backup_tool_duplicity.sh

#!/usr/bin/env bash
set -euo pipefail
# set -x

# --- Configuration & Defaults ---
HOSTNAME="$(hostname)"
readonly HOSTNAME
readonly CONFIG_DIR="${HOME}/.config/duplicity"

# Load local overrides (This is where TARGET_URL is defined per-machine)
if [[ -f "${CONFIG_DIR}/config.conf" ]]; then
	# shellcheck source=/dev/null
	source "${CONFIG_DIR}/config.conf"
fi

# Set pragmatic defaults if not defined in config.conf
readonly TARGET_URL="${TARGET_URL:-file:///backups/${HOSTNAME}-backup}"
readonly ARCHIVE_DIR="${ARCHIVE_DIR:-${HOME}/.cache/duplicity}"
readonly FULL_BACKUP_AGE="${FULL_BACKUP_AGE:-1M}"
readonly RETENTION_AGE="${RETENTION_AGE:-1M}"

# Disable all GPG encryption & passphrase prompts
export PASSPHRASE=""

# --- Duplicity Options ---
OPTS=(
	--verbosity="notice"
	--volsize=200
	--concurrency=4
	--no-encryption
	--exclude-device-files
	--archive-dir="${ARCHIVE_DIR}"
	--exclude-filelist="${CONFIG_DIR}/exclude.conf"
	--include-filelist="${CONFIG_DIR}/include.conf"
	--exclude="**" # ignore everything not explicitly included
)

# --- Functions ---
setup_environment() {
	if ! command -v duplicity >/dev/null 2>&1; then
		echo "Error: duplicity is not installed or not in PATH" >&2
		exit 1
	fi

	# Create config and archive directories
	mkdir -p "${CONFIG_DIR}" "${ARCHIVE_DIR}"

	# Only attempt to create the target directory locally if it is a file:// URL
	if [[ "${TARGET_URL}" == file://* ]]; then
		mkdir -p "${TARGET_URL#file://}"
	fi

	# Ensure filter files exist so duplicity doesn't crash
	touch "${CONFIG_DIR}/exclude.conf" "${CONFIG_DIR}/include.conf"
}

usage() {
	cat <<EOF
Universal Duplicity Backup Script

Usage: $(basename "$0") [OPTIONS] COMMAND

Commands:
    backup          Perform backup and prune old backups
    status          Show backup collection status
    list            List files in latest backup
    verify          Verify latest backup against local files
    prune           Remove backups older than ${RETENTION_AGE}
    prune --all     Remove ALL backups (requires confirmation)
    cleanup         Clean up failed backup attempts
    help            Show this help message

Options:
    --dry-run       Simulate operation without making changes

Configuration:
    Override defaults by creating: ${CONFIG_DIR}/config.conf
    Example config.conf:
        TARGET_URL="sftp://backup_user@192.168.1.100:22//remote-backup"
        FULL_BACKUP_AGE="1M"
        RETENTION_AGE="3M"
EOF
}

notify() {
	local message="$1"
	local title="${2:-Backup}"

	command -v notify-send >/dev/null 2>&1 || return 0
	# notify-send will fail silently in systemd timers, which is expected and safe
	notify-send \
		--icon=drive-harddisk \
		--app-name="System Backup" \
		--urgency=low \
		"${title}" "${message}" || true
}

remove_old_backups() {
	echo "Pruning old backups"
	duplicity remove-older-than "${RETENTION_AGE}" \
		--force \
		"${OPTS[@]}" \
		"${TARGET_URL}"
}

remove_all_backups() {
	echo "WARNING: This will permanently delete ALL backups at ${TARGET_URL}"
	read -r -p "Type 'yes' to confirm: " confirmation
	if [[ "${confirmation}" != "yes" ]]; then
		echo "Aborted."
		exit 0
	fi
	echo "Removing all backups"
	duplicity remove-older-than now \
		--force \
		"${OPTS[@]}" \
		"${TARGET_URL}"
}

backup() {
	local lockfile="/tmp/backup_tool_${HOSTNAME}.lock"
	exec 9>"${lockfile}"
	if ! flock -n 9; then
		echo "Another backup is already running. Exiting." >&2
		exit 1
	fi

	echo "Starting backup to ${TARGET_URL}"
	local output
	output=$(
		duplicity backup \
			"${OPTS[@]}" \
			--full-if-older-than "${FULL_BACKUP_AGE}" \
			/ "${TARGET_URL}" 2>&1
	) || {
		echo "Backup failed! See details below" >&2
		echo "Run '$(basename "$0") cleanup' to attempt to fix the backend" >&2
		echo "${output}" >&2
		notify "Backup failed. Check logs for details." "Backup Failed"
		exit 1
	}

	echo "${output}"
	remove_old_backups

	local summary
	summary=$(echo "${output}" | grep -E "ElapsedTime|NewFiles|DeletedFiles|ChangedFiles|Errors" || true)
	notify "${summary:-Completed}" "Backup Successful"
}

# --- Main ---
if [[ "${1:-}" == "--dry-run" ]]; then
	OPTS+=(--dry-run)
	echo "DRY RUN MODE: No changes will be made"
	shift
fi

case "${1:-}" in
backup)
	setup_environment
	backup
	;;
cleanup)
	setup_environment
	duplicity cleanup "${OPTS[@]}" --force "${TARGET_URL}"
	;;
prune)
	setup_environment
	if [[ "${2:-}" == "--all" ]]; then
		remove_all_backups
	else
		remove_old_backups
	fi
	;;
status)
	setup_environment
	duplicity collection-status "${OPTS[@]}" "${TARGET_URL}"
	;;
list)
	setup_environment
	duplicity list-current-files "${OPTS[@]}" "${TARGET_URL}"
	;;
verify)
	setup_environment
	duplicity verify "${OPTS[@]}" "${TARGET_URL}" /
	;;
help)
	usage
	;;
*)
	echo "Error: unknown command '${1:-}'" >&2
	usage
	exit 1
	;;
esac