Theodore Y. Ts'o wrote: > Finally, if I have a systemd timer file, as well as a crontab entry, > what is the recommended way to decide whether to install/use the > crontab versus the timer unit file?
Unfortunately, there isn't a clean mechanism for that. For systemd unit files, systemd's built-in support for sysvinit scripts automatically ignores a sysvinit script if a corresponding unit file exists, which means you can just install a sysvinit script and a native unit and the latter will supersede the former. However, systemd doesn't have built-in support for cron files; systemd-cron exists, and implements a mechanism to mask cron files if a corresponding systemd timer file exists, but that assumes the use of systemd-cron, which doesn't get installed by default, and it isn't obvious if it's production-ready. (Note that putting a line in your cron entry to exit if under systemd still means cron needs to go run that script and have it exit, which is not ideal.)
