• How many pods are there in the dev environment: 
    kubectl get pods --selector env=dev
  • It is possible to print the output of kubectl get pods without the header, use: 
    kubectl get pods --selector env=dev --no-headers
  • To list all objects in a particular namespace: 
    kubectl get all -selector env=prod --no-headers
  • Can check for multiple labels at the same time and it will show the pod that is included in all of the labels specified: 
    kubectl get all --selector env=prod,bu=finance,tier=frontend
  • A good way to troubleshoot a bad Kubernetes file is via the kubectl create -f <yaml_file.yaml> and Kubernetes will tell you what the problem is.
  • The example replicaset file is replicaset-definition-1: 
    apiVersion: apps/v1
kind: Replicaset
metadata:
name: replicaset-1
spec:
replicas: 2
selector:
  matchLabels:
    tier: front-end
template:
  metadata:
    labels:
      tier: nginx
  spec:
    containers:
    - name: nginx
      image: nginx
  • The replicaset needs the value in tier to match that of template –> metadata= –> labels –> tier
  • What the file looks like after the changes have been made: 
    apiVersion: apps/v1
kind: Replicaset
metadata:
name: replicaset-1
spec:
replicas: 2
selector:
  matchLabels:
    tier: nginx
template:
  metadata:
    labels:
      tier: nginx
  spec:
    containers:
    - name: nginx
      image: nginx

Updated: