title: JupyterHub LocalAuthenticator does not work
body: <p>I am trying to configure and understnad how the most common Jupyter authenticators work. However, I am having trouble understanding how <code>LocalAuthenticator</code> works and how it differs from <code>PAMAuthenticator</code>. The Jupyter documentation states the following: <code>The LocalAuthenticator is a special kind of authenticator that has the ability to manage users on the local system.</code>. Given that I am running everything locally, on my laptop, my uderstading is that I can use the same credentials I use to login to my Linux user. However this doesn't work. The JupyterHub server gives the following message: <code>Failed login for &lt;user&gt;</code>. </p>
  
  <p>My JupyterHub configuration file only contains the following line:</p>
  
  <p><code>c.JupyterHub.authenticator_class = 'jupyterhub.auth.LocalAuthenticator'</code>.</p>
  
  <p>If I change the above line to:</p>
  
  <p><code>c.JupyterHub.authenticator_class = 'jupyterhub.auth.PAMAuthenticator'</code></p>
  
  <p>then everything works just fine and the login is succesfull.</p>
  
  <p>Can someone explain me the differences of the two authenticators and why the <code>LocalAuthenticator</code> does not work in my case? The only difference I am aware of is that (according to the documentation) the <code>LocalAuthenticator</code> creates new users if they don't exist. However, after setting <code>c.LocalAuthenticator.create_system_users = True</code> and trying to login with a non-existent user, no new user is created.</p>
  
  <p>Thank you.</p>
  
  <p>PS: My OS is Debian Testing and I have installed JupyterHub using the instructions provided on its GitHub page.</p>