title: Installation shopware with docker on linux and 503 error on
body: <p>I have been installed shopware 6 with docker on my Ubuntu linux. Generally installation has finished without problems. When I'm trying to run this on localhost:8000 I have 503 service unavailable problem like on the screenshoot:
  <a href="https://i.stack.imgur.com/ADWvj.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/ADWvj.png" alt="enter image description here" /></a></p>
  <p>In console after executing  docker-compose up
  I can observed an errors like:</p>
  <pre><code>app_server_1     | Setting php-fpm user to 0
  app_server_1     | [25-Feb-2021 07:11:13] ERROR: [pool www] please specify user and group other than root
  app_server_1     | [25-Feb-2021 07:11:13] ERROR: [pool www] please specify user and group other than root
  app_server_1     | [25-Feb-2021 07:11:13] ERROR: FPM initialization failed
  app_server_1     | [25-Feb-2021 07:11:13] ERROR: FPM initialization failed
  app_server_1     | 2021-02-25 07:11:13,941 INFO exited: php-fpmd (exit status 78; not expected)
  </code></pre>
  <p>I have added user to docker group:</p>
  <pre><code>sudo usermod -aG docker pirx1988
  </code></pre>
  <p>It didn't help me. How should I solve this problem?
  I would be greateful for help.</p>