TL;DR
kubectl run tmp --image nginx --rm -i --restart=Never -- curl '$IP:$PORT'

Step 1: Deploy a simple application: Nginx

Let’s deploy nginx. To do so, run these two commands:

kubectl create deployment nginx --image nginx --port 80
kubectl expose deployment nginx

If you don’t like the imperative approach, you can apply this manifest:

apiVersion: apps/v1
kind: Deployment
metadata:
  creationTimestamp: null
  labels:
    app: nginx
  name: nginx
spec:
  replicas: 1
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      creationTimestamp: null
      labels:
        app: nginx
    spec:
      containers:
        - image: nginx
          name: nginx
          ports:
            - containerPort: 80
---
apiVersion: v1
kind: Service
metadata:
  creationTimestamp: null
  labels:
    app: nginx
  name: nginx
spec:
  ports:
    - port: 80
      protocol: TCP
      targetPort: 80
  selector:
    app: nginx

Step 2: Test the deployed service

Run the following command in the terminal:
kubectl run tmp --image nginx --rm -i --restart=Never -- curl 'nginx:80'

image

We reach the deployed nginx service, and get the index.html page deployed on the stdin

Explications

We ran a pod called tmp with the following options:

  • --image nginx
    Pod image to run. We use nginx here, but any image containing curl will do the trick.
  • --rm
    Delete the pod after it exit. This is the reason why the pod is temporary.
  • -i
    This option keep stdin open on the container in the pod.
  • --restart=Never
    RestartPolicy of the pod: we specify Never. Meaning that wheter the pod successed of failed, it get deleted at the end. It’s not mandatory, but highly recommended: If RestartPolicy isn’t set to Never it will be set to his default value, Always. If there is a mistake on your command, like a silly typo, the pod will restart until he reach the CrashLoopBackOff state, and you will have to delete it manually, making you loose precious seconds.
  • -- curl 'nginx:80'
    Argument passed to the container.
    We call the curl binairy, specifying the service and the port we want to reach.
    Here I rely on Kubernetes DNS to reach the nginx service. Another option is to write the IP address directly.
    To get the IP adress of a service, type kubectl get svc. In my case the IP adress is172.17.0.4 so the command become curl '172.17.0.4:80'; To get the IP address of a pod, type kubectl get pods -o wide

I hope this was useful, feel free to leave a comment in case you have any questions. Good luck for your exam !

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