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7384b4e78eaab44693c985192276e31322155e32Stephan Bosch - Copyright (C) 2004-2008 Internet Systems Consortium, Inc. ("ISC")
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch - Copyright (C) 2000-2003 Internet Software Consortium.
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch - Permission to use, copy, modify, and distribute this software for any
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch - purpose with or without fee is hereby granted, provided that the above
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch - copyright notice and this permission notice appear in all copies.
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch - THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch - REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch - AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch - INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch - LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
5a7107476ff29592bcbf736d8a1ebb196a5c5726Stephan Bosch - OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch - PERFORMANCE OF THIS SOFTWARE.
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7384b4e78eaab44693c985192276e31322155e32Stephan Bosch<tr><th colspan="3" align="center">host</th></tr>
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5a7107476ff29592bcbf736d8a1ebb196a5c5726Stephan Bosch<a name="man.host"></a><div class="titlepage"></div>
5a7107476ff29592bcbf736d8a1ebb196a5c5726Stephan Bosch<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>
5a7107476ff29592bcbf736d8a1ebb196a5c5726Stephan Bosch<p><span><strong class="command">host</strong></span>
5a7107476ff29592bcbf736d8a1ebb196a5c5726Stephan Bosch is a simple utility for performing DNS lookups.
6e62aa36a3190ef7193bd86158a4245da49132f0Stephan Bosch It is normally used to convert names to IP addresses and vice versa.
d577bb9027e4ceb19ada88d6884265efa5e16b15Stephan Bosch When no arguments or options are given,
d577bb9027e4ceb19ada88d6884265efa5e16b15Stephan Bosch <span><strong class="command">host</strong></span>
d577bb9027e4ceb19ada88d6884265efa5e16b15Stephan Bosch prints a short summary of its command line arguments and options.
d577bb9027e4ceb19ada88d6884265efa5e16b15Stephan Bosch<p><em class="parameter"><code>name</code></em> is the domain name that is to be
d577bb9027e4ceb19ada88d6884265efa5e16b15Stephan Bosch up. It can also be a dotted-decimal IPv4 address or a colon-delimited
6e62aa36a3190ef7193bd86158a4245da49132f0Stephan Bosch IPv6 address, in which case <span><strong class="command">host</strong></span> will by
6e62aa36a3190ef7193bd86158a4245da49132f0Stephan Bosch perform a reverse lookup for that address.
6e62aa36a3190ef7193bd86158a4245da49132f0Stephan Bosch <em class="parameter"><code>server</code></em> is an optional argument which
6e62aa36a3190ef7193bd86158a4245da49132f0Stephan Bosch the name or IP address of the name server that <span><strong class="command">host</strong></span>
5a7107476ff29592bcbf736d8a1ebb196a5c5726Stephan Bosch should query instead of the server or servers listed in
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch <code class="filename">/etc/resolv.conf</code>.
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch The <code class="option">-a</code> (all) option is equivalent to setting the
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch <code class="option">-v</code> option and asking <span><strong class="command">host</strong></span> to make
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch a query of type ANY.
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch When the <code class="option">-C</code> option is used, <span><strong class="command">host</strong></span>
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch will attempt to display the SOA records for zone
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch <em class="parameter"><code>name</code></em> from all the listed
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch authoritative name
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch servers for that zone. The list of name servers is defined by the NS
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch records that are found for the zone.
e0cf44fb802a5e7aa4cbeee5e80ef8f3f6aecdbeStephan Bosch The <code class="option">-c</code> option instructs to make a DNS query of class
5a7107476ff29592bcbf736d8a1ebb196a5c5726Stephan Bosch <em class="parameter"><code>class</code></em>. This can be used to lookup
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch Chaosnet class resource records. The default class is IN (Internet).
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch Verbose output is generated by <span><strong class="command">host</strong></span> when
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch <code class="option">-d</code> or <code class="option">-v</code> option is used. The two
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch options are equivalent. They have been provided for backwards
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch compatibility. In previous versions, the <code class="option">-d</code> option
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch switched on debugging traces and <code class="option">-v</code> enabled verbose
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch List mode is selected by the <code class="option">-l</code> option. This makes
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch <span><strong class="command">host</strong></span> perform a zone transfer for zone
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch <em class="parameter"><code>name</code></em>. Transfer the zone printing out
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch and address records (A/AAAA). If combined with <code class="option">-a</code>
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch all records will be printed.
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch option specifies that reverse lookups of IPv6 addresses should
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch use the IP6.INT domain as defined in RFC1886.
5a7107476ff29592bcbf736d8a1ebb196a5c5726Stephan Bosch The default is to use IP6.ARPA.
5a7107476ff29592bcbf736d8a1ebb196a5c5726Stephan Bosch The <code class="option">-N</code> option sets the number of dots that have to be
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch in <em class="parameter"><code>name</code></em> for it to be considered
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch absolute. The
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch default value is that defined using the ndots statement in
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch <code class="filename">/etc/resolv.conf</code>, or 1 if no ndots
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch present. Names with fewer dots are interpreted as relative names and
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch will be searched for in the domains listed in the <span class="type">search</span>
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch or <span class="type">domain</span> directive in
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch <code class="filename">/etc/resolv.conf</code>.
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch The number of UDP retries for a lookup can be changed with the
5a7107476ff29592bcbf736d8a1ebb196a5c5726Stephan Bosch <code class="option">-R</code> option. <em class="parameter"><code>number</code></em>
d577bb9027e4ceb19ada88d6884265efa5e16b15Stephan Bosch how many times <span><strong class="command">host</strong></span> will repeat a query
d577bb9027e4ceb19ada88d6884265efa5e16b15Stephan Bosch not get answered. The default number of retries is 1. If
d577bb9027e4ceb19ada88d6884265efa5e16b15Stephan Bosch <em class="parameter"><code>number</code></em> is negative or zero, the
d577bb9027e4ceb19ada88d6884265efa5e16b15Stephan Bosch retries will default to 1.
d577bb9027e4ceb19ada88d6884265efa5e16b15Stephan Bosch Non-recursive queries can be made via the <code class="option">-r</code> option.
d577bb9027e4ceb19ada88d6884265efa5e16b15Stephan Bosch Setting this option clears the <span class="type">RD</span> — recursion
d577bb9027e4ceb19ada88d6884265efa5e16b15Stephan Bosch desired — bit in the query which <span><strong class="command">host</strong></span> makes.
d577bb9027e4ceb19ada88d6884265efa5e16b15Stephan Bosch This should mean that the name server receiving the query will not
6e62aa36a3190ef7193bd86158a4245da49132f0Stephan Bosch attempt to resolve <em class="parameter"><code>name</code></em>. The
6e62aa36a3190ef7193bd86158a4245da49132f0Stephan Bosch <code class="option">-r</code> option enables <span><strong class="command">host</strong></span>
6e62aa36a3190ef7193bd86158a4245da49132f0Stephan Bosch the behavior of a name server by making non-recursive queries and
6e62aa36a3190ef7193bd86158a4245da49132f0Stephan Bosch expecting to receive answers to those queries that are usually
6e62aa36a3190ef7193bd86158a4245da49132f0Stephan Bosch referrals to other name servers.
6e62aa36a3190ef7193bd86158a4245da49132f0Stephan Bosch By default <span><strong class="command">host</strong></span> uses UDP when making
6e62aa36a3190ef7193bd86158a4245da49132f0Stephan Bosch <code class="option">-T</code> option makes it use a TCP connection when querying
6e62aa36a3190ef7193bd86158a4245da49132f0Stephan Bosch the name server. TCP will be automatically selected for queries that
d577bb9027e4ceb19ada88d6884265efa5e16b15Stephan Bosch require it, such as zone transfer (AXFR) requests.
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch The <code class="option">-4</code> option forces <span><strong class="command">host</strong></span> to only
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch use IPv4 query transport. The <code class="option">-6</code> option forces
ba592dc74a004ad47dfe58edcfc1ca7297551e39Phil Carmody <span><strong class="command">host</strong></span> to only use IPv6 query transport.
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch The <code class="option">-t</code> option is used to select the query type.
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch <em class="parameter"><code>type</code></em> can be any recognized query
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch NS, SOA, SIG, KEY, AXFR, etc. When no query type is specified,
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch <span><strong class="command">host</strong></span> automatically selects an appropriate
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch type. By default it looks for A records, but if the
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch <code class="option">-C</code> option was given, queries will be made for SOA
5a7107476ff29592bcbf736d8a1ebb196a5c5726Stephan Bosch records, and if <em class="parameter"><code>name</code></em> is a
5a7107476ff29592bcbf736d8a1ebb196a5c5726Stephan Bosch dotted-decimal IPv4
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch address or colon-delimited IPv6 address, <span><strong class="command">host</strong></span> will
5a7107476ff29592bcbf736d8a1ebb196a5c5726Stephan Bosch query for PTR records. If a query type of IXFR is chosen the starting
5a7107476ff29592bcbf736d8a1ebb196a5c5726Stephan Bosch serial number can be specified by appending an equal followed by the
5a7107476ff29592bcbf736d8a1ebb196a5c5726Stephan Bosch starting serial number (e.g. -t IXFR=12345678).
5a7107476ff29592bcbf736d8a1ebb196a5c5726Stephan Bosch The time to wait for a reply can be controlled through the
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch <code class="option">-W</code> and <code class="option">-w</code> options. The
5a7107476ff29592bcbf736d8a1ebb196a5c5726Stephan Bosch <code class="option">-W</code> option makes <span><strong class="command">host</strong></span>
5a7107476ff29592bcbf736d8a1ebb196a5c5726Stephan Bosch <em class="parameter"><code>wait</code></em> seconds. If <em class="parameter"><code>wait</code></em>
7ebcb054e0d3cc4be54038cbf763ec4189d9725bStephan Bosch is less than one, the wait interval is set to one second. When the
7ebcb054e0d3cc4be54038cbf763ec4189d9725bStephan Bosch <code class="option">-w</code> option is used, <span><strong class="command">host</strong></span>
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch effectively wait forever for a reply. The time to wait for a response
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch will be set to the number of seconds given by the hardware's maximum
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch value for an integer quantity.
5a7107476ff29592bcbf736d8a1ebb196a5c5726Stephan Bosch The <code class="option">-s</code> option tells <span><strong class="command">host</strong></span>
5a7107476ff29592bcbf736d8a1ebb196a5c5726Stephan Bosch <span class="emphasis"><em>not</em></span> to send the query to the next nameserver
e904d473a024c4379a06edd36c5da187dc58ddc6Timo Sirainen if any server responds with a SERVFAIL response, which is the
5a7107476ff29592bcbf736d8a1ebb196a5c5726Stephan Bosch reverse of normal stub resolver behavior.
5a7107476ff29592bcbf736d8a1ebb196a5c5726Stephan Bosch The <code class="option">-m</code> can be used to set the memory usage debugging
e904d473a024c4379a06edd36c5da187dc58ddc6Timo Sirainen <em class="parameter"><code>record</code></em>, <em class="parameter"><code>usage</code></em> and
5a7107476ff29592bcbf736d8a1ebb196a5c5726Stephan Bosch <em class="parameter"><code>trace</code></em>.
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch If <span><strong class="command">host</strong></span> has been built with IDN (internationalized
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch domain name) support, it can accept and display non-ASCII domain names.
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch <span><strong class="command">host</strong></span> appropriately converts character encoding of
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch domain name before sending a request to DNS server or displaying a
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch reply from the server.
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch If you'd like to turn off the IDN support for some reason, defines
5a7107476ff29592bcbf736d8a1ebb196a5c5726Stephan Bosch the <code class="envar">IDN_DISABLE</code> environment variable.
5a7107476ff29592bcbf736d8a1ebb196a5c5726Stephan Bosch The IDN support is disabled if the variable is set when
5a7107476ff29592bcbf736d8a1ebb196a5c5726Stephan Bosch <span><strong class="command">host</strong></span> runs.
5a7107476ff29592bcbf736d8a1ebb196a5c5726Stephan Bosch<p><code class="filename">/etc/resolv.conf</code>
5a7107476ff29592bcbf736d8a1ebb196a5c5726Stephan Bosch<p><span class="citerefentry"><span class="refentrytitle">dig</span>(1)</span>,
7384b4e78eaab44693c985192276e31322155e32Stephan Bosch <span class="citerefentry"><span class="refentrytitle">named</span>(8)</span>.
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