[Unit]
Description=Backup to USB when it's plugged in
After=local-fs.target
OnFailure=systemd-email@%n.service

[Service]
ExecStart={{ backup_to_usb_script_path }} {{ mount_point }}/{{ backup_to_usb_subdirectory }} {{ backup_to_usb_source_path }}

[Install]
WantedBy=multi-user.target