containerization-and-devops

Class 13 - Apache Web App Deployment & Debugging

1. Objective

Deploy and manage an Apache web server and:

• Verify it runs
• Modify it
• Scale it
• Debug it

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2. Step-by-Step Flow (IMPORTANT)

Step 1: Run a Pod (Basic)

kubectl run apache-pod --image=httpd
kubectl get pods

👉 Creates a single temporary pod

Step 2: Inspect Pod

kubectl describe pod apache-pod

Check for:

• Image = httpd
• Port = 80
• Events

Step 3: Access App

kubectl port-forward pod/apache-pod 8081:80

Open: http://localhost:8081 👉 You will see: “It works!”

Terminal Output

Step 4: Delete Pod

kubectl delete pod apache-pod

Insight: Pod is deleted permanently. ❌ No recovery.

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3. Why Pod is Not Enough

👉 Pod = Temporary 👉 No self-healing

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4. Convert to Deployment (IMPORTANT)

Step 5: Create Deployment

kubectl create deployment apache --image=httpd
kubectl get deployments
kubectl get pods

👉 Deployment manages pods.

Step 6: Expose Deployment

kubectl expose deployment apache --port=80 --type=NodePort

Access App:

kubectl port-forward service/apache 8082:80

Open: http://localhost:8082

Terminal Output

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5. Scaling (VERY IMPORTANT)

Step 7: Scale

kubectl scale deployment apache --replicas=2
kubectl get pods

👉 Now:

• Multiple pods run the same app
• Better availability

Observation: Refresh the browser. Requests are handled by different pods.

Terminal Output

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6. Debugging (MOST IMPORTANT SKILL)

Step 8: Break App

kubectl set image deployment/apache httpd=wrongimage

Step 9: Diagnose

kubectl get pods
kubectl describe pod <pod-name>

Error: ImagePullBackOff

Step 10: Fix

kubectl set image deployment/apache httpd=httpd

Terminal Output

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7. Work Inside Container

Step 11: Enter Pod

kubectl exec -it <pod-name> -- /bin/bash

Check Files:

ls /usr/local/apache2/htdocs

👉 This is where website files are stored.

Exit:

exit

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8. Modify App (COOL PART)

kubectl exec -it <pod-name> -- /bin/bash
echo "Hello from Kubernetes" > /usr/local/apache2/htdocs/index.html

👉 Refresh browser → Content changes!

Terminal Output

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9. Self-Healing (VERY IMPORTANT CONCEPT)

Step 12: Delete One Pod

kubectl delete pod <pod-name>
kubectl get pods -w

👉 Kubernetes automatically: Creates a new pod.

Insight: Deployment ensures: Desired state = maintained.

Terminal Output

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10. Cleanup

kubectl delete deployment apache
kubectl delete service apache

Terminal Output

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11. Port Forwarding (Important Theory)

Why it blocks the terminal: Runs a live connection with continuous data flow.

Run in Background:

kubectl port-forward pod/apache-pod 8081:80 &

Manage Processes:

jobs
ps aux | grep port-forward
kill %1
kill <PID>
pkill -f port-forward

Best Practice:

tmux new -s pf
kubectl port-forward pod/apache-pod 8081:80

Detach: Ctrl + b, then d

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12. Key Concepts (VERY IMPORTANT FOR EXAM)

Pod vs Deployment

| Feature | Pod | Deployment | |—|—|—| | Lifespan | Temporary | Permanent | | Failure | No recovery | Self-healing | | Management| Manual | Automated |

Port Forwarding

• Only for debugging
• Not for production

Service

• Stable access point

Scaling

• Multiple pods = reliability

Debugging

👉 kubectl describe = Most important command

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🔥 FINAL UNDERSTANDING

This lab teaches:

• Real deployment
• Scaling
• Debugging
• Self-healing
• Container internals

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