IT 3300 : Virtualization

Kubernetes ConfigMap

ConfigMap

ConfigMap is an 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.

A ConfigMap allows you to decouple environment-specific configuration from your container images, so that your applications are easily portable.

ConfigMap Why?

To separate configuration data from application code.

ConfigMap spec

You can write a Pod spec that refers to a ConfigMap and configures the container(s) in that Pod based on the data in the ConfigMap. The Pod and the ConfigMap must be in the same namespace.

ConfigMap yaml example

    apiVersion: v1
    kind: ConfigMap
    metadata:
      name: 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

ways that you can use a ConfigMap to configure a container inside a Pod

  • Inside a container command and args
  • Environment variables for a container
  • Add a file in read-only volume, for the application to read
  • Write code to run inside the Pod that uses the Kubernetes API to read a ConfigMap

Example of how to configure a pod with a config map

See here

Let's look at a few more examples

here