Lab 2: Deploy your first Pod

Introduction

You will learn what a pod is, deploy your first container, configure Kubernetes, and interact with Kubernetes in the command line.

The base elements of Kubernetes are pods. Kubernetes will choose how and where to run them. You can also see a Pod as an object that requests some CPU and RAM. Kubernetes will take those requirements and decide where to run them.

APod can be killed and restarted whenever the system has/wants to. So a Pod is ephemeral and it will be destroyed at some point.

1. Create the Pod

Let’s start to deploy the nginx docker image. It’s a simple webserver that is used widely in the Kubernetes world.

kubectl run nginx --image=nginx 

> kubectl run --generator=deployment/apps.v1 is DEPRECATED and will be removed in a future version. Use kubectl run --generator=run-pod/v1 or kubectl create instead.
> deployment.apps/nginx created

2. List the Pods

Now list all the Pods running in Kubernetes. kubectl get is the ls of Kubernetes.

kubectl get pods

> NAME                     READY   STATUS              RESTARTS   AGE
> nginx-755464dd6c-2rbgj   0/1     ContainerCreating   0          32s

Note the name of the Pod which is randomly generated!

3. Get the yaml manifest

Now we can have a look at the yaml description of our Pod

kubectl get pods <name of pod from step 2> -o yaml

> apiVersion: v1
> kind: Pod
> metadata:
>   creationTimestamp: "2019-11-14T08:51:33Z"
>   generateName: nginx-755464dd6c-
>   labels:
>     pod-template-hash: 755464dd6c
>     run: nginx
>   name: nginx-755464dd6c-2rbgj
>   namespace: default
>   ownerReferences:
...
 

Use the name of the Pod that you wrote down in step #2.

Here is a simplified version that contains the main elements:

apiVersion: v1
kind: Pod
metadata:
  name: nginx-755464dd6c-2rbgj
spec:
  containers:
  - name: nginx
    image: nginx  #hosted on hub.docker.com

The Kubernetes manifest represents a desired state. We do not write the steps to achieve this state. Kubernetes will handle it for us.

Let’s have a look at the most important fields:

• apiVersion: the version of the Kubernetes API we will be using, v1 here
• kind: what resource this object represents, Pod for this example
• metadata: some metadata about this pod, like its name.
• spec: specification of the desired behavior of this Pod
  • containers: the list of containers to start in this Pod
    • name: the name of the container
    • image: which image to start

4. Describe the Pod

Describe gives us a lot of information about the status and events of a Kubernetes object.

kubectl describe pods <name of pod from step 2>

...

Events:
  Type    Reason     Age   From               Message

----    ------     ----  ----               -------

  Normal  Scheduled  90s   default-scheduler  Successfully assigned default/nginx-755464dd6c-2rbgj to minikube
  Normal  Pulling    82s   kubelet, minikube  Pulling image "nginx"
  Normal  Pulled     36s   kubelet, minikube  Successfully pulled image "nginx"
  Normal  Created    36s   kubelet, minikube  Created container nginx
  Normal  Started    34s   kubelet, minikube  Started container nginx

5. Clean-up

Now to wrap this up, let’s delete the Pod

kubectl delete pod nginx

Congratulations!!! This concludes Lab 2 on deploying your first Pod