What is a ConfigMap in Kubernetes?

Today, in the world of application development, it's recommended to separate the configuration from the code. Kubernetes' ConfigMaps helps us do this.

Create a ConfigMap

apiVersion: v1
kind: ConfigMap
metadata:
  name: example-config
data:
  # property-like keys; each key maps to a simple value
  "license": "XXXX"
  "licensedto": "dummy"
  # file-like keys
  app.properties: |
    key1=value1
    key2=value2

Uses of ConfigMap

We can use the ConfigMap for configuration inside a pod in the following ways:

  • Using commands and arguments inside a container.

  • Using environment variables for a container

  • Adding the ConfigMaps as a file in read-only volume, from where the application can read.

  • Using the Kubernetes API in the code running inside the container that can read the configmap.

Example

Here, we load the ConfigMaps values during pod initialization as environment variables.

apiVersion: v1
kind: Pod
metadata:
  name: configmap-example-pod
spec:
  containers:
    - name: example-container
      image: alpine
      command: ["sleep", "3600"]
      env:
        # Define the environment variable
        - name: LICENSE # Environment Variable name, can be different from configmap key
          valueFrom:
            configMapKeyRef:
              name: example-config # The ConfigMap this value comes from.
              key: license # The key to fetch.

Explanation

  • Line 10: We declare that the following lines in spec will set the environment of the container.

  • Line 12: We declare the name of the environment variable.

  • Line 14: We tell Kubernetes that the value of the environment variable is coming from the ConfigMap key.

  • Line 15: We provide the name of the ConfigMap declared in the previous example.

  • Line 16: We declare the key whose value is to be assigned to the environment variable.

Mount ConfigMap as a file in read-only volume

Following is an example of how to use values from a ConfigMap at the time of container initialization:

apiVersion: v1
kind: Pod
metadata:
  name: configmap-demo-pod
spec:
  containers:
    - name: demo
      image: alpine
      command: ["sleep", "3600"]
      volumeMounts:
      - name: config
        mountPath: "/config"
        readOnly: true
  volumes:
  - name: config
    configMap:      
      name: example-config

Explanation

Volumes are set at the pod level, then mounted into containers inside that pod.

  • Line 15: We provide the name of the config volume.

  • Line 17: We assign the name of the ConfigMap that has to be mounted.

The mounted configuration maps are updated automatically when the value in the `ConfigMap` changes.

Conclusion

ConfigMaps are a great mechanism to set up configurations separate from code. The configurations are updated automatically and redeployment is not required.

Note: The above does not hold true if the ConfigMap is marked as immutable.

Free Resources

Attributions:
  1. undefined by undefined
Copyright ©2026 Educative, Inc. All rights reserved