Portable Data with 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.