The Kubernetes Controller Manager service is installed and configured by this script. The CIDR used by the pods needs to be passed to each master. As such a variable file and controller_manager_setup.sh file are copied to each master node.

The controller_manager_setup.sh script will perform the following actions on each master node in a serial order:

Download the kube-controller-manager binary from the upstream Kubernetes release and copy to /usr/local/bin

The kube-controller-manager.kubeconfig file is copied to the /var/lib/kubernetes directory to allow the controller-manager to authenticate to Kubernetes.

A new /etc/systemd/system/kube-controller-manager.service file is created to enable the Controller Manager service.

The /etc/kubernetes/controller-manager configuration file is filled with the necessary configuration data (this includes the pod CIDR taken from the environment variables passed to each controller).

The kube-controller-manager daemon is then started and enabled, after systemctl daemon-reload has been run.