title: Apache/Nifi 1.12.1 Docker Image Issue
body: <p>I have a Dockerfile based on <code>apache/nifi:1.12.1</code> and want to expand it like this:</p>
  <pre><code>FROM apache/nifi:1.12.1
  RUN mkdir -p /opt/nifi/nifi-current/conf/flow
  </code></pre>
  <p>Thing is that the folder isn't created when I'm building the image from Linux distros like Ubuntu and CentOS. Build succeeds, I run it with <code>docker run -it -d --rm --name nifi nifi-test</code> but when I enter the container through <code>docker exec</code> there's no <code>flow</code> dir.</p>
  <p>Strange thing is, that the <code>flow</code> dir is being created normally when I'm building the image through Windows and Docker Desktop. I can't understand why is this happening.</p>
  <p>I've tried things such as <code>USER nifi</code> or <code>RUN chown ...</code> but still...</p>
  <p>For your convenience, this is the base image:
  <a href="https://github.com/apache/nifi/blob/rel/nifi-1.12.1/nifi-docker/dockerhub/Dockerfile" rel="nofollow noreferrer">https://github.com/apache/nifi/blob/rel/nifi-1.12.1/nifi-docker/dockerhub/Dockerfile</a></p>
  <p>Take a look at this as well:
  <a href="https://i.stack.imgur.com/xevgS.png" rel="nofollow noreferrer">This is what looks like at the CLI</a></p>
  <p>Thanks in advance.</p>