···9999 Defines how unit configuration is provided for systemd:
100100101101 `asDropinIfExists` creates a unit file when no unit file is provided by the package
102102- otherwise a drop-in file name `overrides.conf`.
102102+ otherwise it creates a drop-in file named `overrides.conf`.
103103104104 `asDropin` creates a drop-in file named `overrides.conf`.
105105 Mainly needed to define instances for systemd template units (e.g. `systemd-nspawn@mycontainer.service`).