Kubernetes Cluster Upgradation Process- Part 1

🗼Introduction

Upgrading a Kubernetes cluster is a critical task that ensures you are benefiting from the latest features, security patches, and performance improvements. This blog is the part 1 of Kubernetes cluster upgradation process, in this part will guide you through the process of Control Plan node upgrade, focusing on the best practices and commands needed for a smooth upgrade using kubeadm.

🗼Upgrading the Control Plane Node

The first step in upgrading a Kubernetes cluster is to upgrade the control plane node. During this process:

• No new pods can be scheduled.

• The cluster is not accessible using kubectl.

• No new pods will be created if a pod fails.

• Running applications, pods, and nodes are not affected.

🗼Steps of Upgrading with Kubeadm

Step 1: Check the Linux Distribution

First, determine the Linux distribution you are using:

cat /etc/*release*

Step 2: Add the Kubernetes APT Repository

Add the Kubernetes APT repository to your system:

echo "deb [signed-by=/etc/apt/keyrings/kubernetes-apt-keyring.gpg] https://pkgs.k8s.io/core:/stable:/v1.28/deb/ /" | sudo tee /etc/apt/sources.list.d/kubernetes.list

Step 3: Add the Kubernetes APT Key

Add the APT key for the Kubernetes repository:

curl -fsSL https://pkgs.k8s.io/core:/stable:/v1.28/deb/Release.key | sudo gpg --dearmor -o /etc/apt/keyrings/kubernetes-apt-keyring.gpg

Step 4: Update the Package List

Update the package list:

sudo apt-get update

Step 5: Find the Latest Patch Release for Kubernetes

Find the latest patch release for Kubernetes 1.29 using the OS package manager:

sudo apt update
sudo apt-cache madison kubeadm

Step 6: Upgrade the Control Plane Nodes

Upgrade the kubeadm tool:

sudo apt-mark unhold kubeadm
sudo apt-get update
sudo apt-get install -y kubeadm=1.29.x-*
sudo apt-mark hold kubeadm

Make sure to change the kubeadm version to the one obtained in the previous step.

Step 7: Run the Upgrade Plan

Run the upgrade plan to get information about the update and warnings if something might go wrong:

sudo kubeadm upgrade plan

Step 8: Apply the Upgrade

Apply the upgrade to the control plane:

sudo kubeadm upgrade apply v1.29.x

Make sure to change the version appropriately.

Step 9: Upgrade Kubelet and Kubectl

Upgrade kubelet and kubectl:

sudo apt-mark unhold kubelet kubectl
sudo apt-get update
sudo apt-get install -y kubelet=1.29.x-* kubectl=1.29.x-*
sudo apt-mark hold kubelet kubectl

Step 10: Restart the Upgraded Resources

Finally, restart the upgraded resources to ensure all changes take effect:

sudo systemctl daemon-reload
sudo systemctl restart kubelet

🗼Conclusion

Upgrading your Kubernetes cluster using kubeadm ensures you stay up-to-date with the latest improvements and security patches. By following the steps outlined in this guide, you can perform a smooth and efficient upgrade of both control plane and worker nodes. Remember to always backup your cluster and thoroughly test the upgrade process in a staging environment before applying it to production.