pam_rhosts.so 
This module performs the standard network authentication for services, as used by traditional implementations of rlogin and rsh etc.
      The authentication mechanism of this module is based on the contents
      of two files; /etc/hosts.equiv (or
      and ~/.rhosts. Firstly, hosts listed in the
      former file are treated as equivalent to the localhost. Secondly,
      entries in the user's own copy of the latter file is used to map
      "remote-host remote-user" pairs to that user's
      account on the current host. Access is granted to the user if their
      host is present in /etc/hosts.equiv and their
      remote account is identical to their local one, or if their remote
      account has an entry in their personal configuration file.
    
      The module authenticates a remote user (internally specified by the
      item PAM_RUSER connecting from the remote
      host (internally specified by the item PAM_RHOST).
      Accordingly, for applications to be compatible this authentication
      module they must set these items prior to calling
      pam_authenticate().  The module is not capable
      of independently probing the network connection for such information.
    
Print debug information.
Don't print informative messages.
            Handle account as root.
          
            The remote host, remote user name or the local user name
            couldn't be determined or access was denied by
            .rhosts file.
          
User is not known to system.
      To grant a remote user access by /etc/hosts.equiv
      or .rhosts for rsh add the
      following lines to /etc/pam.d/rsh:
      
#%PAM-1.0
#
auth     required       pam_rhosts.so
auth     required       pam_nologin.so
auth     required       pam_env.so
auth     required       pam_unix.so