Upgrading Kubernetes Cluster

1. Introduction

Upgrading a Kubernetes cluster is an essential maintenance task that ensures the cluster runs on the latest features, security patches, and performance improvements. This lesson covers key concepts, strategies, and step-by-step instructions for upgrading your Kubernetes cluster.

2. Pre-requisites

Before proceeding with an upgrade, ensure the following:

• Backup your cluster data.
• Understand the Kubernetes versioning policy.
• Check compatibility of your applications with the new Kubernetes version.
• Have administrative access to your cluster.

3. Upgrade Strategy

It's important to choose an appropriate upgrade strategy:

• In-place Upgrade: Directly upgrading the existing cluster.
• Blue-Green Upgrade: Running a parallel environment for the new version.
• Canary Upgrade: Gradually upgrading a portion of the cluster.

4. Step-by-Step Process

4.1. Check Current Version

First, check the current version of your Kubernetes cluster:

kubectl version --short

4.2. Upgrade Control Plane

To upgrade the control plane, follow these steps:

kubectl drain  --ignore-daemonsets

kubectl upgrade plan

kubectl upgrade apply 

kubectl uncordon 

4.3. Upgrade Worker Nodes

Once the control plane is upgraded, proceed to upgrade each worker node:

kubectl drain  --ignore-daemonsets

kubectl upgrade apply 

kubectl uncordon 

4.4. Verify Upgrade

Finally, verify the upgrade:

kubectl get nodes

5. Best Practices

Follow these best practices for a successful upgrade:

• Always test upgrades in a staging environment first.
• Monitor cluster health during and after the upgrade.
• Review release notes for breaking changes.
• Have a rollback plan ready in case of failure.

6. FAQ