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Latchu@DevOps
Latchu@DevOps

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🎯 Scenario #12 — Mount a ConfigMap as a Volume and Update It Dynamically in Kubernetes

#kubernetes #devops #cicd #containers

In this scenario you will:

✅ Create a ConfigMap
✅ Mount it as a volume inside a Pod
✅ Update the ConfigMap
✅ Watch the Pod automatically see the updated file (no restart needed!)
✅ Test real-time behavior

This is one of the most important Kubernetes features for configuration-driven apps.

✅ Step 1 — Create the ConfigMap

Create a file:

# config-volume-cm.yaml
apiVersion: v1
kind: ConfigMap
metadata:
  name: app-config
data:
  welcome.txt: |
    Welcome version 1
    This is the first config.
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Apply it:

kubectl apply -f config-volume-cm.yaml
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Verify:

kubectl get configmap app-config -o yaml
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✅ Step 2 — Create a Pod That Mounts the ConfigMap as a Volume

Create file:

# config-volume-pod.yaml
apiVersion: v1
kind: Pod
metadata:
  name: config-volume-demo
spec:
  containers:
  - name: nginx
    image: nginx:1.25
    volumeMounts:
    - name: config-volume
      mountPath: /usr/share/nginx/html/config    # Config file available here
  volumes:
  - name: config-volume
    configMap:
      name: app-config
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Apply:

kubectl apply -f config-volume-pod.yaml
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Check pod:

kubectl get pod config-volume-demo
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Wait until Running.

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✅ Step 3 — Verify the Mounted Config File

Exec into the container:

kubectl exec -it config-volume-demo -- bash
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Then check:

cat /usr/share/nginx/html/config/welcome.txt
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You will see:

Welcome version 1
This is the first config.
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✅ Perfect.

Exit:

exit
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✅ Step 4 — Update the ConfigMap (without restarting Pod)

Edit: config-volume-cm.yaml

# update configmap
data:
  welcome.txt: |
    Welcome version 2
    This config was updated dynamically!
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Apply:

kubectl apply -f config-volume-cm.yaml
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✅ Step 5 — Verify Update in the Running Pod (AUTO-UPDATE)

Exec again:

kubectl exec -it config-volume-demo -- bash
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Then:

cat /usr/share/nginx/html/config/welcome.txt
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EXPECTED OUTPUT:

Welcome version 2
This config was updated dynamically!
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✅ ConfigMap volume updates automatically (no restart required).

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✅ Important Note

✅ Volume-mounted ConfigMaps auto-update every ~1–2 seconds, thanks to Kubernetes file projections.
❌ But config from environment variables does NOT auto-update → requires pod restart.

This is why many apps prefer mounting ConfigMaps as volumes.

✅ Step 6 — Clean Up 

kubectl delete pod config-volume-demo
kubectl delete configmap app-config
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🌟 Thanks for reading! If this post added value, a like ❤️, follow, or share would encourage me to keep creating more content.

— Latchu | Senior DevOps & Cloud Engineer

☁️ AWS | GCP | ☸️ Kubernetes | 🔐 Security | ⚡ Automation
📌 Sharing hands-on guides, best practices & real-world cloud solutions

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