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dafcb997e390efa4423883dafd100c975c4095d6Mark Andrews - Copyright (C) 2004, 2005 Internet Systems Consortium, Inc. ("ISC")
a7038d1a0513c8e804937ebc95fc9cb3a46c04f5Mark Andrews - Copyright (C) 2000-2003 Internet Software Consortium.
985687b4e080182c1a3a2173df02b94a5b78b24fBob Halley - Permission to use, copy, modify, and distribute this software for any
985687b4e080182c1a3a2173df02b94a5b78b24fBob Halley - purpose with or without fee is hereby granted, provided that the above
985687b4e080182c1a3a2173df02b94a5b78b24fBob Halley - copyright notice and this permission notice appear in all copies.
dafcb997e390efa4423883dafd100c975c4095d6Mark Andrews - THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
dafcb997e390efa4423883dafd100c975c4095d6Mark Andrews - REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
dafcb997e390efa4423883dafd100c975c4095d6Mark Andrews - AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
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dafcb997e390efa4423883dafd100c975c4095d6Mark Andrews - LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
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dafcb997e390efa4423883dafd100c975c4095d6Mark Andrews - PERFORMANCE OF THIS SOFTWARE.
985687b4e080182c1a3a2173df02b94a5b78b24fBob Halley<!-- $Id: man.host.html,v 1.7 2005/09/09 13:40:38 marka Exp $ -->
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575737b964590103f60542849d4536b5ccd4eb3cBrian Wellington<a name="man.host"></a><div class="titlepage"></div>
575737b964590103f60542849d4536b5ccd4eb3cBrian Wellington<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>
575737b964590103f60542849d4536b5ccd4eb3cBrian Wellington<a name="id2565341"></a><h2>DESCRIPTION</h2>
575737b964590103f60542849d4536b5ccd4eb3cBrian Wellington<p><span><strong class="command">host</strong></span>
575737b964590103f60542849d4536b5ccd4eb3cBrian Wellington is a simple utility for performing DNS lookups.
575737b964590103f60542849d4536b5ccd4eb3cBrian Wellington It is normally used to convert names to IP addresses and vice versa.
575737b964590103f60542849d4536b5ccd4eb3cBrian Wellington When no arguments or options are given,
575737b964590103f60542849d4536b5ccd4eb3cBrian Wellington <span><strong class="command">host</strong></span>
575737b964590103f60542849d4536b5ccd4eb3cBrian Wellington prints a short summary of its command line arguments and options.
985687b4e080182c1a3a2173df02b94a5b78b24fBob Halley<p><em class="parameter"><code>name</code></em> is the domain name that is to be
942d1a339b1fe617f7d17d66cb5fccce798d15aeBrian Wellington up. It can also be a dotted-decimal IPv4 address or a colon-delimited
942d1a339b1fe617f7d17d66cb5fccce798d15aeBrian Wellington IPv6 address, in which case <span><strong class="command">host</strong></span> will by
942d1a339b1fe617f7d17d66cb5fccce798d15aeBrian Wellington perform a reverse lookup for that address.
942d1a339b1fe617f7d17d66cb5fccce798d15aeBrian Wellington <em class="parameter"><code>server</code></em> is an optional argument which
985687b4e080182c1a3a2173df02b94a5b78b24fBob Halley the name or IP address of the name server that <span><strong class="command">host</strong></span>
942d1a339b1fe617f7d17d66cb5fccce798d15aeBrian Wellington should query instead of the server or servers listed in
942d1a339b1fe617f7d17d66cb5fccce798d15aeBrian Wellington <code class="filename">/etc/resolv.conf</code>.
985687b4e080182c1a3a2173df02b94a5b78b24fBob Halley The <code class="option">-a</code> (all) option is equivalent to setting the
985687b4e080182c1a3a2173df02b94a5b78b24fBob Halley <code class="option">-v</code> option and asking <span><strong class="command">host</strong></span> to make
1a69a1a78cfaa86f3b68bbc965232b7876d4da2aDavid Lawrence a query of type ANY.
52637f592f705ca93fadc218e403fd55e8ce4aeaMark Andrews When the <code class="option">-C</code> option is used, <span><strong class="command">host</strong></span>
52637f592f705ca93fadc218e403fd55e8ce4aeaMark Andrews will attempt to display the SOA records for zone
52637f592f705ca93fadc218e403fd55e8ce4aeaMark Andrews <em class="parameter"><code>name</code></em> from all the listed
52637f592f705ca93fadc218e403fd55e8ce4aeaMark Andrews authoritative name
575737b964590103f60542849d4536b5ccd4eb3cBrian Wellington servers for that zone. The list of name servers is defined by the NS
52637f592f705ca93fadc218e403fd55e8ce4aeaMark Andrews records that are found for the zone.
52637f592f705ca93fadc218e403fd55e8ce4aeaMark Andrews The <code class="option">-c</code> option instructs to make a DNS query of class
c1a2cfef7f9156ffd15ded6cca6429a174319cc1Michael Graff <em class="parameter"><code>class</code></em>. This can be used to lookup
52637f592f705ca93fadc218e403fd55e8ce4aeaMark Andrews Chaosnet class resource records. The default class is IN (Internet).
52637f592f705ca93fadc218e403fd55e8ce4aeaMark Andrews Verbose output is generated by <span><strong class="command">host</strong></span> when
52637f592f705ca93fadc218e403fd55e8ce4aeaMark Andrews <code class="option">-d</code> or <code class="option">-v</code> option is used. The two
52637f592f705ca93fadc218e403fd55e8ce4aeaMark Andrews options are equivalent. They have been provided for backwards
52637f592f705ca93fadc218e403fd55e8ce4aeaMark Andrews compatibility. In previous versions, the <code class="option">-d</code> option
52637f592f705ca93fadc218e403fd55e8ce4aeaMark Andrews switched on debugging traces and <code class="option">-v</code> enabled verbose
52637f592f705ca93fadc218e403fd55e8ce4aeaMark Andrews List mode is selected by the <code class="option">-l</code> option. This makes
52637f592f705ca93fadc218e403fd55e8ce4aeaMark Andrews <span><strong class="command">host</strong></span> perform a zone transfer for zone
52637f592f705ca93fadc218e403fd55e8ce4aeaMark Andrews <em class="parameter"><code>name</code></em>. Transfer the zone printing out
52637f592f705ca93fadc218e403fd55e8ce4aeaMark Andrews and address records (A/AAAA). If combined with <code class="option">-a</code>
52637f592f705ca93fadc218e403fd55e8ce4aeaMark Andrews all records will be printed.
52637f592f705ca93fadc218e403fd55e8ce4aeaMark Andrews option specifies that reverse lookups of IPv6 addresses should
52637f592f705ca93fadc218e403fd55e8ce4aeaMark Andrews use the IP6.INT domain as defined in RFC1886.
52637f592f705ca93fadc218e403fd55e8ce4aeaMark Andrews The default is to use IP6.ARPA.
52637f592f705ca93fadc218e403fd55e8ce4aeaMark Andrews The <code class="option">-N</code> option sets the number of dots that have to be
52637f592f705ca93fadc218e403fd55e8ce4aeaMark Andrews in <em class="parameter"><code>name</code></em> for it to be considered
52637f592f705ca93fadc218e403fd55e8ce4aeaMark Andrews absolute. The
575737b964590103f60542849d4536b5ccd4eb3cBrian Wellington default value is that defined using the ndots statement in
52637f592f705ca93fadc218e403fd55e8ce4aeaMark Andrews <code class="filename">/etc/resolv.conf</code>, or 1 if no ndots
52637f592f705ca93fadc218e403fd55e8ce4aeaMark Andrews statement is
52637f592f705ca93fadc218e403fd55e8ce4aeaMark Andrews present. Names with fewer dots are interpreted as relative names and
52637f592f705ca93fadc218e403fd55e8ce4aeaMark Andrews will be searched for in the domains listed in the <span class="type">search</span>
52637f592f705ca93fadc218e403fd55e8ce4aeaMark Andrews or <span class="type">domain</span> directive in
52637f592f705ca93fadc218e403fd55e8ce4aeaMark Andrews <code class="filename">/etc/resolv.conf</code>.
52637f592f705ca93fadc218e403fd55e8ce4aeaMark Andrews The number of UDP retries for a lookup can be changed with the
52637f592f705ca93fadc218e403fd55e8ce4aeaMark Andrews <code class="option">-R</code> option. <em class="parameter"><code>number</code></em>
52637f592f705ca93fadc218e403fd55e8ce4aeaMark Andrews how many times <span><strong class="command">host</strong></span> will repeat a query
52637f592f705ca93fadc218e403fd55e8ce4aeaMark Andrews not get answered. The default number of retries is 1. If
52637f592f705ca93fadc218e403fd55e8ce4aeaMark Andrews <em class="parameter"><code>number</code></em> is negative or zero, the
52637f592f705ca93fadc218e403fd55e8ce4aeaMark Andrews retries will default to 1.
52637f592f705ca93fadc218e403fd55e8ce4aeaMark Andrews Non-recursive queries can be made via the <code class="option">-r</code> option.
29daf5bc7738f1cdab7914562269e1129c81acdcBrian Wellington Setting this option clears the <span class="type">RD</span> — recursion
52637f592f705ca93fadc218e403fd55e8ce4aeaMark Andrews desired — bit in the query which <span><strong class="command">host</strong></span> makes.
575737b964590103f60542849d4536b5ccd4eb3cBrian Wellington This should mean that the name server receiving the query will not
52637f592f705ca93fadc218e403fd55e8ce4aeaMark Andrews attempt to resolve <em class="parameter"><code>name</code></em>. The
52637f592f705ca93fadc218e403fd55e8ce4aeaMark Andrews <code class="option">-r</code> option enables <span><strong class="command">host</strong></span>
52637f592f705ca93fadc218e403fd55e8ce4aeaMark Andrews the behaviour of a name server by making non-recursive queries and
575737b964590103f60542849d4536b5ccd4eb3cBrian Wellington expecting to receive answers to those queries that are usually
8d4bf0c21b742138c9eb3dc2a43e9229f6ce0adcAndreas Gustafsson referrals to other name servers.
29daf5bc7738f1cdab7914562269e1129c81acdcBrian Wellington By default <span><strong class="command">host</strong></span> uses UDP when making
52637f592f705ca93fadc218e403fd55e8ce4aeaMark Andrews queries. The
52637f592f705ca93fadc218e403fd55e8ce4aeaMark Andrews <code class="option">-T</code> option makes it use a TCP connection when querying
52637f592f705ca93fadc218e403fd55e8ce4aeaMark Andrews the name server. TCP will be automatically selected for queries that
52637f592f705ca93fadc218e403fd55e8ce4aeaMark Andrews require it, such as zone transfer (AXFR) requests.
1c33761bcff783815a952e6e1fb9d5e07a3e1363Brian Wellington The <code class="option">-4</code> option forces <span><strong class="command">host</strong></span> to only
1c33761bcff783815a952e6e1fb9d5e07a3e1363Brian Wellington use IPv4 query transport. The <code class="option">-6</code> option forces
52637f592f705ca93fadc218e403fd55e8ce4aeaMark Andrews <span><strong class="command">host</strong></span> to only use IPv6 query transport.
52637f592f705ca93fadc218e403fd55e8ce4aeaMark Andrews The <code class="option">-t</code> option is used to select the query type.
52637f592f705ca93fadc218e403fd55e8ce4aeaMark Andrews <em class="parameter"><code>type</code></em> can be any recognised query
4d180bd2100d9c848831c08e7f08a75cc21a9c0aBrian Wellington NS, SOA, SIG, KEY, AXFR, etc. When no query type is specified,
60103a02c62cadc72fef61b8bdab9694e3fcf57aBrian Wellington <span><strong class="command">host</strong></span> automatically selects an appropriate
4d180bd2100d9c848831c08e7f08a75cc21a9c0aBrian Wellington type. By default it looks for A records, but if the
4d180bd2100d9c848831c08e7f08a75cc21a9c0aBrian Wellington <code class="option">-C</code> option was given, queries will be made for SOA
473af331834c05fd41b36a6de116a724eae77890Brian Wellington records, and if <em class="parameter"><code>name</code></em> is a
52637f592f705ca93fadc218e403fd55e8ce4aeaMark Andrews dotted-decimal IPv4
52637f592f705ca93fadc218e403fd55e8ce4aeaMark Andrews address or colon-delimited IPv6 address, <span><strong class="command">host</strong></span> will
52637f592f705ca93fadc218e403fd55e8ce4aeaMark Andrews query for PTR records. If a query type of IXFR is chosen the starting
c1e7aff941dbf40090fec49300e728ad017d4f0cMark Andrews serial number can be specified by appending an equal followed by the
52637f592f705ca93fadc218e403fd55e8ce4aeaMark Andrews starting serial number (e.g. -t IXFR=12345678).
52637f592f705ca93fadc218e403fd55e8ce4aeaMark Andrews The time to wait for a reply can be controlled through the
52637f592f705ca93fadc218e403fd55e8ce4aeaMark Andrews <code class="option">-W</code> and <code class="option">-w</code> options. The
575737b964590103f60542849d4536b5ccd4eb3cBrian Wellington <code class="option">-W</code> option makes <span><strong class="command">host</strong></span>
52637f592f705ca93fadc218e403fd55e8ce4aeaMark Andrews <em class="parameter"><code>wait</code></em> seconds. If <em class="parameter"><code>wait</code></em>
1ef8965366d91e02a4672c35a187d30aa4a4c72cMark Andrews is less than one, the wait interval is set to one second. When the
942d1a339b1fe617f7d17d66cb5fccce798d15aeBrian Wellington <code class="option">-w</code> option is used, <span><strong class="command">host</strong></span>
1ef8965366d91e02a4672c35a187d30aa4a4c72cMark Andrews effectively wait forever for a reply. The time to wait for a response
d0221bfa6a08f7b284b231886928aa5d8ac87fc2Mark Andrews will be set to the number of seconds given by the hardware's maximum
6a8832f784bd53aa6afbda22f6187cea6490e1e1Andreas Gustafsson value for an integer quantity.
d0221bfa6a08f7b284b231886928aa5d8ac87fc2Mark Andrews The <code class="option">-s</code> option tells <span><strong class="command">host</strong></span>
d0221bfa6a08f7b284b231886928aa5d8ac87fc2Mark Andrews <span class="emphasis"><em>not</em></span> to send the query to the next nameserver
d0221bfa6a08f7b284b231886928aa5d8ac87fc2Mark Andrews if any server responds with a SERVFAIL response, which is the
d0221bfa6a08f7b284b231886928aa5d8ac87fc2Mark Andrews reverse of normal stub resolver behaviour.
1ef8965366d91e02a4672c35a187d30aa4a4c72cMark Andrews The <code class="option">-m</code> can be used to set the memory usage debugging
d0221bfa6a08f7b284b231886928aa5d8ac87fc2Mark Andrews <em class="parameter"><code>record</code></em>, <em class="parameter"><code>usage</code></em> and
1ef8965366d91e02a4672c35a187d30aa4a4c72cMark Andrews If <span><strong class="command">host</strong></span> has been built with IDN (internationalized
1ef8965366d91e02a4672c35a187d30aa4a4c72cMark Andrews domain name) support, it can accept and display non-ASCII domain names.
d0221bfa6a08f7b284b231886928aa5d8ac87fc2Mark Andrews <span><strong class="command">host</strong></span> appropriately converts character encoding of
d0221bfa6a08f7b284b231886928aa5d8ac87fc2Mark Andrews domain name before sending a request to DNS server or displaying a
d0221bfa6a08f7b284b231886928aa5d8ac87fc2Mark Andrews reply from the server.
d0221bfa6a08f7b284b231886928aa5d8ac87fc2Mark Andrews If you'd like to turn off the IDN support for some reason, defines
575737b964590103f60542849d4536b5ccd4eb3cBrian Wellington the <code class="envar">IDN_DISABLE</code> environment variable.
d0221bfa6a08f7b284b231886928aa5d8ac87fc2Mark Andrews The IDN support is disabled if the variable is set when
d0221bfa6a08f7b284b231886928aa5d8ac87fc2Mark Andrews <span><strong class="command">host</strong></span> runs.
d0221bfa6a08f7b284b231886928aa5d8ac87fc2Mark Andrews<p><code class="filename">/etc/resolv.conf</code>
d0221bfa6a08f7b284b231886928aa5d8ac87fc2Mark Andrews<p><span class="citerefentry"><span class="refentrytitle">dig</span>(1)</span>,
1ef8965366d91e02a4672c35a187d30aa4a4c72cMark Andrews <span class="citerefentry"><span class="refentrytitle">named</span>(8)</span>.
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