Perform a Rolling Update and Rollback¶

Goal¶

In this tutorial you will learn how to safely update an application in Kubernetes and roll back to a previous version if something goes wrong.

You will learn how to:

• perform a rolling update
• monitor deployment progress
• roll back to a previous release

Problem¶

Applications often need to be updated with new versions.

Updating containers incorrectly can cause:

• downtime
• service interruptions
• failed deployments

Kubernetes solves this with rolling updates, which gradually replace old pods with new ones.

Architecture¶

During a rolling update Kubernetes replaces pods one at a time.

Old Pods → New Pods

Traffic continues flowing to healthy pods during the update.

Example:

Version 1 Pods → Version 2 Pods

Prerequisites¶

Ensure:

• Kubernetes cluster is running
• kubectl configured

Verify access:

kubectl get nodes

Expected output:

NAME           STATUS
worker-node1   Ready

Step 1 : Deploy the Initial Application¶

Create a deployment file deployment.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: web-app
spec:
  replicas: 3
  selector:
    matchLabels:
      app: web-app
  template:
    metadata:
      labels:
        app: web-app
    spec:
      containers:
        - name: web
          image: nginx:1.21
          ports:
            - containerPort: 80

Apply the deployment.

kubectl apply -f deployment.yaml

Verify the pods.

kubectl get pods

Example output:

NAME                     READY   STATUS
web-app-abc123           1/1     Running
web-app-def456           1/1     Running
web-app-ghi789           1/1     Running

Step 2 : Update the Container Image¶

Update the deployment to use a newer version.

Run:

kubectl set image deployment/web-app web=nginx:1.25

Step 3 : Monitor the Rollout¶

Watch the rollout progress.

kubectl rollout status deployment web-app

Expected output:

deployment "web-app" successfully rolled out

You can also watch pods being replaced.

kubectl get pods -w

You will see new pods created while old pods terminate.

Step 4 : View Deployment History¶

Kubernetes tracks rollout history.

Run:

kubectl rollout history deployment web-app

Example output:

REVISION  CHANGE-CAUSE
1         nginx:1.21
2         nginx:1.25

Each update creates a new revision.

Step 5 : Simulate a Failed Deployment¶

Update the image to an invalid version.

kubectl set image deployment/web-app web=nginx:invalid

Check the pod status.

kubectl get pods

You may see:

ImagePullBackOff

Step 6 : Roll Back the Deployment¶

Roll back to the previous working version.

kubectl rollout undo deployment web-app

Verify the rollout.

kubectl rollout status deployment web-app

Verify the Rollback¶

Check the running image.

kubectl describe deployment web-app

Look for:

Image: nginx:1.25

What Just Happened¶

Kubernetes performed two important operations:

This allows updates without downtime.

Troubleshooting¶

Rollout Stuck

Check deployment status.

kubectl describe deployment web-app

Pods Failing

Inspect pod logs.

kubectl logs <pod-name>

Image Pull Errors

Verify the image exists.

docker pull nginx:1.25

Clean Up¶

Delete the deployment when finished.

kubectl delete deployment web-app

Key Takeaways¶

You learned how to:

• update applications using rolling deployments
• monitor rollout progress
• view deployment revision history
• roll back to a previous version

Rolling updates are the standard deployment strategy in Kubernetes.

→ Next: Part 6 – Expose App With Ingress