🍼 First Deployment

First Deployment #

Now that we can create a Kubernetes cluster using kind we have everything we need to make our first actual Kubernetes Deployment. We will use kubectl for this.

Applying YAML to a cluster #

If we create a file nginx-deployment.yaml with the following content

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
  labels:
    app: nginx
spec:
  replicas: 3
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx:1.14.2
        ports:
        - containerPort: 80

And then run

kubectl apply -f nginx-deployment.yaml

Then we are telling Kubernetes to make that desired state a reality. In the YAML we see that we told it to run 3 replicas of the pod. Let’s check if it managed to make that the actual state:

kubectl get pods

This should give an output similar to

NAME                                READY   STATUS    RESTARTS   AGE
nginx-deployment-647677fc66-jpp5k   1/1     Running   0          11s
nginx-deployment-647677fc66-tfqbn   1/1     Running   0          11s
nginx-deployment-647677fc66-xqdqc   1/1     Running   0          11s

To check that the nginx application is actually running we can use port-forwarding to port-forward one of the pods to our host machine

kubectl port-forward deployments/nginx-deployment 8080:80

This will make requests to localhost:8080 on our host machine hit one of the pods of the deployment, and you should see the default “Welcome to nginx!” message in the browser.

Exercises #

Deploy nginx with HTML from configmap #

  • Run the above example, but where you mount HTML from a configmap.
  • Port forward and verify in the browser.

Deploy the go application #

  • Use kind load docker-image to copy the go application we built earlier to your kind cluster.
  • Duplicate exercises/kubernetes/first_deployment/nginx-deployment.yaml to a file called go-deployment.yaml.
  • Open the file and edit fields so that it will deploy our go application.
  • Apply it to the cluster and use port-forwarding to verify that it works.

The Kubernetes default pull policy is IfNotPresent unless the image tag is :latest or omitted (and implicitly :latest) in which case the default policy is Always. IfNotPresent causes the Kubelet to skip pulling an image if it already exists. If you want those images loaded into node to work as expected, please:

  • don’t use a :latest tag

and / or:

  • specify imagePullPolicy: IfNotPresent or imagePullPolicy: Never on your container(s).

See Kubernetes imagePullPolicy for more information.

August 17, 2025