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5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus<hr>
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus</div>
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus<div class="refentry" lang="en">
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus<a name="man.host"></a><div class="titlepage"></div>
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus<div class="refnamediv">
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus<h2>Name</h2>
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus<p>host &#8212; DNS lookup utility</p>
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus</div>
ff2835d14868672e6192c19f768bceda1a7b635cludo<div class="refsynopsisdiv">
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus<h2>Synopsis</h2>
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus<div class="cmdsynopsis"><p><code class="command">host</code> [<code class="option">-aCdlnrsTwv</code>] [<code class="option">-c <em class="replaceable"><code>class</code></em></code>] [<code class="option">-N <em class="replaceable"><code>ndots</code></em></code>] [<code class="option">-R <em class="replaceable"><code>number</code></em></code>] [<code class="option">-t <em class="replaceable"><code>type</code></em></code>] [<code class="option">-W <em class="replaceable"><code>wait</code></em></code>] [<code class="option">-m <em class="replaceable"><code>flag</code></em></code>] [<code class="option">-4</code>] [<code class="option">-6</code>] {name} [server]</p></div>
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus</div>
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus<div class="refsect1" lang="en">
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus<a name="id2611256"></a><h2>DESCRIPTION</h2>
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus<p><span><strong class="command">host</strong></span>
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus is a simple utility for performing DNS lookups.
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus It is normally used to convert names to IP addresses and vice versa.
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus When no arguments or options are given,
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus <span><strong class="command">host</strong></span>
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus prints a short summary of its command line arguments and options.
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus </p>
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus<p><em class="parameter"><code>name</code></em> is the domain name that is to be
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus looked
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus up. It can also be a dotted-decimal IPv4 address or a colon-delimited
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus IPv6 address, in which case <span><strong class="command">host</strong></span> will by
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus default
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus perform a reverse lookup for that address.
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus <em class="parameter"><code>server</code></em> is an optional argument which
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus is either
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus the name or IP address of the name server that <span><strong class="command">host</strong></span>
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus should query instead of the server or servers listed in
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus <code class="filename">/etc/resolv.conf</code>.
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus </p>
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus<p>
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus The <code class="option">-a</code> (all) option is equivalent to setting the
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus <code class="option">-v</code> option and asking <span><strong class="command">host</strong></span> to make
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus a query of type ANY.
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus </p>
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus<p>
220fbf31a324e487da4c3a3199083b6cffb84005jpikus When the <code class="option">-C</code> option is used, <span><strong class="command">host</strong></span>
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus will attempt to display the SOA records for zone
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus <em class="parameter"><code>name</code></em> from all the listed
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus authoritative name
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus servers for that zone. The list of name servers is defined by the NS
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus records that are found for the zone.
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus </p>
f43bf60164dfc1ac60e5332f7a17ca1425c88268matthew<p>
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus The <code class="option">-c</code> option instructs to make a DNS query of class
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus <em class="parameter"><code>class</code></em>. This can be used to lookup
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus Hesiod or
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus Chaosnet class resource records. The default class is IN (Internet).
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus </p>
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus<p>
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus Verbose output is generated by <span><strong class="command">host</strong></span> when
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus the
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus <code class="option">-d</code> or <code class="option">-v</code> option is used. The two
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus options are equivalent. They have been provided for backwards
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus compatibility. In previous versions, the <code class="option">-d</code> option
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus switched on debugging traces and <code class="option">-v</code> enabled verbose
ff2835d14868672e6192c19f768bceda1a7b635cludo output.
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus </p>
ff2835d14868672e6192c19f768bceda1a7b635cludo<p>
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus List mode is selected by the <code class="option">-l</code> option. This makes
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus <span><strong class="command">host</strong></span> perform a zone transfer for zone
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus <em class="parameter"><code>name</code></em>. Transfer the zone printing out
ff2835d14868672e6192c19f768bceda1a7b635cludo the NS, PTR
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus and address records (A/AAAA). If combined with <code class="option">-a</code>
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus all records will be printed.
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus </p>
ff2835d14868672e6192c19f768bceda1a7b635cludo<p>
ff2835d14868672e6192c19f768bceda1a7b635cludo The <code class="option">-i</code>
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus option specifies that reverse lookups of IPv6 addresses should
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus use the IP6.INT domain as defined in RFC1886.
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus The default is to use IP6.ARPA.
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus </p>
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus<p>
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus The <code class="option">-N</code> option sets the number of dots that have to be
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus in <em class="parameter"><code>name</code></em> for it to be considered
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus absolute. The
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus default value is that defined using the ndots statement in
ff2835d14868672e6192c19f768bceda1a7b635cludo <code class="filename">/etc/resolv.conf</code>, or 1 if no ndots
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus statement is
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus present. Names with fewer dots are interpreted as relative names and
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus will be searched for in the domains listed in the <span class="type">search</span>
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus or <span class="type">domain</span> directive in
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus <code class="filename">/etc/resolv.conf</code>.
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus </p>
5a3bd0ef762b8a3238869ac9963194555e39e6a7jpikus<p>
The number of UDP retries for a lookup can be changed with the
<code class="option">-R</code> option. <em class="parameter"><code>number</code></em>
indicates
how many times <span><strong class="command">host</strong></span> will repeat a query
that does
not get answered. The default number of retries is 1. If
<em class="parameter"><code>number</code></em> is negative or zero, the
number of
retries will default to 1.
</p>
<p>
Non-recursive queries can be made via the <code class="option">-r</code> option.
Setting this option clears the <span class="type">RD</span> &#8212; recursion
desired &#8212; bit in the query which <span><strong class="command">host</strong></span> makes.
This should mean that the name server receiving the query will not
attempt to resolve <em class="parameter"><code>name</code></em>. The
<code class="option">-r</code> option enables <span><strong class="command">host</strong></span>
to mimic
the behavior of a name server by making non-recursive queries and
expecting to receive answers to those queries that are usually
referrals to other name servers.
</p>
<p>
By default, <span><strong class="command">host</strong></span> uses UDP when making
queries. The
<code class="option">-T</code> option makes it use a TCP connection when querying
the name server. TCP will be automatically selected for queries that
require it, such as zone transfer (AXFR) requests.
</p>
<p>
The <code class="option">-4</code> option forces <span><strong class="command">host</strong></span> to only
use IPv4 query transport. The <code class="option">-6</code> option forces
<span><strong class="command">host</strong></span> to only use IPv6 query transport.
</p>
<p>
The <code class="option">-t</code> option is used to select the query type.
<em class="parameter"><code>type</code></em> can be any recognized query
type: CNAME,
NS, SOA, SIG, KEY, AXFR, etc. When no query type is specified,
<span><strong class="command">host</strong></span> automatically selects an appropriate
query
type. By default, it looks for A, AAAA, and MX records, but if the
<code class="option">-C</code> option was given, queries will be made for SOA
records, and if <em class="parameter"><code>name</code></em> is a
dotted-decimal IPv4
address or colon-delimited IPv6 address, <span><strong class="command">host</strong></span> will
query for PTR records. If a query type of IXFR is chosen the starting
serial number can be specified by appending an equal followed by the
starting serial number (e.g. -t IXFR=12345678).
</p>
<p>
The time to wait for a reply can be controlled through the
<code class="option">-W</code> and <code class="option">-w</code> options. The
<code class="option">-W</code> option makes <span><strong class="command">host</strong></span>
wait for
<em class="parameter"><code>wait</code></em> seconds. If <em class="parameter"><code>wait</code></em>
is less than one, the wait interval is set to one second. When the
<code class="option">-w</code> option is used, <span><strong class="command">host</strong></span>
will
effectively wait forever for a reply. The time to wait for a response
will be set to the number of seconds given by the hardware's maximum
value for an integer quantity.
</p>
<p>
The <code class="option">-s</code> option tells <span><strong class="command">host</strong></span>
<span class="emphasis"><em>not</em></span> to send the query to the next nameserver
if any server responds with a SERVFAIL response, which is the
reverse of normal stub resolver behavior.
</p>
<p>
The <code class="option">-m</code> can be used to set the memory usage debugging
flags
<em class="parameter"><code>record</code></em>, <em class="parameter"><code>usage</code></em> and
<em class="parameter"><code>trace</code></em>.
</p>
</div>
<div class="refsect1" lang="en">
<a name="id2612112"></a><h2>IDN SUPPORT</h2>
<p>
If <span><strong class="command">host</strong></span> has been built with IDN (internationalized
domain name) support, it can accept and display non-ASCII domain names.
<span><strong class="command">host</strong></span> appropriately converts character encoding of
domain name before sending a request to DNS server or displaying a
reply from the server.
If you'd like to turn off the IDN support for some reason, defines
the <code class="envar">IDN_DISABLE</code> environment variable.
The IDN support is disabled if the variable is set when
<span><strong class="command">host</strong></span> runs.
</p>
</div>
<div class="refsect1" lang="en">
<a name="id2612140"></a><h2>FILES</h2>
<p><code class="filename">/etc/resolv.conf</code>
</p>
</div>
<div class="refsect1" lang="en">
<a name="id2612154"></a><h2>SEE ALSO</h2>
<p><span class="citerefentry"><span class="refentrytitle">dig</span>(1)</span>,
<span class="citerefentry"><span class="refentrytitle">named</span>(8)</span>.
</p>
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