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<div class="refentry">
<div class="refnamediv">
<h2>Name</h2>
<p>
<span class="application">named</span>
— Internet domain name server
</p>
</div>
<div class="refsynopsisdiv">
<h2>Synopsis</h2>
<div class="cmdsynopsis"><p>
<code class="command">named</code>
[
[<code class="option">-4</code>]
| [<code class="option">-6</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">-D <em class="replaceable"><code>string</code></em></code>]
[<code class="option">-E <em class="replaceable"><code>engine-name</code></em></code>]
[<code class="option">-f</code>]
[<code class="option">-g</code>]
[<code class="option">-L <em class="replaceable"><code>logfile</code></em></code>]
[<code class="option">-M <em class="replaceable"><code>option</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">-s</code>]
[<code class="option">-S <em class="replaceable"><code>#max-socks</code></em></code>]
[<code class="option">-t <em class="replaceable"><code>directory</code></em></code>]
[<code class="option">-U <em class="replaceable"><code>#listeners</code></em></code>]
[<code class="option">-u <em class="replaceable"><code>user</code></em></code>]
[<code class="option">-v</code>]
[<code class="option">-V</code>]
[<code class="option">-X <em class="replaceable"><code>lock-file</code></em></code>]
[<code class="option">-x <em class="replaceable"><code>cache-file</code></em></code>]
</p></div>
</div>
<div class="refsection">
<a name="id-1.14.19.7"></a><h2>DESCRIPTION</h2>
<p><span class="command"><strong>named</strong></span>
is a Domain Name System (DNS) server,
part of the BIND 9 distribution from ISC. For more
information on the DNS, see RFCs 1033, 1034, and 1035.
</p>
<p>
When invoked without arguments, <span class="command"><strong>named</strong></span>
will
read the default configuration file
data, and listen for queries.
</p>
</div>
<div class="refsection">
<a name="id-1.14.19.8"></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,
ensure that reloading the configuration file continues
to work after the server has changed its working
directory due to to a possible
<code class="option">directory</code> option in the configuration
file, <em class="replaceable"><code>config-file</code></em> should be
an absolute pathname.
</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>named</strong></span> become
more verbose as the debug level increases.
</p>
</dd>
<dt><span class="term">-D <em class="replaceable"><code>string</code></em></span></dt>
<dd>
<p>
Specifies a string that is used to identify a instance of
<span class="command"><strong>named</strong></span> in a process listing. The contents
of <em class="replaceable"><code>string</code></em> are
not examined.
</p>
</dd>
<dt><span class="term">-E <em class="replaceable"><code>engine-name</code></em></span></dt>
<dd>
<p>
When applicable, specifies the hardware to use for
cryptographic operations, such as a secure key store used
for signing.
</p>
<p>
When BIND is built with OpenSSL PKCS#11 support, this defaults
to the string "pkcs11", which identifies an OpenSSL engine
that can drive a cryptographic accelerator or hardware service
module. When BIND is built with native PKCS#11 cryptography
(--enable-native-pkcs11), it defaults to the path of the PKCS#11
provider library specified via "--with-pkcs11".
</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">-L <em class="replaceable"><code>logfile</code></em></span></dt>
<dd>
<p>
Log to the file <code class="option">logfile</code> by default
instead of the system log.
</p>
</dd>
<dt><span class="term">-M <em class="replaceable"><code>option</code></em></span></dt>
<dd>
<p>
Sets the default memory context options. Currently
the only supported option is
<em class="replaceable"><code>external</code></em>,
which causes the internal memory manager to be bypassed
in favor of system-provided memory allocation functions.
</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>named</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 queries on port <em class="replaceable"><code>port</code></em>. If not
specified, the default is port 53.
</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">-S <em class="replaceable"><code>#max-socks</code></em></span></dt>
<dd>
<p>
Allow <span class="command"><strong>named</strong></span> to use up to
<em class="replaceable"><code>#max-socks</code></em> sockets.
The default value is 4096 on systems built with default
configuration options, and 21000 on systems built with
"configure --with-tuning=large".
</p>
<div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;">
<h3 class="title">Warning</h3>
<p>
This option should be unnecessary for the vast majority
of users.
The use of this option could even be harmful because the
specified value may exceed the limitation of the
underlying system API.
It is therefore set only when the default configuration
causes exhaustion of file descriptors and the
operational environment is known to support the
specified number of sockets.
Note also that the actual maximum number is normally a little
fewer than the specified value because
<span class="command"><strong>named</strong></span> reserves some file descriptors
for its internal use.
</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>#listeners</code></em></span></dt>
<dd>
<p>
Use <em class="replaceable"><code>#listeners</code></em>
worker threads to listen for incoming UDP packets on each
address. If not specified, <span class="command"><strong>named</strong></span> will
calculate a default value based on the number of detected
CPUs: 1 for 1 CPU, and the number of detected CPUs
minus one for machines with more than 1 CPU. This cannot
be increased to a value higher than the number of CPUs.
If <code class="option">-n</code> has been set to a higher value than
the number of detected CPUs, then <code class="option">-U</code> may
be increased as high as that value, but no higher.
On Windows, the number of UDP listeners is hardwired to 1
and this option has no effect.
</p>
</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>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<h3 class="title">Note</h3>
<p>
On Linux, <span class="command"><strong>named</strong></span> uses the kernel's
capability mechanism to drop all root privileges
except the ability to <code class="function">bind(2)</code> to
a
privileged port and set process resource limits.
Unfortunately, this means that the <code class="option">-u</code>
option only works when <span class="command"><strong>named</strong></span> is
run
on kernel 2.2.18 or later, or kernel 2.3.99-pre3 or
later, since previous kernels did not allow privileges
to be retained after <code class="function">setuid(2)</code>.
</p>
</div>
</dd>
<dt><span class="term">-v</span></dt>
<dd>
<p>
Report the version number and exit.
</p>
</dd>
<dt><span class="term">-V</span></dt>
<dd>
<p>
Report the version number and build options, and exit.
</p>
</dd>
<dt><span class="term">-X <em class="replaceable"><code>lock-file</code></em></span></dt>
<dd>
<p>
Acquire a lock on the specified file at runtime; this
helps to prevent duplicate <span class="command"><strong>named</strong></span> instances
from running simultaneously.
Use of this option overrides the <span class="command"><strong>lock-file</strong></span>
If set to <code class="literal">none</code>, the lock file check
is disabled.
</p>
</dd>
<dt><span class="term">-x <em class="replaceable"><code>cache-file</code></em></span></dt>
<dd>
<p>
Load data from <em class="replaceable"><code>cache-file</code></em> into the
cache of the default view.
</p>
<div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;">
<h3 class="title">Warning</h3>
<p>
This option must not be used. It is only of interest
to BIND 9 developers and may be removed or changed in a
future release.
</p>
</div>
</dd>
</dl></div>
</div>
<div class="refsection">
<a name="id-1.14.19.9"></a><h2>SIGNALS</h2>
<p>
In routine operation, signals should not be used to control
the nameserver; <span class="command"><strong>rndc</strong></span> should be used
instead.
</p>
<div class="variablelist"><dl class="variablelist">
<dt><span class="term">SIGHUP</span></dt>
<dd>
<p>
Force a reload of the server.
</p>
</dd>
<dt><span class="term">SIGINT, SIGTERM</span></dt>
<dd>
<p>
Shut down the server.
</p>
</dd>
</dl></div>
<p>
The result of sending any other signals to the server is undefined.
</p>
</div>
<div class="refsection">
<a name="id-1.14.19.10"></a><h2>CONFIGURATION</h2>
<p>
The <span class="command"><strong>named</strong></span> configuration file is too complex
to describe in detail here. A complete description is provided
in the
<em class="citetitle">BIND 9 Administrator Reference Manual</em>.
</p>
<p>
<span class="command"><strong>named</strong></span> inherits the <code class="function">umask</code>
(file creation mode mask) from the parent process. If files
created by <span class="command"><strong>named</strong></span>, such as journal files,
need to have custom permissions, the <code class="function">umask</code>
should be set explicitly in the script used to start the
<span class="command"><strong>named</strong></span> process.
</p>
</div>
<div class="refsection">
<a name="id-1.14.19.11"></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-1.14.19.12"></a><h2>SEE ALSO</h2>
<p><em class="citetitle">RFC 1033</em>,
<em class="citetitle">RFC 1034</em>,
<em class="citetitle">RFC 1035</em>,
<span class="citerefentry">
<span class="refentrytitle">named-checkconf</span>
(8)
</span>,
<span class="citerefentry">
<span class="refentrytitle">named-checkzone</span>
(8)
</span>,
<span class="citerefentry">
<span class="refentrytitle">rndc</span>
(8)
</span>,
<span class="citerefentry">
<span class="refentrytitle">lwresd</span>
(8)
</span>,
<span class="citerefentry">
(5)
</span>,
<em class="citetitle">BIND 9 Administrator Reference Manual</em>.
</p>
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