Environment variable

Learn to mount a ConfigMap as environment variables.

As environment variables

ConfigMap values are given to a container as environment variables in two ways: one at a time with valueFrom.configMapKeyRef, or all keys at once with envFrom:

      containers:
        - name: api
          image: api:1.0
          envFrom:
            - configMapRef:
                name: api-ayar
          env:
            - name: SEVIYE
              valueFrom:
                configMapKeyRef:
                  name: api-ayar
                  key: LOG_LEVEL

Errors and optionality

If the ConfigMap a pod uses doesn't exist, the container stays in CreateContainerConfigError. If it's allowed to be missing, optional: true is written:

$ kubectl get pod api-5d8f7c9b4-qrstu
NAME                  READY   STATUS                       RESTARTS
api-5d8f7c9b4-qrstu   0/1     CreateContainerConfigError   0
$ kubectl describe pod api-5d8f7c9b4-qrstu | grep -i configmap
  Warning  Failed  configmap "api-ayar" not found

Exercise Give the config to the container

Write a Deployment's container section (starting with containers:): container named api, image api:1.0; all keys of the api-ayar ConfigMap with envFrom; under env, the SEVIYE variable from the LOG_LEVEL key of api-ayar with configMapKeyRef.

Show example solution

containers:
  - name: api
    image: api:1.0
    envFrom:
      - configMapRef:
          name: api-ayar
    env:
      - name: SEVIYE
        valueFrom:
          configMapKeyRef:
            name: api-ayar
            key: LOG_LEVEL

Test yourself

When a value in the ConfigMap changes, what does a running pod using it as an environment variable see?
- The pod crashes
- The old value; it doesn't change until the pod restarts
- The new value immediately
- An empty value
Show answer

The old value; it doesn't change until the pod restarts — Environment variables are read when the process starts; kubectl rollout restart is needed.

Make all keys of the ConfigMap environment variables.

          ____:
            - configMapRef:
                name: api-ayar

Show answer

          envFrom:
            - configMapRef:
                name: api-ayar

Match.

envFrom

All keys
configMapKeyRef

A single key
CreateContainerConfigError

ConfigMap not found
optional: true

Fine if missing

Next lesson: Mounting as a volume

We Are Enhancing Your Experience

Cookie Preferences

Strictly Necessary Cookies

Analytical Cookies