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<html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>5.2. Use of syslog(3)</title><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot"><link rel="home" href="Linux-PAM_MWG.html" title="The Linux-PAM Module Writers' Guide"><link rel="up" href="mwg-see-programming.html" title="Chapter 5. Programming notes"><link rel="prev" href="mwg-see-programming-sec.html" title="5.1. Security issues for module creation"><link rel="next" href="mwg-see-programming-libs.html" title="5.3. Modules that require system libraries"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">5.2. Use of <span class="citerefentry"><span class="refentrytitle">syslog</span>(3)</span></th></tr><tr><td width="20%" align="left"><a accesskey="p" href="mwg-see-programming-sec.html">Prev</a> </td><th width="60%" align="center">Chapter 5. Programming notes</th><td width="20%" align="right"> <a accesskey="n" href="mwg-see-programming-libs.html">Next</a></td></tr></table><hr></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="mwg-see-programming-syslog"></a>5.2. Use of <span class="citerefentry"><span class="refentrytitle">syslog</span>(3)</span></h2></div></div></div><p>
        Only rarely should error information be directed to the user.
        Usually, this is to be limited to
        <span class="quote">“<span class="quote"><span class="emphasis"><em>sorry you cannot login now</em></span></span>”</span>
        type messages. Information concerning errors in the configuration
        file, <code class="filename">/etc/pam.conf</code>, or due to some system
        failure encountered by the module, should be written to
        <span class="citerefentry"><span class="refentrytitle">syslog</span>(3)</span> with <span class="emphasis"><em>facility-type</em></span>
        <span class="emphasis"><em>LOG_AUTHPRIV</em></span>.
      </p><p>
        With a few exceptions, the level of logging is, at the discretion
        of the module developer. Here is the recommended usage of different
        logging levels:
      </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>
            As a general rule, errors encountered by a module should be
            logged at the <span class="emphasis"><em>LOG_ERR</em></span> level. However,
            information regarding an unrecognized argument, passed to a
            module from an entry in the <code class="filename">/etc/pam.conf</code>
            file, is <span class="emphasis"><em>required</em></span> to be logged at the
            <span class="emphasis"><em>LOG_ERR</em></span> level.
          </p></li><li class="listitem"><p>
            Debugging information, as activated by the
            <span class="command"><strong>debug</strong></span> argument to the module in
            <code class="filename">/etc/pam.conf</code>, should be logged
            at the <span class="emphasis"><em>LOG_DEBUG</em></span> level.
          </p></li><li class="listitem"><p>
            If a module discovers that its personal configuration
            file or some system file it uses for information is
            corrupted or somehow unusable, it should indicate this
            by logging messages at level, <span class="emphasis"><em>LOG_ALERT</em></span>.
          </p></li><li class="listitem"><p>
            Shortages of system resources, such as a failure to
            manipulate a file or <code class="function">malloc()</code> failures
            should be logged at level <span class="emphasis"><em>LOG_CRIT</em></span>.
          </p></li><li class="listitem"><p>
            Authentication failures, associated with an incorrectly
            typed password should be logged at level,
            <span class="emphasis"><em>LOG_NOTICE</em></span>.
          </p></li></ul></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="mwg-see-programming-sec.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="mwg-see-programming.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="mwg-see-programming-libs.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">5.1. Security issues for module creation </td><td width="20%" align="center"><a accesskey="h" href="Linux-PAM_MWG.html">Home</a></td><td width="40%" align="right" valign="top"> 5.3. Modules that require system libraries</td></tr></table></div></body></html>