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c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden - Copyright (C) 2004-2015 Internet Systems Consortium, Inc. ("ISC")
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden - Copyright (C) 2000-2003 Internet Software Consortium.
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden - Permission to use, copy, modify, and/or distribute this software for any
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden - purpose with or without fee is hereby granted, provided that the above
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c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden - THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden - REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
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c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden<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>] [<code class="option">-v</code>] [<code class="option">-V</code>] {name} [server]</p></div>
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden<p><span><strong class="command">host</strong></span>
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden is a simple utility for performing DNS lookups.
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden It is normally used to convert names to IP addresses and vice versa.
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden When no arguments or options are given,
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden <span><strong class="command">host</strong></span>
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden prints a short summary of its command line arguments and options.
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden<p><em class="parameter"><code>name</code></em> is the domain name that is to be
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden up. It can also be a dotted-decimal IPv4 address or a colon-delimited
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden IPv6 address, in which case <span><strong class="command">host</strong></span> will by
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden perform a reverse lookup for that address.
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden <em class="parameter"><code>server</code></em> is an optional argument which
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden the name or IP address of the name server that <span><strong class="command">host</strong></span>
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden should query instead of the server or servers listed in
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden The <code class="option">-a</code> (all) option is equivalent to setting the
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden <code class="option">-v</code> option and asking <span><strong class="command">host</strong></span> to make
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden a query of type ANY.
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden When the <code class="option">-C</code> option is used, <span><strong class="command">host</strong></span>
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden will attempt to display the SOA records for zone
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden <em class="parameter"><code>name</code></em> from all the listed
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden authoritative name
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden servers for that zone. The list of name servers is defined by the NS
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden records that are found for the zone.
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden The <code class="option">-c</code> option instructs to make a DNS query of class
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden <em class="parameter"><code>class</code></em>. This can be used to lookup
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden Chaosnet class resource records. The default class is IN (Internet).
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden Verbose output is generated by <span><strong class="command">host</strong></span> when
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden <code class="option">-d</code> or <code class="option">-v</code> option is used. The two
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden options are equivalent. They have been provided for backwards
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden compatibility. In previous versions, the <code class="option">-d</code> option
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden switched on debugging traces and <code class="option">-v</code> enabled verbose
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden output. Verbose output can also be enabled by setting the
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden <em class="parameter"><code>debug</code></em> option in
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden List mode is selected by the <code class="option">-l</code> option. This makes
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden <span><strong class="command">host</strong></span> perform a zone transfer for zone
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden <em class="parameter"><code>name</code></em>. Transfer the zone printing out
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden and address records (A/AAAA). If combined with <code class="option">-a</code>
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden all records will be printed.
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden option specifies that reverse lookups of IPv6 addresses should
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden use the IP6.INT domain as defined in RFC1886.
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden The default is to use IP6.ARPA.
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden The <code class="option">-N</code> option sets the number of dots that have to be
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden in <em class="parameter"><code>name</code></em> for it to be considered
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden absolute. The
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden default value is that defined using the ndots statement in
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden <code class="filename">/etc/resolv.conf</code>, or 1 if no ndots
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden statement is
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden present. Names with fewer dots are interpreted as relative names and
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden will be searched for in the domains listed in the <span class="type">search</span>
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden or <span class="type">domain</span> directive in
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden The number of UDP retries for a lookup can be changed with the
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden <code class="option">-R</code> option. <em class="parameter"><code>number</code></em>
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden how many times <span><strong class="command">host</strong></span> will repeat a query
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden not get answered. If
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden <em class="parameter"><code>number</code></em> is negative or zero, the
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden retries will default to 1. The default value is 1, or
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden the value of the <em class="parameter"><code>attempts</code></em> option in
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden <code class="filename">/etc/resolv.conf</code>, if set.
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden Non-recursive queries can be made via the <code class="option">-r</code> option.
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden Setting this option clears the <span class="type">RD</span> — recursion
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden desired — bit in the query which <span><strong class="command">host</strong></span> makes.
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden This should mean that the name server receiving the query will not
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden attempt to resolve <em class="parameter"><code>name</code></em>. The
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden <code class="option">-r</code> option enables <span><strong class="command">host</strong></span>
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden the behavior of a name server by making non-recursive queries and
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden expecting to receive answers to those queries that are usually
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden referrals to other name servers.
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden By default, <span><strong class="command">host</strong></span> uses UDP when making
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden queries. The
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden <code class="option">-T</code> option makes it use a TCP connection when querying
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden the name server. TCP will be automatically selected for queries that
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden require it, such as zone transfer (AXFR) requests.
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden The <code class="option">-4</code> option forces <span><strong class="command">host</strong></span> to only
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden use IPv4 query transport. The <code class="option">-6</code> option forces
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden <span><strong class="command">host</strong></span> to only use IPv6 query transport.
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden The <code class="option">-t</code> option is used to select the query type.
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden <em class="parameter"><code>type</code></em> can be any recognized query
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden type: CNAME,
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden NS, SOA, SIG, KEY, AXFR, etc. When no query type is specified,
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden <span><strong class="command">host</strong></span> automatically selects an appropriate
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden type. By default, it looks for A, AAAA, and MX records, but if the
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden <code class="option">-C</code> option was given, queries will be made for SOA
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden records, and if <em class="parameter"><code>name</code></em> is a
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden dotted-decimal IPv4
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden address or colon-delimited IPv6 address, <span><strong class="command">host</strong></span> will
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden query for PTR records. If a query type of IXFR is chosen the starting
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden serial number can be specified by appending an equal followed by the
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden starting serial number (e.g. -t IXFR=12345678).
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden The time to wait for a reply can be controlled through the
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden <code class="option">-W</code> and <code class="option">-w</code> options. The
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden <code class="option">-W</code> option makes <span><strong class="command">host</strong></span>
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden <em class="parameter"><code>wait</code></em> seconds. If <em class="parameter"><code>wait</code></em>
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden is less than one, the wait interval is set to one second. When the
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden <code class="option">-w</code> option is used, <span><strong class="command">host</strong></span>
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden effectively wait forever for a reply. The time to wait for a response
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden will be set to the number of seconds given by the hardware's maximum
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden value for an integer quantity. By default, <span><strong class="command">host</strong></span>
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden will wait for 5 seconds for UDP responses and 10 seconds for TCP
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden connections. These defaults can be overridden by the
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden <em class="parameter"><code>timeout</code></em> option in
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden The <code class="option">-s</code> option tells <span><strong class="command">host</strong></span>
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden <span class="emphasis"><em>not</em></span> to send the query to the next nameserver
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden if any server responds with a SERVFAIL response, which is the
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden reverse of normal stub resolver behavior.
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden The <code class="option">-m</code> can be used to set the memory usage debugging
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden <em class="parameter"><code>record</code></em>, <em class="parameter"><code>usage</code></em> and
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden The <code class="option">-V</code> option causes <span><strong class="command">host</strong></span>
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden to print the version number and exit.
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden If <span><strong class="command">host</strong></span> has been built with IDN (internationalized
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden domain name) support, it can accept and display non-ASCII domain names.
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden <span><strong class="command">host</strong></span> appropriately converts character encoding of
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden domain name before sending a request to DNS server or displaying a
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden reply from the server.
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden If you'd like to turn off the IDN support for some reason, defines
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden the <code class="envar">IDN_DISABLE</code> environment variable.
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden The IDN support is disabled if the variable is set when
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden <span><strong class="command">host</strong></span> runs.
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden<p><code class="filename">/etc/resolv.conf</code>
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden<p><span class="citerefentry"><span class="refentrytitle">dig</span>(1)</span>,
c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden <span class="citerefentry"><span class="refentrytitle">named</span>(8)</span>.
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c44bbf5d2025d672efe11a37ea6e9c867e78b691Neil Madden<p style="text-align: center;">BIND 9.11.0pre-alpha</p>