docs/community/samples/serving/helloworld-r/service.yaml

apiVersion: serving.knative.dev/v1alpha1
kind: Service
metadata:
  name: helloworld-r
  namespace: default
spec:
  template:
    spec:
      containers:
      - image: docker.io/akitsch/helloworld-r
        env:
        - name: TARGET
          value: "R Sample v1"