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c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews - Copyright (C) 2004-2015 Internet Systems Consortium, Inc. ("ISC")
a7c412f37cc73d0332887a746e81220cbf09dd00Mark Andrews - Copyright (C) 2000-2003 Internet Software Consortium.
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews - Permission to use, copy, modify, and/or distribute this software for any
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews - purpose with or without fee is hereby granted, provided that the above
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark 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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2ae159b376dac23870d8005563c585acf85a4b5aEvan Hunt<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
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews a query of type ANY.
ba751492fcc4f161a18b983d4f018a1a52938cb9Evan Hunt When the <code class="option">-C</code> option is used, <span><strong class="command">host</strong></span>
ba751492fcc4f161a18b983d4f018a1a52938cb9Evan Hunt will attempt to display the SOA records for zone
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews <em class="parameter"><code>name</code></em> from all the listed
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews authoritative name
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews servers for that zone. The list of name servers is defined by the NS
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews records that are found for the zone.
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews The <code class="option">-c</code> option instructs to make a DNS query of class
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews <em class="parameter"><code>class</code></em>. This can be used to lookup
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark 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
1059bc2e42e8214f8b73d3b4cd181d8394a94a6aFrancis Dupont <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>.
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews List mode is selected by the <code class="option">-l</code> option. This makes
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews <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
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews not get answered. If
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews <em class="parameter"><code>number</code></em> is negative or zero, the
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews retries will default to 1. The default value is 1, or
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews the value of the <em class="parameter"><code>attempts</code></em> option in
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews <code class="filename">/etc/resolv.conf</code>, if set.
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews Non-recursive queries can be made via the <code class="option">-r</code> option.
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews Setting this option clears the <span class="type">RD</span> — recursion
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews desired — bit in the query which <span><strong class="command">host</strong></span> makes.
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews This should mean that the name server receiving the query will not
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews 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
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews 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
98922b2b2b024dcca25be7c220cf3b16b1e6c4b5Evan Hunt 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,
98922b2b2b024dcca25be7c220cf3b16b1e6c4b5Evan Hunt NS, SOA, SIG, KEY, AXFR, etc. When no query type is specified,
98922b2b2b024dcca25be7c220cf3b16b1e6c4b5Evan Hunt <span><strong class="command">host</strong></span> automatically selects an appropriate
98922b2b2b024dcca25be7c220cf3b16b1e6c4b5Evan Hunt type. By default, it looks for A, AAAA, and MX records, but if the
98922b2b2b024dcca25be7c220cf3b16b1e6c4b5Evan Hunt <code class="option">-C</code> option was given, queries will be made for SOA
98922b2b2b024dcca25be7c220cf3b16b1e6c4b5Evan Hunt records, and if <em class="parameter"><code>name</code></em> is a
98922b2b2b024dcca25be7c220cf3b16b1e6c4b5Evan Hunt dotted-decimal IPv4
98922b2b2b024dcca25be7c220cf3b16b1e6c4b5Evan Hunt address or colon-delimited IPv6 address, <span><strong class="command">host</strong></span> will
98922b2b2b024dcca25be7c220cf3b16b1e6c4b5Evan Hunt query for PTR records. If a query type of IXFR is chosen the starting
98922b2b2b024dcca25be7c220cf3b16b1e6c4b5Evan Hunt serial number can be specified by appending an equal followed by the
98922b2b2b024dcca25be7c220cf3b16b1e6c4b5Evan Hunt 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
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews <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
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews <em class="parameter"><code>timeout</code></em> option in
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews <code class="filename">/etc/resolv.conf</code>.
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews The <code class="option">-s</code> option tells <span><strong class="command">host</strong></span>
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews <span class="emphasis"><em>not</em></span> to send the query to the next nameserver
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews if any server responds with a SERVFAIL response, which is the
2ae159b376dac23870d8005563c585acf85a4b5aEvan Hunt reverse of normal stub resolver behavior.
c3c8823fed039b3a2b8e5ca8bc2f3301d1dd840eMark Andrews 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 9.11.0pre-alpha</p>