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841179549b6433e782c164a562eb3422f603533dAndreas Gustafsson - Copyright (C) 2004-2008 Internet Systems Consortium, Inc. ("ISC")
841179549b6433e782c164a562eb3422f603533dAndreas Gustafsson - Copyright (C) 2000-2003 Internet Software Consortium.
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington - Permission to use, copy, modify, and distribute this software for any
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington - purpose with or without fee is hereby granted, provided that the above
841179549b6433e782c164a562eb3422f603533dAndreas Gustafsson - copyright notice and this permission notice appear in all copies.
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington - THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington - REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington - AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington - INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington - LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington - OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington - PERFORMANCE OF THIS SOFTWARE.
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3970098dcd2a7122541667b4b56cea8abce8ccf2Mark Andrews<link rel="start" href="Bv9ARM.html" title="BIND 9 Administrator Reference Manual">
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0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington<tr><th colspan="3" align="center">host</th></tr>
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0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington<a name="man.host"></a><div class="titlepage"></div>
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington<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>
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington<a name="id2601854"></a><h2>DESCRIPTION</h2>
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington<p><span><strong class="command">host</strong></span>
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington is a simple utility for performing DNS lookups.
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington It is normally used to convert names to IP addresses and vice versa.
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington When no arguments or options are given,
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington <span><strong class="command">host</strong></span>
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington prints a short summary of its command line arguments and options.
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington<p><em class="parameter"><code>name</code></em> is the domain name that is to be
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington up. It can also be a dotted-decimal IPv4 address or a colon-delimited
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington IPv6 address, in which case <span><strong class="command">host</strong></span> will by
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington perform a reverse lookup for that address.
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington <em class="parameter"><code>server</code></em> is an optional argument which
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington the name or IP address of the name server that <span><strong class="command">host</strong></span>
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington should query instead of the server or servers listed in
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington <code class="filename">/etc/resolv.conf</code>.
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington The <code class="option">-a</code> (all) option is equivalent to setting the
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington <code class="option">-v</code> option and asking <span><strong class="command">host</strong></span> to make
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington a query of type ANY.
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington When the <code class="option">-C</code> option is used, <span><strong class="command">host</strong></span>
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington will attempt to display the SOA records for zone
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington <em class="parameter"><code>name</code></em> from all the listed
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington authoritative name
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington servers for that zone. The list of name servers is defined by the NS
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington records that are found for the zone.
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington The <code class="option">-c</code> option instructs to make a DNS query of class
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington <em class="parameter"><code>class</code></em>. This can be used to lookup
3970098dcd2a7122541667b4b56cea8abce8ccf2Mark Andrews Chaosnet class resource records. The default class is IN (Internet).
3970098dcd2a7122541667b4b56cea8abce8ccf2Mark Andrews Verbose output is generated by <span><strong class="command">host</strong></span> when
3970098dcd2a7122541667b4b56cea8abce8ccf2Mark Andrews <code class="option">-d</code> or <code class="option">-v</code> option is used. The two
3970098dcd2a7122541667b4b56cea8abce8ccf2Mark Andrews options are equivalent. They have been provided for backwards
3970098dcd2a7122541667b4b56cea8abce8ccf2Mark Andrews compatibility. In previous versions, the <code class="option">-d</code> option
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington switched on debugging traces and <code class="option">-v</code> enabled verbose
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington List mode is selected by the <code class="option">-l</code> option. This makes
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington <span><strong class="command">host</strong></span> perform a zone transfer for zone
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington <em class="parameter"><code>name</code></em>. Transfer the zone printing out
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington and address records (A/AAAA). If combined with <code class="option">-a</code>
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington all records will be printed.
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington option specifies that reverse lookups of IPv6 addresses should
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington use the IP6.INT domain as defined in RFC1886.
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington The default is to use IP6.ARPA.
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington The <code class="option">-N</code> option sets the number of dots that have to be
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington in <em class="parameter"><code>name</code></em> for it to be considered
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington absolute. The
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington default value is that defined using the ndots statement in
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington <code class="filename">/etc/resolv.conf</code>, or 1 if no ndots
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington present. Names with fewer dots are interpreted as relative names and
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington will be searched for in the domains listed in the <span class="type">search</span>
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington or <span class="type">domain</span> directive in
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington <code class="filename">/etc/resolv.conf</code>.
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington The number of UDP retries for a lookup can be changed with the
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington <code class="option">-R</code> option. <em class="parameter"><code>number</code></em>
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington how many times <span><strong class="command">host</strong></span> will repeat a query
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington not get answered. The default number of retries is 1. If
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington <em class="parameter"><code>number</code></em> is negative or zero, the
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington retries will default to 1.
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington Non-recursive queries can be made via the <code class="option">-r</code> option.
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington Setting this option clears the <span class="type">RD</span> — recursion
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington desired — bit in the query which <span><strong class="command">host</strong></span> makes.
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington This should mean that the name server receiving the query will not
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington attempt to resolve <em class="parameter"><code>name</code></em>. The
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington <code class="option">-r</code> option enables <span><strong class="command">host</strong></span>
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington the behavior of a name server by making non-recursive queries and
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington expecting to receive answers to those queries that are usually
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington referrals to other name servers.
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington By default <span><strong class="command">host</strong></span> uses UDP when making
3970098dcd2a7122541667b4b56cea8abce8ccf2Mark Andrews queries. The
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington <code class="option">-T</code> option makes it use a TCP connection when querying
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington the name server. TCP will be automatically selected for queries that
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington require it, such as zone transfer (AXFR) requests.
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington The <code class="option">-4</code> option forces <span><strong class="command">host</strong></span> to only
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington use IPv4 query transport. The <code class="option">-6</code> option forces
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington <span><strong class="command">host</strong></span> to only use IPv6 query transport.
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington The <code class="option">-t</code> option is used to select the query type.
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington <em class="parameter"><code>type</code></em> can be any recognized query
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington NS, SOA, SIG, KEY, AXFR, etc. When no query type is specified,
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington <span><strong class="command">host</strong></span> automatically selects an appropriate
3970098dcd2a7122541667b4b56cea8abce8ccf2Mark Andrews type. By default it looks for A, AAAA, and MX records, but if the
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington <code class="option">-C</code> option was given, queries will be made for SOA
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington records, and if <em class="parameter"><code>name</code></em> is a
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington dotted-decimal IPv4
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington address or colon-delimited IPv6 address, <span><strong class="command">host</strong></span> will
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington query for PTR records. If a query type of IXFR is chosen the starting
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington serial number can be specified by appending an equal followed by the
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington starting serial number (e.g. -t IXFR=12345678).
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington The time to wait for a reply can be controlled through the
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington <code class="option">-W</code> and <code class="option">-w</code> options. The
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington <code class="option">-W</code> option makes <span><strong class="command">host</strong></span>
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington <em class="parameter"><code>wait</code></em> seconds. If <em class="parameter"><code>wait</code></em>
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington is less than one, the wait interval is set to one second. When the
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington <code class="option">-w</code> option is used, <span><strong class="command">host</strong></span>
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington effectively wait forever for a reply. The time to wait for a response
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington will be set to the number of seconds given by the hardware's maximum
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington value for an integer quantity.
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington The <code class="option">-s</code> option tells <span><strong class="command">host</strong></span>
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington <span class="emphasis"><em>not</em></span> to send the query to the next nameserver
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington if any server responds with a SERVFAIL response, which is the
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington reverse of normal stub resolver behavior.
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington The <code class="option">-m</code> can be used to set the memory usage debugging
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington <em class="parameter"><code>record</code></em>, <em class="parameter"><code>usage</code></em> and
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington <em class="parameter"><code>trace</code></em>.
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington<a name="id2602437"></a><h2>IDN SUPPORT</h2>
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington If <span><strong class="command">host</strong></span> has been built with IDN (internationalized
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington domain name) support, it can accept and display non-ASCII domain names.
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington <span><strong class="command">host</strong></span> appropriately converts character encoding of
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington domain name before sending a request to DNS server or displaying a
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington reply from the server.
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington If you'd like to turn off the IDN support for some reason, defines
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington the <code class="envar">IDN_DISABLE</code> environment variable.
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington The IDN support is disabled if the variable is set when
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington <span><strong class="command">host</strong></span> runs.
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington<p><code class="filename">/etc/resolv.conf</code>
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington<p><span class="citerefentry"><span class="refentrytitle">dig</span>(1)</span>,
0b062f4990db5cc6db2fe3398926f71b92a67407Brian Wellington <span class="citerefentry"><span class="refentrytitle">named</span>(8)</span>.
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