Kubernetes ReplicationController example of manifest file

apiVersion: v1
kind: ReplicationController
metadata:
  name: rc-nginx
spec:
  replicas: 3
  template:
    metadata:
      name: nginx
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx-container
	image: nginx

We have 2 metadata sections in the definition file: one for ReplicationController, another for the Pod - and the same for spec sections: one for each.

The selector is not a required field in case of ReplicationController, but it is still available. When you skip it, it assumes that it is the same as the Pod labels provided in definition file.