Why configuration separation matters in Kubernetes - See It in Action

Why Configuration Separation Matters in Kubernetes

📖 Scenario: You are managing a simple web application deployed on Kubernetes. You want to keep your application code separate from its configuration settings, such as environment variables and resource limits. This helps you update configuration without changing the application container image.

🎯 Goal: Learn how to separate configuration from application code by creating a Kubernetes Deployment and a ConfigMap, then link them together. Finally, display the configuration inside the running container.

📋 What You'll Learn

Create a ConfigMap with specific configuration data

Create a Deployment that uses the ConfigMap as environment variables

Verify the configuration is accessible inside the container

💡 Why This Matters

🌍 Real World

Separating configuration from code is a best practice in Kubernetes to manage settings independently and securely.

💼 Career

DevOps engineers and SREs often create and manage ConfigMaps and Secrets to configure applications in production environments.

1

Create a ConfigMap with app configuration

Create a Kubernetes ConfigMap named app-config with these exact key-value pairs: APP_MODE=production and LOG_LEVEL=info.

Kubernetes

# Your code here to create the ConfigMap named app-config with APP_MODE and LOG_LEVEL keys

Need a hint?

Use kind: ConfigMap and put your key-value pairs under data:.

2

Create a Deployment using the ConfigMap

Create a Kubernetes Deployment named web-app with one replica. Use the image busybox and set environment variables APP_MODE and LOG_LEVEL from the ConfigMap app-config.

Kubernetes

apiVersion: v1
kind: ConfigMap
metadata:
  name: app-config
data:
  APP_MODE: "production"
  LOG_LEVEL: "info"

# Your code here to create Deployment named web-app using busybox image and env from app-config

Need a hint?

Use envFrom: with configMapRef: to load all keys as environment variables.

3

Add a command to print environment variables

Modify the Deployment's container command to print the environment variables APP_MODE and LOG_LEVEL using sh -c and then sleep. Use the command: sh -c "echo APP_MODE=$APP_MODE LOG_LEVEL=$LOG_LEVEL && sleep 3600".

Kubernetes

apiVersion: v1
kind: ConfigMap
metadata:
  name: app-config
data:
  APP_MODE: "production"
  LOG_LEVEL: "info"
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: web-app
spec:
  replicas: 1
  selector:
    matchLabels:
      app: web-app
  template:
    metadata:
      labels:
        app: web-app
    spec:
      containers:
      - name: busybox-container
        image: busybox
        # Your code here to change command to print env vars and sleep
        envFrom:
        - configMapRef:
            name: app-config

Need a hint?

Use command: ["sh", "-c", "..."] to run multiple shell commands.

4

Display the configuration output

Run kubectl apply -f on your YAML file and then run kubectl logs on the pod created by the web-app Deployment to display the output showing APP_MODE=production and LOG_LEVEL=info.

Kubernetes

apiVersion: v1
kind: ConfigMap
metadata:
  name: app-config
data:
  APP_MODE: "production"
  LOG_LEVEL: "info"
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: web-app
spec:
  replicas: 1
  selector:
    matchLabels:
      app: web-app
  template:
    metadata:
      labels:
        app: web-app
    spec:
      containers:
      - name: busybox-container
        image: busybox
        command: ["sh", "-c", "echo APP_MODE=$APP_MODE LOG_LEVEL=$LOG_LEVEL && sleep 3600"]
        envFrom:
        - configMapRef:
            name: app-config

# Your code here to print the output from the pod logs

Need a hint?

Use kubectl logs on the pod to see the printed environment variables.