title: Cannot start PostgreSQL after installing in conda environment
body: <p>I am running an <code>Ubuntu 18.04.2 LTS</code>. I installed postgresql by typing <code>conda install postgresql</code> in my <code>conda</code> environment. Now I have postgresql 11.2 installed only in my environment.</p>
  
  <p>My understanding is that the postgres server should start automatically, so when I run <code>sudo -u postgres psql</code> I will log in as user postgres. Instead, when I run this command, I get:</p>
  
  <pre><code>sudo: unknown user: postgres
  sudo: unable to initialize policy plugin
  </code></pre>
  
  <p>Then I ran only <code>psql</code> which yielded another error:</p>
  
  <pre><code>psql: could not connect to server: No such file or directory
      Is the server running locally and accepting
      connections on Unix domain socket "/tmp/.s.PGSQL.5432"?
  </code></pre>
  
  <p>Finally, when checking my running processes, there is nothing for <code>postgres</code>, so I guess that the server is not running at all.</p>
  
  <p>Now, I can find my way around and start the server eventually, but I don't understand how I got myself in this situation. My question are:</p>
  
  <ol>
  <li>Why did the server not start on his own?</li>
  <li>When installing postgresql, is it good to install it in an environment on the first place, or is it better to use <code>sudo apt install postgresql</code> and have it installed on the server globally?</li>
  <li>How to fix this situation in the best possible way?</li>
  </ol>
  
  <p>Thanks!</p>