title: Postgresql won't work on ubuntu 16.04
body: <p>I have installed postgresql 9.5.13, but it seems not to work. I get continiosly this message: </p>
  
  <blockquote>
    <p>createuser: could not connect to database postgres: could not connect to    server: No such file or directory
        Is the server running locally and accepting
        connections on Unix domain socket "/var/run/postgresql/.s.PGSQL.5432"?</p>
  </blockquote>
  
  <p>when i try to create user. I have seen that this is common problem, but i can't find solution for this.</p>