Snapper snapshots clone tool to mountable attached storage

snapper-clone.service

[Unit]
Description=Snapper Clone Service

[Service]
ExecStart=/bin/bash -c 'chmod +x /home/senz/bin/snapper-clone.sh && /home/senz/b
in/snapper-clone.sh'
User=root
Group=root
Type=simple

[Install]
WantedBy=multi-user.target

snapper-clone.sh

#!/usr/bin/zsh

# This script is used to clone snapper snapshots from one subvolume to another
# Incremental backups are supported, the first snapshot will be a full backup

# Mountpoint of the backup drive
BACKUP_MOUNTPOINT=/mnt/fw1tb

# List of snapper configs to clone
# Opposite backup-<config> needs to exist before running this script. Disable timeline for the backup-<config> config
CONFIGS=(
    root
)

VERBOSE=0

if [ "$EUID" -ne 0 ]; then
    echo "Please run as root"
    exit
fi

if mountpoint -q "$BACKUP_MOUNTPOINT"; then
    echo "Backup already mounted"
else
    echo "Mounting Backup"
    mount "$BACKUP_MOUNTPOINT"
    if mountpoint -q /backup; then
        echo "Backup now mounted"
    else
        echo "Still can't find Backup"
        exit
    fi
fi

# Clone snapshots from source to target
# Supports seeding the first snapshot (full backup)
backup_snapshots() {
    local source=$1
    local target=$2
    local source_snapshots=$(snapper -c $source list --disable-used-space --columns number | tr -d " " | grep "^[0-9]")
    local target_snapshots=$(snapper -c $target list --disable-used-space --columns number | tr -d " " | grep "^[0-9]")

    echo -n "Snapshots in $source: "
    echo $source_snapshots | wc -w
    echo -n "Snapshots in $target: "
    echo $target_snapshots | wc -w

    if [[ $(echo $target_snapshots | wc -w) -eq 0 ]]; then
        # Send the full first snapshot
        first_snapshot=$(echo $source_snapshots | awk '{print $1}')
        mkdir -p $BACKUP_MOUNTPOINT/.snapshots/$first_snapshot
        cp /home/.snapshots/$first_snapshot/info.xml $BACKUP_MOUNTPOINT/.snapshots/$first_snapshot/
        btrfs send /home/.snapshots/$first_snapshot/snapshot | btrfs receive $BACKUP_MOUNTPOINT/.snapshots/$first_snapshot
    fi

    local y=0

    for x in $(diff -u <(echo $source_snapshots) <(echo $target_snapshots) | grep -B 1 -E "^-[0-9]" | tr -d "-"); do
        if [[ $y -gt 0 ]]; then
            # TODO support different subvolumes
            mkdir -p $BACKUP_MOUNTPOINT/.snapshots/$x
            # FIXME this is a hack for my current layout
            cp /home/.snapshots/$x/info.xml $BACKUP_MOUNTPOINT/.snapshots/$x/
            echo "Sending $x"
            local receive_opts=""
            if [[ $VERBOSE -eq 1 ]]; then
                receive_opts="-v"
            fi
            btrfs send -p /home/.snapshots/$y/snapshot /home/.snapshots/$x/snapshot | btrfs $receive_opts receive $BACKUP_MOUNTPOINT/.snapshots/$x
        fi
        y=$x
    done
}

for config in $CONFIGS; do
    backup_snapshots $config backup-$config
done

snapper-clone.timer

[Unit]
Description=Run snapper clone every hour

[Timer]
OnCalendar=hourly
Persistent=true

[Install]
WantedBy=timers.target