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1fdd2470b625a58b57d0b155e6caf8c4fc0afe8aAutomatic Updater - Copyright (C) 2004-2011 Internet Systems Consortium, Inc. ("ISC")
75c0816e8295e180f4bc7f10db3d0d880383bc1cMark Andrews - Copyright (C) 2000-2003 Internet Software Consortium.
4a14ce5ba00ab7bc55c99ffdcf59c7a4ab902721Automatic Updater - Permission to use, copy, modify, and/or distribute this software for any
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein - purpose with or without fee is hereby granted, provided that the above
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein - copyright notice and this permission notice appear in all copies.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein - THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein - REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein - AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein - INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein - LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein - OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein - PERFORMANCE OF THIS SOFTWARE.
3a5fe5abf08f16b8d31ab8ee9a788063110ef000Automatic Updater<!-- $Id: man.host.html,v 1.166 2011/04/30 01:14:42 tbox Exp $ -->
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60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<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>
3a5fe5abf08f16b8d31ab8ee9a788063110ef000Automatic Updater<a name="id2610459"></a><h2>DESCRIPTION</h2>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<p><span><strong class="command">host</strong></span>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein is a simple utility for performing DNS lookups.
3a5fe5abf08f16b8d31ab8ee9a788063110ef000Automatic Updater It is normally used to convert names to IP addresses and vice versa.
3a5fe5abf08f16b8d31ab8ee9a788063110ef000Automatic Updater When no arguments or options are given,
3a5fe5abf08f16b8d31ab8ee9a788063110ef000Automatic Updater <span><strong class="command">host</strong></span>
3a5fe5abf08f16b8d31ab8ee9a788063110ef000Automatic Updater prints a short summary of its command line arguments and options.
3a5fe5abf08f16b8d31ab8ee9a788063110ef000Automatic Updater<p><em class="parameter"><code>name</code></em> is the domain name that is to be
3a5fe5abf08f16b8d31ab8ee9a788063110ef000Automatic Updater up. It can also be a dotted-decimal IPv4 address or a colon-delimited
3a5fe5abf08f16b8d31ab8ee9a788063110ef000Automatic Updater IPv6 address, in which case <span><strong class="command">host</strong></span> will by
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein perform a reverse lookup for that address.
3a5fe5abf08f16b8d31ab8ee9a788063110ef000Automatic Updater <em class="parameter"><code>server</code></em> is an optional argument which
3a5fe5abf08f16b8d31ab8ee9a788063110ef000Automatic Updater the name or IP address of the name server that <span><strong class="command">host</strong></span>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein should query instead of the server or servers listed in
3a5fe5abf08f16b8d31ab8ee9a788063110ef000Automatic Updater <code class="filename">/etc/resolv.conf</code>.
3a5fe5abf08f16b8d31ab8ee9a788063110ef000Automatic Updater The <code class="option">-a</code> (all) option is equivalent to setting the
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <code class="option">-v</code> option and asking <span><strong class="command">host</strong></span> to make
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein a query of type ANY.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein When the <code class="option">-C</code> option is used, <span><strong class="command">host</strong></span>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein will attempt to display the SOA records for zone
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <em class="parameter"><code>name</code></em> from all the listed
71c66a876ecca77923638d3f94cc0783152b2f03Mark Andrews authoritative name
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein servers for that zone. The list of name servers is defined by the NS
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrews records that are found for the zone.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein The <code class="option">-c</code> option instructs to make a DNS query of class
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <em class="parameter"><code>class</code></em>. This can be used to lookup
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein Chaosnet class resource records. The default class is IN (Internet).
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein Verbose output is generated by <span><strong class="command">host</strong></span> when
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <code class="option">-d</code> or <code class="option">-v</code> option is used. The two
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrews options are equivalent. They have been provided for backwards
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrews compatibility. In previous versions, the <code class="option">-d</code> option
58d9e9169e7ab4355a0b0bfc13bc616bc5247dfeAutomatic Updater switched on debugging traces and <code class="option">-v</code> enabled verbose
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrews List mode is selected by the <code class="option">-l</code> option. This makes
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrews <span><strong class="command">host</strong></span> perform a zone transfer for zone
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <em class="parameter"><code>name</code></em>. Transfer the zone printing out
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein and address records (A/AAAA). If combined with <code class="option">-a</code>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein all records will be printed.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein option specifies that reverse lookups of IPv6 addresses should
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein use the IP6.INT domain as defined in RFC1886.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein The default is to use IP6.ARPA.
3cddb2c552ee6582e8db0849c28747f6b6ca57feAutomatic Updater The <code class="option">-N</code> option sets the number of dots that have to be
3cddb2c552ee6582e8db0849c28747f6b6ca57feAutomatic Updater in <em class="parameter"><code>name</code></em> for it to be considered
852ccdd42a71550c974111b49415204ffeca6573Automatic Updater default value is that defined using the ndots statement in
3cddb2c552ee6582e8db0849c28747f6b6ca57feAutomatic Updater <code class="filename">/etc/resolv.conf</code>, or 1 if no ndots
3cddb2c552ee6582e8db0849c28747f6b6ca57feAutomatic Updater present. Names with fewer dots are interpreted as relative names and
ca67ebfe9eef0b8f04179f7e511a19e0337a5422Automatic Updater will be searched for in the domains listed in the <span class="type">search</span>
3cddb2c552ee6582e8db0849c28747f6b6ca57feAutomatic Updater or <span class="type">domain</span> directive in
852ccdd42a71550c974111b49415204ffeca6573Automatic Updater <code class="filename">/etc/resolv.conf</code>.
acb72d5e2c83b597332e3eb0c7d59e1142f1adfdMark Andrews The number of UDP retries for a lookup can be changed with the
852ccdd42a71550c974111b49415204ffeca6573Automatic Updater <code class="option">-R</code> option. <em class="parameter"><code>number</code></em>
acb72d5e2c83b597332e3eb0c7d59e1142f1adfdMark Andrews how many times <span><strong class="command">host</strong></span> will repeat a query
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein not get answered. The default number of retries is 1. If
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <em class="parameter"><code>number</code></em> is negative or zero, the
38417cbfb1a328c20b5b723b8584a02c57f88897Automatic Updater retries will default to 1.
38417cbfb1a328c20b5b723b8584a02c57f88897Automatic Updater Non-recursive queries can be made via the <code class="option">-r</code> option.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein Setting this option clears the <span class="type">RD</span> — recursion
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein desired — bit in the query which <span><strong class="command">host</strong></span> makes.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein This should mean that the name server receiving the query will not
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein attempt to resolve <em class="parameter"><code>name</code></em>. The
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <code class="option">-r</code> option enables <span><strong class="command">host</strong></span>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein the behavior of a name server by making non-recursive queries and
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein expecting to receive answers to those queries that are usually
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein referrals to other name servers.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein By default, <span><strong class="command">host</strong></span> uses UDP when making
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein queries. The
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <code class="option">-T</code> option makes it use a TCP connection when querying
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein the name server. TCP will be automatically selected for queries that
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein require it, such as zone transfer (AXFR) requests.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein The <code class="option">-4</code> option forces <span><strong class="command">host</strong></span> to only
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein use IPv4 query transport. The <code class="option">-6</code> option forces
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <span><strong class="command">host</strong></span> to only use IPv6 query transport.
3a5fe5abf08f16b8d31ab8ee9a788063110ef000Automatic Updater The <code class="option">-t</code> option is used to select the query type.
3a5fe5abf08f16b8d31ab8ee9a788063110ef000Automatic Updater <em class="parameter"><code>type</code></em> can be any recognized query
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein NS, SOA, SIG, KEY, AXFR, etc. When no query type is specified,
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <span><strong class="command">host</strong></span> automatically selects an appropriate
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein type. By default, it looks for A, AAAA, and MX records, but if the
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <code class="option">-C</code> option was given, queries will be made for SOA
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein records, and if <em class="parameter"><code>name</code></em> is a
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein dotted-decimal IPv4
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein address or colon-delimited IPv6 address, <span><strong class="command">host</strong></span> will
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein query for PTR records. If a query type of IXFR is chosen the starting
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein serial number can be specified by appending an equal followed by the
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein starting serial number (e.g. -t IXFR=12345678).
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein The time to wait for a reply can be controlled through the
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <code class="option">-W</code> and <code class="option">-w</code> options. The
b05bdb520d83f7ecaad708fe305268c3420be01dMark Andrews <code class="option">-W</code> option makes <span><strong class="command">host</strong></span>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <em class="parameter"><code>wait</code></em> seconds. If <em class="parameter"><code>wait</code></em>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein is less than one, the wait interval is set to one second. When the
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <code class="option">-w</code> option is used, <span><strong class="command">host</strong></span>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein effectively wait forever for a reply. The time to wait for a response
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein will be set to the number of seconds given by the hardware's maximum
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein value for an integer quantity.
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrews The <code class="option">-s</code> option tells <span><strong class="command">host</strong></span>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <span class="emphasis"><em>not</em></span> to send the query to the next nameserver
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein if any server responds with a SERVFAIL response, which is the
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein reverse of normal stub resolver behavior.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein The <code class="option">-m</code> can be used to set the memory usage debugging
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <em class="parameter"><code>record</code></em>, <em class="parameter"><code>usage</code></em> and
71c66a876ecca77923638d3f94cc0783152b2f03Mark Andrews If <span><strong class="command">host</strong></span> has been built with IDN (internationalized
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein domain name) support, it can accept and display non-ASCII domain names.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <span><strong class="command">host</strong></span> appropriately converts character encoding of
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein domain name before sending a request to DNS server or displaying a
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein reply from the server.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein If you'd like to turn off the IDN support for some reason, defines
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein the <code class="envar">IDN_DISABLE</code> environment variable.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein The IDN support is disabled if the variable is set when
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <span><strong class="command">host</strong></span> runs.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<p><code class="filename">/etc/resolv.conf</code>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<p><span class="citerefentry"><span class="refentrytitle">dig</span>(1)</span>,
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