Challenge - ConfigMap

Write a ConfigMap and mount it as env in a Pod.

Challenge: externalize the config

Instead of baking an nginx site's config file into the image, you'll move it into a ConfigMap. The file will be mounted as a volume; when the config changes, the file will update without restarting the pods, and nginx will be told to reload.

kubectl create configmap nginx-ayar --from-file=default.conf
# ... volumes: configMap: nginx-ayar  ->  /etc/nginx/conf.d
kubectl create configmap nginx-ayar --from-file=default.conf --dry-run=client -o yaml | kubectl apply -f -
kubectl exec deploy/web -- nginx -s reload

Exercise A deployment template with a volume

Write a Deployment template's spec section (starting with spec:): an ayar volume from the nginx-ayar ConfigMap under volumes; container named nginx, image nginx:1.27; mount ayar at /etc/nginx/conf.d with readOnly: true.

Show example solution

spec:
  volumes:
    - name: ayar
      configMap:
        name: nginx-ayar
  containers:
    - name: nginx
      image: nginx:1.27
      volumeMounts:
        - name: ayar
          mountPath: /etc/nginx/conf.d
          readOnly: true

Exercise Update the config

Write three commands: generate the nginx-ayar ConfigMap from the default.conf file as YAML without creating it and pipe it into kubectl apply -f -; check the file by running cat /etc/nginx/conf.d/default.conf in deploy/web; run nginx -s reload in deploy/web.

Show example solution

kubectl create configmap nginx-ayar --from-file=default.conf --dry-run=client -o yaml | kubectl apply -f -
kubectl exec deploy/web -- cat /etc/nginx/conf.d/default.conf
kubectl exec deploy/web -- nginx -s reload

Test yourself

In this setup, what would happen if the config file were mounted with subPath?
- There'd be no difference
- The ConfigMap update wouldn't reach the file
- The file would never appear
- nginx would crash
Show answer

The ConfigMap update wouldn't reach the file — subPath mounts aren't refreshed automatically.

Make nginx reload its config.

kubectl exec deploy/web -- nginx -s ____

Show answer

kubectl exec deploy/web -- nginx -s reload

Match.

--from-file=default.conf

ConfigMap from a file
configMap volume

Mount as a file
| kubectl apply -f -

Update
nginx -s reload

Reload

Next lesson: Challenge - Intermediate project

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