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ab023a65562e62b85a824509d829b6fad87e00b1Rob Austein<tr><th colspan="3" align="center">host</th></tr>
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ab023a65562e62b85a824509d829b6fad87e00b1Rob Austein</div>
ab023a65562e62b85a824509d829b6fad87e00b1Rob Austein<div class="refentry" lang="en">
ab023a65562e62b85a824509d829b6fad87e00b1Rob Austein<a name="man.host"></a><div class="titlepage"></div>
ab023a65562e62b85a824509d829b6fad87e00b1Rob Austein<div class="refnamediv">
ab023a65562e62b85a824509d829b6fad87e00b1Rob Austein<h2>Name</h2>
c7817270552b2faab56466b89731b6f290b352a4Mark Andrews<p>host &#8212; DNS lookup utility</p>
c7817270552b2faab56466b89731b6f290b352a4Mark Andrews</div>
c7817270552b2faab56466b89731b6f290b352a4Mark Andrews<div class="refsynopsisdiv">
f57cf8a2706c15bcb5fc1cb19faa0260b5111b0bMark Andrews<h2>Synopsis</h2>
f57cf8a2706c15bcb5fc1cb19faa0260b5111b0bMark Andrews<div class="cmdsynopsis"><p><code class="command">host</code> [<code class="option">-aCdlnrTwv</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>
ab023a65562e62b85a824509d829b6fad87e00b1Rob Austein</div>
1378841691ad112fce2376d9f2e54e02676057d3Michael Sawyer<div class="refsect1" lang="en">
1378841691ad112fce2376d9f2e54e02676057d3Michael Sawyer<a name="id2565085"></a><h2>DESCRIPTION</h2>
1378841691ad112fce2376d9f2e54e02676057d3Michael Sawyer<p><span><strong class="command">host</strong></span>
1378841691ad112fce2376d9f2e54e02676057d3Michael Sawyer is a simple utility for performing DNS lookups.
1378841691ad112fce2376d9f2e54e02676057d3Michael Sawyer It is normally used to convert names to IP addresses and vice versa.
1378841691ad112fce2376d9f2e54e02676057d3Michael Sawyer When no arguments or options are given,
1378841691ad112fce2376d9f2e54e02676057d3Michael Sawyer <span><strong class="command">host</strong></span>
1378841691ad112fce2376d9f2e54e02676057d3Michael Sawyer prints a short summary of its command line arguments and options.
1378841691ad112fce2376d9f2e54e02676057d3Michael Sawyer </p>
1378841691ad112fce2376d9f2e54e02676057d3Michael Sawyer<p><em class="parameter"><code>name</code></em> is the domain name that is to be
1378841691ad112fce2376d9f2e54e02676057d3Michael Sawyer looked
1378841691ad112fce2376d9f2e54e02676057d3Michael Sawyer up. It can also be a dotted-decimal IPv4 address or a colon-delimited
dd0fdd442633c66003c996ddf7dd229c8630ddc9Brian Wellington IPv6 address, in which case <span><strong class="command">host</strong></span> will by
dd0fdd442633c66003c996ddf7dd229c8630ddc9Brian Wellington default
dd0fdd442633c66003c996ddf7dd229c8630ddc9Brian Wellington perform a reverse lookup for that address.
c062bee4953be00fc5a04f023d5304810a171254Andreas Gustafsson <em class="parameter"><code>server</code></em> is an optional argument which
50bd180f4bd49cd6d6483e9b39e7f8165cd1dd8fDavid Lawrence is either
ab023a65562e62b85a824509d829b6fad87e00b1Rob Austein the name or IP address of the name server that <span><strong class="command">host</strong></span>
b6007467ebe8aaf72a1507d5da1b65b3ead5c7f3Andreas Gustafsson should query instead of the server or servers listed in
57b3597444bc8716459f0fb3022b2c12f4eee2aeAndreas Gustafsson <code class="filename">/etc/resolv.conf</code>.
1378841691ad112fce2376d9f2e54e02676057d3Michael Sawyer </p>
1378841691ad112fce2376d9f2e54e02676057d3Michael Sawyer<p>
1378841691ad112fce2376d9f2e54e02676057d3Michael Sawyer The <code class="option">-a</code> (all) option is equivalent to setting the
1378841691ad112fce2376d9f2e54e02676057d3Michael Sawyer <code class="option">-v</code> option and asking <span><strong class="command">host</strong></span> to make
40f53fa8d9c6a4fc38c0014495e7a42b08f52481David Lawrence a query of type ANY.
552a117791c17878c5c1b94b0fc3ac4e8491543eMark Andrews </p>
552a117791c17878c5c1b94b0fc3ac4e8491543eMark Andrews<p>
c062bee4953be00fc5a04f023d5304810a171254Andreas Gustafsson When the <code class="option">-C</code> option is used, <span><strong class="command">host</strong></span>
1378841691ad112fce2376d9f2e54e02676057d3Michael Sawyer will attempt to display the SOA records for zone
1378841691ad112fce2376d9f2e54e02676057d3Michael Sawyer <em class="parameter"><code>name</code></em> from all the listed
c062bee4953be00fc5a04f023d5304810a171254Andreas Gustafsson authoritative name
f57cf8a2706c15bcb5fc1cb19faa0260b5111b0bMark Andrews servers for that zone. The list of name servers is defined by the NS
records that are found for the zone.
</p>
<p>
The <code class="option">-c</code> option instructs to make a DNS query of class
<em class="parameter"><code>class</code></em>. This can be used to lookup
Hesiod or
Chaosnet class resource records. The default class is IN (Internet).
</p>
<p>
Verbose output is generated by <span><strong class="command">host</strong></span> when
the
<code class="option">-d</code> or <code class="option">-v</code> option is used. The two
options are equivalent. They have been provided for backwards
compatibility. In previous versions, the <code class="option">-d</code> option
switched on debugging traces and <code class="option">-v</code> enabled verbose
output.
</p>
<p>
List mode is selected by the <code class="option">-l</code> option. This makes
<span><strong class="command">host</strong></span> perform a zone transfer for zone
<em class="parameter"><code>name</code></em>. Transfer the zone printing out
the NS, PTR
and address records (A/AAAA). If combined with <code class="option">-a</code>
all records will be printed.
</p>
<p>
The <code class="option">-i</code>
option specifies that reverse lookups of IPv6 addresses should
use the IP6.INT domain as defined in RFC1886.
The default is to use IP6.ARPA.
</p>
<p>
The <code class="option">-N</code> option sets the number of dots that have to be
in <em class="parameter"><code>name</code></em> for it to be considered
absolute. The
default value is that defined using the ndots statement in
<code class="filename">/etc/resolv.conf</code>, or 1 if no ndots
statement is
present. Names with fewer dots are interpreted as relative names and
will be searched for in the domains listed in the <span class="type">search</span>
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 behaviour 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 recognised 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">-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="id2565721"></a><h2>FILES</h2>
<p><code class="filename">/etc/resolv.conf</code>
</p>
</div>
<div class="refsect1" lang="en">
<a name="id2565735"></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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