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ConfigMaps

A ConfigMap is a type of resource used to store the configurations required by applications. It is used to store configuration data or configuration files in key-value pairs.

A ConfigMap allows you to decouple configurations from your environments, so that your environments can use different configurations. Compared with environment variables, ConfigMaps referenced in pods can be updated in real time. After the ConfigMap data is updated, the ConfigMaps referenced in pods are updated synchronously.

Creating a ConfigMap

In the following example, a ConfigMap named configmap-test is created. The ConfigMap configuration data is defined in the data field.

apiVersion: v1
kind: ConfigMap
metadata:
  name: configmap-test
data:                     # Configuration data
  property_1: Hello
  property_2: World

Referencing a ConfigMap as an Environment Variable

ConfigMaps are usually referenced as environment variables and in volumes.

In the following example, property_1 of configmap-test is used as the value of the environment variable EXAMPLE_PROPERTY_1. After the container is started, it will reference the value of property_1 as the value of EXAMPLE_PROPERTY_1, that is, Hello.

apiVersion: v1
kind: Pod
metadata:
  name: nginx
spec:
  containers:
  - image: nginx:alpine
    resources:
      limits:
        cpu: 100m
        memory: 200Mi
      requests:
        cpu: 100m
        memory: 200Mi
    env:
    - name: EXAMPLE_PROPERTY_1
      valueFrom:
        configMapKeyRef:          # Reference the ConfigMap.
          name: configmap-test
          key: property_1
  imagePullSecrets:
  - name: default-secret

Referencing a ConfigMap in a Volume

Referencing a ConfigMap in a volume is to fill its data in configuration files in the volume. Each piece of data is saved in a file. The key is the file name, and the key value is the file content.

In the following example, create a volume named vol-configmap, reference the ConfigMap named configmap-test in the volume, and mount the volume to the /tmp directory of the container. After the pod is created, the two files property_1 and property_2 are generated in the /tmp directory of the container, and the values are Hello and World.

apiVersion: v1
kind: Pod
metadata:
  name: nginx
spec:
  containers:
  - image: nginx:alpine
    resources:
      limits:
        cpu: 100m
        memory: 200Mi
      requests:
        cpu: 100m
        memory: 200Mi
    volumeMounts:
    - name: vol-configmap           # Mount the volume named vol-configmap.
      mountPath: "/tmp"
  imagePullSecrets:
  - name: default-secret
  volumes:
  - name: vol-configmap
    configMap:                      # Reference the ConfigMap.
      name: configmap-test
Parent topic: Configuration Management