Selectors

Can be used to search a group of objects that match Labels inside the kubernetes cluster. The following command will match all the pods that contains the app: app1.

kubectl get pods --selector app=app1

Selectors are also used to connect kubernetes objects. For example to connect a ReplicaSet to a group of Pods.

apiVersion: apps/v1
kind: ReplicaSet
spec:
  replicas: 3
  selector:
    matchLabels:
      app: app1
      function: front-end

  template:
    metadata:
      labels:
        app: app1
        function: front-end
    spec:
      containers:
      -  name: simple-webapp
         image: simple-webapp