9.1.1 Customizing init scripts

The easiest way to control the behavior of an init script is by changing environment variable assignments in the file named like the init script in the /etc/default directory. [ 39] For example, /etc/default/hotplug can be used to control how /etc/init.d/hotplug works. The /etc/default/rcS file can be used to customize boot-time defaults for motd, sulogin, etc.

If you cannot get the behavior you want by changing such variables then you can modify the init scripts themselves: they are all configuration files.