Why

As Clusterio is constantly sending rcon commands to the headless client, it is not possible to completely pause a headless client even when auto_pause: true is enabled in the server-settings.cfg file.

This mod will also save the evolution state and restore it when next a player rejoins.

This mod allows for Clusterio server admins to still have their base running, free of worry that biters will not be able to attack the base while no one is online.

I Do Not Use Clusterio

That's totally fine, this mod still works perfectly without Clusterio which is why it is not marked as a dependency.
If you as a server admin would like for your base to keep running while players are not online, but you do not want the worry of biters attacking your base while nobody is there to protect it, then this mod is for you.

Per World configurations

You're able to use this mod on multiple servers connected to the same Clusterio master, with different settings in each server without the need for your players to re-download any mod-settings data which saves a restart of the client.
All settings are stored in the Map Settings area, allowing you to customise the mods parameters in real time.

How Do I Know This Is Working?

Personally I use the following command to ensure that the server is being paused:

cat factorio-current.log | grep CBC

You will see the server log to file whenever the server gets paused.