Debian policy states that packages providing system services need to start those services by default, and that the starting of the service should be done by way of the /usr/sbin/invoke-rc.d script. This script will execute a program /usr/sbin/policy-rc.d if it exists, allowing the local system administrator to override behaviour if wanted by creating a policy script accordin to the interface specified and installing it under the correct name. This interface is however somewhat problematic, as explained in https://bugs.debian.org/911290.

This package attempts to provide a solution by shipping a policy-rc.d script that allows system administrators to define policies in a declarative way through one or more configuration files, rather than providing one script that may be overwritten.