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2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore - Copyright (C) 2004-2014 Internet Systems Consortium, Inc. ("ISC")
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore - Copyright (C) 2000-2003 Internet Software Consortium.
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore - Permission to use, copy, modify, and/or distribute this software for any
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore - purpose with or without fee is hereby granted, provided that the above
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore - copyright notice and this permission notice appear in all copies.
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore - THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore - REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore - AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore - INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
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2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore - PERFORMANCE OF THIS SOFTWARE.
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2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore<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>
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore<p><span><strong class="command">host</strong></span>
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore is a simple utility for performing DNS lookups.
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore It is normally used to convert names to IP addresses and vice versa.
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore When no arguments or options are given,
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore <span><strong class="command">host</strong></span>
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore prints a short summary of its command line arguments and options.
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore<p><em class="parameter"><code>name</code></em> is the domain name that is to be
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore up. It can also be a dotted-decimal IPv4 address or a colon-delimited
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore IPv6 address, in which case <span><strong class="command">host</strong></span> will by
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore perform a reverse lookup for that address.
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore <em class="parameter"><code>server</code></em> is an optional argument which
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore the name or IP address of the name server that <span><strong class="command">host</strong></span>
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore should query instead of the server or servers listed in
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore <code class="filename">/etc/resolv.conf</code>.
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore The <code class="option">-a</code> (all) option is equivalent to setting the
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore <code class="option">-v</code> option and asking <span><strong class="command">host</strong></span> to make
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore a query of type ANY.
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore When the <code class="option">-C</code> option is used, <span><strong class="command">host</strong></span>
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore will attempt to display the SOA records for zone
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore <em class="parameter"><code>name</code></em> from all the listed
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore authoritative name
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore servers for that zone. The list of name servers is defined by the NS
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore records that are found for the zone.
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore The <code class="option">-c</code> option instructs to make a DNS query of class
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore <em class="parameter"><code>class</code></em>. This can be used to lookup
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore Chaosnet class resource records. The default class is IN (Internet).
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore Verbose output is generated by <span><strong class="command">host</strong></span> when
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore <code class="option">-d</code> or <code class="option">-v</code> option is used. The two
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore options are equivalent. They have been provided for backwards
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore compatibility. In previous versions, the <code class="option">-d</code> option
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore switched on debugging traces and <code class="option">-v</code> enabled verbose
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore List mode is selected by the <code class="option">-l</code> option. This makes
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore <span><strong class="command">host</strong></span> perform a zone transfer for zone
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore <em class="parameter"><code>name</code></em>. Transfer the zone printing out
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore and address records (A/AAAA). If combined with <code class="option">-a</code>
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore all records will be printed.
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore option specifies that reverse lookups of IPv6 addresses should
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore use the IP6.INT domain as defined in RFC1886.
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore The default is to use IP6.ARPA.
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore The <code class="option">-N</code> option sets the number of dots that have to be
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore in <em class="parameter"><code>name</code></em> for it to be considered
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore absolute. The
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore default value is that defined using the ndots statement in
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore <code class="filename">/etc/resolv.conf</code>, or 1 if no ndots
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore present. Names with fewer dots are interpreted as relative names and
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore will be searched for in the domains listed in the <span class="type">search</span>
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore or <span class="type">domain</span> directive in
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore <code class="filename">/etc/resolv.conf</code>.
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore The number of UDP retries for a lookup can be changed with the
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore <code class="option">-R</code> option. <em class="parameter"><code>number</code></em>
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore how many times <span><strong class="command">host</strong></span> will repeat a query
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore not get answered. The default number of retries is 1. If
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore <em class="parameter"><code>number</code></em> is negative or zero, the
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore retries will default to 1.
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore Non-recursive queries can be made via the <code class="option">-r</code> option.
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore Setting this option clears the <span class="type">RD</span> — recursion
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore desired — bit in the query which <span><strong class="command">host</strong></span> makes.
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore This should mean that the name server receiving the query will not
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore attempt to resolve <em class="parameter"><code>name</code></em>. The
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore <code class="option">-r</code> option enables <span><strong class="command">host</strong></span>
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore the behavior of a name server by making non-recursive queries and
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore expecting to receive answers to those queries that are usually
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore referrals to other name servers.
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore By default, <span><strong class="command">host</strong></span> uses UDP when making
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore <code class="option">-T</code> option makes it use a TCP connection when querying
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore the name server. TCP will be automatically selected for queries that
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore require it, such as zone transfer (AXFR) requests.
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore The <code class="option">-4</code> option forces <span><strong class="command">host</strong></span> to only
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore use IPv4 query transport. The <code class="option">-6</code> option forces
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore <span><strong class="command">host</strong></span> to only use IPv6 query transport.
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore The <code class="option">-t</code> option is used to select the query type.
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore <em class="parameter"><code>type</code></em> can be any recognized query
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore NS, SOA, SIG, KEY, AXFR, etc. When no query type is specified,
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore <span><strong class="command">host</strong></span> automatically selects an appropriate
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore type. By default, it looks for A, AAAA, and MX records, but if the
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore <code class="option">-C</code> option was given, queries will be made for SOA
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore records, and if <em class="parameter"><code>name</code></em> is a
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore dotted-decimal IPv4
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore address or colon-delimited IPv6 address, <span><strong class="command">host</strong></span> will
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore query for PTR records. If a query type of IXFR is chosen the starting
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore serial number can be specified by appending an equal followed by the
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore starting serial number (e.g. -t IXFR=12345678).
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore The time to wait for a reply can be controlled through the
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore <code class="option">-W</code> and <code class="option">-w</code> options. The
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore <code class="option">-W</code> option makes <span><strong class="command">host</strong></span>
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore <em class="parameter"><code>wait</code></em> seconds. If <em class="parameter"><code>wait</code></em>
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore is less than one, the wait interval is set to one second. When the
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore <code class="option">-w</code> option is used, <span><strong class="command">host</strong></span>
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore effectively wait forever for a reply. The time to wait for a response
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore will be set to the number of seconds given by the hardware's maximum
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore value for an integer quantity.
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore The <code class="option">-s</code> option tells <span><strong class="command">host</strong></span>
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore <span class="emphasis"><em>not</em></span> to send the query to the next nameserver
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore if any server responds with a SERVFAIL response, which is the
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore reverse of normal stub resolver behavior.
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore The <code class="option">-m</code> can be used to set the memory usage debugging
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore <em class="parameter"><code>record</code></em>, <em class="parameter"><code>usage</code></em> and
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore <em class="parameter"><code>trace</code></em>.
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore If <span><strong class="command">host</strong></span> has been built with IDN (internationalized
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore domain name) support, it can accept and display non-ASCII domain names.
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore <span><strong class="command">host</strong></span> appropriately converts character encoding of
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore domain name before sending a request to DNS server or displaying a
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore reply from the server.
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore If you'd like to turn off the IDN support for some reason, defines
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore the <code class="envar">IDN_DISABLE</code> environment variable.
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore The IDN support is disabled if the variable is set when
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore <span><strong class="command">host</strong></span> runs.
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore<p><code class="filename">/etc/resolv.conf</code>
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore<p><span class="citerefentry"><span class="refentrytitle">dig</span>(1)</span>,
2da1cd3a39e2d3da7f9d15071ea9462919c011acGarrett D'Amore <span class="citerefentry"><span class="refentrytitle">named</span>(8)</span>.
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