Using ConfigMaps as environment variables in Kubernetes - Mini Project: Build & Apply

Using ConfigMaps as Environment Variables in Kubernetes

📖 Scenario: You are deploying a simple web application on Kubernetes. You want to manage configuration settings like the app's greeting message using ConfigMaps. This way, you can change the message without changing the app code.

🎯 Goal: Create a ConfigMap with a greeting message, then configure a Pod to use this ConfigMap as environment variables. Finally, verify the Pod prints the greeting message from the ConfigMap.

📋 What You'll Learn

Create a ConfigMap named app-config with a key GREETING and value Hello, Kubernetes!

Create a Pod named greeting-pod that uses the app-config ConfigMap as environment variables

The Pod should run a container using the busybox image and print the GREETING environment variable

Verify the Pod output shows the greeting message from the ConfigMap

💡 Why This Matters

🌍 Real World

ConfigMaps let you separate configuration from code in Kubernetes. This helps you change app settings without rebuilding containers.

💼 Career

Knowing how to use ConfigMaps as environment variables is a key skill for Kubernetes administrators and DevOps engineers managing cloud-native apps.

1

Create the ConfigMap with the greeting message

Create a ConfigMap named app-config with a key GREETING and value Hello, Kubernetes! using the kubectl create configmap command.

Kubernetes

# Use kubectl create configmap app-config --from-literal=GREETING="Hello, Kubernetes!"
# Your command here

Need a hint?

Use kubectl create configmap with --from-literal to add the key and value.

2

Create the Pod manifest using the ConfigMap as environment variables

Create a Pod manifest YAML named greeting-pod.yaml with a Pod named greeting-pod. Use the busybox image and set the environment variable GREETING from the ConfigMap app-config using envFrom.

Kubernetes

# Write the Pod YAML manifest with envFrom referencing configMapRef name: app-config
# Your YAML here

Need a hint?

Use envFrom with configMapRef to load all keys from the ConfigMap as environment variables.

3

Apply the Pod manifest to create the Pod

Use the command kubectl apply -f greeting-pod.yaml to create the Pod named greeting-pod in the cluster.

Kubernetes

apiVersion: v1
kind: Pod
metadata:
  name: greeting-pod
spec:
  containers:
  - name: busybox-container
    image: busybox
    command: ["sh", "-c", "echo $GREETING && sleep 3600"]
    envFrom:
    - configMapRef:
        name: app-config

# Run kubectl apply -f greeting-pod.yaml to create the Pod
# Your command here

Need a hint?

Use kubectl apply -f greeting-pod.yaml to create or update the Pod from the YAML file.

4

Check the Pod logs to see the greeting message

Run kubectl logs greeting-pod to display the logs of the Pod. The output should show the greeting message Hello, Kubernetes! from the ConfigMap environment variable.

Kubernetes

apiVersion: v1
kind: Pod
metadata:
  name: greeting-pod
spec:
  containers:
  - name: busybox-container
    image: busybox
    command: ["sh", "-c", "echo $GREETING && sleep 3600"]
    envFrom:
    - configMapRef:
        name: app-config

kubectl apply -f greeting-pod.yaml

# Run kubectl logs greeting-pod to see the greeting message
# Your command here

Need a hint?

Use kubectl logs greeting-pod to see the output printed by the container.