ConfigMaps

ConfigMaps are used to pass configuration data in the form of key-value pairs.

Creating a ConfigMap, the imperative way:

# command syntax:
kubectl create configmap ${configName} --from-literal=${key}=${value}

# example:
kubectl create configmap app-config \
  --from-literal=APP_COLOR=blue \
  --from-literal=APP_MOD=prod

# getting the key-value pairs from a file
kubectl create configmap app-config \
  --from-file=app_config.properties

ConfigMap, the declarative way:

apiVersion: v1
kind: ConfigMap
metadata:
  name: app-config
data:
  APP_COLOR: blue
  APP_MODE: prod

WARNING: a ConfigMap definition file doesn't need a spec.

ConfigMap in Pods:

# ... pod's definition
spec:
  containers:
    - # ...
      envFrom:
        - configMapRef:
          name: ${configMapName}

3 ways to use ConfigMaps in Pods:

• env var from whole config map
• single env var from the config map
• volume

# env var from whole config map
pod.spec.containers:
  - envFrom:
    - configMapRef:
        name: app-config


# single env var from the config map
pod.spec.containers:
  env:
    - name: APP_COLOR
      valueFrom:
        configMapKeyRef:
          name: app-config
          key: APP_COLOR


# volume
pod.spec.containers:
  volumes:
  - name: app-config-volume
    configMap:
      name: app-config

practicing: https://kodekloud.com/topic/configmaps-2/