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0c27b3fe77ac1d5094ba3521e8142d9e7973133fMark Andrews - Copyright (C) 2004, 2005, 2007, 2008 Internet Systems Consortium, Inc. ("ISC")
d4ef65050feac78554addf6e16a06c6e2e0bd331Brian Wellington - Copyright (C) 2000-2002 Internet Software Consortium.
0c27b3fe77ac1d5094ba3521e8142d9e7973133fMark Andrews - Permission to use, copy, modify, and distribute this software for any
0c27b3fe77ac1d5094ba3521e8142d9e7973133fMark Andrews - purpose with or without fee is hereby granted, provided that the above
d4ef65050feac78554addf6e16a06c6e2e0bd331Brian Wellington - copyright notice and this permission notice appear in all copies.
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt - THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
83a28ca274521e15086fc39febde507bcc4e145eMark Andrews - REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt - AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt - INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt - LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
c40265eba0c99708887d68e67901924065ba2514Brian Wellington - OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt - PERFORMANCE OF THIS SOFTWARE.
c40265eba0c99708887d68e67901924065ba2514Brian Wellington<!-- $Id: host.html,v 1.28 2008/04/05 01:09:34 tbox Exp $ -->
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c40265eba0c99708887d68e67901924065ba2514Brian Wellington<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="refentry" lang="en">
268a4475065fe6a8cd7cc707820982cf5e98f430Rob Austein<a name="man.host"></a><div class="titlepage"></div>
141132c272ebc41da4c55d69c49810fafadbbc11Mark Andrews<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>
20f2d1d74b67d096f858dc70cedf9af6dcc38dc7Automatic Updater<a name="id2543431"></a><h2>DESCRIPTION</h2>
339d2a4d4b3b2e0be9e43afec6e84fe468edfaeeAutomatic Updater<p><span><strong class="command">host</strong></span>
3b398443f0dca316ba7a6e057ba2d1b8ab4ddf70Tinderbox User is a simple utility for performing DNS lookups.
5c6b95ba1b2e35f8dd6b0a7f25aacba91fff3aa2Tinderbox User It is normally used to convert names to IP addresses and vice versa.
e676a596869d8a80a644c99a848afb53d1c5975eMark Andrews When no arguments or options are given,
6a6ceba6fe09c81558362f238dd727576af7108dTinderbox User <span><strong class="command">host</strong></span>
0c27b3fe77ac1d5094ba3521e8142d9e7973133fMark Andrews prints a short summary of its command line arguments and options.
268a4475065fe6a8cd7cc707820982cf5e98f430Rob Austein<p><em class="parameter"><code>name</code></em> is the domain name that is to be
268a4475065fe6a8cd7cc707820982cf5e98f430Rob Austein up. It can also be a dotted-decimal IPv4 address or a colon-delimited
c40265eba0c99708887d68e67901924065ba2514Brian Wellington IPv6 address, in which case <span><strong class="command">host</strong></span> will by
a903095bf4512dae561c7f6fc7854a51bebf334aMark Andrews perform a reverse lookup for that address.
a903095bf4512dae561c7f6fc7854a51bebf334aMark Andrews <em class="parameter"><code>server</code></em> is an optional argument which
c40265eba0c99708887d68e67901924065ba2514Brian Wellington the name or IP address of the name server that <span><strong class="command">host</strong></span>
c40265eba0c99708887d68e67901924065ba2514Brian Wellington should query instead of the server or servers listed in
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt The <code class="option">-a</code> (all) option is equivalent to setting the
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt <code class="option">-v</code> option and asking <span><strong class="command">host</strong></span> to make
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt a query of type ANY.
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt When the <code class="option">-C</code> option is used, <span><strong class="command">host</strong></span>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt will attempt to display the SOA records for zone
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt <em class="parameter"><code>name</code></em> from all the listed
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt authoritative name
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt servers for that zone. The list of name servers is defined by the NS
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt records that are found for the zone.
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt The <code class="option">-c</code> option instructs to make a DNS query of class
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt <em class="parameter"><code>class</code></em>. This can be used to lookup
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt Chaosnet class resource records. The default class is IN (Internet).
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt Verbose output is generated by <span><strong class="command">host</strong></span> when
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt <code class="option">-d</code> or <code class="option">-v</code> option is used. The two
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt options are equivalent. They have been provided for backwards
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt compatibility. In previous versions, the <code class="option">-d</code> option
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt switched on debugging traces and <code class="option">-v</code> enabled verbose
a903095bf4512dae561c7f6fc7854a51bebf334aMark Andrews List mode is selected by the <code class="option">-l</code> option. This makes
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt <span><strong class="command">host</strong></span> perform a zone transfer for zone
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt <em class="parameter"><code>name</code></em>. Transfer the zone printing out
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt and address records (A/AAAA). If combined with <code class="option">-a</code>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt all records will be printed.
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt option specifies that reverse lookups of IPv6 addresses should
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt use the IP6.INT domain as defined in RFC1886.
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt The default is to use IP6.ARPA.
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt The <code class="option">-N</code> option sets the number of dots that have to be
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt in <em class="parameter"><code>name</code></em> for it to be considered
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt absolute. The
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt default value is that defined using the ndots statement in
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt <code class="filename">/etc/resolv.conf</code>, or 1 if no ndots
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt statement is
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt present. Names with fewer dots are interpreted as relative names and
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt will be searched for in the domains listed in the <span class="type">search</span>
c40265eba0c99708887d68e67901924065ba2514Brian Wellington The number of UDP retries for a lookup can be changed with the
c40265eba0c99708887d68e67901924065ba2514Brian Wellington <code class="option">-R</code> option. <em class="parameter"><code>number</code></em>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt how many times <span><strong class="command">host</strong></span> will repeat a query
268a4475065fe6a8cd7cc707820982cf5e98f430Rob Austein not get answered. The default number of retries is 1. If
268a4475065fe6a8cd7cc707820982cf5e98f430Rob Austein <em class="parameter"><code>number</code></em> is negative or zero, the
268a4475065fe6a8cd7cc707820982cf5e98f430Rob Austein retries will default to 1.
a903095bf4512dae561c7f6fc7854a51bebf334aMark Andrews Non-recursive queries can be made via the <code class="option">-r</code> option.
a903095bf4512dae561c7f6fc7854a51bebf334aMark Andrews Setting this option clears the <span class="type">RD</span> — recursion
a903095bf4512dae561c7f6fc7854a51bebf334aMark Andrews desired — bit in the query which <span><strong class="command">host</strong></span> makes.
a903095bf4512dae561c7f6fc7854a51bebf334aMark Andrews This should mean that the name server receiving the query will not
a903095bf4512dae561c7f6fc7854a51bebf334aMark Andrews attempt to resolve <em class="parameter"><code>name</code></em>. The
a903095bf4512dae561c7f6fc7854a51bebf334aMark Andrews <code class="option">-r</code> option enables <span><strong class="command">host</strong></span>
8b9fc7617b8f54641708c985697848e6cc10a5bbMark Andrews the behavior of a name server by making non-recursive queries and
a903095bf4512dae561c7f6fc7854a51bebf334aMark Andrews expecting to receive answers to those queries that are usually
a903095bf4512dae561c7f6fc7854a51bebf334aMark Andrews referrals to other name servers.
c40265eba0c99708887d68e67901924065ba2514Brian Wellington By default <span><strong class="command">host</strong></span> uses UDP when making
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt queries. The
30eec077db2bdcb6f2a0dc388a3cdde2ede75ec1Mark Andrews <code class="option">-T</code> option makes it use a TCP connection when querying
c40265eba0c99708887d68e67901924065ba2514Brian Wellington the name server. TCP will be automatically selected for queries that
c40265eba0c99708887d68e67901924065ba2514Brian Wellington require it, such as zone transfer (AXFR) requests.
268a4475065fe6a8cd7cc707820982cf5e98f430Rob Austein The <code class="option">-4</code> option forces <span><strong class="command">host</strong></span> to only
268a4475065fe6a8cd7cc707820982cf5e98f430Rob Austein use IPv4 query transport. The <code class="option">-6</code> option forces
268a4475065fe6a8cd7cc707820982cf5e98f430Rob Austein <span><strong class="command">host</strong></span> to only use IPv6 query transport.
c40265eba0c99708887d68e67901924065ba2514Brian Wellington The <code class="option">-t</code> option is used to select the query type.
c40265eba0c99708887d68e67901924065ba2514Brian Wellington <em class="parameter"><code>type</code></em> can be any recognized query
0f8c9b5eed7e8714ceb7d6d3675555df9c5f6350Mark Andrews type: CNAME,
0f8c9b5eed7e8714ceb7d6d3675555df9c5f6350Mark Andrews NS, SOA, SIG, KEY, AXFR, etc. When no query type is specified,
0f8c9b5eed7e8714ceb7d6d3675555df9c5f6350Mark Andrews <span><strong class="command">host</strong></span> automatically selects an appropriate
0f8c9b5eed7e8714ceb7d6d3675555df9c5f6350Mark Andrews type. By default it looks for A, AAAA, and MX records, but if the
0f8c9b5eed7e8714ceb7d6d3675555df9c5f6350Mark Andrews <code class="option">-C</code> option was given, queries will be made for SOA
0f8c9b5eed7e8714ceb7d6d3675555df9c5f6350Mark Andrews records, and if <em class="parameter"><code>name</code></em> is a
0f8c9b5eed7e8714ceb7d6d3675555df9c5f6350Mark Andrews dotted-decimal IPv4
0f8c9b5eed7e8714ceb7d6d3675555df9c5f6350Mark Andrews address or colon-delimited IPv6 address, <span><strong class="command">host</strong></span> will
c40265eba0c99708887d68e67901924065ba2514Brian Wellington query for PTR records. If a query type of IXFR is chosen the starting
c40265eba0c99708887d68e67901924065ba2514Brian Wellington serial number can be specified by appending an equal followed by the
268a4475065fe6a8cd7cc707820982cf5e98f430Rob Austein starting serial number (e.g. -t IXFR=12345678).
268a4475065fe6a8cd7cc707820982cf5e98f430Rob Austein The time to wait for a reply can be controlled through the
268a4475065fe6a8cd7cc707820982cf5e98f430Rob Austein <code class="option">-W</code> and <code class="option">-w</code> options. The
c40265eba0c99708887d68e67901924065ba2514Brian Wellington <code class="option">-W</code> option makes <span><strong class="command">host</strong></span>
a26ad011f382d12058478704cb5e90e6f4366d01Andreas Gustafsson <em class="parameter"><code>wait</code></em> seconds. If <em class="parameter"><code>wait</code></em>
a26ad011f382d12058478704cb5e90e6f4366d01Andreas Gustafsson is less than one, the wait interval is set to one second. When the
268a4475065fe6a8cd7cc707820982cf5e98f430Rob Austein <code class="option">-w</code> option is used, <span><strong class="command">host</strong></span>
268a4475065fe6a8cd7cc707820982cf5e98f430Rob Austein effectively wait forever for a reply. The time to wait for a response
268a4475065fe6a8cd7cc707820982cf5e98f430Rob Austein will be set to the number of seconds given by the hardware's maximum
268a4475065fe6a8cd7cc707820982cf5e98f430Rob Austein value for an integer quantity.
a26ad011f382d12058478704cb5e90e6f4366d01Andreas Gustafsson The <code class="option">-s</code> option tells <span><strong class="command">host</strong></span>
7791dd06ea69d0fb2494788ad4c24d568f40bcdfMark Andrews <span class="emphasis"><em>not</em></span> to send the query to the next nameserver
e9359db5e958bf05f9b9c5fe3c27d533f0f05550Mark Andrews if any server responds with a SERVFAIL response, which is the
7791dd06ea69d0fb2494788ad4c24d568f40bcdfMark Andrews reverse of normal stub resolver behavior.
578e3196076b409c509c6c0a0873e7bfe54f4d61Evan Hunt The <code class="option">-m</code> can be used to set the memory usage debugging
578e3196076b409c509c6c0a0873e7bfe54f4d61Evan Hunt <em class="parameter"><code>record</code></em>, <em class="parameter"><code>usage</code></em> and
578e3196076b409c509c6c0a0873e7bfe54f4d61Evan Hunt If <span><strong class="command">host</strong></span> has been built with IDN (internationalized
578e3196076b409c509c6c0a0873e7bfe54f4d61Evan Hunt domain name) support, it can accept and display non-ASCII domain names.
578e3196076b409c509c6c0a0873e7bfe54f4d61Evan Hunt <span><strong class="command">host</strong></span> appropriately converts character encoding of
268a4475065fe6a8cd7cc707820982cf5e98f430Rob Austein domain name before sending a request to DNS server or displaying a
7791dd06ea69d0fb2494788ad4c24d568f40bcdfMark Andrews reply from the server.
268a4475065fe6a8cd7cc707820982cf5e98f430Rob Austein If you'd like to turn off the IDN support for some reason, defines
7791dd06ea69d0fb2494788ad4c24d568f40bcdfMark Andrews the <code class="envar">IDN_DISABLE</code> environment variable.
c40265eba0c99708887d68e67901924065ba2514Brian Wellington The IDN support is disabled if the variable is set when
c40265eba0c99708887d68e67901924065ba2514Brian Wellington <span><strong class="command">host</strong></span> runs.
268a4475065fe6a8cd7cc707820982cf5e98f430Rob Austein<p><code class="filename">/etc/resolv.conf</code>
c5223c9cb7c22620d5ee6611228673e95b48a270Mark Andrews<p><span class="citerefentry"><span class="refentrytitle">dig</span>(1)</span>,
c5223c9cb7c22620d5ee6611228673e95b48a270Mark Andrews <span class="citerefentry"><span class="refentrytitle">named</span>(8)</span>.