[Kubernetes] Defining a Pod with YAML

1. Define a yml file: nginx.pod.yml:

apiVersion: v1
kind: Pod
metadata:
  name: my-nginx
  labels:
    app: nginx
    rel: stable

spec:
  containers:
  - name: my-nginx
    image: nginx:alpine
    ports:
    - containerPort: 80
    resources:

It creates my-nginx pod.

2. We the yml file with kubectl:

kubectl create -f nginx.pod.yml --save-config   

We use '--save-config' option. 

If we run:

kubectl get pods my-nginx -o yaml

It outpus the configurations for my-nginx pod:

...
metadata:
  annotations:
    kubectl.kubernetes.io/last-applied-configuration: |
      {"apiVersion":"v1","kind":"Pod","metadata":{"annotations":{},"labels":{"app":"nginx","rel":"stable"},"name":"my-nginx","namespace":"default"},"spec":{"containers":[{"image":"nginx:alpine","name":"my-nginx","ports":[{"containerPort":80}],"resources":null}]}}
...

It save the the configuration for this pod, so later if I udpated the yml file, it will diff the changes, and only apply the changes to the pod.

3. apply vs create:

kubectl apply -f nginx.pod.yml  // pod/my-nginx configured

The nice thing of 'apply' is: if the pod is not there, it will create the resource, if the pod is there, then it will update the resource.

4. Get into the pod:

kubectl exec my-nginx -it sh

Quite you can type:

exit

5. Delete the pod:

This time actually we only have pod, without develoyment, so we can delete the pod by:

kubectl delete pod my-nginx

kubectl delete -f nginx.pod.yml