [DEST]"
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echo
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echo " SOURCE a path to the subvolume to backup"
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echo " DEST an optional path to the backup destination"
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echo " only required for initialization"
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exit 1
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}
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if [ $# -lt 1 ]; then
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echo -e "missing source"
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echo
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usage
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fi
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SRC=$(readlink -e "$1")
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if [ $SRC == "/" ]; then
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SRC=""
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fi
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if [ -h "$SRC/.backup/destination" ]; then
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DEST=$(readlink -e "$SRC/.backup/destination")
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elif [ $# -ne 2 ] ; then
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echo -e "missing destination"
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echo
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usage
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else
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DEST=$(readlink -e $2)
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fi
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# create directories if not existing
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mkdir -p "$SRC/.backup/"
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mkdir -p "$DEST/"
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# create symbolic links if not existing
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ln -snf "$DEST/" "$SRC/.backup/destination"
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ln -snf "$SRC/" "$DEST/source"
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# name for the new snapshot
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SNAPSHOT=$(date +%F_%H-%M-%S)
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LATEST="$SRC/.backup/$SNAPSHOT"
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# snapshot the current state
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btrfs subvolume snapshot -r "$SRC/" "$LATEST/"
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# send changes
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if [ -h "$DEST/latest-source" ]; then
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PREVIOUS=$(readlink -e "$DEST/latest-source")
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btrfs send -p "$PREVIOUS/" "$LATEST/" | pv | btrfs receive "$DEST/"
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else
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btrfs send "$LATEST/" | pv | btrfs receive "$DEST/"
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fi
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# delete old snapshot in source fs
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if [ -n "$PREVIOUS" ]; then
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btrfs subvolume delete "$PREVIOUS/"
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fi
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# update links to last backup
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ln -rsfT "$DEST/$SNAPSHOT" "$DEST/latest"
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ln -sfT "$LATEST" "$DEST/latest-source"
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