e class="literal">pam</code></span></dt><dd><p>
          Authenticate using the Pluggable Authentication Modules
          (PAM) service provided by the operating system.  See <a class="xref" href="auth-pam.html" title="21.13. PAM Authentication">Section 21.13</a> for details.
         </p></dd><dt><span class="term"><code class="literal">bsd</code></span></dt><dd><p>
          Authenticate using the BSD Authentication service provided by the
          operating system. See <a class="xref" href="auth-bsd