Scenario

You have a Kubernetes cluster where the deployment webapp in namespace prod is stuck in CrashLoopBackOff.

The application exposes a health check endpoint at /healthz on port 8080. The container image already includes a config directory with the required files, but the deployment configuration has issues preventing the pod from starting correctly.

Because the config directory already exists and is used by the application, mounting a ConfigMap over the entire directory would overwrite it and cause the app to fail. The deployment needs to be fixed so configuration is injected without replacing the existing directory.

Task

Fix the pod so it reaches Running state with 1/1 Ready

Step 1: Check pod status

kubectl get pods -n prod

Observe the pod in CrashLoopBackOff state. Note the pod name for later use.

Step 2: Check pod logs

kubectl logs -n prod <pod-name>

Replace <pod-name> with actual pod name. Look for error about missing config file.

Step 3: Verify ConfigMap exists

kubectl get configmap webapp-config -n prod -o yaml

Confirms the ConfigMap exists and shows its data.

Step 4: Edit the deployment to fix both issues

kubectl edit deployment webapp -n prod

Fix two issues:

1. ConfigMap mount - Add subPath to mount the ConfigMap key as a file (not directory):

volumeMounts:
- name: config-volume
  mountPath: /etc/webapp/config.yaml
  subPath: config.yaml

2. Readiness probe - Correct the path to match the application's health endpoint:

readinessProbe:
  httpGet:
    path: /healthz
    port: 8080
  initialDelaySeconds: 5
  periodSeconds: 10

Save and exit. Kubernetes will automatically roll out new pods with the fixes.

Step 5: Wait for new pod and verify status

kubectl get pods -n prod -w

Watch as old pod terminates and new pod becomes Running and Ready (1/1). Press Ctrl+C to stop.

Step 6: Verify config file is accessible

kubectl exec -n prod <pod-name> -- cat /etc/webapp/config.yaml

Replace <pod-name> with the new pod name. Should display ConfigMap content, confirming the subPath fix worked.