334 lines
12 KiB
Python
334 lines
12 KiB
Python
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<!--
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- Copyright (C) 2000-2002, 2004, 2005, 2007-2009, 2014-2017 Internet Systems Consortium, Inc. ("ISC")
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-
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- This Source Code Form is subject to the terms of the Mozilla Public
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- License, v. 2.0. If a copy of the MPL was not distributed with this
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- file, You can obtain one at http://mozilla.org/MPL/2.0/.
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-->
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<html lang="en">
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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 V1.78.1">
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</head>
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<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="refentry">
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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>
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host
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— DNS lookup utility
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</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>
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<code class="command">host</code>
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[<code class="option">-aCdlnrsTUwv</code>]
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[<code class="option">-c <em class="replaceable"><code>class</code></em></code>]
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[<code class="option">-N <em class="replaceable"><code>ndots</code></em></code>]
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[<code class="option">-R <em class="replaceable"><code>number</code></em></code>]
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[<code class="option">-t <em class="replaceable"><code>type</code></em></code>]
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[<code class="option">-W <em class="replaceable"><code>wait</code></em></code>]
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[<code class="option">-m <em class="replaceable"><code>flag</code></em></code>]
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[
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[<code class="option">-4</code>]
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| [<code class="option">-6</code>]
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]
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[<code class="option">-v</code>]
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[<code class="option">-V</code>]
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{name}
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[server]
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</p></div>
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</div>
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<div class="refsection">
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<a name="id-1.7"></a><h2>DESCRIPTION</h2>
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<p><span class="command"><strong>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 class="command"><strong>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 class="command"><strong>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 class="command"><strong>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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</div>
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<div class="refsection">
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<a name="id-1.8"></a><h2>OPTIONS</h2>
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<div class="variablelist"><dl class="variablelist">
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<dt><span class="term">-4</span></dt>
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<dd>
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<p>
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Use IPv4 only for query transport.
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See also the <code class="option">-6</code> option.
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</p>
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</dd>
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<dt><span class="term">-6</span></dt>
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<dd>
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<p>
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Use IPv6 only for query transport.
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See also the <code class="option">-4</code> option.
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</p>
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</dd>
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<dt><span class="term">-a</span></dt>
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<dd>
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<p>
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"All". The <code class="option">-a</code> option is normally equivalent
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to <code class="option">-v -t <code class="literal">ANY</code></code>.
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It also affects the behaviour of the <code class="option">-l</code>
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list zone option.
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</p>
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</dd>
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<dt><span class="term">-c <em class="replaceable"><code>class</code></em></span></dt>
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<dd>
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<p>
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Query class: This can be used to lookup HS (Hesiod) or CH
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(Chaosnet) class resource records. The default class is IN
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(Internet).
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</p>
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</dd>
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<dt><span class="term">-C</span></dt>
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<dd>
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<p>
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Check consistency: <span class="command"><strong>host</strong></span> will query the
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SOA records for zone <em class="parameter"><code>name</code></em> from all
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the listed authoritative name servers for that zone. The
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list of name servers is defined by the NS records that are
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found for the zone.
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</p>
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</dd>
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<dt><span class="term">-d</span></dt>
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<dd>
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<p>
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Print debugging traces.
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Equivalent to the <code class="option">-v</code> verbose option.
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</p>
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</dd>
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<dt><span class="term">-i</span></dt>
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<dd>
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<p>
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Obsolete.
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Use the IP6.INT domain for reverse lookups of IPv6
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addresses as defined in RFC1886 and deprecated in RFC4159.
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The default is to use IP6.ARPA as specified in RFC3596.
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</p>
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</dd>
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<dt><span class="term">-l</span></dt>
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<dd>
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<p>
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List zone:
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The <span class="command"><strong>host</strong></span> command performs a zone transfer of
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zone <em class="parameter"><code>name</code></em> and prints out the NS,
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PTR and address records (A/AAAA).
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</p>
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<p>
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Together, the <code class="option">-l -a</code>
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options print all records in the zone.
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</p>
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</dd>
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<dt><span class="term">-N <em class="replaceable"><code>ndots</code></em></span></dt>
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<dd>
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<p>
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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 default value is that defined using the
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ndots statement in <code class="filename">/etc/resolv.conf</code>,
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or 1 if no ndots statement is present. Names with fewer
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dots are interpreted as relative names and will be
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searched for in the domains listed in
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the <span class="type">search</span> or <span class="type">domain</span> directive
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in <code class="filename">/etc/resolv.conf</code>.
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</p>
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</dd>
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<dt><span class="term">-r</span></dt>
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<dd>
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<p>
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Non-recursive query:
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Setting this option clears the RD (recursion desired) bit
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in the query. This should mean that the name server
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receiving the query will not attempt to
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resolve <em class="parameter"><code>name</code></em>.
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The <code class="option">-r</code> option
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enables <span class="command"><strong>host</strong></span> to mimic the behavior of a
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name server by making non-recursive queries and expecting
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to receive answers to those queries that can be
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referrals to other name servers.
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</p>
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</dd>
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<dt><span class="term">-R <em class="replaceable"><code>number</code></em></span></dt>
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<dd>
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<p>
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Number of retries for UDP queries:
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If <em class="parameter"><code>number</code></em> is negative or zero, the
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number of retries will default to 1. The default value is
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1, or the value of the <em class="parameter"><code>attempts</code></em>
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option in <code class="filename">/etc/resolv.conf</code>, if set.
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</p>
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</dd>
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<dt><span class="term">-s</span></dt>
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<dd>
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<p>
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Do <span class="emphasis"><em>not</em></span> send the query to the next
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nameserver if any server responds with a SERVFAIL
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response, which is the reverse of normal stub resolver
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behavior.
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</p>
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</dd>
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<dt><span class="term">-t <em class="replaceable"><code>type</code></em></span></dt>
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<dd>
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<p>
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Query type:
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The <em class="parameter"><code>type</code></em> argument can be any
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recognized query type: CNAME, NS, SOA, TXT, DNSKEY, AXFR, etc.
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</p>
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<p>
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When no query type is specified, <span class="command"><strong>host</strong></span>
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automatically selects an appropriate query type. By default, it
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looks for A, AAAA, and MX records.
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If the <code class="option">-C</code> option is given, queries will
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be made for SOA records.
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If <em class="parameter"><code>name</code></em> is a dotted-decimal IPv4
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address or colon-delimited IPv6
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address, <span class="command"><strong>host</strong></span> will query for PTR
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records.
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</p>
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<p>
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If a query type of IXFR is chosen the starting serial
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number can be specified by appending an equal followed by
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the starting serial number
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(like <code class="option">-t <code class="literal">IXFR=12345678</code></code>).
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</p>
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</dd>
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<dt>
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<span class="term">-T, </span><span class="term">-U</span>
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</dt>
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<dd>
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<p>
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TCP/UDP:
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By default, <span class="command"><strong>host</strong></span> uses UDP when making
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queries. The <code class="option">-T</code> option makes it use a TCP
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connection when querying the name server. TCP will be
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automatically selected for queries that require it, such
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as zone transfer (AXFR) requests. Type ANY queries default
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to TCP but can be forced to UDP initially using <code class="option">-U</code>.
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</p>
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</dd>
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<dt><span class="term">-m <em class="replaceable"><code>flag</code></em></span></dt>
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<dd>
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<p>
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Memory usage debugging: the flag can
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be <em class="parameter"><code>record</code></em>, <em class="parameter"><code>usage</code></em>,
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or <em class="parameter"><code>trace</code></em>. You can specify
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the <code class="option">-m</code> option more than once to set
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multiple flags.
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</p>
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</dd>
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<dt><span class="term">-v</span></dt>
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<dd>
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<p>
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Verbose output.
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Equivalent to the <code class="option">-d</code> debug option.
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Verbose output can also be enabled by setting
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the <em class="parameter"><code>debug</code></em> option
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in <code class="filename">/etc/resolv.conf</code>.
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</p>
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</dd>
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<dt><span class="term">-V</span></dt>
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<dd>
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<p>
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Print the version number and exit.
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</p>
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</dd>
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<dt><span class="term">-w</span></dt>
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<dd>
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<p>
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Wait forever: The query timeout is set to the maximum possible.
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See also the <code class="option">-W</code> option.
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</p>
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</dd>
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<dt><span class="term">-W <em class="replaceable"><code>wait</code></em></span></dt>
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<dd>
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<p>
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Timeout: Wait for up to <em class="parameter"><code>wait</code></em>
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seconds for a reply. If <em class="parameter"><code>wait</code></em> is
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less than one, the wait interval is set to one second.
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</p>
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<p>
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By default, <span class="command"><strong>host</strong></span> will wait for 5
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seconds for UDP responses and 10 seconds for TCP
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connections. These defaults can be overridden by
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the <em class="parameter"><code>timeout</code></em> option
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in <code class="filename">/etc/resolv.conf</code>.
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</p>
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<p>
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See also the <code class="option">-w</code> option.
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</p>
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</dd>
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</dl></div>
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</div>
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<div class="refsection">
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<a name="id-1.9"></a><h2>IDN SUPPORT</h2>
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<p>
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If <span class="command"><strong>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 class="command"><strong>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 class="command"><strong>host</strong></span> runs.
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</p>
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</div>
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<div class="refsection">
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<a name="id-1.10"></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="refsection">
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<a name="id-1.11"></a><h2>SEE ALSO</h2>
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<p><span class="citerefentry">
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<span class="refentrytitle">dig</span>(1)
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</span>,
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<span class="citerefentry">
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<span class="refentrytitle">named</span>(8)
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</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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