Pods

A Pod is the smallest thing Kubernetes can run. It wraps one (or sometimes a few tightly-coupled) containers and gives them a shared network and storage context. When people say “Kubernetes runs my container,” what they really mean is “Kubernetes runs my container inside a Pod.”

Before you can run a Pod, you need an image for it to run – so let’s start where you’re already comfortable: building a container image with Docker.

🛠️ Build the sample app

The project already contains a tiny Node.js web app. Open server.js to see it – it does just one thing: respond with its version and the name of the pod it’s running in. That makes it perfect for watching Kubernetes do its job later.

This cluster has its own container registry at registry.dockerlabs.xyz. You’ll build the image and push it there so the cluster can pull it.

1. Build the image, tagging it for the in-cluster registry:

   docker build -t registry.dockerlabs.xyz/k8s-101/web:1.0 .
   

2. Push it so the cluster can pull it:

   docker push registry.dockerlabs.xyz/k8s-101/web:1.0
   

📦 Run your first Pod

The k8s/pod.yaml manifest describes a single Pod running the image you just pushed. Take a look – notice it declares what you want (a container named web using your image), not how to start it.

1. Apply the manifest to create the Pod:

   kubectl apply -f k8s/pod.yaml
   

2. Watch it come to life. Run this a couple of times until STATUS is Running:

   kubectl get pods
   

3. Get the full story on your Pod – events, image, node, IP, and more:

   kubectl describe pod web
   

4. Check the app’s logs, just like docker logs:

   kubectl logs web
   

   You should see a line like web v1.0 listening on :3000.

🔍 Reach inside the Pod

The Pod has its own internal IP, but let’s verify the app responds by running a command inside the container – similar to docker exec:

kubectl exec web -- wget -qO- http://localhost:3000/api

You’ll get back JSON showing the version and the pod name, something like:

{"version":"1.0","pod":"web"}

🎉 Your container is running on Kubernetes!

💥 Why a bare Pod isn’t enough

A lone Pod is fragile. If it dies, nothing brings it back. Let’s prove it.

1. Delete the Pod:

   kubectl delete pod web
   

2. Check what’s running:

   kubectl get pods
   

   It’s gone – and it’s not coming back. Nothing is watching over it.

In the real world, containers crash, nodes reboot, and things fail. You don’t want your app to simply disappear. In the next section you’ll meet the Deployment – the object that keeps your app running no matter what. 🚀