lwresd.html revision 170222
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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> 188