KodeKloud Notes

Kubernetes lets you inject configuration data into Pods via environment variables. This declarative approach mirrors Docker’s -e flag but offers tighter integration with Kubernetes primitives like ConfigMaps and Secrets.

Why Use Environment Variables?

Decouple configuration from container images
Simplify application customization across environments
Secure sensitive data using Secrets

Prerequisites

A running Kubernetes cluster
kubectl configured against your cluster
Basic knowledge of Pods and YAML manifests

1. Direct Assignment with `value`

To set an environment variable directly in your Pod spec, use the env array under the container definition:

apiVersion: v1
kind: Pod
metadata:
  name: simple-webapp-color
spec:
  containers:
    - name: simple-webapp-color
      image: simple-webapp-color
      ports:
        - containerPort: 8080
      env:
        - name: APP_COLOR
          value: pink

This makes APP_COLOR=pink available inside the container.

Note

Direct assignment is ideal for non-sensitive, static configuration values.

You can replicate this behavior in Docker with:

docker run -e APP_COLOR=pink simple-webapp-color

2. Decoupling Config with `valueFrom`

Rather than embedding values in your Pod spec, you can reference external sources:

env:
  # From a ConfigMap
  - name: APP_COLOR
    valueFrom:
      configMapKeyRef:
        name: my-configmap
        key: color.value

  # From a Secret
  - name: DB_PASSWORD
    valueFrom:
      secretKeyRef:
        name: my-secret
        key: db.password

Warning

Secrets are only base64-encoded by default and not encrypted at rest. Use encryption providers or external secret stores for stronger security.

3. Comparison at a Glance

Configuration Source	Field	When to Use
Direct	`value`	Static, non-sensitive values
ConfigMap	`valueFrom.configMapKeyRef`	Application settings shared across Pods
Secret	`valueFrom.secretKeyRef`	Sensitive data (passwords, tokens, certificates)

4. References

Watch Video

Watch video content