Summary - ConfigMap

Combine YAML and volume mount to write a configurable Pod.

Summary: ConfigMap

In this group:

A ConfigMap separates non-secret settings from the image; data values are strings.
Creation: --from-literal, --from-file, --from-env-file or YAML.
Environment variables: envFrom.configMapRef (all) or configMapKeyRef (one); the pod is restarted for changes.
Volume: each key becomes a file; updates show up by themselves (except with subPath).
Updating: --dry-run=client -o yaml | kubectl apply -f - and rollout restart.

kubectl create cm api-ayar --from-env-file=api.env
kubectl rollout restart deploy/api

Exercise Config from an env file

Write three commands: create the api-ayar ConfigMap from the api.env file with --from-env-file; show it in detail; restart the api deployment.

Show example solution

kubectl create configmap api-ayar --from-env-file=api.env
kubectl describe configmap api-ayar
kubectl rollout restart deployment/api

Test yourself

Which method is chosen so a config change reaches the application without restarting the pod?
- configMapKeyRef
- Baking it into the image
- Mounting as a volume (without subPath) and the app rereading the file
- envFrom
Show answer

Mounting as a volume (without subPath) and the app rereading the file — Environment variables are only read when the process starts.
List the ConfigMaps.
```
kubectl get ____
```
Show answer
```
kubectl get cm
```
Match.

envFrom

Environment variable
volume

File
rollout restart

Make it read the new value
Secret

For secret data

Next lesson: What is a Secret?

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