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bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik - Copyright (C) 2004-2008 Internet Systems Consortium, Inc. ("ISC")
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik - Copyright (C) 2000-2003 Internet Software Consortium.
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik - Permission to use, copy, modify, and distribute this software for any
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik - purpose with or without fee is hereby granted, provided that the above
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik - copyright notice and this permission notice appear in all copies.
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik - THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik - REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik - AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik - INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
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bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik - PERFORMANCE OF THIS SOFTWARE.
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bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik<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>
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik<p><span><strong class="command">host</strong></span>
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik is a simple utility for performing DNS lookups.
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik It is normally used to convert names to IP addresses and vice versa.
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik When no arguments or options are given,
b305c3e5d7fc952767ec752e151c23279cdb0f9cTrond Norbye <span><strong class="command">host</strong></span>
b305c3e5d7fc952767ec752e151c23279cdb0f9cTrond Norbye prints a short summary of its command line arguments and options.
b305c3e5d7fc952767ec752e151c23279cdb0f9cTrond Norbye<p><em class="parameter"><code>name</code></em> is the domain name that is to be
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik up. It can also be a dotted-decimal IPv4 address or a colon-delimited
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik IPv6 address, in which case <span><strong class="command">host</strong></span> will by
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik perform a reverse lookup for that address.
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik <em class="parameter"><code>server</code></em> is an optional argument which
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik the name or IP address of the name server that <span><strong class="command">host</strong></span>
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik should query instead of the server or servers listed in
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik <code class="filename">/etc/resolv.conf</code>.
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik The <code class="option">-a</code> (all) option is equivalent to setting the
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik <code class="option">-v</code> option and asking <span><strong class="command">host</strong></span> to make
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik a query of type ANY.
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik When the <code class="option">-C</code> option is used, <span><strong class="command">host</strong></span>
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik will attempt to display the SOA records for zone
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik <em class="parameter"><code>name</code></em> from all the listed
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik authoritative name
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik servers for that zone. The list of name servers is defined by the NS
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik records that are found for the zone.
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik The <code class="option">-c</code> option instructs to make a DNS query of class
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik <em class="parameter"><code>class</code></em>. This can be used to lookup
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik Chaosnet class resource records. The default class is IN (Internet).
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik Verbose output is generated by <span><strong class="command">host</strong></span> when
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik <code class="option">-d</code> or <code class="option">-v</code> option is used. The two
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik options are equivalent. They have been provided for backwards
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik compatibility. In previous versions, the <code class="option">-d</code> option
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik switched on debugging traces and <code class="option">-v</code> enabled verbose
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik List mode is selected by the <code class="option">-l</code> option. This makes
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik <span><strong class="command">host</strong></span> perform a zone transfer for zone
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik <em class="parameter"><code>name</code></em>. Transfer the zone printing out
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik and address records (A/AAAA). If combined with <code class="option">-a</code>
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik all records will be printed.
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik option specifies that reverse lookups of IPv6 addresses should
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik use the IP6.INT domain as defined in RFC1886.
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik The default is to use IP6.ARPA.
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik The <code class="option">-N</code> option sets the number of dots that have to be
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik in <em class="parameter"><code>name</code></em> for it to be considered
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik absolute. The
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik default value is that defined using the ndots statement in
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik <code class="filename">/etc/resolv.conf</code>, or 1 if no ndots
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik present. Names with fewer dots are interpreted as relative names and
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik will be searched for in the domains listed in the <span class="type">search</span>
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik or <span class="type">domain</span> directive in
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik <code class="filename">/etc/resolv.conf</code>.
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik The number of UDP retries for a lookup can be changed with the
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik <code class="option">-R</code> option. <em class="parameter"><code>number</code></em>
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik how many times <span><strong class="command">host</strong></span> will repeat a query
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik not get answered. The default number of retries is 1. If
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik <em class="parameter"><code>number</code></em> is negative or zero, the
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik retries will default to 1.
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik Non-recursive queries can be made via the <code class="option">-r</code> option.
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik Setting this option clears the <span class="type">RD</span> — recursion
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik desired — bit in the query which <span><strong class="command">host</strong></span> makes.
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik This should mean that the name server receiving the query will not
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik attempt to resolve <em class="parameter"><code>name</code></em>. The
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik <code class="option">-r</code> option enables <span><strong class="command">host</strong></span>
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik the behavior of a name server by making non-recursive queries and
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik expecting to receive answers to those queries that are usually
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik referrals to other name servers.
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik By default <span><strong class="command">host</strong></span> uses UDP when making
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik <code class="option">-T</code> option makes it use a TCP connection when querying
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik the name server. TCP will be automatically selected for queries that
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik require it, such as zone transfer (AXFR) requests.
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik The <code class="option">-4</code> option forces <span><strong class="command">host</strong></span> to only
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik use IPv4 query transport. The <code class="option">-6</code> option forces
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik <span><strong class="command">host</strong></span> to only use IPv6 query transport.
57065c0b4d57ca1e0182adda16962b22987a5b95Knut Anders Hatlen The <code class="option">-t</code> option is used to select the query type.
57065c0b4d57ca1e0182adda16962b22987a5b95Knut Anders Hatlen <em class="parameter"><code>type</code></em> can be any recognized query
57065c0b4d57ca1e0182adda16962b22987a5b95Knut Anders Hatlen NS, SOA, SIG, KEY, AXFR, etc. When no query type is specified,
57065c0b4d57ca1e0182adda16962b22987a5b95Knut Anders Hatlen <span><strong class="command">host</strong></span> automatically selects an appropriate
57065c0b4d57ca1e0182adda16962b22987a5b95Knut Anders Hatlen type. By default it looks for A, AAAA, and MX records, but if the
57065c0b4d57ca1e0182adda16962b22987a5b95Knut Anders Hatlen <code class="option">-C</code> option was given, queries will be made for SOA
57065c0b4d57ca1e0182adda16962b22987a5b95Knut Anders Hatlen records, and if <em class="parameter"><code>name</code></em> is a
57065c0b4d57ca1e0182adda16962b22987a5b95Knut Anders Hatlen dotted-decimal IPv4
57065c0b4d57ca1e0182adda16962b22987a5b95Knut Anders Hatlen address or colon-delimited IPv6 address, <span><strong class="command">host</strong></span> will
57065c0b4d57ca1e0182adda16962b22987a5b95Knut Anders Hatlen query for PTR records. If a query type of IXFR is chosen the starting
57065c0b4d57ca1e0182adda16962b22987a5b95Knut Anders Hatlen serial number can be specified by appending an equal followed by the
57065c0b4d57ca1e0182adda16962b22987a5b95Knut Anders Hatlen starting serial number (e.g. -t IXFR=12345678).
57065c0b4d57ca1e0182adda16962b22987a5b95Knut Anders Hatlen The time to wait for a reply can be controlled through the
57065c0b4d57ca1e0182adda16962b22987a5b95Knut Anders Hatlen <code class="option">-W</code> and <code class="option">-w</code> options. The
57065c0b4d57ca1e0182adda16962b22987a5b95Knut Anders Hatlen <code class="option">-W</code> option makes <span><strong class="command">host</strong></span>
57065c0b4d57ca1e0182adda16962b22987a5b95Knut Anders Hatlen <em class="parameter"><code>wait</code></em> seconds. If <em class="parameter"><code>wait</code></em>
57065c0b4d57ca1e0182adda16962b22987a5b95Knut Anders Hatlen is less than one, the wait interval is set to one second. When the
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik <code class="option">-w</code> option is used, <span><strong class="command">host</strong></span>
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik effectively wait forever for a reply. The time to wait for a response
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik will be set to the number of seconds given by the hardware's maximum
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik value for an integer quantity.
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik The <code class="option">-s</code> option tells <span><strong class="command">host</strong></span>
57065c0b4d57ca1e0182adda16962b22987a5b95Knut Anders Hatlen <span class="emphasis"><em>not</em></span> to send the query to the next nameserver
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik if any server responds with a SERVFAIL response, which is the
bbd7133c7aacadbc73edf866899dffef6d9ddbfdJorgen Austvik reverse of normal stub resolver behavior.