title: Do docker images have access to the tmp dir?
body: <p>I'm trying to understand to what extent a docker image has access to a /tmp/ directory. </p>
  
  <p>In my case I'm using the frolvlad/alpine-oraclejdk8:slim image and my app needs to write to a temp folder. </p>
  
  <p>When i define tmpfs like this in my docker-compose (v2) file:
  <code>
  df_server:
      image: "${DF_IMAGE}"
      build: .
      tmpfs:
        - /tmp
  </code>
  I get an error saying that the directory exists already. When I try to access the directory from my webapp, I get an error saying the directory does not exist. </p>
  
  <p>When I define the tmpfs dir as anything else, e.g.
  <code>
      tmpfs:
        - /foobar
  </code>
  My webapp can access and use the the directory foobar.</p>