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0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila - Copyright (C) 2004, 2005, 2007-2009, 2014 Internet Systems Consortium, Inc. ("ISC")
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila - Copyright (C) 2000-2002 Internet Software Consortium.
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila - Permission to use, copy, modify, and/or distribute this software for any
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila - purpose with or without fee is hereby granted, provided that the above
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila - copyright notice and this permission notice appear in all copies.
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila - THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila - REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila - AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila - INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila - LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
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0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila - PERFORMANCE OF THIS SOFTWARE.
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0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila<a name="man.host"></a><div class="titlepage"></div>
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila<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>
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila<p><span><strong class="command">host</strong></span>
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila is a simple utility for performing DNS lookups.
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila It is normally used to convert names to IP addresses and vice versa.
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila When no arguments or options are given,
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila <span><strong class="command">host</strong></span>
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila prints a short summary of its command line arguments and options.
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila<p><em class="parameter"><code>name</code></em> is the domain name that is to be
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila up. It can also be a dotted-decimal IPv4 address or a colon-delimited
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila IPv6 address, in which case <span><strong class="command">host</strong></span> will by
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila perform a reverse lookup for that address.
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila <em class="parameter"><code>server</code></em> is an optional argument which
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila the name or IP address of the name server that <span><strong class="command">host</strong></span>
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila should query instead of the server or servers listed in
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila <code class="filename">/etc/resolv.conf</code>.
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila The <code class="option">-a</code> (all) option is equivalent to setting the
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila <code class="option">-v</code> option and asking <span><strong class="command">host</strong></span> to make
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila a query of type ANY.
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila When the <code class="option">-C</code> option is used, <span><strong class="command">host</strong></span>
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila will attempt to display the SOA records for zone
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila <em class="parameter"><code>name</code></em> from all the listed
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila authoritative name
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila servers for that zone. The list of name servers is defined by the NS
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila records that are found for the zone.
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila The <code class="option">-c</code> option instructs to make a DNS query of class
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila <em class="parameter"><code>class</code></em>. This can be used to lookup
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila Chaosnet class resource records. The default class is IN (Internet).
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila Verbose output is generated by <span><strong class="command">host</strong></span> when
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila <code class="option">-d</code> or <code class="option">-v</code> option is used. The two
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila options are equivalent. They have been provided for backwards
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila compatibility. In previous versions, the <code class="option">-d</code> option
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila switched on debugging traces and <code class="option">-v</code> enabled verbose
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila List mode is selected by the <code class="option">-l</code> option. This makes
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila <span><strong class="command">host</strong></span> perform a zone transfer for zone
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila <em class="parameter"><code>name</code></em>. Transfer the zone printing out
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila and address records (A/AAAA). If combined with <code class="option">-a</code>
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila all records will be printed.
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila option specifies that reverse lookups of IPv6 addresses should
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila use the IP6.INT domain as defined in RFC1886.
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila The default is to use IP6.ARPA.
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila The <code class="option">-N</code> option sets the number of dots that have to be
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila in <em class="parameter"><code>name</code></em> for it to be considered
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila absolute. The
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila default value is that defined using the ndots statement in
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila <code class="filename">/etc/resolv.conf</code>, or 1 if no ndots
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila present. Names with fewer dots are interpreted as relative names and
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila will be searched for in the domains listed in the <span class="type">search</span>
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila or <span class="type">domain</span> directive in
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila <code class="filename">/etc/resolv.conf</code>.
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila The number of UDP retries for a lookup can be changed with the
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila <code class="option">-R</code> option. <em class="parameter"><code>number</code></em>
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila how many times <span><strong class="command">host</strong></span> will repeat a query
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila not get answered. The default number of retries is 1. If
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila <em class="parameter"><code>number</code></em> is negative or zero, the
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila retries will default to 1.
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila Non-recursive queries can be made via the <code class="option">-r</code> option.
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila Setting this option clears the <span class="type">RD</span> — recursion
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila desired — bit in the query which <span><strong class="command">host</strong></span> makes.
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila This should mean that the name server receiving the query will not
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila attempt to resolve <em class="parameter"><code>name</code></em>. The
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila <code class="option">-r</code> option enables <span><strong class="command">host</strong></span>
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila the behavior of a name server by making non-recursive queries and
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila expecting to receive answers to those queries that are usually
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila referrals to other name servers.
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila By default, <span><strong class="command">host</strong></span> uses UDP when making
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila <code class="option">-T</code> option makes it use a TCP connection when querying
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila the name server. TCP will be automatically selected for queries that
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila require it, such as zone transfer (AXFR) requests.
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila The <code class="option">-4</code> option forces <span><strong class="command">host</strong></span> to only
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila use IPv4 query transport. The <code class="option">-6</code> option forces
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila <span><strong class="command">host</strong></span> to only use IPv6 query transport.
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila The <code class="option">-t</code> option is used to select the query type.
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila <em class="parameter"><code>type</code></em> can be any recognized query
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila NS, SOA, SIG, KEY, AXFR, etc. When no query type is specified,
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila <span><strong class="command">host</strong></span> automatically selects an appropriate
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila type. By default, it looks for A, AAAA, and MX records, but if the
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila <code class="option">-C</code> option was given, queries will be made for SOA
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila records, and if <em class="parameter"><code>name</code></em> is a
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila dotted-decimal IPv4
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila address or colon-delimited IPv6 address, <span><strong class="command">host</strong></span> will
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila query for PTR records. If a query type of IXFR is chosen the starting
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila serial number can be specified by appending an equal followed by the
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila starting serial number (e.g. -t IXFR=12345678).
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila The time to wait for a reply can be controlled through the
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila <code class="option">-W</code> and <code class="option">-w</code> options. The
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila <code class="option">-W</code> option makes <span><strong class="command">host</strong></span>
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila <em class="parameter"><code>wait</code></em> seconds. If <em class="parameter"><code>wait</code></em>
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila is less than one, the wait interval is set to one second. When the
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila <code class="option">-w</code> option is used, <span><strong class="command">host</strong></span>
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila effectively wait forever for a reply. The time to wait for a response
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila will be set to the number of seconds given by the hardware's maximum
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila value for an integer quantity.
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila The <code class="option">-s</code> option tells <span><strong class="command">host</strong></span>
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila <span class="emphasis"><em>not</em></span> to send the query to the next nameserver
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila if any server responds with a SERVFAIL response, which is the
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila reverse of normal stub resolver behavior.
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila The <code class="option">-m</code> can be used to set the memory usage debugging
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila <em class="parameter"><code>record</code></em>, <em class="parameter"><code>usage</code></em> and
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila <em class="parameter"><code>trace</code></em>.
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila The <code class="option">-V</code> option causes <span><strong class="command">host</strong></span>
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila to print the version number and exit.
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila If <span><strong class="command">host</strong></span> has been built with IDN (internationalized
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila domain name) support, it can accept and display non-ASCII domain names.
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila <span><strong class="command">host</strong></span> appropriately converts character encoding of
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila domain name before sending a request to DNS server or displaying a
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila reply from the server.
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila If you'd like to turn off the IDN support for some reason, defines
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila the <code class="envar">IDN_DISABLE</code> environment variable.
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila The IDN support is disabled if the variable is set when
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila <span><strong class="command">host</strong></span> runs.
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila<p><code class="filename">/etc/resolv.conf</code>
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila<p><span class="citerefentry"><span class="refentrytitle">dig</span>(1)</span>,
0605ff6f25783f7c69c1148f9f3a7bd4c34c098fTeemu Huovila <span class="citerefentry"><span class="refentrytitle">named</span>(8)</span>.