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Overview
Joining to a Kubernetes Cluster is done from the joining machine and verified on the Control Panel (e.g. master) machine. The joining process itself is pretty straight forward and require only one command. The command which was given to us when we initialized the cluster.
So let's get going.
Joint to the cluster
Be sure that you installed the necessary packages from the introduction section. Once this is done we can add the node to the cluster as follow:
Add node
root@node-1:~# kubeadm join 192.168.50.10:6443 --token k7cnjt.c0vkn3i6sc9qp2it --discovery-token-ca-cert-hash sha256:8c7874be67b9670c52a729b7a26bdefb4b55f5a49402624c0d262c0253732228
W0421 10:28:13.551137 21280 join.go:346] [preflight] WARNING: JoinControlPane.controlPlane settings will be ignored when control-plane flag is not set.
[preflight] Running pre-flight checks
[WARNING IsDockerSystemdCheck]: detected "cgroupfs" as the Docker cgroup driver. The recommended driver is "systemd". Please follow the guide at https://kubernetes.io/docs/setup/cri/
[preflight] Reading configuration from the cluster...
[preflight] FYI: You can look at this config file with 'kubectl -n kube-system get cm kubeadm-config -oyaml'
[kubelet-start] Downloading configuration for the kubelet from the "kubelet-config-1.18" ConfigMap in the kube-system namespace
[kubelet-start] Writing kubelet configuration to file "/var/lib/kubelet/config.yaml"
[kubelet-start] Writing kubelet environment file with flags to file "/var/lib/kubelet/kubeadm-flags.env"
[kubelet-start] Starting the kubelet
[kubelet-start] Waiting for the kubelet to perform the TLS Bootstrap...
This node has joined the cluster:
* Certificate signing request was sent to apiserver and a response was received.
* The Kubelet was informed of the new secure connection details.
Run 'kubectl get nodes' on the control-plane to see this node join the cluster.
root@node-1:~#
As with the master node, it might take sometime until you see the node as Ready and all components running from the Control Panel Machine:
Check the newly added Node
ubuntu@k8s-master:~/.kube$ kubectl get nodes NAME STATUS ROLES AGE VERSION k8s-master Ready master 67m v1.18.2 node-1 Ready <none> 82s v1.18.2 ubuntu@k8s-master:~/.kube$ ubuntu@k8s-master:~/.kube$ kubectl get pods --all-namespaces NAMESPACE NAME READY STATUS RESTARTS AGE kube-system calico-kube-controllers-77c5fc8d7f-88lsl 1/1 Running 0 65m kube-system calico-node-bqw8q 1/1 Running 0 65m kube-system calico-node-wwfc5 0/1 Running 0 75s kube-system coredns-66bff467f8-rgh8d 1/1 Running 0 67m kube-system coredns-66bff467f8-tql72 1/1 Running 0 67m kube-system etcd-k8s-master 1/1 Running 0 67m kube-system kube-apiserver-k8s-master 1/1 Running 0 67m kube-system kube-controller-manager-k8s-master 1/1 Running 2 67m kube-system kube-proxy-hnmxb 1/1 Running 0 75s kube-system kube-proxy-jkmql 1/1 Running 0 67m kube-system kube-scheduler-k8s-master 1/1 Running 2 67m
Please execute that step on all nodes. In the end you should have something like this:
Check the newly added Node
ubuntu@k8s-master:~/.kube$ kubectl get nodes NAME STATUS ROLES AGE VERSION k8s-master Ready master 77m v1.18.2 node-1 Ready <none> 11m v1.18.2 node-2 Ready <none> 88s v1.18.2 ubuntu@k8s-master:~/.kube$ kubectl get pods --all-namespaces NAMESPACE NAME READY STATUS RESTARTS AGE kube-system calico-kube-controllers-77c5fc8d7f-88lsl 1/1 Running 0 75m kube-system calico-node-bqw8q 1/1 Running 0 75m kube-system calico-node-fl6ft 1/1 Running 0 84s kube-system calico-node-wwfc5 1/1 Running 0 11m kube-system coredns-66bff467f8-rgh8d 1/1 Running 0 77m kube-system coredns-66bff467f8-tql72 1/1 Running 0 77m kube-system etcd-k8s-master 1/1 Running 0 77m kube-system kube-apiserver-k8s-master 1/1 Running 0 77m kube-system kube-controller-manager-k8s-master 1/1 Running 2 77m kube-system kube-proxy-hnmxb 1/1 Running 0 11m kube-system kube-proxy-jkmql 1/1 Running 0 77m kube-system kube-proxy-s4nrh 1/1 Running 0 84s kube-system kube-scheduler-k8s-master 1/1 Running 2 77m
Assign role to a Node
You saw that our nodes have no roles. We have 1 master and that is that :)
Nodes' roles
ubuntu@k8s-master:~/.kube$ kubectl get nodes NAME STATUS ROLES AGE VERSION k8s-master Ready master 77m v1.18.2 node-1 Ready <none> 11m v1.18.2 node-2 Ready <none> 88s v1.18.2 </Code So, how to assign roles to the node. Well, in Kubernetes, we assign labels. Labels are assigned as follows: <Code:none|Assign label> kubectl label node <node name> node-role.kubernetes.io/<role name>=<key - (any name)> - To assign the label kubectl label node <node name> node-role.kubernetes.io/<role name> - To remove the label
So let's assign worker to our node-1 and node-2
Assign Labels to Node-1 and Node-2
ubuntu@k8s-master:~/.kube$ kubectl label node node-1 node-role.kubernetes.io/worker=worker node/node-1 labeled ubuntu@k8s-master:~/.kube$ kubectl label node node-2 node-role.kubernetes.io/worker=worker node/node-2 labeled ubuntu@k8s-master:~/.kube$ kubectl get nodes NAME STATUS ROLES AGE VERSION k8s-master Ready master 83m v1.18.2 node-1 Ready worker 17m v1.18.2 node-2 Ready worker 7m39s v1.18.2 ubuntu@k8s-master:~/.kube$
Alternatively we can remove a label from a node. So let's remove and add that label again on Node-2:
Remove and Add Label on Node-2
ubuntu@k8s-master:~/.kube$ kubectl label node node-2 node-role.kubernetes.io/worker- node/node-2 labeled ubuntu@k8s-master:~/.kube$ kubectl get nodes NAME STATUS ROLES AGE VERSION k8s-master Ready master 86m v1.18.2 node-1 Ready worker 20m v1.18.2 node-2 Ready <none> 10m v1.18.2 ubuntu@k8s-master:~/.kube$ kubectl label node node-2 node-role.kubernetes.io/worker=worker node/node-2 labeled ubuntu@k8s-master:~/.kube$ kubectl get nodes NAME STATUS ROLES AGE VERSION k8s-master Ready master 87m v1.18.2 node-1 Ready worker 20m v1.18.2 node-2 Ready worker 11m v1.18.2 ubuntu@k8s-master:~/.kube$