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7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User<div class="refentry" lang="en">
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User<a name="man.host"></a><div class="titlepage"></div>
1e9517ea2156b990be21f44676d3370318eacf17Tinderbox User<div class="refnamediv">
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User<h2>Name</h2>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User<p>host &#8212; DNS lookup utility</p>
1e9517ea2156b990be21f44676d3370318eacf17Tinderbox User</div>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User<div class="refsynopsisdiv">
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User<h2>Synopsis</h2>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User<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>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User</div>
1e9517ea2156b990be21f44676d3370318eacf17Tinderbox User<div class="refsect1" lang="en">
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User<a name="id2604615"></a><h2>DESCRIPTION</h2>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User<p><span><strong class="command">host</strong></span>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User is a simple utility for performing DNS lookups.
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User It is normally used to convert names to IP addresses and vice versa.
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User When no arguments or options are given,
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User <span><strong class="command">host</strong></span>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User prints a short summary of its command line arguments and options.
7e71f05d8643aca84914437c900cb716444507e4Tinderbox User </p>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User<p><em class="parameter"><code>name</code></em> is the domain name that is to be
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User looked
1e9517ea2156b990be21f44676d3370318eacf17Tinderbox User up. It can also be a dotted-decimal IPv4 address or a colon-delimited
1e9517ea2156b990be21f44676d3370318eacf17Tinderbox User IPv6 address, in which case <span><strong class="command">host</strong></span> will by
1e9517ea2156b990be21f44676d3370318eacf17Tinderbox User default
1e9517ea2156b990be21f44676d3370318eacf17Tinderbox User perform a reverse lookup for that address.
1e9517ea2156b990be21f44676d3370318eacf17Tinderbox User <em class="parameter"><code>server</code></em> is an optional argument which
1e9517ea2156b990be21f44676d3370318eacf17Tinderbox User is either
1e9517ea2156b990be21f44676d3370318eacf17Tinderbox User the name or IP address of the name server that <span><strong class="command">host</strong></span>
1e9517ea2156b990be21f44676d3370318eacf17Tinderbox User should query instead of the server or servers listed in
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User <code class="filename">/etc/resolv.conf</code>.
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User </p>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User<p>
7e71f05d8643aca84914437c900cb716444507e4Tinderbox User The <code class="option">-a</code> (all) option is equivalent to setting the
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User <code class="option">-v</code> option and asking <span><strong class="command">host</strong></span> to make
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User a query of type ANY.
1e9517ea2156b990be21f44676d3370318eacf17Tinderbox User </p>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User<p>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User When the <code class="option">-C</code> option is used, <span><strong class="command">host</strong></span>
1e9517ea2156b990be21f44676d3370318eacf17Tinderbox User will attempt to display the SOA records for zone
1e9517ea2156b990be21f44676d3370318eacf17Tinderbox User <em class="parameter"><code>name</code></em> from all the listed
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User authoritative name
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User servers for that zone. The list of name servers is defined by the NS
1e9517ea2156b990be21f44676d3370318eacf17Tinderbox User records that are found for the zone.
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User </p>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User<p>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User The <code class="option">-c</code> option instructs to make a DNS query of class
7e71f05d8643aca84914437c900cb716444507e4Tinderbox User <em class="parameter"><code>class</code></em>. This can be used to lookup
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User Hesiod or
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User Chaosnet class resource records. The default class is IN (Internet).
1e9517ea2156b990be21f44676d3370318eacf17Tinderbox User </p>
1e9517ea2156b990be21f44676d3370318eacf17Tinderbox User<p>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User Verbose output is generated by <span><strong class="command">host</strong></span> when
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User the
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User <code class="option">-d</code> or <code class="option">-v</code> option is used. The two
7e71f05d8643aca84914437c900cb716444507e4Tinderbox User options are equivalent. They have been provided for backwards
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User compatibility. In previous versions, the <code class="option">-d</code> option
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User switched on debugging traces and <code class="option">-v</code> enabled verbose
1e9517ea2156b990be21f44676d3370318eacf17Tinderbox User output.
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User </p>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User<p>
1e9517ea2156b990be21f44676d3370318eacf17Tinderbox User List mode is selected by the <code class="option">-l</code> option. This makes
1e9517ea2156b990be21f44676d3370318eacf17Tinderbox User <span><strong class="command">host</strong></span> perform a zone transfer for zone
1e9517ea2156b990be21f44676d3370318eacf17Tinderbox User <em class="parameter"><code>name</code></em>. Transfer the zone printing out
1e9517ea2156b990be21f44676d3370318eacf17Tinderbox User the NS, PTR
1e9517ea2156b990be21f44676d3370318eacf17Tinderbox User and address records (A/AAAA). If combined with <code class="option">-a</code>
1e9517ea2156b990be21f44676d3370318eacf17Tinderbox User all records will be printed.
1e9517ea2156b990be21f44676d3370318eacf17Tinderbox User </p>
1e9517ea2156b990be21f44676d3370318eacf17Tinderbox User<p>
1e9517ea2156b990be21f44676d3370318eacf17Tinderbox User The <code class="option">-i</code>
1e9517ea2156b990be21f44676d3370318eacf17Tinderbox User option specifies that reverse lookups of IPv6 addresses should
1e9517ea2156b990be21f44676d3370318eacf17Tinderbox User use the IP6.INT domain as defined in RFC1886.
1e9517ea2156b990be21f44676d3370318eacf17Tinderbox User The default is to use IP6.ARPA.
1e9517ea2156b990be21f44676d3370318eacf17Tinderbox User </p>
1e9517ea2156b990be21f44676d3370318eacf17Tinderbox User<p>
1e9517ea2156b990be21f44676d3370318eacf17Tinderbox User The <code class="option">-N</code> option sets the number of dots that have to be
1e9517ea2156b990be21f44676d3370318eacf17Tinderbox User in <em class="parameter"><code>name</code></em> for it to be considered
1e9517ea2156b990be21f44676d3370318eacf17Tinderbox User absolute. The
1e9517ea2156b990be21f44676d3370318eacf17Tinderbox User default value is that defined using the ndots statement in
1e9517ea2156b990be21f44676d3370318eacf17Tinderbox User <code class="filename">/etc/resolv.conf</code>, or 1 if no ndots
1e9517ea2156b990be21f44676d3370318eacf17Tinderbox User statement is
c313914d0e66b20969215e519bbf2ab4ecf39512Tinderbox User present. Names with fewer dots are interpreted as relative names and
1e9517ea2156b990be21f44676d3370318eacf17Tinderbox User will be searched for in the domains listed in the <span class="type">search</span>
1e9517ea2156b990be21f44676d3370318eacf17Tinderbox User or <span class="type">domain</span> directive in
<code class="filename">/etc/resolv.conf</code>.
</p>
<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="id2605197"></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="id2605226"></a><h2>FILES</h2>
<p><code class="filename">/etc/resolv.conf</code>
</p>
</div>
<div class="refsect1" lang="en">
<a name="id2605240"></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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