Update a Deployment Without Downtime

Step-by-step guide on updating a running Kubernetes Deployment to a new version without downtime using rolling updates.

Your Kubernetes server must be at or later than version v1.2. To check the version, enter kubectl version.

Updating a Deployment with Rolling Updates

Kubernetes lets you update a running application without downtime by using rolling updates. It replaces old Pods with new ones gradually, ensuring new Pods are ready before old ones are removed. This keeps the application available throughout the update process.

Prerequisites

  • A running Kubernetes cluster
  • kubectl configured to access the cluster
  • An existing Deployment (e.g., nginx-deployment)

Step 1: Check the current Deployment

First, see the current Deployment and its version:

kubectl get deployments
kubectl describe deployment nginx-deployment

You should see the current image version, number of replicas, and Pod status.

Step 2: Update the Deployment

Update the Deployment with a new container image version:

kubectl set image deployment/nginx-deployment nginx=nginx:1.25.0
  • nginx-deployment – your Deployment name
  • nginx – container name in the Deployment
  • nginx:1.25.0 – new image version

You should see output simlar to this:

deployment.apps/nginx-deployment image updated

Step 3: Verify the update

kubectl get deployment nginx-deployment -o=jsonpath='{.spec.template.spec.containers[0].image}'

Output:

nginx:1.25.0

That confirms the Deployment was updated.

Check that all Pods are running the new version:

kubectl describe deployment nginx-deployment

Look for:

Image: nginx:1.25.0

This completes the rolling update process for a Kubernetes Deployment without interrupting the service.

Step 4: Watch the rolling update progress

Monitor the update to ensure it is applied gradually and without downtime:

kubectl rollout status deployment/nginx-deployment

You should see output simlar to this:

deployment "nginx-deployment" successfully rolled out

Roll back if needed

If something goes wrong, you can roll back to the previous version:

kubectl rollout undo deployment/nginx-deployment

Notes

  • Rolling updates avoid downtime by ensuring at least some Pods remain available at all times.

If kubernetes is telling you it cannot find a Deployment called nginx-deployment in your current namespace. The kubectl set image command only works on existing resources.

Step 1: Check what Deployments exist

Run:

kubectl get deployments

This will list all Deployments in the current namespace.

  • If you see nginx-deployment listed → maybe you need to be in a different namespace.

  • If nothing is listed → you haven’t created it yet.

Step 2: Create the Deployment (if it doesn’t exist)

If you haven’t deployed nginx yet, here is how you can do that:

kubectl create deployment nginx-deployment --image=nginx:1.24.0

Then you can upgrade it:

kubectl set image deployment/nginx-deployment nginx=nginx:1.25.0

Verify the update

kubectl get deployment nginx-deployment -o=jsonpath='{.spec.template.spec.containers[0].image}'

Output:

nginx:1.25.0

That confirms the Deployment was updated.

You can also:

Check the deployment status

kubectl get deployment nginx-deployment

You should see output simlar to this:

NAME               READY   UP-TO-DATE   AVAILABLE   AGE
nginx-deployment   1/1     1            1           110m
Last modified January 27, 2026 at 2:41 PM PST: docs: clarify rolling update deployment task (14d7fb2446)