kubevarsubexample.yaml

kind: ConfigMap
apiVersion: v1
metadata:
  name: myconfig
data:
  HELLO: world
  SPAM: eggs
---
apiVersion: v1
kind: Pod
metadata:
  name: mypod
spec:
  restartPolicy: Never
  containers:
    - name: mycontainer
      image: registry.k8s.io/busybox
      command:
        - /bin/echo
        - Hello world!
        - Env var HELLO is "$HELLO"—surprise!. # Incorrect shell form.
        - Env var SPAM is "$(SPAM)"—expected. # Correct $(VAR_NAME) Kubernetes substitution syntax—see https://kubernetes.io/docs/tasks/configure-pod-container/configure-pod-configmap/#use-configmap-defined-environment-variables-in-pod-commands.
      envFrom:
        - configMapRef:
            name: myconfig