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c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews - Copyright (C) 2004-2014 Internet Systems Consortium, Inc. ("ISC")
f6b909274159da7aaad8463c90f15018136cf6cbTinderbox User - Copyright (C) 2000-2003 Internet Software Consortium.
0c27b3fe77ac1d5094ba3521e8142d9e7973133fMark Andrews - Permission to use, copy, modify, and/or distribute this software for any
0c27b3fe77ac1d5094ba3521e8142d9e7973133fMark Andrews - purpose with or without fee is hereby granted, provided that the above
0c27b3fe77ac1d5094ba3521e8142d9e7973133fMark Andrews - copyright notice and this permission notice appear in all copies.
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews - THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews - REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews - AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
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c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews<a name="man.host"></a><div class="titlepage"></div>
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark 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>] [<code class="option">-v</code>] [<code class="option">-V</code>] {name} [server]</p></div>
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews<p><span><strong class="command">host</strong></span>
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews is a simple utility for performing DNS lookups.
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews It is normally used to convert names to IP addresses and vice versa.
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews When no arguments or options are given,
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews <span><strong class="command">host</strong></span>
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews prints a short summary of its command line arguments and options.
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews<p><em class="parameter"><code>name</code></em> is the domain name that is to be
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews up. It can also be a dotted-decimal IPv4 address or a colon-delimited
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews IPv6 address, in which case <span><strong class="command">host</strong></span> will by
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews perform a reverse lookup for that address.
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews <em class="parameter"><code>server</code></em> is an optional argument which
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews the name or IP address of the name server that <span><strong class="command">host</strong></span>
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews should query instead of the server or servers listed in
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews <code class="filename">/etc/resolv.conf</code>.
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews The <code class="option">-a</code> (all) option is equivalent to setting the
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews <code class="option">-v</code> option and asking <span><strong class="command">host</strong></span> to make
9f5443280fcfd625a06f63a1b457ed2335840278Mark Andrews a query of type ANY.
095c47be5456c17087d7b39dfc97ebee65e0dfbbMark Andrews When the <code class="option">-C</code> option is used, <span><strong class="command">host</strong></span>
095c47be5456c17087d7b39dfc97ebee65e0dfbbMark Andrews will attempt to display the SOA records for zone
095c47be5456c17087d7b39dfc97ebee65e0dfbbMark Andrews <em class="parameter"><code>name</code></em> from all the listed
095c47be5456c17087d7b39dfc97ebee65e0dfbbMark Andrews authoritative name
095c47be5456c17087d7b39dfc97ebee65e0dfbbMark Andrews servers for that zone. The list of name servers is defined by the NS
095c47be5456c17087d7b39dfc97ebee65e0dfbbMark Andrews records that are found for the zone.
095c47be5456c17087d7b39dfc97ebee65e0dfbbMark Andrews The <code class="option">-c</code> option instructs to make a DNS query of class
095c47be5456c17087d7b39dfc97ebee65e0dfbbMark Andrews <em class="parameter"><code>class</code></em>. This can be used to lookup
095c47be5456c17087d7b39dfc97ebee65e0dfbbMark Andrews Chaosnet class resource records. The default class is IN (Internet).
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews Verbose output is generated by <span><strong class="command">host</strong></span> when
cc51cd2d2076e33117c60c9effcb8caccde4983bWitold Krecicki <code class="option">-d</code> or <code class="option">-v</code> option is used. The two
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews options are equivalent. They have been provided for backwards
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews compatibility. In previous versions, the <code class="option">-d</code> option
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews switched on debugging traces and <code class="option">-v</code> enabled verbose
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews output. Verbose output can also be enabled by setting the
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews <em class="parameter"><code>debug</code></em> option in
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews <code class="filename">/etc/resolv.conf</code>.
1059bc2e42e8214f8b73d3b4cd181d8394a94a6aFrancis Dupont List mode is selected by the <code class="option">-l</code> option. This makes
1059bc2e42e8214f8b73d3b4cd181d8394a94a6aFrancis Dupont <span><strong class="command">host</strong></span> perform a zone transfer for zone
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews <em class="parameter"><code>name</code></em>. Transfer the zone printing out
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews and address records (A/AAAA). If combined with <code class="option">-a</code>
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews all records will be printed.
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews option specifies that reverse lookups of IPv6 addresses should
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews use the IP6.INT domain as defined in RFC1886.
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews The default is to use IP6.ARPA.
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews The <code class="option">-N</code> option sets the number of dots that have to be
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews in <em class="parameter"><code>name</code></em> for it to be considered
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews absolute. The
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews default value is that defined using the ndots statement in
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews <code class="filename">/etc/resolv.conf</code>, or 1 if no ndots
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews statement is
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews present. Names with fewer dots are interpreted as relative names and
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews will be searched for in the domains listed in the <span class="type">search</span>
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews or <span class="type">domain</span> directive in
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews <code class="filename">/etc/resolv.conf</code>.
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews The number of UDP retries for a lookup can be changed with the
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews <code class="option">-R</code> option. <em class="parameter"><code>number</code></em>
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews how many times <span><strong class="command">host</strong></span> will repeat a query
cc51cd2d2076e33117c60c9effcb8caccde4983bWitold Krecicki not get answered. If
45fd95544cd650a8e6a0fc39b656d1109b811ac0Evan Hunt <em class="parameter"><code>number</code></em> is negative or zero, the
cc51cd2d2076e33117c60c9effcb8caccde4983bWitold Krecicki retries will default to 1. The default value is 1, or
cc51cd2d2076e33117c60c9effcb8caccde4983bWitold Krecicki the value of the <em class="parameter"><code>attempts</code></em> option in
cc51cd2d2076e33117c60c9effcb8caccde4983bWitold Krecicki <code class="filename">/etc/resolv.conf</code>, if set.
cc51cd2d2076e33117c60c9effcb8caccde4983bWitold Krecicki Non-recursive queries can be made via the <code class="option">-r</code> option.
cc51cd2d2076e33117c60c9effcb8caccde4983bWitold Krecicki Setting this option clears the <span class="type">RD</span> — recursion
cc51cd2d2076e33117c60c9effcb8caccde4983bWitold Krecicki desired — bit in the query which <span><strong class="command">host</strong></span> makes.
cc51cd2d2076e33117c60c9effcb8caccde4983bWitold Krecicki This should mean that the name server receiving the query will not
cc51cd2d2076e33117c60c9effcb8caccde4983bWitold Krecicki attempt to resolve <em class="parameter"><code>name</code></em>. The
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews <code class="option">-r</code> option enables <span><strong class="command">host</strong></span>
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews the behavior of a name server by making non-recursive queries and
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews expecting to receive answers to those queries that are usually
cc51cd2d2076e33117c60c9effcb8caccde4983bWitold Krecicki referrals to other name servers.
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews By default, <span><strong class="command">host</strong></span> uses UDP when making
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews queries. The
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews <code class="option">-T</code> option makes it use a TCP connection when querying
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews the name server. TCP will be automatically selected for queries that
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews require it, such as zone transfer (AXFR) requests.
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews The <code class="option">-4</code> option forces <span><strong class="command">host</strong></span> to only
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews use IPv4 query transport. The <code class="option">-6</code> option forces
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews <span><strong class="command">host</strong></span> to only use IPv6 query transport.
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews The <code class="option">-t</code> option is used to select the query type.
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews <em class="parameter"><code>type</code></em> can be any recognized query
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews type: CNAME,
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews NS, SOA, SIG, KEY, AXFR, etc. When no query type is specified,
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews <span><strong class="command">host</strong></span> automatically selects an appropriate
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews type. By default, it looks for A, AAAA, and MX records, but if the
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews <code class="option">-C</code> option was given, queries will be made for SOA
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews records, and if <em class="parameter"><code>name</code></em> is a
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews dotted-decimal IPv4
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews address or colon-delimited IPv6 address, <span><strong class="command">host</strong></span> will
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews query for PTR records. If a query type of IXFR is chosen the starting
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews serial number can be specified by appending an equal followed by the
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews starting serial number (e.g. -t IXFR=12345678).
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews The time to wait for a reply can be controlled through the
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews <code class="option">-W</code> and <code class="option">-w</code> options. The
98922b2b2b024dcca25be7c220cf3b16b1e6c4b5Evan Hunt <code class="option">-W</code> option makes <span><strong class="command">host</strong></span>
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews <em class="parameter"><code>wait</code></em> seconds. If <em class="parameter"><code>wait</code></em>
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews is less than one, the wait interval is set to one second. When the
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews <code class="option">-w</code> option is used, <span><strong class="command">host</strong></span>
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews effectively wait forever for a reply. The time to wait for a response
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews will be set to the number of seconds given by the hardware's maximum
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews value for an integer quantity. By default, <span><strong class="command">host</strong></span>
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews will wait for 5 seconds for UDP responses and 10 seconds for TCP
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews connections. These defaults can be overridden by the
98922b2b2b024dcca25be7c220cf3b16b1e6c4b5Evan Hunt <em class="parameter"><code>timeout</code></em> option in
98922b2b2b024dcca25be7c220cf3b16b1e6c4b5Evan Hunt The <code class="option">-s</code> option tells <span><strong class="command">host</strong></span>
98922b2b2b024dcca25be7c220cf3b16b1e6c4b5Evan Hunt <span class="emphasis"><em>not</em></span> to send the query to the next nameserver
98922b2b2b024dcca25be7c220cf3b16b1e6c4b5Evan Hunt if any server responds with a SERVFAIL response, which is the
98922b2b2b024dcca25be7c220cf3b16b1e6c4b5Evan Hunt reverse of normal stub resolver behavior.
98922b2b2b024dcca25be7c220cf3b16b1e6c4b5Evan Hunt The <code class="option">-m</code> can be used to set the memory usage debugging
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews <em class="parameter"><code>record</code></em>, <em class="parameter"><code>usage</code></em> and
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews The <code class="option">-V</code> option causes <span><strong class="command">host</strong></span>
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews to print the version number and exit.
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews If <span><strong class="command">host</strong></span> has been built with IDN (internationalized
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews domain name) support, it can accept and display non-ASCII domain names.
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews <span><strong class="command">host</strong></span> appropriately converts character encoding of
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews domain name before sending a request to DNS server or displaying a
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews reply from the server.
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews If you'd like to turn off the IDN support for some reason, defines
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews the <code class="envar">IDN_DISABLE</code> environment variable.
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews The IDN support is disabled if the variable is set when
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews <span><strong class="command">host</strong></span> runs.
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews<p><code class="filename">/etc/resolv.conf</code>
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews<p><span class="citerefentry"><span class="refentrytitle">dig</span>(1)</span>,
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews <span class="citerefentry"><span class="refentrytitle">named</span>(8)</span>.
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c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews<p style="text-align: center;">BIND Version 9.11</p>