contrib/bind9/bin/named/lwresd.html

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  18 <html>
  19 <head>
  20 <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
  21 <title>lwresd</title>
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  24 <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="refentry" lang="en">
  25 <a name="id2476275"></a><div class="titlepage"></div>
  26 <div class="refnamediv">
  27 <h2>Name</h2>
  28 <p><span class="application">lwresd</span> &#8212; lightweight resolver daemon</p>
  29 </div>
  30 <div class="refsynopsisdiv">
  31 <h2>Synopsis</h2>
  32 <div class="cmdsynopsis"><p><code class="command">lwresd</code>  [<code class="option">-C <em class="replaceable"><code>config-file</code></em></code>] [<code class="option">-d <em class="replaceable"><code>debug-level</code></em></code>] [<code class="option">-f</code>] [<code class="option">-g</code>] [<code class="option">-i <em class="replaceable"><code>pid-file</code></em></code>] [<code class="option">-n <em class="replaceable"><code>#cpus</code></em></code>] [<code class="option">-P <em class="replaceable"><code>port</code></em></code>] [<code class="option">-p <em class="replaceable"><code>port</code></em></code>] [<code class="option">-s</code>] [<code class="option">-t <em class="replaceable"><code>directory</code></em></code>] [<code class="option">-u <em class="replaceable"><code>user</code></em></code>] [<code class="option">-v</code>]</p></div>
  33 </div>
  34 <div class="refsect1" lang="en">
  35 <a name="id2543435"></a><h2>DESCRIPTION</h2>
  36 <p><span><strong class="command">lwresd</strong></span>
  37       is the daemon providing name lookup
  38       services to clients that use the BIND 9 lightweight resolver
  39       library.  It is essentially a stripped-down, caching-only name
  40       server that answers queries using the BIND 9 lightweight
  41       resolver protocol rather than the DNS protocol.
  42     </p>
  43 <p><span><strong class="command">lwresd</strong></span>
  44       listens for resolver queries on a
  45       UDP port on the IPv4 loopback interface, 127.0.0.1.  This
  46       means that <span><strong class="command">lwresd</strong></span> can only be used by
  47       processes running on the local machine.  By default UDP port
  48       number 921 is used for lightweight resolver requests and
  49       responses.
  50     </p>
  51 <p>
  52       Incoming lightweight resolver requests are decoded by the
  53       server which then resolves them using the DNS protocol.  When
  54       the DNS lookup completes, <span><strong class="command">lwresd</strong></span> encodes
  55       the answers in the lightweight resolver format and returns
  56       them to the client that made the request.
  57     </p>
  58 <p>
  59       If <code class="filename">/etc/resolv.conf</code> contains any
  60       <code class="option">nameserver</code> entries, <span><strong class="command">lwresd</strong></span>
  61       sends recursive DNS queries to those servers.  This is similar
  62       to the use of forwarders in a caching name server.  If no
  63       <code class="option">nameserver</code> entries are present, or if
  64       forwarding fails, <span><strong class="command">lwresd</strong></span> resolves the
  65       queries autonomously starting at the root name servers, using
  66       a built-in list of root server hints.
  67     </p>
  68 </div>
  69 <div class="refsect1" lang="en">
  70 <a name="id2543482"></a><h2>OPTIONS</h2>
  71 <div class="variablelist"><dl>
  72 <dt><span class="term">-C <em class="replaceable"><code>config-file</code></em></span></dt>
  73 <dd><p>
  74             Use <em class="replaceable"><code>config-file</code></em> as the
  75             configuration file instead of the default,
  76             <code class="filename">/etc/resolv.conf</code>.
  77           </p></dd>
  78 <dt><span class="term">-d <em class="replaceable"><code>debug-level</code></em></span></dt>
  79 <dd><p>
  80             Set the daemon's debug level to <em class="replaceable"><code>debug-level</code></em>.
  81             Debugging traces from <span><strong class="command">lwresd</strong></span> become
  82                         more verbose as the debug level increases.
  83           </p></dd>
  84 <dt><span class="term">-f</span></dt>
  85 <dd><p>
  86             Run the server in the foreground (i.e. do not daemonize).
  87           </p></dd>
  88 <dt><span class="term">-g</span></dt>
  89 <dd><p>
  90             Run the server in the foreground and force all logging
  91             to <code class="filename">stderr</code>.
  92           </p></dd>
  93 <dt><span class="term">-n <em class="replaceable"><code>#cpus</code></em></span></dt>
  94 <dd><p>
  95             Create <em class="replaceable"><code>#cpus</code></em> worker threads
  96             to take advantage of multiple CPUs.  If not specified,
  97             <span><strong class="command">lwresd</strong></span> will try to determine the
  98             number of CPUs present and create one thread per CPU.
  99             If it is unable to determine the number of CPUs, a
 100             single worker thread will be created.
 101           </p></dd>
 102 <dt><span class="term">-P <em class="replaceable"><code>port</code></em></span></dt>
 103 <dd><p>
 104             Listen for lightweight resolver queries on port
 105             <em class="replaceable"><code>port</code></em>.  If
 106                         not specified, the default is port 921.
 107           </p></dd>
 108 <dt><span class="term">-p <em class="replaceable"><code>port</code></em></span></dt>
 109 <dd><p>
 110             Send DNS lookups to port <em class="replaceable"><code>port</code></em>.  If not
 111             specified, the default is port 53.  This provides a
 112             way of testing the lightweight resolver daemon with a
 113             name server that listens for queries on a non-standard
 114             port number.
 115           </p></dd>
 116 <dt><span class="term">-s</span></dt>
 117 <dd>
 118 <p>
 119             Write memory usage statistics to <code class="filename">stdout</code>
 120             on exit.
 121           </p>
 122 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
 123 <h3 class="title">Note</h3>
 124 <p>
 125               This option is mainly of interest to BIND 9 developers
 126               and may be removed or changed in a future release.
 127             </p>
 128 </div>
 129 </dd>
 130 <dt><span class="term">-t <em class="replaceable"><code>directory</code></em></span></dt>
 131 <dd>
 132 <p><code class="function">chroot()</code>
 133             to <em class="replaceable"><code>directory</code></em> after
 134             processing the command line arguments, but before
 135             reading the configuration file.
 136           </p>
 137 <div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;">
 138 <h3 class="title">Warning</h3>
 139 <p>
 140               This option should be used in conjunction with the
 141               <code class="option">-u</code> option, as chrooting a process
 142               running as root doesn't enhance security on most
 143               systems; the way <code class="function">chroot()</code> is
 144               defined allows a process with root privileges to
 145               escape a chroot jail.
 146             </p>
 147 </div>
 148 </dd>
 149 <dt><span class="term">-u <em class="replaceable"><code>user</code></em></span></dt>
 150 <dd><p><code class="function">setuid()</code>
 151             to <em class="replaceable"><code>user</code></em> after completing
 152             privileged operations, such as creating sockets that
 153             listen on privileged ports.
 154           </p></dd>
 155 <dt><span class="term">-v</span></dt>
 156 <dd><p>
 157             Report the version number and exit.
 158           </p></dd>
 159 </dl></div>
 160 </div>
 161 <div class="refsect1" lang="en">
 162 <a name="id2543746"></a><h2>FILES</h2>
 163 <div class="variablelist"><dl>
 164 <dt><span class="term"><code class="filename">/etc/resolv.conf</code></span></dt>
 165 <dd><p>
 166             The default configuration file.
 167           </p></dd>
 168 <dt><span class="term"><code class="filename">/var/run/lwresd.pid</code></span></dt>
 169 <dd><p>
 170             The default process-id file.
 171           </p></dd>
 172 </dl></div>
 173 </div>
 174 <div class="refsect1" lang="en">
 175 <a name="id2543785"></a><h2>SEE ALSO</h2>
 176 <p><span class="citerefentry"><span class="refentrytitle">named</span>(8)</span>,
 177       <span class="citerefentry"><span class="refentrytitle">lwres</span>(3)</span>,
 178       <span class="citerefentry"><span class="refentrytitle">resolver</span>(5)</span>.
 179     </p>
 180 </div>
 181 <div class="refsect1" lang="en">
 182 <a name="id2543819"></a><h2>AUTHOR</h2>
 183 <p><span class="corpauthor">Internet Systems Consortium</span>
 184     </p>
 185 </div>
 186 </div></body>
 187 </html>