ConfigMaps

ConfigMaps

A similar API resource to Secrets is the ConfigMap, except the data is not encoded. In keeping with the concept of decoupling in Kubernetes, using a ConfigMap decouples a container image from configuration artifacts.

They store data as sets of key-value pairs or plain configuration files in any format. The data can come from a collection of files or all files in a directory. It can also be populated from a literal value.

A ConfigMap can be used in several different ways. A container can use the data as environmental variables from one or more sources. The values contained inside can be passed to commands inside the Pod. A Volume or a file in a Volume can be created, including different names and particular access modes. In addition, cluster components like controllers can use the data.

Let's say you have a file on your local filesystem called config.js. You can create a ConfigMap that contains this file. The configmap object will have a data section containing the content of the file:

kubectl get configmap foobar -o yaml

kind: ConfigMap
apiVersion: v1
metadata:
    name: foobar
data:
    config.js: |
         {
...

ConfigMaps can be consumed in various ways:

• Pod environmental variables from single or multiple ConfigMaps
• Use ConfigMap values in Pod commands
• Populate Volume from ConfigMap
• Add ConfigMap data to specific path in Volume
• Set file names and access mode in Volume from ConfigMap data
• Can be used by system components and controllers.

Using ConfigMap

ConfigMaps can be consumed similar to Secrets by using environmental variables or mounting volumes.

To use as environmental variables, the Pod manifest will use valueFrom key and configMapKeyRef value to read the values:

env:
- name: SPECIAL_LEVEL_KEY
  valueFrom:
    configMapKeyRef:
      name: special-config
      key: special.how

To use with volumes:

volumes:
  - name: config-volume
    configMap:
      name: special-config