Add Compute Nodes

1. on the master node, generate an invitation: kubeadm token create --print-join-command

2. on the new node, paste the output from the above command: kubeadm join <master ip addr>:6443 --token y2..lg.a3..vs --discovery-token-ca-cert-hash sha256:798...358

if all went fine, the new node just joined the cluster is now available to receive scheduled pods.