eda14e83f2
security patches to the 9.6.1 version, as well as many other bug fixes. This version also incorporates a different fix for the problem we had patched in contrib/bind9/bin/dig/dighost.c, so that file is now back to being the same as the vendor version. Due to the fact that the DNSSEC algorithm that will be used to sign the root zone is only included in this version and in 9.7.x those who wish to do validation MUST upgrade to one of these prior to July 2010.
213 lines
11 KiB
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213 lines
11 KiB
HTML
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<!-- $Id: host.html,v 1.28.114.2 2009/07/11 01:55:20 tbox Exp $ -->
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<html>
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
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<title>host</title>
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<meta name="generator" content="DocBook XSL Stylesheets V1.71.1">
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</head>
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<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="refentry" lang="en">
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<a name="man.host"></a><div class="titlepage"></div>
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<div class="refnamediv">
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<h2>Name</h2>
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<p>host — DNS lookup utility</p>
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</div>
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<div class="refsynopsisdiv">
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<h2>Synopsis</h2>
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<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>
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</div>
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<div class="refsect1" lang="en">
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<a name="id2543434"></a><h2>DESCRIPTION</h2>
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<p><span><strong class="command">host</strong></span>
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is a simple utility for performing DNS lookups.
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It is normally used to convert names to IP addresses and vice versa.
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When no arguments or options are given,
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<span><strong class="command">host</strong></span>
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prints a short summary of its command line arguments and options.
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</p>
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<p><em class="parameter"><code>name</code></em> is the domain name that is to be
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looked
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up. It can also be a dotted-decimal IPv4 address or a colon-delimited
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IPv6 address, in which case <span><strong class="command">host</strong></span> will by
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default
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perform a reverse lookup for that address.
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<em class="parameter"><code>server</code></em> is an optional argument which
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is either
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the name or IP address of the name server that <span><strong class="command">host</strong></span>
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should query instead of the server or servers listed in
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<code class="filename">/etc/resolv.conf</code>.
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</p>
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<p>
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The <code class="option">-a</code> (all) option is equivalent to setting the
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<code class="option">-v</code> option and asking <span><strong class="command">host</strong></span> to make
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a query of type ANY.
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</p>
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<p>
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When the <code class="option">-C</code> option is used, <span><strong class="command">host</strong></span>
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will attempt to display the SOA records for zone
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<em class="parameter"><code>name</code></em> from all the listed
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authoritative name
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servers for that zone. The list of name servers is defined by the NS
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records that are found for the zone.
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</p>
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<p>
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The <code class="option">-c</code> option instructs to make a DNS query of class
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<em class="parameter"><code>class</code></em>. This can be used to lookup
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Hesiod or
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Chaosnet class resource records. The default class is IN (Internet).
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</p>
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<p>
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Verbose output is generated by <span><strong class="command">host</strong></span> when
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the
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<code class="option">-d</code> or <code class="option">-v</code> option is used. The two
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options are equivalent. They have been provided for backwards
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compatibility. In previous versions, the <code class="option">-d</code> option
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switched on debugging traces and <code class="option">-v</code> enabled verbose
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output.
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</p>
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<p>
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List mode is selected by the <code class="option">-l</code> option. This makes
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<span><strong class="command">host</strong></span> perform a zone transfer for zone
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<em class="parameter"><code>name</code></em>. Transfer the zone printing out
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the NS, PTR
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and address records (A/AAAA). If combined with <code class="option">-a</code>
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all records will be printed.
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</p>
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<p>
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The <code class="option">-i</code>
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option specifies that reverse lookups of IPv6 addresses should
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use the IP6.INT domain as defined in RFC1886.
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The default is to use IP6.ARPA.
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</p>
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<p>
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The <code class="option">-N</code> option sets the number of dots that have to be
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in <em class="parameter"><code>name</code></em> for it to be considered
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absolute. The
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default value is that defined using the ndots statement in
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<code class="filename">/etc/resolv.conf</code>, or 1 if no ndots
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statement is
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present. Names with fewer dots are interpreted as relative names and
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will be searched for in the domains listed in the <span class="type">search</span>
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or <span class="type">domain</span> directive in
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<code class="filename">/etc/resolv.conf</code>.
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</p>
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<p>
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The number of UDP retries for a lookup can be changed with the
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<code class="option">-R</code> option. <em class="parameter"><code>number</code></em>
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indicates
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how many times <span><strong class="command">host</strong></span> will repeat a query
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that does
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not get answered. The default number of retries is 1. If
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<em class="parameter"><code>number</code></em> is negative or zero, the
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number of
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retries will default to 1.
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</p>
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<p>
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Non-recursive queries can be made via the <code class="option">-r</code> option.
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Setting this option clears the <span class="type">RD</span> — recursion
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desired — bit in the query which <span><strong class="command">host</strong></span> makes.
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This should mean that the name server receiving the query will not
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attempt to resolve <em class="parameter"><code>name</code></em>. The
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<code class="option">-r</code> option enables <span><strong class="command">host</strong></span>
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to mimic
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the behavior of a name server by making non-recursive queries and
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expecting to receive answers to those queries that are usually
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referrals to other name servers.
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</p>
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<p>
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By default, <span><strong class="command">host</strong></span> uses UDP when making
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queries. The
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<code class="option">-T</code> option makes it use a TCP connection when querying
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the name server. TCP will be automatically selected for queries that
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require it, such as zone transfer (AXFR) requests.
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</p>
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<p>
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The <code class="option">-4</code> option forces <span><strong class="command">host</strong></span> to only
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use IPv4 query transport. The <code class="option">-6</code> option forces
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<span><strong class="command">host</strong></span> to only use IPv6 query transport.
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</p>
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<p>
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The <code class="option">-t</code> option is used to select the query type.
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<em class="parameter"><code>type</code></em> can be any recognized query
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type: CNAME,
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NS, SOA, SIG, KEY, AXFR, etc. When no query type is specified,
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<span><strong class="command">host</strong></span> automatically selects an appropriate
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query
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type. By default, it looks for A, AAAA, and MX records, but if the
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<code class="option">-C</code> option was given, queries will be made for SOA
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records, and if <em class="parameter"><code>name</code></em> is a
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dotted-decimal IPv4
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address or colon-delimited IPv6 address, <span><strong class="command">host</strong></span> will
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query for PTR records. If a query type of IXFR is chosen the starting
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serial number can be specified by appending an equal followed by the
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starting serial number (e.g. -t IXFR=12345678).
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</p>
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<p>
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The time to wait for a reply can be controlled through the
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<code class="option">-W</code> and <code class="option">-w</code> options. The
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<code class="option">-W</code> option makes <span><strong class="command">host</strong></span>
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wait for
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<em class="parameter"><code>wait</code></em> seconds. If <em class="parameter"><code>wait</code></em>
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is less than one, the wait interval is set to one second. When the
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<code class="option">-w</code> option is used, <span><strong class="command">host</strong></span>
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will
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effectively wait forever for a reply. The time to wait for a response
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will be set to the number of seconds given by the hardware's maximum
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value for an integer quantity.
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</p>
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<p>
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The <code class="option">-s</code> option tells <span><strong class="command">host</strong></span>
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<span class="emphasis"><em>not</em></span> to send the query to the next nameserver
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if any server responds with a SERVFAIL response, which is the
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reverse of normal stub resolver behavior.
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</p>
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<p>
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The <code class="option">-m</code> can be used to set the memory usage debugging
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flags
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<em class="parameter"><code>record</code></em>, <em class="parameter"><code>usage</code></em> and
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<em class="parameter"><code>trace</code></em>.
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</p>
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</div>
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<div class="refsect1" lang="en">
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<a name="id2543800"></a><h2>IDN SUPPORT</h2>
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<p>
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If <span><strong class="command">host</strong></span> has been built with IDN (internationalized
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domain name) support, it can accept and display non-ASCII domain names.
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<span><strong class="command">host</strong></span> appropriately converts character encoding of
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domain name before sending a request to DNS server or displaying a
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reply from the server.
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If you'd like to turn off the IDN support for some reason, defines
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the <code class="envar">IDN_DISABLE</code> environment variable.
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The IDN support is disabled if the variable is set when
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<span><strong class="command">host</strong></span> runs.
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</p>
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</div>
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<div class="refsect1" lang="en">
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<a name="id2543822"></a><h2>FILES</h2>
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<p><code class="filename">/etc/resolv.conf</code>
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</p>
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</div>
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<div class="refsect1" lang="en">
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<a name="id2543834"></a><h2>SEE ALSO</h2>
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<p><span class="citerefentry"><span class="refentrytitle">dig</span>(1)</span>,
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<span class="citerefentry"><span class="refentrytitle">named</span>(8)</span>.
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</p>
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</div>
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</div></body>
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</html>
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