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653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico - Copyright (C) 2004-2013 Internet Systems Consortium, Inc. ("ISC")
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico - Copyright (C) 2000-2003 Internet Software Consortium.
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico - Permission to use, copy, modify, and/or distribute this software for any
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico - purpose with or without fee is hereby granted, provided that the above
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico - copyright notice and this permission notice appear in all copies.
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico - THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico - REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico - AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
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653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico - LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
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653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico<a name="man.host"></a><div class="titlepage"></div>
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico<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>
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico<p><span><strong class="command">host</strong></span>
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico is a simple utility for performing DNS lookups.
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico It is normally used to convert names to IP addresses and vice versa.
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico When no arguments or options are given,
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico <span><strong class="command">host</strong></span>
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico prints a short summary of its command line arguments and options.
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico<p><em class="parameter"><code>name</code></em> is the domain name that is to be
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico up. It can also be a dotted-decimal IPv4 address or a colon-delimited
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico IPv6 address, in which case <span><strong class="command">host</strong></span> will by
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico perform a reverse lookup for that address.
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico <em class="parameter"><code>server</code></em> is an optional argument which
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico the name or IP address of the name server that <span><strong class="command">host</strong></span>
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico should query instead of the server or servers listed in
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico The <code class="option">-a</code> (all) option is equivalent to setting the
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico <code class="option">-v</code> option and asking <span><strong class="command">host</strong></span> to make
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico a query of type ANY.
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico When the <code class="option">-C</code> option is used, <span><strong class="command">host</strong></span>
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico will attempt to display the SOA records for zone
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico <em class="parameter"><code>name</code></em> from all the listed
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico authoritative name
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico servers for that zone. The list of name servers is defined by the NS
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico records that are found for the zone.
bcceefd876f22bacb6aeb206512ddb1539d2ced8apenner The <code class="option">-c</code> option instructs to make a DNS query of class
bcceefd876f22bacb6aeb206512ddb1539d2ced8apenner <em class="parameter"><code>class</code></em>. This can be used to lookup
bcceefd876f22bacb6aeb206512ddb1539d2ced8apenner Chaosnet class resource records. The default class is IN (Internet).
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico Verbose output is generated by <span><strong class="command">host</strong></span> when
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico <code class="option">-d</code> or <code class="option">-v</code> option is used. The two
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico options are equivalent. They have been provided for backwards
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico compatibility. In previous versions, the <code class="option">-d</code> option
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico switched on debugging traces and <code class="option">-v</code> enabled verbose
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico List mode is selected by the <code class="option">-l</code> option. This makes
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico <span><strong class="command">host</strong></span> perform a zone transfer for zone
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico <em class="parameter"><code>name</code></em>. Transfer the zone printing out
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico and address records (A/AAAA). If combined with <code class="option">-a</code>
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico all records will be printed.
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico option specifies that reverse lookups of IPv6 addresses should
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico use the IP6.INT domain as defined in RFC1886.
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico The default is to use IP6.ARPA.
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico The <code class="option">-N</code> option sets the number of dots that have to be
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico in <em class="parameter"><code>name</code></em> for it to be considered
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico absolute. The
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico default value is that defined using the ndots statement in
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico <code class="filename">/etc/resolv.conf</code>, or 1 if no ndots
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico statement is
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico present. Names with fewer dots are interpreted as relative names and
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico will be searched for in the domains listed in the <span class="type">search</span>
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico The number of UDP retries for a lookup can be changed with the
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico <code class="option">-R</code> option. <em class="parameter"><code>number</code></em>
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico how many times <span><strong class="command">host</strong></span> will repeat a query
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico not get answered. The default number of retries is 1. If
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico <em class="parameter"><code>number</code></em> is negative or zero, the
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico retries will default to 1.
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico Non-recursive queries can be made via the <code class="option">-r</code> option.
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico Setting this option clears the <span class="type">RD</span> — recursion
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico desired — bit in the query which <span><strong class="command">host</strong></span> makes.
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico This should mean that the name server receiving the query will not
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico attempt to resolve <em class="parameter"><code>name</code></em>. The
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico <code class="option">-r</code> option enables <span><strong class="command">host</strong></span>
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico the behavior of a name server by making non-recursive queries and
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico expecting to receive answers to those queries that are usually
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico referrals to other name servers.
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico By default, <span><strong class="command">host</strong></span> uses UDP when making
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico queries. The
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico <code class="option">-T</code> option makes it use a TCP connection when querying
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico the name server. TCP will be automatically selected for queries that
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico require it, such as zone transfer (AXFR) requests.
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico The <code class="option">-4</code> option forces <span><strong class="command">host</strong></span> to only
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico use IPv4 query transport. The <code class="option">-6</code> option forces
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico <span><strong class="command">host</strong></span> to only use IPv6 query transport.
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico The <code class="option">-t</code> option is used to select the query type.
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico <em class="parameter"><code>type</code></em> can be any recognized query
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico type: CNAME,
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico NS, SOA, SIG, KEY, AXFR, etc. When no query type is specified,
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico <span><strong class="command">host</strong></span> automatically selects an appropriate
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico type. By default, it looks for A, AAAA, and MX records, but if the
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico <code class="option">-C</code> option was given, queries will be made for SOA
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico records, and if <em class="parameter"><code>name</code></em> is a
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico dotted-decimal IPv4
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico address or colon-delimited IPv6 address, <span><strong class="command">host</strong></span> will
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico query for PTR records. If a query type of IXFR is chosen the starting
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico serial number can be specified by appending an equal followed by the
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico starting serial number (e.g. -t IXFR=12345678).
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico The time to wait for a reply can be controlled through the
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico <code class="option">-W</code> and <code class="option">-w</code> options. The
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico <code class="option">-W</code> option makes <span><strong class="command">host</strong></span>
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico <em class="parameter"><code>wait</code></em> seconds. If <em class="parameter"><code>wait</code></em>
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico is less than one, the wait interval is set to one second. When the
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico <code class="option">-w</code> option is used, <span><strong class="command">host</strong></span>
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico effectively wait forever for a reply. The time to wait for a response
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico will be set to the number of seconds given by the hardware's maximum
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico value for an integer quantity.
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico The <code class="option">-s</code> option tells <span><strong class="command">host</strong></span>
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico <span class="emphasis"><em>not</em></span> to send the query to the next nameserver
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico if any server responds with a SERVFAIL response, which is the
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico reverse of normal stub resolver behavior.
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico The <code class="option">-m</code> can be used to set the memory usage debugging
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico <em class="parameter"><code>record</code></em>, <em class="parameter"><code>usage</code></em> and
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico If <span><strong class="command">host</strong></span> has been built with IDN (internationalized
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico domain name) support, it can accept and display non-ASCII domain names.
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico <span><strong class="command">host</strong></span> appropriately converts character encoding of
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico domain name before sending a request to DNS server or displaying a
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico reply from the server.
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico If you'd like to turn off the IDN support for some reason, defines
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico the <code class="envar">IDN_DISABLE</code> environment variable.
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico The IDN support is disabled if the variable is set when
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico <span><strong class="command">host</strong></span> runs.
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico<p><span class="citerefentry"><span class="refentrytitle">dig</span>(1)</span>,
653120e3d1bee132d5e36aa09ffd9e1835d0567bJazzyNico <span class="citerefentry"><span class="refentrytitle">named</span>(8)</span>.
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