We need root access to copy backup files with the filesystem backend

src/scripts/cpbackup.sh

@@ -0,0 +1,27 @@
+#!/bin/bash
+
+# This is part of the storage/filesystem backend!
+
+set -eu -o pipefail
+
+if [[ ${EUID} -ne 0 ]]; then
+    echo "This script should be run as root." > /dev/stderr
+    exit 1
+fi
+
+if [[ $# == 1 && "$1" == "--check" ]]; then
+    echo "OK"
+    exit 0
+fi
+
+if [[ $# -lt 2 ]]; then
+    echo "Usage: cpbackup.sh <source> <destination>"
+    exit 1
+fi
+
+# ensure destination path
+readonly DEST_PATH=$(dirname "${2}")
+mkdir -p "${DEST_PATH}"
+
+# copy the file
+cp "${1}" "${2}"