ConfigMap

Contents

Use a ConfigMap for setting configuration data separately from application code.
ConfigMap does not provide secrecy or encryption. If the data you want to store are confidential, use a Secret rather than a ConfigMap.

Terminology

a ConfigMap can have one to many entries
an entry is a key/value pair

Once data is stored in a ConfigMap, it can be injected into containers at run-time via any of the fllowing methods

env variable
arguent to the container's startup command
files in a volume

NOTE: Kubernetes natives app can access ConfigMap data from the API... but this is rare.

Config Map Definition

Configuration File

apiVersion: v1
kind: ConfigMap
metadata:
  name: customer1
data:
  customer-first: John
  customer-last: Doo
  customer-address: somewhere in the sky

Kubectl

kubectl create configmap my-config --from-literal key1=value1 --from-literal key2=value2
or
kubectl create configmap my-config --from-literal=key1=value1 --from-literal=key2=value2

kubectl create configmap my-config --from-file foo.txt

the key name is the name of the file (including its extension)
the value is the content of the file

NOTE: --from-file can use directories instead of providing one --from-file statement per file.

Property file

First, we need to create a file permission-reset.properties with the following configuration data:

permission=read-only
allowed="true"
resetCount=3

We can then create the ConfigMap with the following command:

kubectl create configmap permission-config --from-file=<path/to/>permission-reset.properties

Here, permission-config contains a single key (permission-reset.properties). The value is the full content of the file.

ConfigMap usage Inside Pods

Using environment variables

IMPORTANT any update you make to the values in a config map will NOT be reflected in running containers!

Full config Map usage

...
  containers:
  - name: myapp-full-container
    image: myapp
    envFrom:
    - configMapRef:
      name: full-config-map
...

Partial config Map usage

...
  containers:
  - name: myapp-specific-container
    image: myapp
    env:
    - name: SPECIFIC_ENV_VAR1
      valueFrom:
        configMapKeyRef:
          name: config-map-1
          key: key-in-map-1
    - name: SPECIFIC_ENV_VAR2
      valueFrom:
        configMapKeyRef:
          name: config-map-2
          key: key-in-map-2
...

List env variables

kubectl exec <my-pod-name> -- /bin/bash -c 'env'