Arvados

One implementation option: Python's argparse module can read arguments from a file, if you build your ArgumentParser with "fromfile_prefix_chars":https://docs.python.org/2/library/argparse.html#fromfile-prefix-chars. If we turned that on, we could ship a systemd service file that runs the command python3 -m arvados_docker.cleaner @/etc/arvados/docker-cleaner/config.

It's not especially elegant, but it would be the cheapest implementation, since it builds on the configuration we already have, already implements well-defined rules for if an option is specified in both a file and the command line, etc.