title: Kubernetes: How to refer to one environment variable from another?
body: <p>I've a <code>Deployment</code> object where I expose the POD ID using the <a href="https://kubernetes.io/docs/tasks/inject-data-application/environment-variable-expose-pod-information/" rel="noreferrer">Downward API</a>. That works fine. However, I want to set up another env variable, log path, with reference to the POD ID. But, setting that variable value to <code>/var/log/mycompany/${POD_ID}/logs</code> isn't working, no logs are created in the container.
  I can make the entrypoint script or the app aware of the POD ID, and build up the log path, but I'd rather not do that.</p>