Upgrading and rolling back releases in Kubernetes - Commands & Configuration

Introduction

Sometimes you need to update your running application to a new version or fix a problem by going back to an older version. Kubernetes lets you upgrade your app smoothly and roll back if something goes wrong.

When you want to update your app to a new version without downtime

When a new app version has bugs and you need to quickly return to the previous stable version

When testing new features in production but want an easy way to undo changes

When automating deployment pipelines that require version control of app releases

When managing multiple app versions and switching between them safely

Config File - deployment.yaml

deployment.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-app
  labels:
    app: my-app
spec:
  replicas: 2
  selector:
    matchLabels:
      app: my-app
  template:
    metadata:
      labels:
        app: my-app
    spec:
      containers:
      - name: my-app-container
        image: nginx:1.19
        ports:
        - containerPort: 80

This file defines a Deployment named my-app running 2 replicas of an Nginx container version 1.19. The spec.template.spec.containers.image field is what you change to upgrade the app version.

Commands

This command creates or updates the Deployment with the configuration in deployment.yaml. It starts 2 pods running nginx version 1.19.

Terminal

kubectl apply -f deployment.yaml

Expected Output

deployment.apps/my-app created

This checks the status of the Deployment rollout to confirm the pods are running the desired version.

Terminal

kubectl rollout status deployment/my-app

Expected Output

deployment "my-app" successfully rolled out

This command upgrades the app by changing the container image to nginx version 1.21. Kubernetes will update pods one by one.

Terminal

kubectl set image deployment/my-app my-app-container=nginx:1.21

Expected Output

deployment.apps/my-app image updated

Check again to make sure the upgrade completed successfully and all pods run the new version.

Terminal

kubectl rollout status deployment/my-app

Expected Output

deployment "my-app" successfully rolled out

If the new version has problems, this command rolls back the Deployment to the previous working version.

Terminal

kubectl rollout undo deployment/my-app

Expected Output

deployment.apps/my-app rolled back

Verify the rollback completed and pods are running the old stable version again.

Terminal

kubectl rollout status deployment/my-app

Expected Output

deployment "my-app" successfully rolled out

Key Concept

If you remember nothing else from this pattern, remember: Kubernetes lets you upgrade your app version smoothly and roll back instantly if needed using rollout commands.

Common Mistakes

Changing the image in the deployment.yaml file but not applying it with kubectl apply

The cluster does not get the update, so pods keep running the old version.

Always run kubectl apply -f deployment.yaml after editing the file to update the Deployment.

Not checking rollout status after upgrading or rolling back

You might miss errors or pods stuck in crash loops, causing downtime.

Always run kubectl rollout status deployment/my-app to confirm success.

Using kubectl set image without specifying the correct container name

The image update fails silently or updates the wrong container.

Use the exact container name from the Deployment spec when running kubectl set image.

Summary

Use kubectl apply to create or update your Deployment with the desired app version.

Use kubectl set image to upgrade the app container image smoothly.

Use kubectl rollout status to monitor the progress of upgrades or rollbacks.

Use kubectl rollout undo to quickly revert to the previous stable version if needed.