simple-yaml.md

Getting started with config files.

In addition to the imperative style commands described elsewhere, Kubernetes supports declarative YAML or JSON configuration files. Often times config files are preferable to imperative commands, since they can be checked into version control and changes to the files can be code reviewed, producing a more robust, reliable and archival system.

Running a container from a pod configuration file

cd kubernetes
kubectl create -f pod.yaml

Where pod.yaml contains something like:

apiVersion: v1beta3
kind: Pod
metadata:
  labels:
    app: nginx
  name: nginx
  namespace: default
spec:
  containers:
  - image: nginx
    imagePullPolicy: IfNotPresent
    name: nginx
    ports:
    - containerPort: 80
      protocol: TCP
  restartPolicy: Always

You can see your cluster's pods:

kubectl get pods

and delete the pod you just created:

kubectl delete pods nginx

Running a replicated set of containers from a configuration file

To run replicated containers, you need a Replication Controller. A replication controller is responsible for ensuring that a specific number of pods exist in the cluster.

cd kubernetes
kubectl create -f replication.yaml

Where replication.yaml contains:

apiVersion: v1beta3
kind: ReplicationController
metadata:
  name: nginx
  namespace: default
spec:
  replicas: 3
  selector:
    app: nginx
  template:
    metadata:
      name: nginx
      labels:
        app: nginx
    spec:
      containers:
      - image: nginx
        imagePullPolicy: IfNotPresent
        name: nginx
        ports:
        - containerPort: 80
          protocol: TCP
      restartPolicy: Always

To delete the replication controller (and the pods it created):

kubectl delete rc nginx