Kubernetes-ConfigMaps

ConfigMaps

A ConfigMap is a Kubernetes API object used to store non-confidential data in key-value pairs. Pods can consume ConfigMaps as environment variables, command-line arguments, or as configuration files in a volume. 

  apiVersion: v1
  kind: ConfigMap
  metadata:
    name: game-demo
    labels:
      app: game-demo
  data:
    # property-like keys; each key maps to a simple value
    player_initial_lives: "3"
    ui_properties_file_name: "user-interface.properties"
  
    # file-like keys
    game.properties: |
      enemy.types=aliens,monsters
      player.maximum-lives=5    
    user-interface.properties: |
      color.good=purple
      color.bad=yellow
      allow.textmode=true

Creating a ConfigMap

  • From files
  kubectl create configmap [name] --from-file=[filepath]
  • From environment variables
  kubectl create configmap [name] --from-env-file=[filepath]

Using ConfigMaps in Pods

apiVersion: v1
kind: Pod
metadata:
  name: configmap-demo-pod
spec:
  containers:
    - name: demo
      image: alpine
      command: ["sleep", "3600"]
      env:
        # Define the environment variable
        - name: PLAYER_INITIAL_LIVES # Notice that the case is different here
                                     # from the key name in the ConfigMap.
          valueFrom:
            configMapKeyRef:
              name: game-demo           # The ConfigMap this value comes from.
              key: player_initial_lives # The key to fetch.
        - name: UI_PROPERTIES_FILE_NAME
          valueFrom:
            configMapKeyRef:
              name: game-demo
              key: ui_properties_file_name
      volumeMounts:
      - name: config
        mountPath: "/config"
        readOnly: true
  volumes:
    # You set volumes at the Pod level, then mount them into containers inside that Pod
    - name: config
      configMap:
        # Provide the name of the ConfigMap you want to mount.
        name: game-demo
        # An array of keys from the ConfigMap to create as files
        items:
        - key: "game.properties"
          path: "game.properties"
        - key: "user-interface.properties"
          path: "user-interface.properties"

References: