Start by deleting the existing Pod and creating the Deployment:
kubectl delete pod simple-web
kubectl apply -f ./labs/kubernetes/specs/update/deployment.yaml
Check the Pods now and you'll see one with a random name; that was created by the Deployment:
kubectl get pods
Browse to http://localhost:8099/ and you'll see the environment is DEV again.
This sample solution adds the ConfigMap reference to the Pod template, loading the data as environment variables:
You can change the Deployment object by running apply again:
kubectl apply -f ./labs/kubernetes/lab/deployment.yaml
List the Pods again and you'll see a different random name - the Pod spec has changed, so the Deployment deletes the old Pod and creates a new one:
kubectl get pods
Refresh the app and you'll see the config is loaded from the ConfigMap.