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k8s_cluster_mentainance
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Upgrade Kubernetes Cluster [Master & Worker Nodes]
To upgrade a Kubernetes cluster is very important to keep up with the latest security features and bug fixes, as well as benefit from new features being released
on an ongoing basis. This is especially important when we have installed a really outdated version or if we want to automate the process and always be on top of
the latest supported version.
Here, we demonstrate Draining & Uncordoning by upgrading the kubeadm, kubectl & kubelet on the Control Plane node & Worker node in our Kubernetes set up one by one:
Control Plane Upgrade Steps:
a) Upgrade kubeadm on the Control Plane node
b) Drain the Control Plane node
c) Plan the upgrade (kubeadm upgrade plan)
d) Apply the upgrade (kubeadm upgrade apply)
e) Upgrade kubelet & kubectl on the control Plane node
f) Uncordon the Control Plane node
Worker Node Upgrade Steps:
a) Drain the node
b) Upgrade kubeadm on the node
c) Upgrade the kubelet configuration (kubeadm upgrade node)
d) Upgrade kubelet & kubectl
e) Uncordon the node
Starting with the Control node, the following is the configuration:
1) Upgrade kubeadm
sudo apt-get update && \
> sudo apt-get install -y — allow-change-held-packages kubelet=1.20.2–00 kubectl=1.20.2–00
Kubeadm version for the Control node is shown as ‘v1.20.2’, but it is not applied yet. The output of ‘kubectl get nodes’ clearly shows that the version is
still ‘v1.20.1’
2) Drain the Control node
kubectl drain k8s-control --ignore-daemonsets
3) Plan the upgrade
sudo kubeadm upgrade plan v1.20.2
4) Apply the upgrade
sudo kubeadm upgrade apply v1.20.2
The Cluster is upgraded to v1.20.2
5) Upgrade kubelet & kubectl
sudo apt-get install -y --allow-change-held-packages kubelet=1.20.2-00 kubectl=1.20.2-00
6) Uncordon the node
Note: It may be possible that the upgrade may change the kubelet unit file, so daemon-reload is executed in order that systemctl sees the new kubelet unit file.
Next restart the kubelet
sudo systemctl daemon-reload
sudo systemctl restart kubelet
kubectl uncordon k8s-control
Finally, the latest version of the components of the Control node can be checked on executing ‘kubectl get nodes’:
Steps for the Worker node:
1) Drain the Worker node (from the Control node console)
kubectl drain k8s-worker1 --ignore-daemonsets --force
2) Upgrade kubeadm
sudo apt-get update && \
> sudo apt-get install -y --allow-change-held-packages kubeadm=1.20.2-00
Version on which kubeadm will be upgraded: ‘kubeadm version’
3) Upgrade the kubelet configuration
sudo kubeadm upgrade node
4) Upgrade kubelet & kubectl
sudo apt-get update && \
> sudo apt-get install -y --allow-change-held-packages kubelet=1.20.2-00 kubectl=1.20.2-00
5) Restart kubelet & Uncordon the Worker node
sudo systemctl daemon-reload
sudo systemctl restart kubelet
6) Uncordon the Worker node (from the control node console)
kubectl uncordon k8s-worker1
Till this point, our Kubernetes setup has a Control plane node & Worker node-1 in an upgraded and functional state. The same set of steps will be followed
for Worker node-2 to have it in the upgraded state.
# https://k21academy.com/docker-kubernetes/cka-day-9-live-session-review/