Using env variable inside yaml deployment file in Kubernetes

Question

How do I use env variable defined inside deployment? For example, In yaml file dow below I try to use env CONT_NAME for setting container name, but it does not succeed. Could you help please with it, how to do it?

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
  labels:
    app: nginx
spec:
  replicas: 1
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: $CONT_NAME
        image: nginx:1.7.9
        env:
        - name: CONT_NAME
          value: nginx
        ports:
        - containerPort: 80

Answer 1

You can't use variables to set values inside deployment natively. If you want to do that you have to process the file before executing the kubectl, take a look at this post. The best option to do this which it's focused on parametrize and standardize deployments is to use Helm

Answer 2

In those situations I just replace the $CONT_NAME in the yaml with the correct value right before applying the yaml.

sed -ie "s/\$COUNT_NAME/$COUNT_NAME/g" yourYamlFile.yaml

Answer 3

If your using fluxcd, it has the ability to do variable interpolation link