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2670cd577aa57eb9f915a4f4220ae48c9b4fc5fbTimo Sirainen - Copyright (C) 2004-2009 Internet Systems Consortium, Inc. ("ISC")
2670cd577aa57eb9f915a4f4220ae48c9b4fc5fbTimo Sirainen - Copyright (C) 2000-2003 Internet Software Consortium.
bdd36cfdba3ff66d25570a9ff568d69e1eb543cfTimo Sirainen - Permission to use, copy, modify, and/or distribute this software for any
2670cd577aa57eb9f915a4f4220ae48c9b4fc5fbTimo Sirainen - purpose with or without fee is hereby granted, provided that the above
2670cd577aa57eb9f915a4f4220ae48c9b4fc5fbTimo Sirainen - copyright notice and this permission notice appear in all copies.
2670cd577aa57eb9f915a4f4220ae48c9b4fc5fbTimo Sirainen - THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
2670cd577aa57eb9f915a4f4220ae48c9b4fc5fbTimo Sirainen - REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
9522aa5f33cc37fe8ccd0d647cc51dd3ba6a9b55Timo Sirainen - AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
2670cd577aa57eb9f915a4f4220ae48c9b4fc5fbTimo Sirainen - INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
2670cd577aa57eb9f915a4f4220ae48c9b4fc5fbTimo Sirainen - LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
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2670cd577aa57eb9f915a4f4220ae48c9b4fc5fbTimo Sirainen - PERFORMANCE OF THIS SOFTWARE.
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2670cd577aa57eb9f915a4f4220ae48c9b4fc5fbTimo Sirainen<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>
e2a88d59c0d47d63ce1ad5b1fd95e487124a3fd4Timo Sirainen<p><span><strong class="command">host</strong></span>
2670cd577aa57eb9f915a4f4220ae48c9b4fc5fbTimo Sirainen is a simple utility for performing DNS lookups.
2670cd577aa57eb9f915a4f4220ae48c9b4fc5fbTimo Sirainen It is normally used to convert names to IP addresses and vice versa.
8b16d3b00f051401c97568697ccdbba48663759aTimo Sirainen When no arguments or options are given,
8b16d3b00f051401c97568697ccdbba48663759aTimo Sirainen <span><strong class="command">host</strong></span>
8b16d3b00f051401c97568697ccdbba48663759aTimo Sirainen prints a short summary of its command line arguments and options.
8b16d3b00f051401c97568697ccdbba48663759aTimo Sirainen<p><em class="parameter"><code>name</code></em> is the domain name that is to be
8b16d3b00f051401c97568697ccdbba48663759aTimo Sirainen up. It can also be a dotted-decimal IPv4 address or a colon-delimited
8b16d3b00f051401c97568697ccdbba48663759aTimo Sirainen IPv6 address, in which case <span><strong class="command">host</strong></span> will by
8b16d3b00f051401c97568697ccdbba48663759aTimo Sirainen perform a reverse lookup for that address.
8b16d3b00f051401c97568697ccdbba48663759aTimo Sirainen <em class="parameter"><code>server</code></em> is an optional argument which
8b16d3b00f051401c97568697ccdbba48663759aTimo Sirainen the name or IP address of the name server that <span><strong class="command">host</strong></span>
8b16d3b00f051401c97568697ccdbba48663759aTimo Sirainen should query instead of the server or servers listed in
8b16d3b00f051401c97568697ccdbba48663759aTimo Sirainen <code class="filename">/etc/resolv.conf</code>.
8b16d3b00f051401c97568697ccdbba48663759aTimo Sirainen The <code class="option">-a</code> (all) option is equivalent to setting the
8b16d3b00f051401c97568697ccdbba48663759aTimo Sirainen <code class="option">-v</code> option and asking <span><strong class="command">host</strong></span> to make
8b16d3b00f051401c97568697ccdbba48663759aTimo Sirainen a query of type ANY.
8b16d3b00f051401c97568697ccdbba48663759aTimo Sirainen When the <code class="option">-C</code> option is used, <span><strong class="command">host</strong></span>
8b16d3b00f051401c97568697ccdbba48663759aTimo Sirainen will attempt to display the SOA records for zone
8b16d3b00f051401c97568697ccdbba48663759aTimo Sirainen <em class="parameter"><code>name</code></em> from all the listed
8b16d3b00f051401c97568697ccdbba48663759aTimo Sirainen authoritative name
8b16d3b00f051401c97568697ccdbba48663759aTimo Sirainen servers for that zone. The list of name servers is defined by the NS
8b16d3b00f051401c97568697ccdbba48663759aTimo Sirainen records that are found for the zone.
8b16d3b00f051401c97568697ccdbba48663759aTimo Sirainen The <code class="option">-c</code> option instructs to make a DNS query of class
8b16d3b00f051401c97568697ccdbba48663759aTimo Sirainen <em class="parameter"><code>class</code></em>. This can be used to lookup
e2a88d59c0d47d63ce1ad5b1fd95e487124a3fd4Timo Sirainen Chaosnet class resource records. The default class is IN (Internet).
8b16d3b00f051401c97568697ccdbba48663759aTimo Sirainen Verbose output is generated by <span><strong class="command">host</strong></span> when
2670cd577aa57eb9f915a4f4220ae48c9b4fc5fbTimo Sirainen <code class="option">-d</code> or <code class="option">-v</code> option is used. The two
2670cd577aa57eb9f915a4f4220ae48c9b4fc5fbTimo Sirainen options are equivalent. They have been provided for backwards
4fda77c9e9fc68feb292c4dacae1fac49dd08165Timo Sirainen compatibility. In previous versions, the <code class="option">-d</code> option
2670cd577aa57eb9f915a4f4220ae48c9b4fc5fbTimo Sirainen switched on debugging traces and <code class="option">-v</code> enabled verbose
8c2b4a45f17a5cb13bb01058ca37798cf48d91baTimo Sirainen List mode is selected by the <code class="option">-l</code> option. This makes
4fda77c9e9fc68feb292c4dacae1fac49dd08165Timo Sirainen <span><strong class="command">host</strong></span> perform a zone transfer for zone
4fda77c9e9fc68feb292c4dacae1fac49dd08165Timo Sirainen <em class="parameter"><code>name</code></em>. Transfer the zone printing out
4fda77c9e9fc68feb292c4dacae1fac49dd08165Timo Sirainen and address records (A/AAAA). If combined with <code class="option">-a</code>
4fda77c9e9fc68feb292c4dacae1fac49dd08165Timo Sirainen all records will be printed.
4fda77c9e9fc68feb292c4dacae1fac49dd08165Timo Sirainen option specifies that reverse lookups of IPv6 addresses should
e4194f4703eeec32b432371ae30fc8f25ab720d8Timo Sirainen use the IP6.INT domain as defined in RFC1886.
e4194f4703eeec32b432371ae30fc8f25ab720d8Timo Sirainen The default is to use IP6.ARPA.
4fda77c9e9fc68feb292c4dacae1fac49dd08165Timo Sirainen The <code class="option">-N</code> option sets the number of dots that have to be
4fda77c9e9fc68feb292c4dacae1fac49dd08165Timo Sirainen in <em class="parameter"><code>name</code></em> for it to be considered
4fda77c9e9fc68feb292c4dacae1fac49dd08165Timo Sirainen absolute. The
4fda77c9e9fc68feb292c4dacae1fac49dd08165Timo Sirainen default value is that defined using the ndots statement in
4fda77c9e9fc68feb292c4dacae1fac49dd08165Timo Sirainen <code class="filename">/etc/resolv.conf</code>, or 1 if no ndots
8c2b4a45f17a5cb13bb01058ca37798cf48d91baTimo Sirainen present. Names with fewer dots are interpreted as relative names and
8c2b4a45f17a5cb13bb01058ca37798cf48d91baTimo Sirainen will be searched for in the domains listed in the <span class="type">search</span>
8c2b4a45f17a5cb13bb01058ca37798cf48d91baTimo Sirainen or <span class="type">domain</span> directive in
4fda77c9e9fc68feb292c4dacae1fac49dd08165Timo Sirainen <code class="filename">/etc/resolv.conf</code>.
2670cd577aa57eb9f915a4f4220ae48c9b4fc5fbTimo Sirainen The number of UDP retries for a lookup can be changed with the
2670cd577aa57eb9f915a4f4220ae48c9b4fc5fbTimo Sirainen <code class="option">-R</code> option. <em class="parameter"><code>number</code></em>
2670cd577aa57eb9f915a4f4220ae48c9b4fc5fbTimo Sirainen how many times <span><strong class="command">host</strong></span> will repeat a query
e4194f4703eeec32b432371ae30fc8f25ab720d8Timo Sirainen not get answered. The default number of retries is 1. If
e4194f4703eeec32b432371ae30fc8f25ab720d8Timo Sirainen <em class="parameter"><code>number</code></em> is negative or zero, the
e4194f4703eeec32b432371ae30fc8f25ab720d8Timo Sirainen retries will default to 1.
e4194f4703eeec32b432371ae30fc8f25ab720d8Timo Sirainen Non-recursive queries can be made via the <code class="option">-r</code> option.
e4194f4703eeec32b432371ae30fc8f25ab720d8Timo Sirainen Setting this option clears the <span class="type">RD</span> — recursion
e4194f4703eeec32b432371ae30fc8f25ab720d8Timo Sirainen desired — bit in the query which <span><strong class="command">host</strong></span> makes.
e4194f4703eeec32b432371ae30fc8f25ab720d8Timo Sirainen This should mean that the name server receiving the query will not
e4194f4703eeec32b432371ae30fc8f25ab720d8Timo Sirainen attempt to resolve <em class="parameter"><code>name</code></em>. The
e4194f4703eeec32b432371ae30fc8f25ab720d8Timo Sirainen <code class="option">-r</code> option enables <span><strong class="command">host</strong></span>
e4194f4703eeec32b432371ae30fc8f25ab720d8Timo Sirainen the behavior of a name server by making non-recursive queries and
e4194f4703eeec32b432371ae30fc8f25ab720d8Timo Sirainen expecting to receive answers to those queries that are usually
e4194f4703eeec32b432371ae30fc8f25ab720d8Timo Sirainen referrals to other name servers.
e4194f4703eeec32b432371ae30fc8f25ab720d8Timo Sirainen By default, <span><strong class="command">host</strong></span> uses UDP when making
e2a88d59c0d47d63ce1ad5b1fd95e487124a3fd4Timo Sirainen <code class="option">-T</code> option makes it use a TCP connection when querying
e4194f4703eeec32b432371ae30fc8f25ab720d8Timo Sirainen the name server. TCP will be automatically selected for queries that
e4194f4703eeec32b432371ae30fc8f25ab720d8Timo Sirainen require it, such as zone transfer (AXFR) requests.
e4194f4703eeec32b432371ae30fc8f25ab720d8Timo Sirainen The <code class="option">-4</code> option forces <span><strong class="command">host</strong></span> to only
e4194f4703eeec32b432371ae30fc8f25ab720d8Timo Sirainen use IPv4 query transport. The <code class="option">-6</code> option forces
e4194f4703eeec32b432371ae30fc8f25ab720d8Timo Sirainen <span><strong class="command">host</strong></span> to only use IPv6 query transport.
e4194f4703eeec32b432371ae30fc8f25ab720d8Timo Sirainen The <code class="option">-t</code> option is used to select the query type.
e4194f4703eeec32b432371ae30fc8f25ab720d8Timo Sirainen <em class="parameter"><code>type</code></em> can be any recognized query
e4194f4703eeec32b432371ae30fc8f25ab720d8Timo Sirainen NS, SOA, SIG, KEY, AXFR, etc. When no query type is specified,
e4194f4703eeec32b432371ae30fc8f25ab720d8Timo Sirainen <span><strong class="command">host</strong></span> automatically selects an appropriate
e4194f4703eeec32b432371ae30fc8f25ab720d8Timo Sirainen type. By default, it looks for A, AAAA, and MX records, but if the
e4194f4703eeec32b432371ae30fc8f25ab720d8Timo Sirainen <code class="option">-C</code> option was given, queries will be made for SOA
e4194f4703eeec32b432371ae30fc8f25ab720d8Timo Sirainen records, and if <em class="parameter"><code>name</code></em> is a
e4194f4703eeec32b432371ae30fc8f25ab720d8Timo Sirainen dotted-decimal IPv4
e4194f4703eeec32b432371ae30fc8f25ab720d8Timo Sirainen address or colon-delimited IPv6 address, <span><strong class="command">host</strong></span> will
e4194f4703eeec32b432371ae30fc8f25ab720d8Timo Sirainen query for PTR records. If a query type of IXFR is chosen the starting
e4194f4703eeec32b432371ae30fc8f25ab720d8Timo Sirainen serial number can be specified by appending an equal followed by the
e4194f4703eeec32b432371ae30fc8f25ab720d8Timo Sirainen starting serial number (e.g. -t IXFR=12345678).
e4194f4703eeec32b432371ae30fc8f25ab720d8Timo Sirainen The time to wait for a reply can be controlled through the
e2a88d59c0d47d63ce1ad5b1fd95e487124a3fd4Timo Sirainen <code class="option">-W</code> and <code class="option">-w</code> options. The
e4194f4703eeec32b432371ae30fc8f25ab720d8Timo Sirainen <code class="option">-W</code> option makes <span><strong class="command">host</strong></span>
e4194f4703eeec32b432371ae30fc8f25ab720d8Timo Sirainen <em class="parameter"><code>wait</code></em> seconds. If <em class="parameter"><code>wait</code></em>
e4194f4703eeec32b432371ae30fc8f25ab720d8Timo Sirainen is less than one, the wait interval is set to one second. When the
2670cd577aa57eb9f915a4f4220ae48c9b4fc5fbTimo Sirainen <code class="option">-w</code> option is used, <span><strong class="command">host</strong></span>
2670cd577aa57eb9f915a4f4220ae48c9b4fc5fbTimo Sirainen effectively wait forever for a reply. The time to wait for a response
cf9d67e4a9bfee31cf3be05244555d51a3d1b9feTimo Sirainen will be set to the number of seconds given by the hardware's maximum
2670cd577aa57eb9f915a4f4220ae48c9b4fc5fbTimo Sirainen value for an integer quantity.
2670cd577aa57eb9f915a4f4220ae48c9b4fc5fbTimo Sirainen The <code class="option">-s</code> option tells <span><strong class="command">host</strong></span>
2670cd577aa57eb9f915a4f4220ae48c9b4fc5fbTimo Sirainen <span class="emphasis"><em>not</em></span> to send the query to the next nameserver
3c296d819c54e21ce05c3d2eeeedc79be42ac593Timo Sirainen if any server responds with a SERVFAIL response, which is the
2670cd577aa57eb9f915a4f4220ae48c9b4fc5fbTimo Sirainen reverse of normal stub resolver behavior.
242abe3ad2423776e9cf05e1304eb8fda4831b23Timo Sirainen The <code class="option">-m</code> can be used to set the memory usage debugging
2670cd577aa57eb9f915a4f4220ae48c9b4fc5fbTimo Sirainen <em class="parameter"><code>record</code></em>, <em class="parameter"><code>usage</code></em> and
2670cd577aa57eb9f915a4f4220ae48c9b4fc5fbTimo Sirainen <em class="parameter"><code>trace</code></em>.
cf9d67e4a9bfee31cf3be05244555d51a3d1b9feTimo Sirainen If <span><strong class="command">host</strong></span> has been built with IDN (internationalized
2670cd577aa57eb9f915a4f4220ae48c9b4fc5fbTimo Sirainen domain name) support, it can accept and display non-ASCII domain names.
cf9d67e4a9bfee31cf3be05244555d51a3d1b9feTimo Sirainen <span><strong class="command">host</strong></span> appropriately converts character encoding of
0a53eb0283d7ec28c6105f61e118b96fce8ecb95Timo Sirainen domain name before sending a request to DNS server or displaying a
2670cd577aa57eb9f915a4f4220ae48c9b4fc5fbTimo Sirainen reply from the server.
e2a88d59c0d47d63ce1ad5b1fd95e487124a3fd4Timo Sirainen If you'd like to turn off the IDN support for some reason, defines
2670cd577aa57eb9f915a4f4220ae48c9b4fc5fbTimo Sirainen the <code class="envar">IDN_DISABLE</code> environment variable.
2670cd577aa57eb9f915a4f4220ae48c9b4fc5fbTimo Sirainen The IDN support is disabled if the variable is set when
2670cd577aa57eb9f915a4f4220ae48c9b4fc5fbTimo Sirainen <span><strong class="command">host</strong></span> runs.
2670cd577aa57eb9f915a4f4220ae48c9b4fc5fbTimo Sirainen<p><code class="filename">/etc/resolv.conf</code>
2670cd577aa57eb9f915a4f4220ae48c9b4fc5fbTimo Sirainen<p><span class="citerefentry"><span class="refentrytitle">dig</span>(1)</span>,
cf9d67e4a9bfee31cf3be05244555d51a3d1b9feTimo Sirainen <span class="citerefentry"><span class="refentrytitle">named</span>(8)</span>.
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