Kubernetes Upgrade and EKS Upgrade: A Complete Guide for Smooth Cluster Upgrades

Upgrading Kubernetes clusters is a critical part of maintaining a secure, high-performing, and compliant infrastructure. Whether you’re managing Kubernetes on your own or using managed services like Amazon EKS, understanding the upgrade process is essential for reducing downtime and ensuring compatibility.

In this post, we’ll walk through the what, why, and how of a Kubernetes upgrade, with a special focus on EKS upgrade processes, challenges, and best practices.

Why Perform a Kubernetes Upgrade?

Kubernetes follows a rapid release cycle with new versions coming out approximately every three months. Upgrading your cluster ensures:

• Security patches are applied promptly

• Access to new features and performance improvements

• Compatibility with newer APIs and tools

• Support from the Kubernetes community (older versions are deprecated after 12-14 months)

Delaying upgrades increases technical debt and exposes your environment to vulnerabilities and breaking changes in the future.

Kubernetes Upgrade: Key Considerations

Before you jump into the upgrade, here are several things to plan for:

1. Check Version Compatibility

Ensure all your workloads, CRDs (Custom Resource Definitions), controllers, and plugins are compatible with the version you’re upgrading to. Kubernetes has deprecated APIs between versions (e.g., extensions/v1beta1 in v1.22), so testing is crucial.

2. Understand the Upgrade Path

You can only upgrade one minor version at a time. For example, to go from v1.24 to v1.26, you must first upgrade to v1.25. Skipping versions is not supported.

3. Test in a Staging Environment

Replicate your production workloads in a staging cluster and run the upgrade there first. This allows you to identify API deprecations, configuration issues, or controller problems ahead of time.

EKS Upgrade: How It Works

Amazon Elastic Kubernetes Service (EKS) simplifies Kubernetes upgrades with a managed experience, but it still requires strategic planning. An EKS upgrade involves two key components:

• Control Plane Upgrade: Managed by AWS; typically a push-button operation through the console, CLI, or API.

• Node Group Upgrade: Performed by the user; AWS does not automatically upgrade worker nodes or Fargate profiles.

EKS Upgrade Steps

1. Upgrade the EKS Control Plane

   • Navigate to the EKS console or use aws eks update-cluster-version.

   • Choose the next minor version.

   • Monitor the control plane upgrade status (usually takes 10–15 minutes).

2. Upgrade Managed Node Groups

   • Use eksctl or AWS Console to upgrade node groups.

   • Rolling updates are recommended to prevent workload disruption.

   • Drain and cordon old nodes using kubectl drain.

3. Manually Upgrade Add-ons

   • AWS-managed add-ons (e.g., CoreDNS, kube-proxy, VPC CNI) must also be upgraded.

   • Use eksctl utils update-addon or the AWS Console.

4. Test Your Workloads

   • Verify application health and pod status post-upgrade.

   • Check for API deprecation warnings using kubectl get events or audit logs.

Best Practices for Kubernetes and EKS Upgrades

Whether you’re managing your own Kubernetes cluster or doing an EKS upgrade, these best practices will keep your upgrades safe and reliable:

✅ Automate with Infrastructure-as-Code

Tools like Terraform, Helm, and eksctl allow you to declaratively manage versions and rollbacks, reducing human error.

✅ Perform Blue-Green or Canary Upgrades

Run parallel node groups with different versions and shift workloads gradually to reduce risk.

✅ Backup Before Upgrade

Use etcd snapshots or cluster backup tools (e.g., Velero) to safeguard data before initiating any Kubernetes upgrade.

✅ Monitor API Deprecations

Use kubectl get --raw "/metrics" or kubectl api-resources to detect usage of deprecated APIs that could break after an upgrade.

✅ Upgrade Regularly

Staying one or two versions behind the latest release is a safe and sustainable upgrade strategy. Avoid falling multiple versions behind, as it increases upgrade complexity.

Common Pitfalls and How to Avoid Them

• Forgetting Add-ons: Upgrading the control plane but forgetting to upgrade CoreDNS or the CNI plugin can cause network issues.

• Not Draining Nodes: Terminating old nodes without draining them leads to pod loss and potential data corruption.

• API Breakages: Jumping to a new version without checking for deprecated APIs is a recipe for broken deployments.

Always read the Kubernetes Release Notes and EKS Documentation before performing an upgrade.

Tools That Simplify the Upgrade Process

Several tools can help manage and automate Kubernetes and EKS upgrades:

• eksctl: Official CLI tool for EKS cluster management.

• Terraform EKS Modules: Manage version upgrades declaratively.

• Kured: Automates node reboots after security patches.

• kube-no-trouble (kubent): Checks for deprecated APIs before upgrading.

• Velero: Backup and restore Kubernetes resources.

Conclusion: Mastering Kubernetes and EKS Upgrades

Regular and well-planned Kubernetes upgrades are crucial for cluster health, security, and access to new features. In managed environments like AWS, an EKS upgrade provides some abstraction, but you still need to actively upgrade node groups and add-ons to complete the process.

By following best practices, testing thoroughly, and leveraging automation, you can make upgrades a routine and reliable part of your DevOps lifecycle—not a stressful fire drill.