15.4. Use Cases: Consuming ConfigMaps in pods

Procedure

• You can consume the keys of this ConfigMap in a pod using configMapKeyRef sections.

  Sample Pod specification configured to inject specific environment variables

  apiVersion: v1
  kind: Pod
  metadata:
    name: dapi-test-pod
  spec:
    containers:
      - name: test-container
        image: gcr.io/google_containers/busybox
        command: [ "/bin/sh", "-c", "env" ]
        env: 

  1

  
          - name: SPECIAL_LEVEL_KEY 

  2

  
            valueFrom:
              configMapKeyRef:
                name: special-config 

  3

  
                key: special.how 

  4

  
          - name: SPECIAL_TYPE_KEY
            valueFrom:
              configMapKeyRef:
                name: special-config 

  5

  
                key: special.type 

  6

  
                optional: true 

  7

  
        envFrom: 

  8

  
          - configMapRef:
              name: env-config 

  9

  
    restartPolicy: Never

  1

  Stanza to pull the specified environment variables from a ConfigMap.

  2

  Name of a Pod environment variable that you are injecting a key’s value into.

  3 5

  Name of the ConfigMap to pull specific environment variables from.

  4 6

  Environment variable to pull from the ConfigMap.

  7

  Makes the environment variable optional. As optional, the Pod will be started even if the specified ConfigMap and keys do not exist.

  8

  Stanza to pull all environment variables from a ConfigMap.

  9

  Name of the ConfigMap to pull all environment variables from.

  When this Pod is run, the Pod logs will include the following output:

  SPECIAL_LEVEL_KEY=very
  log_level=INFO

Procedure

• To inject values into a command in a container, you must consume the keys you want to use as environment variables, as in the consuming ConfigMaps in environment variables use case. Then you can refer to them in a container’s command using the $(VAR_NAME) syntax.

  Sample Pod specification configured to inject specific environment variables

  apiVersion: v1
  kind: Pod
  metadata:
    name: dapi-test-pod
  spec:
    containers:
      - name: test-container
        image: gcr.io/google_containers/busybox
        command: [ "/bin/sh", "-c", "echo $(SPECIAL_LEVEL_KEY) $(SPECIAL_TYPE_KEY)" ] 

  1

  
        env:
          - name: SPECIAL_LEVEL_KEY
            valueFrom:
              configMapKeyRef:
                name: special-config
                key: special.how
          - name: SPECIAL_TYPE_KEY
            valueFrom:
              configMapKeyRef:
                name: special-config
                key: special.type
    restartPolicy: Never

  1

  Inject the values into a command in a container using the keys you want to use as environment variables.

  When this Pod is run, the output from the echo command run in the test-container container is as follows:

  very charm

• The most basic way to inject content into a volume by using a config map is to populate the volume with files where the key is the file name and the content of the file is the value of the key:

  apiVersion: v1
  kind: Pod
  metadata:
    name: dapi-test-pod
  spec:
    containers:
      - name: test-container
        image: gcr.io/google_containers/busybox
        command: [ "/bin/sh", "cat", "/etc/config/special.how" ]
        volumeMounts:
        - name: config-volume
          mountPath: /etc/config
    volumes:
      - name: config-volume
        configMap:
          name: special-config 

  1

  
    restartPolicy: Never

  1

  File containing key.

  When this pod is run, the output of the cat command will be:

  very

• You can also control the paths within the volume where ConfigMap keys are projected:

  apiVersion: v1
  kind: Pod
  metadata:
    name: dapi-test-pod
  spec:
    containers:
      - name: test-container
        image: gcr.io/google_containers/busybox
        command: [ "/bin/sh", "cat", "/etc/config/path/to/special-key" ]
        volumeMounts:
        - name: config-volume
          mountPath: /etc/config
    volumes:
      - name: config-volume
        configMap:
          name: special-config
          items:
          - key: special.how
            path: path/to/special-key 

  1

  
    restartPolicy: Never

  1

  Path to ConfigMap key.

  When this pod is run, the output of the cat command will be:

  very