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40e5cf3e8f0ddda79b1650df77d0f847a22822bfJazzyNico - Copyright (C) 2004-2009 Internet Systems Consortium, Inc. ("ISC")
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico - Copyright (C) 2000-2003 Internet Software Consortium.
d048f1c15089c16b8ca1b264513a2f92ff86e703JazzyNico - Permission to use, copy, modify, and/or distribute this software for any
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico - purpose with or without fee is hereby granted, provided that the above
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico - copyright notice and this permission notice appear in all copies.
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico - THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico - REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
40e5cf3e8f0ddda79b1650df77d0f847a22822bfJazzyNico - AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
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40e5cf3e8f0ddda79b1650df77d0f847a22822bfJazzyNico<a name="man.host"></a><div class="titlepage"></div>
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico<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>
40e5cf3e8f0ddda79b1650df77d0f847a22822bfJazzyNico<p><span><strong class="command">host</strong></span>
40e5cf3e8f0ddda79b1650df77d0f847a22822bfJazzyNico is a simple utility for performing DNS lookups.
40e5cf3e8f0ddda79b1650df77d0f847a22822bfJazzyNico It is normally used to convert names to IP addresses and vice versa.
40e5cf3e8f0ddda79b1650df77d0f847a22822bfJazzyNico When no arguments or options are given,
40e5cf3e8f0ddda79b1650df77d0f847a22822bfJazzyNico <span><strong class="command">host</strong></span>
40e5cf3e8f0ddda79b1650df77d0f847a22822bfJazzyNico prints a short summary of its command line arguments and options.
40e5cf3e8f0ddda79b1650df77d0f847a22822bfJazzyNico<p><em class="parameter"><code>name</code></em> is the domain name that is to be
40e5cf3e8f0ddda79b1650df77d0f847a22822bfJazzyNico up. It can also be a dotted-decimal IPv4 address or a colon-delimited
40e5cf3e8f0ddda79b1650df77d0f847a22822bfJazzyNico IPv6 address, in which case <span><strong class="command">host</strong></span> will by
40e5cf3e8f0ddda79b1650df77d0f847a22822bfJazzyNico perform a reverse lookup for that address.
40e5cf3e8f0ddda79b1650df77d0f847a22822bfJazzyNico <em class="parameter"><code>server</code></em> is an optional argument which
40e5cf3e8f0ddda79b1650df77d0f847a22822bfJazzyNico the name or IP address of the name server that <span><strong class="command">host</strong></span>
40e5cf3e8f0ddda79b1650df77d0f847a22822bfJazzyNico should query instead of the server or servers listed in
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico The <code class="option">-a</code> (all) option is equivalent to setting the
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico <code class="option">-v</code> option and asking <span><strong class="command">host</strong></span> to make
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico a query of type ANY.
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico When the <code class="option">-C</code> option is used, <span><strong class="command">host</strong></span>
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico will attempt to display the SOA records for zone
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico <em class="parameter"><code>name</code></em> from all the listed
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico authoritative name
40e5cf3e8f0ddda79b1650df77d0f847a22822bfJazzyNico servers for that zone. The list of name servers is defined by the NS
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico records that are found for the zone.
40e5cf3e8f0ddda79b1650df77d0f847a22822bfJazzyNico The <code class="option">-c</code> option instructs to make a DNS query of class
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico <em class="parameter"><code>class</code></em>. This can be used to lookup
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico Chaosnet class resource records. The default class is IN (Internet).
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico Verbose output is generated by <span><strong class="command">host</strong></span> when
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico <code class="option">-d</code> or <code class="option">-v</code> option is used. The two
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico options are equivalent. They have been provided for backwards
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico compatibility. In previous versions, the <code class="option">-d</code> option
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico switched on debugging traces and <code class="option">-v</code> enabled verbose
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico List mode is selected by the <code class="option">-l</code> option. This makes
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico <span><strong class="command">host</strong></span> perform a zone transfer for zone
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico <em class="parameter"><code>name</code></em>. Transfer the zone printing out
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico and address records (A/AAAA). If combined with <code class="option">-a</code>
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico all records will be printed.
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico option specifies that reverse lookups of IPv6 addresses should
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico use the IP6.INT domain as defined in RFC1886.
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico The default is to use IP6.ARPA.
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico The <code class="option">-N</code> option sets the number of dots that have to be
40e5cf3e8f0ddda79b1650df77d0f847a22822bfJazzyNico in <em class="parameter"><code>name</code></em> for it to be considered
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico absolute. The
40e5cf3e8f0ddda79b1650df77d0f847a22822bfJazzyNico default value is that defined using the ndots statement in
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico <code class="filename">/etc/resolv.conf</code>, or 1 if no ndots
40e5cf3e8f0ddda79b1650df77d0f847a22822bfJazzyNico statement is
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico present. Names with fewer dots are interpreted as relative names and
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico will be searched for in the domains listed in the <span class="type">search</span>
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico The number of UDP retries for a lookup can be changed with the
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico <code class="option">-R</code> option. <em class="parameter"><code>number</code></em>
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico how many times <span><strong class="command">host</strong></span> will repeat a query
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico not get answered. The default number of retries is 1. If
40e5cf3e8f0ddda79b1650df77d0f847a22822bfJazzyNico <em class="parameter"><code>number</code></em> is negative or zero, the
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico retries will default to 1.
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico Non-recursive queries can be made via the <code class="option">-r</code> option.
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico Setting this option clears the <span class="type">RD</span> — recursion
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico desired — bit in the query which <span><strong class="command">host</strong></span> makes.
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico This should mean that the name server receiving the query will not
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico attempt to resolve <em class="parameter"><code>name</code></em>. The
40e5cf3e8f0ddda79b1650df77d0f847a22822bfJazzyNico <code class="option">-r</code> option enables <span><strong class="command">host</strong></span>
40e5cf3e8f0ddda79b1650df77d0f847a22822bfJazzyNico the behavior of a name server by making non-recursive queries and
40e5cf3e8f0ddda79b1650df77d0f847a22822bfJazzyNico expecting to receive answers to those queries that are usually
40e5cf3e8f0ddda79b1650df77d0f847a22822bfJazzyNico referrals to other name servers.
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico By default, <span><strong class="command">host</strong></span> uses UDP when making
40e5cf3e8f0ddda79b1650df77d0f847a22822bfJazzyNico queries. The
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico <code class="option">-T</code> option makes it use a TCP connection when querying
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico the name server. TCP will be automatically selected for queries that
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico require it, such as zone transfer (AXFR) requests.
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico The <code class="option">-4</code> option forces <span><strong class="command">host</strong></span> to only
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico use IPv4 query transport. The <code class="option">-6</code> option forces
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico <span><strong class="command">host</strong></span> to only use IPv6 query transport.
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico The <code class="option">-t</code> option is used to select the query type.
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico <em class="parameter"><code>type</code></em> can be any recognized query
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico type: CNAME,
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico NS, SOA, SIG, KEY, AXFR, etc. When no query type is specified,
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico <span><strong class="command">host</strong></span> automatically selects an appropriate
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico type. By default, it looks for A, AAAA, and MX records, but if the
40e5cf3e8f0ddda79b1650df77d0f847a22822bfJazzyNico <code class="option">-C</code> option was given, queries will be made for SOA
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico records, and if <em class="parameter"><code>name</code></em> is a
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico dotted-decimal IPv4
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico address or colon-delimited IPv6 address, <span><strong class="command">host</strong></span> will
40e5cf3e8f0ddda79b1650df77d0f847a22822bfJazzyNico query for PTR records. If a query type of IXFR is chosen the starting
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico serial number can be specified by appending an equal followed by the
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico starting serial number (e.g. -t IXFR=12345678).
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico The time to wait for a reply can be controlled through the
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico <code class="option">-W</code> and <code class="option">-w</code> options. The
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico <code class="option">-W</code> option makes <span><strong class="command">host</strong></span>
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico <em class="parameter"><code>wait</code></em> seconds. If <em class="parameter"><code>wait</code></em>
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico is less than one, the wait interval is set to one second. When the
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico <code class="option">-w</code> option is used, <span><strong class="command">host</strong></span>
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico effectively wait forever for a reply. The time to wait for a response
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico will be set to the number of seconds given by the hardware's maximum
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico value for an integer quantity.
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico The <code class="option">-s</code> option tells <span><strong class="command">host</strong></span>
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico <span class="emphasis"><em>not</em></span> to send the query to the next nameserver
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico if any server responds with a SERVFAIL response, which is the
40e5cf3e8f0ddda79b1650df77d0f847a22822bfJazzyNico reverse of normal stub resolver behavior.
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico The <code class="option">-m</code> can be used to set the memory usage debugging
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico <em class="parameter"><code>record</code></em>, <em class="parameter"><code>usage</code></em> and
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico If <span><strong class="command">host</strong></span> has been built with IDN (internationalized
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico domain name) support, it can accept and display non-ASCII domain names.
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico <span><strong class="command">host</strong></span> appropriately converts character encoding of
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico domain name before sending a request to DNS server or displaying a
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico reply from the server.
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico If you'd like to turn off the IDN support for some reason, defines
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico the <code class="envar">IDN_DISABLE</code> environment variable.
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico The IDN support is disabled if the variable is set when
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico <span><strong class="command">host</strong></span> runs.
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico<p><span class="citerefentry"><span class="refentrytitle">dig</span>(1)</span>,
88395eed42de4d59f54795b60c8c0a7ab881e153JazzyNico <span class="citerefentry"><span class="refentrytitle">named</span>(8)</span>.
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