kubectl apply command does not work, gives connection refused error

Basically, when you start Kubernetes you start the services on port 6443, however the above command is searching for services running on port 8080. This is because when you run sudo, it runs using the variable from sudo which doesn't have information about the port on which Kubernetes is running, so it defaults to 8080. Run the following command as root user on the master node.

cp -i /etc/kubernetes/admin.conf $HOME/

Now run the kubectl apply command as below as root user.

kubectl apply -f https://docs.projectcalico.org/v3.1/getting-started/kubernetes/installation/hosted/rbac-kdd.yaml

Found that it's an issue with kubectl not being configured properly.

Fixed the issued by using the following commands for calico network(change accordingly for your network addon plugin)

sudo kubeadm init --pod-network-cidr=192.168.0.0/16
mkdir -p $HOME/.kube
sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
sudo chown $(id -u):$(id -g) $HOME/.kube/config

and then run

sudo kubectl apply -f https://docs.projectcalico.org/v3.1/getting-started/kubernetes/installation/hosted/rbac-kdd.yaml

and follow the rest accordingly

The following issue leads me to the conclusion that the api-server might not be running.

I recommend to check the status of the kubelet service on the master node

systemctl status kubelet.service 

And check the logs for for more information to see why the api-server is not running and how to fix the problem

journalctl -xn --unit kubelet.service