pam_shells.so 
      pam_shells is a PAM module that only allows access to the
      system if the users shell is listed in /etc/shells.
    
      It also checks if /etc/shells is a plain
      file and not world writable.
    
Access to the system was denied.
            The users login shell was listed as valid shell in
            /etc/shells.
          
The module was not able to get the name of the user.