snapperのデイリースナップショットから増分バックアップ (for Ubuntu 16.04.2 LTS)

backup.sh

#!/bin/bash
ARCEXT="btrfs.xz"
NICE="nice -n 19 ionice -c 2 -n 7"

cd "$(dirname "$(readlink -f "${BASH_SOURCE:-$0}")")"
do_backup () {
    CONFIG="$1"
    SSPATH="$2"
    if [ ! -d "$CONFIG" ]; then
        mkdir "$CONFIG" || exit
    fi
    # Find today first snapshot
    TODAYNUM=$(snapper -c "$CONFIG" --iso list -t single | sed -ne "s/^\([0-9]\+\) | $(date '+%Y-%m-%d') .\+$/\1/p" | sed -n 1p)
    if [ -z "$TODAYNUM" ]; then
        echo "[$CONFIG] Error: snapshot not found"
        return
    fi
    # Find last backup archive
    LASTNUM=$(find "$CONFIG" -maxdepth 1 -name "*.$ARCEXT" -printf "%f\n" | sort -nr | sed -ne "1s/^\([0-9]\+\)\..\+$/\1/p")
    if [ "$TODAYNUM" = "$LASTNUM" ]; then
        echo "[$CONFIG] Error: already backup"
        return
    elif [ -n "$LASTNUM" ]; then
        # Incremental backup
        $NICE btrfs send -p "$SSPATH/$LASTNUM/snapshot" "$SSPATH/$TODAYNUM/snapshot" 2> btrfs-send.log | $NICE xz -8 > "$CONFIG/$TODAYNUM.$ARCEXT"
    else
        # Full backup
        $NICE btrfs send "$SSPATH/$TODAYNUM/snapshot" 2> btrfs-send.log | $NICE xz -8 > "$CONFIG/$TODAYNUM.$ARCEXT"
    fi
    # result check
    if [ "${PIPESTATUS[0]}" -ne 0 ]; then
        cat btrfs-send.log
        echo "[$CONFIG] Error: btrfs send failed"
        rm "$CONFIG/$TODAYNUM.$ARCEXT"
    fi
    rm btrfs-send.log
}

do_backup "root" "/.snapshots"
do_backup "home" "/home/.snapshots"