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<div class="refentry">
<div class="refnamediv">
<h2>Name</h2>
<p>
<span class="application">lwresd</span>
— lightweight resolver daemon
</p>
</div>
<div class="refsynopsisdiv">
<h2>Synopsis</h2>
<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">-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">-m <em class="replaceable"><code>flag</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>]
[
[<code class="option">-4</code>]
| [<code class="option">-6</code>]
]
</p></div>
</div>
<div class="refsection">
<a name="id-1.14.18.7"></a><h2>DESCRIPTION</h2>
<p><span class="command"><strong>lwresd</strong></span>
is the daemon providing name lookup
services to clients that use the BIND 9 lightweight resolver
library. It is essentially a stripped-down, caching-only name
server that answers queries using the BIND 9 lightweight
resolver protocol rather than the DNS protocol.
</p>
<p><span class="command"><strong>lwresd</strong></span>
listens for resolver queries on a
UDP port on the IPv4 loopback interface, 127.0.0.1. This
means that <span class="command"><strong>lwresd</strong></span> can only be used by
processes running on the local machine. By default, UDP port
number 921 is used for lightweight resolver requests and
responses.
</p>
<p>
Incoming lightweight resolver requests are decoded by the
server which then resolves them using the DNS protocol. When
the DNS lookup completes, <span class="command"><strong>lwresd</strong></span> encodes
the answers in the lightweight resolver format and returns
them to the client that made the request.
</p>
<p>
<code class="option">nameserver</code> entries, <span class="command"><strong>lwresd</strong></span>
sends recursive DNS queries to those servers. This is similar
to the use of forwarders in a caching name server. If no
<code class="option">nameserver</code> entries are present, or if
forwarding fails, <span class="command"><strong>lwresd</strong></span> resolves the
queries autonomously starting at the root name servers, using
a built-in list of root server hints.
</p>
</div>
<div class="refsection">
<a name="id-1.14.18.8"></a><h2>OPTIONS</h2>
<div class="variablelist"><dl class="variablelist">
<dt><span class="term">-4</span></dt>
<dd>
<p>
Use IPv4 only even if the host machine is capable of IPv6.
<code class="option">-4</code> and <code class="option">-6</code> are mutually
exclusive.
</p>
</dd>
<dt><span class="term">-6</span></dt>
<dd>
<p>
Use IPv6 only even if the host machine is capable of IPv4.
<code class="option">-4</code> and <code class="option">-6</code> are mutually
exclusive.
</p>
</dd>
<dt><span class="term">-c <em class="replaceable"><code>config-file</code></em></span></dt>
<dd>
<p>
Use <em class="replaceable"><code>config-file</code></em> as the
configuration file instead of the default,
<code class="option">-c</code> can not be used with <code class="option">-C</code>.
</p>
</dd>
<dt><span class="term">-C <em class="replaceable"><code>config-file</code></em></span></dt>
<dd>
<p>
Use <em class="replaceable"><code>config-file</code></em> as the
configuration file instead of the default,
<code class="option">-C</code> can not be used with <code class="option">-c</code>.
</p>
</dd>
<dt><span class="term">-d <em class="replaceable"><code>debug-level</code></em></span></dt>
<dd>
<p>
Set the daemon's debug level to <em class="replaceable"><code>debug-level</code></em>.
Debugging traces from <span class="command"><strong>lwresd</strong></span> become
more verbose as the debug level increases.
</p>
</dd>
<dt><span class="term">-f</span></dt>
<dd>
<p>
Run the server in the foreground (i.e. do not daemonize).
</p>
</dd>
<dt><span class="term">-g</span></dt>
<dd>
<p>
Run the server in the foreground and force all logging
to <code class="filename">stderr</code>.
</p>
</dd>
<dt><span class="term">-i <em class="replaceable"><code>pid-file</code></em></span></dt>
<dd>
<p>
Use <em class="replaceable"><code>pid-file</code></em> as the
PID file instead of the default,
</p>
</dd>
<dt><span class="term">-m <em class="replaceable"><code>flag</code></em></span></dt>
<dd>
<p>
Turn on memory usage debugging flags. Possible flags are
<em class="replaceable"><code>usage</code></em>,
<em class="replaceable"><code>trace</code></em>,
<em class="replaceable"><code>record</code></em>,
<em class="replaceable"><code>size</code></em>, and
<em class="replaceable"><code>mctx</code></em>.
These correspond to the ISC_MEM_DEBUGXXXX flags described in
</p>
</dd>
<dt><span class="term">-n <em class="replaceable"><code>#cpus</code></em></span></dt>
<dd>
<p>
Create <em class="replaceable"><code>#cpus</code></em> worker threads
to take advantage of multiple CPUs. If not specified,
<span class="command"><strong>lwresd</strong></span> will try to determine the
number of CPUs present and create one thread per CPU.
If it is unable to determine the number of CPUs, a
single worker thread will be created.
</p>
</dd>
<dt><span class="term">-P <em class="replaceable"><code>port</code></em></span></dt>
<dd>
<p>
Listen for lightweight resolver queries on port
<em class="replaceable"><code>port</code></em>. If
not specified, the default is port 921.
</p>
</dd>
<dt><span class="term">-p <em class="replaceable"><code>port</code></em></span></dt>
<dd>
<p>
Send DNS lookups to port <em class="replaceable"><code>port</code></em>. If not
specified, the default is port 53. This provides a
way of testing the lightweight resolver daemon with a
name server that listens for queries on a non-standard
port number.
</p>
</dd>
<dt><span class="term">-s</span></dt>
<dd>
<p>
Write memory usage statistics to <code class="filename">stdout</code>
on exit.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<h3 class="title">Note</h3>
<p>
This option is mainly of interest to BIND 9 developers
and may be removed or changed in a future release.
</p>
</div>
</dd>
<dt><span class="term">-t <em class="replaceable"><code>directory</code></em></span></dt>
<dd>
<p>Chroot
to <em class="replaceable"><code>directory</code></em> after
processing the command line arguments, but before
reading the configuration file.
</p>
<div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;">
<h3 class="title">Warning</h3>
<p>
This option should be used in conjunction with the
<code class="option">-u</code> option, as chrooting a process
running as root doesn't enhance security on most
systems; the way <code class="function">chroot(2)</code> is
defined allows a process with root privileges to
escape a chroot jail.
</p>
</div>
</dd>
<dt><span class="term">-u <em class="replaceable"><code>user</code></em></span></dt>
<dd>
<p>Setuid
to <em class="replaceable"><code>user</code></em> after completing
privileged operations, such as creating sockets that
listen on privileged ports.
</p>
</dd>
<dt><span class="term">-v</span></dt>
<dd>
<p>
Report the version number and exit.
</p>
</dd>
</dl></div>
</div>
<div class="refsection">
<a name="id-1.14.18.9"></a><h2>FILES</h2>
<div class="variablelist"><dl class="variablelist">
<dd>
<p>
The default configuration file.
</p>
</dd>
<dd>
<p>
The default process-id file.
</p>
</dd>
</dl></div>
</div>
<div class="refsection">
<a name="id-1.14.18.10"></a><h2>SEE ALSO</h2>
<p><span class="citerefentry">
<span class="refentrytitle">named</span>(8)
</span>,
<span class="citerefentry">
<span class="refentrytitle">lwres</span>(3)
</span>,
<span class="citerefentry">
<span class="refentrytitle">resolver</span>(5)
</span>.
</p>
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