Creating your own workloads

Pods

Pod is the smallest workload in Kubernetes. Try these things out:

• kubectl explain pod
• kubectl explain pod.metadata
• kubectl explain pod.spec
• kubectl explain pod.spec.containers

Let's start off by creating just one pod. You don't usually create pods by themselves but this might make labels and other identifiers easier to understand.

Create a file called pod.yaml with the following content:

apiVersion: v1
kind: Pod
metadata:
  name: demo-pod
  labels:
    app: demo
    style: web-server
spec:
  containers:
  - image: nginxinc/nginx-unprivileged
    name: nginx
    ports:
    - containerPort: 8080

This will create a single pod with an nginx image. Run kubectl apply -f pod.yaml.

Use kubectl to inspect the pod. Try running kubectl get pod and figuring out how to view your app.

Try to figure out what your pod's IP address is, you'll need it soon.

You can also create one-off pods with kubectl run like:

kubectl run --restart=Never --rm -it --image=curlimages/curl call-demo -- http://<your pod IP>:8080

Now you can delete your pod. Either destroy it directly with kubectl delete or kubectl delete -f.

Deployments

Let's create an actual deployment then. Copy this into a file called deployment.yaml:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: demo
  labels:
    app: demo
spec:
  replicas: 2
  selector:
    matchLabels:
      app: demo-pod
  template:
    metadata:
      labels:
        app: demo-pod
    spec:
      containers:
      - image: nginxinc/nginx-unprivileged
        name: nginx
        ports:
        - containerPort: 8080

Use kubectl to apply it. You can use kubectl get pods to see that a deployment created pods automatically.

New deployment

Now create a new deployment file, but instead use gcr.io/kubernetes-e2e-test-images/echoserver:2.2 or e2eteam/echoserver:2.2 from Docker Hub as the image.

You'll need to edit spec.selector.matchLabelsand spec.template.metadata.labels.app, use a different label and selector than your existing deployment. Change the container name as well to something else besides nginx. No other changes are necessary since the container uses the same port number.

These labels are the way Kubernetes handles the number of pods that are attached to a deployment. This is also used by services.

Jobs and Cronjobs

You might want to try your hand at creating a job or cronjob:

apiVersion: batch/v1
kind: Job
metadata:
  name: pi
spec:
  template:
    spec:
      containers:
      - name: pi
        image: perl:5.34.0
        command: ["perl",  "-Mbignum=bpi", "-wle", "print bpi(2000)"]
      restartPolicy: Never
  backoffLimit: 4

apiVersion: batch/v1
kind: CronJob
metadata:
  name: hello
spec:
  schedule: "* * * * *"
  jobTemplate:
    spec:
      template:
        spec:
          containers:
          - name: hello
            image: busybox:1.28
            imagePullPolicy: IfNotPresent
            command:
            - /bin/sh
            - -c
            - date; echo Hello from the Kubernetes cluster
          restartPolicy: OnFailure