title: how to start puma with unix socket
body: <p>I have followed <a href="http://ruby-journal.com/how-to-setup-rails-app-with-puma-and-nginx/" rel="nofollow noreferrer">this link </a> to configure nginx with puma
  but when I start the server with<br>
  <code>bundle exec puma -e development -b unix:///var/run/my_app.sock</code><br>
  it throws <code>Permission denied - &quot;/var/run/my_app.sock&quot; (Errno::EACCES) error</code>.</p>
  <p>but when I start the server with <code>bundle exec puma -e development</code><br>
  it is started with  <code>tcp://0.0.0.0:9292</code></p>
  <p><code>my_app.sock file does not exist in /var/run/</code></p>
  <p>how do I start the server with unix socket and access the application through the domain name given in the <code>my_app.conf</code> file.</p>
  <p>Can you please anyone help me?.</p>