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460b427411b72da26b1836b9424e2e70d65d9394David Lawrence<hr>
460b427411b72da26b1836b9424e2e70d65d9394David Lawrence</div>
460b427411b72da26b1836b9424e2e70d65d9394David Lawrence<div class="refentry" lang="en">
fcb54ce0a4f7377486df5bec83b3aa4711bf4131Mark Andrews<a name="man.host"></a><div class="titlepage"></div>
460b427411b72da26b1836b9424e2e70d65d9394David Lawrence<div class="refnamediv">
460b427411b72da26b1836b9424e2e70d65d9394David Lawrence<h2>Name</h2>
460b427411b72da26b1836b9424e2e70d65d9394David Lawrence<p>host &#8212; DNS lookup utility</p>
460b427411b72da26b1836b9424e2e70d65d9394David Lawrence</div>
460b427411b72da26b1836b9424e2e70d65d9394David Lawrence<div class="refsynopsisdiv">
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley<h2>Synopsis</h2>
12e63bfe1d111ccb57f482b28d56c785cccc7cf7David Lawrence<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>
12e63bfe1d111ccb57f482b28d56c785cccc7cf7David Lawrence</div>
12e63bfe1d111ccb57f482b28d56c785cccc7cf7David Lawrence<div class="refsect1" lang="en">
12e63bfe1d111ccb57f482b28d56c785cccc7cf7David Lawrence<a name="id2597954"></a><h2>DESCRIPTION</h2>
12e63bfe1d111ccb57f482b28d56c785cccc7cf7David Lawrence<p><span><strong class="command">host</strong></span>
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley is a simple utility for performing DNS lookups.
12e63bfe1d111ccb57f482b28d56c785cccc7cf7David Lawrence It is normally used to convert names to IP addresses and vice versa.
460b427411b72da26b1836b9424e2e70d65d9394David Lawrence When no arguments or options are given,
12e63bfe1d111ccb57f482b28d56c785cccc7cf7David Lawrence <span><strong class="command">host</strong></span>
460b427411b72da26b1836b9424e2e70d65d9394David Lawrence prints a short summary of its command line arguments and options.
12e63bfe1d111ccb57f482b28d56c785cccc7cf7David Lawrence </p>
460b427411b72da26b1836b9424e2e70d65d9394David Lawrence<p><em class="parameter"><code>name</code></em> is the domain name that is to be
12e63bfe1d111ccb57f482b28d56c785cccc7cf7David Lawrence looked
460b427411b72da26b1836b9424e2e70d65d9394David Lawrence up. It can also be a dotted-decimal IPv4 address or a colon-delimited
12e63bfe1d111ccb57f482b28d56c785cccc7cf7David Lawrence IPv6 address, in which case <span><strong class="command">host</strong></span> will by
460b427411b72da26b1836b9424e2e70d65d9394David Lawrence default
12e63bfe1d111ccb57f482b28d56c785cccc7cf7David Lawrence perform a reverse lookup for that address.
c32b87bc54abacf95fb3b063d72b7d1855c1643bMichael Graff <em class="parameter"><code>server</code></em> is an optional argument which
0014d6342b0d50ae37126ac16d5bf821d02ffff7David Lawrence is either
460b427411b72da26b1836b9424e2e70d65d9394David Lawrence the name or IP address of the name server that <span><strong class="command">host</strong></span>
12e63bfe1d111ccb57f482b28d56c785cccc7cf7David Lawrence should query instead of the server or servers listed in
12e63bfe1d111ccb57f482b28d56c785cccc7cf7David Lawrence <code class="filename">/etc/resolv.conf</code>.
12e63bfe1d111ccb57f482b28d56c785cccc7cf7David Lawrence </p>
460b427411b72da26b1836b9424e2e70d65d9394David Lawrence<p>
12e63bfe1d111ccb57f482b28d56c785cccc7cf7David Lawrence The <code class="option">-a</code> (all) option is equivalent to setting the
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley <code class="option">-v</code> option and asking <span><strong class="command">host</strong></span> to make
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley a query of type ANY.
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley </p>
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley<p>
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley When the <code class="option">-C</code> option is used, <span><strong class="command">host</strong></span>
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley will attempt to display the SOA records for zone
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley <em class="parameter"><code>name</code></em> from all the listed
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley authoritative name
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley servers for that zone. The list of name servers is defined by the NS
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley records that are found for the zone.
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley </p>
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley<p>
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley The <code class="option">-c</code> option instructs to make a DNS query of class
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley <em class="parameter"><code>class</code></em>. This can be used to lookup
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley Hesiod or
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley Chaosnet class resource records. The default class is IN (Internet).
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley </p>
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley<p>
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley Verbose output is generated by <span><strong class="command">host</strong></span> when
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley the
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley <code class="option">-d</code> or <code class="option">-v</code> option is used. The two
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley options are equivalent. They have been provided for backwards
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley compatibility. In previous versions, the <code class="option">-d</code> option
0014d6342b0d50ae37126ac16d5bf821d02ffff7David Lawrence switched on debugging traces and <code class="option">-v</code> enabled verbose
0014d6342b0d50ae37126ac16d5bf821d02ffff7David Lawrence output.
0014d6342b0d50ae37126ac16d5bf821d02ffff7David Lawrence </p>
0014d6342b0d50ae37126ac16d5bf821d02ffff7David Lawrence<p>
0014d6342b0d50ae37126ac16d5bf821d02ffff7David Lawrence List mode is selected by the <code class="option">-l</code> option. This makes
0014d6342b0d50ae37126ac16d5bf821d02ffff7David Lawrence <span><strong class="command">host</strong></span> perform a zone transfer for zone
0014d6342b0d50ae37126ac16d5bf821d02ffff7David Lawrence <em class="parameter"><code>name</code></em>. Transfer the zone printing out
0014d6342b0d50ae37126ac16d5bf821d02ffff7David Lawrence the NS, PTR
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley and address records (A/AAAA). If combined with <code class="option">-a</code>
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley all records will be printed.
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley </p>
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley<p>
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley The <code class="option">-i</code>
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley option specifies that reverse lookups of IPv6 addresses should
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley use the IP6.INT domain as defined in RFC1886.
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley The default is to use IP6.ARPA.
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley </p>
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley<p>
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley The <code class="option">-N</code> option sets the number of dots that have to be
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley in <em class="parameter"><code>name</code></em> for it to be considered
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley absolute. The
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley default value is that defined using the ndots statement in
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley <code class="filename">/etc/resolv.conf</code>, or 1 if no ndots
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley statement is
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley present. Names with fewer dots are interpreted as relative names and
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley will be searched for in the domains listed in the <span class="type">search</span>
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley or <span class="type">domain</span> directive in
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley <code class="filename">/etc/resolv.conf</code>.
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley </p>
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley<p>
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley The number of UDP retries for a lookup can be changed with the
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley <code class="option">-R</code> option. <em class="parameter"><code>number</code></em>
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley indicates
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley how many times <span><strong class="command">host</strong></span> will repeat a query
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley that does
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley not get answered. The default number of retries is 1. If
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley <em class="parameter"><code>number</code></em> is negative or zero, the
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley number of
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley retries will default to 1.
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley </p>
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley<p>
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley Non-recursive queries can be made via the <code class="option">-r</code> option.
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley Setting this option clears the <span class="type">RD</span> &#8212; recursion
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley desired &#8212; bit in the query which <span><strong class="command">host</strong></span> makes.
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley This should mean that the name server receiving the query will not
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley attempt to resolve <em class="parameter"><code>name</code></em>. The
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley <code class="option">-r</code> option enables <span><strong class="command">host</strong></span>
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley to mimic
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley the behavior of a name server by making non-recursive queries and
0b72c791466d0807bcf22522b5ddb7da902c2720Bob Halley 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 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="id2598400"></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="id2598428"></a><h2>FILES</h2>
<p><code class="filename">/etc/resolv.conf</code>
</p>
</div>
<div class="refsect1" lang="en">
<a name="id2598442"></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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