Environment Variables

Configuring application in pods:

• command Line Arguments

• Environment Variables

• ConfigMaps

Environment Variables inside Pods

• User defined

• System defined

Warning

Environment Variables can’t be updated once the pod is created

Defining Environment Variables

apiVersion: v1
kind: Pod
metadata:
  name: pod-env
spec:
  containers:
  - name: producer
    image: busybox
    command: ["sh", "-c", "while true; do echo $NAME >> /tmp/index.html; sleep 10; done"]
    env:
    - name: NAME
      value: Hello World

apply and check the file

vagrant@k8s-master:~$ kubectl apply -f pod-env.yml
pod/pod-env created
vagrant@k8s-master:~$ kubectl get pods
NAME      READY   STATUS    RESTARTS   AGE
pod-env   1/1     Running   0          17s
vagrant@k8s-master:~$ kubectl exec pod-env -- more /tmp/index.html
Hello World
Hello World
Hello World
Hello World

Another example for MySQL containers

apiVersion: v1
kind: Pod
metadata:
  name: mysql
spec:
  containers:
  - name: mysql
    image: mysql:8.0
    env:
    - name: MYSQL_ROOT_PASSWORD
      value: root