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96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen - Copyright (C) 2004-2014 Internet Systems Consortium, Inc. ("ISC")
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen - Copyright (C) 2000-2003 Internet Software Consortium.
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96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen<a name="man.host"></a><div class="titlepage"></div>
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen<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>
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen<p><span><strong class="command">host</strong></span>
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen is a simple utility for performing DNS lookups.
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen It is normally used to convert names to IP addresses and vice versa.
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen When no arguments or options are given,
dee5e0b6c29ca22cbf67d28fbee195d70b0dde72Tom Gundersen <span><strong class="command">host</strong></span>
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen prints a short summary of its command line arguments and options.
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen<p><em class="parameter"><code>name</code></em> is the domain name that is to be
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen up. It can also be a dotted-decimal IPv4 address or a colon-delimited
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen IPv6 address, in which case <span><strong class="command">host</strong></span> will by
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen perform a reverse lookup for that address.
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen <em class="parameter"><code>server</code></em> is an optional argument which
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen the name or IP address of the name server that <span><strong class="command">host</strong></span>
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen should query instead of the server or servers listed in
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen <code class="filename">/etc/resolv.conf</code>.
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen The <code class="option">-a</code> (all) option is equivalent to setting the
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen <code class="option">-v</code> option and asking <span><strong class="command">host</strong></span> to make
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen a query of type ANY.
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen When the <code class="option">-C</code> option is used, <span><strong class="command">host</strong></span>
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen will attempt to display the SOA records for zone
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen <em class="parameter"><code>name</code></em> from all the listed
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen authoritative name
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen servers for that zone. The list of name servers is defined by the NS
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen records that are found for the zone.
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen The <code class="option">-c</code> option instructs to make a DNS query of class
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen <em class="parameter"><code>class</code></em>. This can be used to lookup
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen Chaosnet class resource records. The default class is IN (Internet).
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen Verbose output is generated by <span><strong class="command">host</strong></span> when
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen <code class="option">-d</code> or <code class="option">-v</code> option is used. The two
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen options are equivalent. They have been provided for backwards
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen compatibility. In previous versions, the <code class="option">-d</code> option
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen switched on debugging traces and <code class="option">-v</code> enabled verbose
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen output. Verbose output can also be enabled by setting the
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen <em class="parameter"><code>debug</code></em> option in
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen <code class="filename">/etc/resolv.conf</code>.
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen List mode is selected by the <code class="option">-l</code> option. This makes
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen <span><strong class="command">host</strong></span> perform a zone transfer for zone
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen <em class="parameter"><code>name</code></em>. Transfer the zone printing out
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen and address records (A/AAAA). If combined with <code class="option">-a</code>
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen all records will be printed.
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen option specifies that reverse lookups of IPv6 addresses should
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen use the IP6.INT domain as defined in RFC1886.
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen The default is to use IP6.ARPA.
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen The <code class="option">-N</code> option sets the number of dots that have to be
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen in <em class="parameter"><code>name</code></em> for it to be considered
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen absolute. The
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen default value is that defined using the ndots statement in
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen <code class="filename">/etc/resolv.conf</code>, or 1 if no ndots
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen present. Names with fewer dots are interpreted as relative names and
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen will be searched for in the domains listed in the <span class="type">search</span>
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen or <span class="type">domain</span> directive in
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen <code class="filename">/etc/resolv.conf</code>.
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen The number of UDP retries for a lookup can be changed with the
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen <code class="option">-R</code> option. <em class="parameter"><code>number</code></em>
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen how many times <span><strong class="command">host</strong></span> will repeat a query
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen not get answered. If
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen <em class="parameter"><code>number</code></em> is negative or zero, the
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen retries will default to 1. The default value is 1, or
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen the value of the <em class="parameter"><code>attempts</code></em> option in
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen <code class="filename">/etc/resolv.conf</code>, if set.
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen Non-recursive queries can be made via the <code class="option">-r</code> option.
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen Setting this option clears the <span class="type">RD</span> — recursion
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen desired — bit in the query which <span><strong class="command">host</strong></span> makes.
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen This should mean that the name server receiving the query will not
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen attempt to resolve <em class="parameter"><code>name</code></em>. The
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen <code class="option">-r</code> option enables <span><strong class="command">host</strong></span>
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen the behavior of a name server by making non-recursive queries and
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen expecting to receive answers to those queries that are usually
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen referrals to other name servers.
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen By default, <span><strong class="command">host</strong></span> uses UDP when making
54f0b4d9a3e3e1b955d0b0021d9678571d91a5efTom Gundersen <code class="option">-T</code> option makes it use a TCP connection when querying
54f0b4d9a3e3e1b955d0b0021d9678571d91a5efTom Gundersen the name server. TCP will be automatically selected for queries that
54f0b4d9a3e3e1b955d0b0021d9678571d91a5efTom Gundersen require it, such as zone transfer (AXFR) requests.
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen The <code class="option">-4</code> option forces <span><strong class="command">host</strong></span> to only
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen use IPv4 query transport. The <code class="option">-6</code> option forces
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen <span><strong class="command">host</strong></span> to only use IPv6 query transport.
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen The <code class="option">-t</code> option is used to select the query type.
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen <em class="parameter"><code>type</code></em> can be any recognized query
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen NS, SOA, SIG, KEY, AXFR, etc. When no query type is specified,
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen <span><strong class="command">host</strong></span> automatically selects an appropriate
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen type. By default, it looks for A, AAAA, and MX records, but if the
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen <code class="option">-C</code> option was given, queries will be made for SOA
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen records, and if <em class="parameter"><code>name</code></em> is a
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen dotted-decimal IPv4
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen address or colon-delimited IPv6 address, <span><strong class="command">host</strong></span> will
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen query for PTR records. If a query type of IXFR is chosen the starting
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen serial number can be specified by appending an equal followed by the
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen starting serial number (e.g. -t IXFR=12345678).
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen The time to wait for a reply can be controlled through the
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen <code class="option">-W</code> and <code class="option">-w</code> options. The
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen <code class="option">-W</code> option makes <span><strong class="command">host</strong></span>
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen <em class="parameter"><code>wait</code></em> seconds. If <em class="parameter"><code>wait</code></em>
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen is less than one, the wait interval is set to one second. When the
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen <code class="option">-w</code> option is used, <span><strong class="command">host</strong></span>
54f0b4d9a3e3e1b955d0b0021d9678571d91a5efTom Gundersen effectively wait forever for a reply. The time to wait for a response
54f0b4d9a3e3e1b955d0b0021d9678571d91a5efTom Gundersen will be set to the number of seconds given by the hardware's maximum
54f0b4d9a3e3e1b955d0b0021d9678571d91a5efTom Gundersen value for an integer quantity. By default, <span><strong class="command">host</strong></span>
54f0b4d9a3e3e1b955d0b0021d9678571d91a5efTom Gundersen will wait for 5 seconds for UDP responses and 10 seconds for TCP
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen connections. These defaults can be overridden by the
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen <em class="parameter"><code>timeout</code></em> option in
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen <code class="filename">/etc/resolv.conf</code>.
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen The <code class="option">-s</code> option tells <span><strong class="command">host</strong></span>
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen <span class="emphasis"><em>not</em></span> to send the query to the next nameserver
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen if any server responds with a SERVFAIL response, which is the
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen reverse of normal stub resolver behavior.
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen The <code class="option">-m</code> can be used to set the memory usage debugging
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen <em class="parameter"><code>record</code></em>, <em class="parameter"><code>usage</code></em> and
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen <em class="parameter"><code>trace</code></em>.
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen The <code class="option">-V</code> option causes <span><strong class="command">host</strong></span>
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen to print the version number and exit.
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen If <span><strong class="command">host</strong></span> has been built with IDN (internationalized
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen domain name) support, it can accept and display non-ASCII domain names.
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen <span><strong class="command">host</strong></span> appropriately converts character encoding of
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen domain name before sending a request to DNS server or displaying a
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen reply from the server.
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen If you'd like to turn off the IDN support for some reason, defines
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen the <code class="envar">IDN_DISABLE</code> environment variable.
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen The IDN support is disabled if the variable is set when
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen <span><strong class="command">host</strong></span> runs.
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen<p><code class="filename">/etc/resolv.conf</code>
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen<p><span class="citerefentry"><span class="refentrytitle">dig</span>(1)</span>,
96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen <span class="citerefentry"><span class="refentrytitle">named</span>(8)</span>.
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96df036fe3d25525a44f5efdb2fc8560e82e6cfdTom Gundersen<p style="text-align: center;">BIND Version 9.11</p>