20.14. BSD Authentication
  This authentication method operates similarly to
  
   password
  
  except that it uses BSD Authentication
    to verify the password. BSD Authentication is used only
    to validate user name/password pairs. Therefore the user's role must
    already exist in the database before BSD Authentication can be used
    for authentication. The BSD Authentication framework is currently
    only available on OpenBSD.
 
  BSD Authentication in
  
   PostgreSQL
  
  uses
    the
  
   auth-postgresql
  
  login type and authenticates with
    the
  
   postgresql
  
  login class if that's defined
    in
  
   login.conf
  
  . By default that login class does not
    exist, and
  
   PostgreSQL
  
  will use the default login class.
 
Note
   To use BSD Authentication, the PostgreSQL user account (that is, the
     operating system user running the server) must first be added to
     the
   
    auth
   
   group.  The
   
    auth
   
   group
     exists by default on OpenBSD systems.