title: How to pass kubernetes pod instance id to within the pod upon start up?
body: <p>So I'm researching how to use Kubernetes for my case. I installed it and played a bit.</p>
  
  <p>The question is when the replication controller starts couple of replicas they have something like an id in their name:</p>
  
  <ol>
  <li>How unique is this id? Is it uniqueness for the lifetime of kubernetes? Is it unique across different kubernetes runs (i.e. if I restart kubernetes)?</li>
  <li>How to pass this id to the app in the container? Can I specify some kind of template in the yaml so for example the id will be assigned to environment variable or something similar?</li>
  <li>Alternatively is there a way for the app in the container to ask for this id?</li>
  </ol>
  
  <p>More explanation of the use case. I have an application that writes some session files inside a directory. I want to guarantee unique for the session ids in the system. This means if one app instance is running on VM1 and another instance on VM2, I want to prepend some kind of identifier to the ids like app-1-dajk4l and app-2-dajk4l, where app is the name of the app and 1, 2 is the instance identifier, which should come from the replication controller because it is dynamic and can not be configured manually. dajk4l is some identifier like the current timestamp or similar.</p>
  
  <p>Thanks.</p>