Kubernetes: How to push ConfigMap values as environment variables

2 min read | by Jordi Prats

We can read values from a ConfigMap as a volume but we can present them to a Pod as an environment variable

Let's assume we have the following ConfigMap that we want to use to populate environment variables to a Deployment:

apiVersion: v1
kind: ConfigMap
metadata:
  name: envvars-cm
data:
  VALUE_FROM_CONFIGMAP: '99'

We can read the values from the ConfigMap and push them as environment variables to a container using envFrom and configMapRef as follows:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: demo
spec:
  replicas: 1
  selector:
    matchLabels:
      app: demo
  template:
    metadata:
      labels:
        app: demo
    spec:
      containers:
        - name: ampa
          image: alpine:latest
          args: [ "sleep", "3600" ]
          env:
            - name: DIRECT_VALUE
              value: '00'
          envFrom:
            - configMapRef:
                name: envvars-cm

We can see how the data we have on the ConfigMap can be retrieved from the container that has the envFrom.configMapRef as an environment variable:

$ kubectl exec -i deploy/demo -- env | grep VALUE
VALUE_FROM_CONFIGMAP=99
DIRECT_VALUE=00

Posted on 27/10/2022

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