Kubernetes equivalent of env-file in Docker

You can populate a container’s environment variables through the use of Secrets or ConfigMaps. Use Secrets when the data you are working with is sensitive (e.g. passwords), and ConfigMaps when it is not.

In your Pod definition specify that the container should pull values from a Secret:

apiVersion: v1
kind: Pod
metadata: 
  labels: 
    context: docker-k8s-lab
    name: mysql-pod
  name: mysql-pod
spec: 
  containers:
  - image: "mysql:latest"
    name: mysql
    ports: 
    - containerPort: 3306
    envFrom:
      - secretRef:
         name: mysql-secret

Note that this syntax is only available in Kubernetes 1.6 or later. On an earlier version of Kubernetes you will have to specify each value manually, e.g.:

env: 
- name: MYSQL_USER
  valueFrom:
    secretKeyRef:
      name: mysql-secret
      key: MYSQL_USER

(Note that env take an array as value)

And repeating for every value.

Whichever approach you use, you can now define two different Secrets, one for production and one for dev.

dev-secret.yaml:

apiVersion: v1
kind: Secret
metadata:
  name: mysql-secret
type: Opaque
data:
  MYSQL_USER: bXlzcWwK
  MYSQL_PASSWORD: bXlzcWwK
  MYSQL_DATABASE: c2FtcGxlCg==
  MYSQL_ROOT_PASSWORD: c3VwZXJzZWNyZXQK

prod-secret.yaml:

apiVersion: v1
kind: Secret
metadata:
  name: mysql-secret
type: Opaque
data:
  MYSQL_USER: am9obgo=
  MYSQL_PASSWORD: c2VjdXJlCg==
  MYSQL_DATABASE: cHJvZC1kYgo=
  MYSQL_ROOT_PASSWORD: cm9vdHkK

And deploy the correct secret to the correct Kubernetes cluster:

kubectl config use-context dev
kubectl create -f dev-secret.yaml

kubectl config use-context prod
kubectl create -f prod-secret.yaml

Now whenever a Pod starts it will populate its environment variables from the values specified in the Secret.