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3b4098640dd85040270f39b9a5ee5e22de99d3d6Mark Andrews - Copyright (C) 2004-2008 Internet Systems Consortium, Inc. ("ISC")
75c0816e8295e180f4bc7f10db3d0d880383bc1cMark Andrews - Copyright (C) 2000-2003 Internet Software Consortium.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein - Permission to use, copy, modify, and 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
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60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein - PERFORMANCE OF THIS SOFTWARE.
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60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<a name="man.host"></a><div class="titlepage"></div>
71c66a876ecca77923638d3f94cc0783152b2f03Mark Andrews<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>
71c66a876ecca77923638d3f94cc0783152b2f03Mark Andrews<p><span><strong class="command">host</strong></span>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein is a simple utility for performing DNS lookups.
71c66a876ecca77923638d3f94cc0783152b2f03Mark Andrews It is normally used to convert names to IP addresses and vice versa.
71c66a876ecca77923638d3f94cc0783152b2f03Mark Andrews When no arguments or options are given,
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <span><strong class="command">host</strong></span>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein prints a short summary of its command line arguments and options.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<p><em class="parameter"><code>name</code></em> is the domain name that is to be
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrews up. It can also be a dotted-decimal IPv4 address or a colon-delimited
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrews IPv6 address, in which case <span><strong class="command">host</strong></span> will by
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein perform a reverse lookup for that address.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <em class="parameter"><code>server</code></em> is an optional argument which
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein 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
71c66a876ecca77923638d3f94cc0783152b2f03Mark Andrews <code class="filename">/etc/resolv.conf</code>.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein 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
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein authoritative name
727f5b8846457a33d06f515a10a7e1aa849ddf18Andreas Gustafsson servers for that zone. The list of name servers is defined by the NS
f293a69bcd1c1dd7bdac8f4102fc2398b9e475c8Eric Luce records that are found for the zone.
f293a69bcd1c1dd7bdac8f4102fc2398b9e475c8Eric Luce The <code class="option">-c</code> option instructs to make a DNS query of class
f293a69bcd1c1dd7bdac8f4102fc2398b9e475c8Eric Luce <em class="parameter"><code>class</code></em>. This can be used to lookup
f293a69bcd1c1dd7bdac8f4102fc2398b9e475c8Eric Luce Chaosnet class resource records. The default class is IN (Internet).
f293a69bcd1c1dd7bdac8f4102fc2398b9e475c8Eric Luce 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
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein options are equivalent. They have been provided for backwards
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein compatibility. In previous versions, the <code class="option">-d</code> option
71c66a876ecca77923638d3f94cc0783152b2f03Mark Andrews switched on debugging traces and <code class="option">-v</code> enabled verbose
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein List mode is selected by the <code class="option">-l</code> option. This makes
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <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
8e245ec21beee31a780de9b89ba1e8bb2b9f4c9aAndreas Gustafsson and address records (A/AAAA). If combined with <code class="option">-a</code>
575e532437cf7f203707765e21767db92fa1e480Mark Andrews all records will be printed.
f293a69bcd1c1dd7bdac8f4102fc2398b9e475c8Eric Luce option specifies that reverse lookups of IPv6 addresses should
f293a69bcd1c1dd7bdac8f4102fc2398b9e475c8Eric Luce use the IP6.INT domain as defined in RFC1886.
f293a69bcd1c1dd7bdac8f4102fc2398b9e475c8Eric Luce The default is to use IP6.ARPA.
f293a69bcd1c1dd7bdac8f4102fc2398b9e475c8Eric Luce The <code class="option">-N</code> option sets the number of dots that have to be
f293a69bcd1c1dd7bdac8f4102fc2398b9e475c8Eric Luce in <em class="parameter"><code>name</code></em> for it to be considered
f293a69bcd1c1dd7bdac8f4102fc2398b9e475c8Eric Luce absolute. The
f293a69bcd1c1dd7bdac8f4102fc2398b9e475c8Eric Luce default value is that defined using the ndots statement in
f293a69bcd1c1dd7bdac8f4102fc2398b9e475c8Eric Luce <code class="filename">/etc/resolv.conf</code>, or 1 if no ndots
f293a69bcd1c1dd7bdac8f4102fc2398b9e475c8Eric Luce statement is
f293a69bcd1c1dd7bdac8f4102fc2398b9e475c8Eric Luce present. Names with fewer dots are interpreted as relative names and
f293a69bcd1c1dd7bdac8f4102fc2398b9e475c8Eric Luce will be searched for in the domains listed in the <span class="type">search</span>
f293a69bcd1c1dd7bdac8f4102fc2398b9e475c8Eric Luce The number of UDP retries for a lookup can be changed with the
f293a69bcd1c1dd7bdac8f4102fc2398b9e475c8Eric Luce <code class="option">-R</code> option. <em class="parameter"><code>number</code></em>
f293a69bcd1c1dd7bdac8f4102fc2398b9e475c8Eric Luce how many times <span><strong class="command">host</strong></span> will repeat a query
f293a69bcd1c1dd7bdac8f4102fc2398b9e475c8Eric Luce not get answered. The default number of retries is 1. If
f293a69bcd1c1dd7bdac8f4102fc2398b9e475c8Eric Luce <em class="parameter"><code>number</code></em> is negative or zero, the
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein retries will default to 1.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein Non-recursive queries can be made via the <code class="option">-r</code> option.
71c66a876ecca77923638d3f94cc0783152b2f03Mark Andrews 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
71c66a876ecca77923638d3f94cc0783152b2f03Mark Andrews 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.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein The <code class="option">-t</code> option is used to select the query type.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <em class="parameter"><code>type</code></em> can be any recognized query
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein type: CNAME,
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
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <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.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein 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
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein 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>,
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <span class="citerefentry"><span class="refentrytitle">named</span>(8)</span>.
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