title: Rails: "Permission denied - /tmp/cache/assets/development/sprockets/..."?
body: <p>When I run a rails app and navigate with browser to them I get an error from <code>rails</code>:</p>
  
  <pre><code>Permission denied - /path/to/my_rails_app/tmp/cache/assets/development/sprockets/37b5a12047376b10a57191a10d3af30a rails error
  </code></pre>
  
  <p>And I have no such file/folders behind the <code>./tmp/</code>. What is the problem?</p>