host.html revision 83217b5fdc70ea66fedf2ab3e9b9169c2b8a200a
863f2bc9983c33221f5936421fc9c06caf21639aTimo Sirainen<!--
863f2bc9983c33221f5936421fc9c06caf21639aTimo Sirainen - Copyright (C) 2004 Internet Systems Consortium, Inc. ("ISC")
3faa1040e5a3f9f35ffad29110216094ab2f5880Timo Sirainen - Copyright (C) 2000-2002 Internet Software Consortium
8d3278a82b964217d95c340ec6f82037cdc59d19Timo Sirainen -
8d3278a82b964217d95c340ec6f82037cdc59d19Timo Sirainen - Permission to use, copy, modify, and distribute this software for any
8d3278a82b964217d95c340ec6f82037cdc59d19Timo Sirainen - purpose with or without fee is hereby granted, provided that the above
e479250007aaa49c9f38aa294f5cfb024cbcec73Timo Sirainen - copyright notice and this permission notice appear in all copies.
8d3278a82b964217d95c340ec6f82037cdc59d19Timo Sirainen -
cf3894a2a22dc76247275e7ad7a5417fa5f27a28Timo Sirainen - THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
b8efab7ea8876c0a33a73ee0d08eddada31320f8Timo Sirainen - REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
96d19229e5f322411eb84446e5477d8170cfa5afTimo Sirainen - AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
863f2bc9983c33221f5936421fc9c06caf21639aTimo Sirainen - INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
7ab70e15c63c172c1715a40c8ffcff0285b6f05eTimo Sirainen - LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
8d3278a82b964217d95c340ec6f82037cdc59d19Timo Sirainen - OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
8d3278a82b964217d95c340ec6f82037cdc59d19Timo Sirainen - PERFORMANCE OF THIS SOFTWARE.
83879fb63453dc3b96269d2217339e14dca753b4Timo Sirainen-->
83942ac160cdfb922c3a2f29ddfae2a13ebf8b5dTimo Sirainen<!-- $Id: host.html,v 1.15 2005/05/12 23:54:23 sra Exp $ -->
83942ac160cdfb922c3a2f29ddfae2a13ebf8b5dTimo Sirainen<html>
d176f84ce5ca2073f4dfbafb457b9c74f6bf0d76Timo Sirainen<head>
d47a87c927ca77e780480f4eaf575511698d42c8Timo Sirainen<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
cf0ad1a0bddb0787f3d7b408a96d721a8b2a98a3Timo Sirainen<title>host</title>
cf0ad1a0bddb0787f3d7b408a96d721a8b2a98a3Timo Sirainen<meta name="generator" content="DocBook XSL Stylesheets V1.68.1">
8d3278a82b964217d95c340ec6f82037cdc59d19Timo Sirainen</head>
8761992b5aa05862e7ec3a460cdc17af41a4a0f5Timo Sirainen<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="refentry" lang="en">
8d3278a82b964217d95c340ec6f82037cdc59d19Timo Sirainen<a name="id2456693"></a><div class="titlepage"></div>
5d03d9f439e41c90215a3c938ffebe4c2a8ae257Timo Sirainen<div class="refnamediv">
3faa1040e5a3f9f35ffad29110216094ab2f5880Timo Sirainen<h2>Name</h2>
f29756821a4c6b12b73e4a2a3e1c230117a43773Timo Sirainen<p>host &#8212; DNS lookup utility</p>
b63e20ea9bc84f1aa90a551f217d01385e070b73Timo Sirainen</div>
8d3278a82b964217d95c340ec6f82037cdc59d19Timo Sirainen<div class="refsynopsisdiv">
8d3278a82b964217d95c340ec6f82037cdc59d19Timo Sirainen<h2>Synopsis</h2>
9874b30b34224c1372800be017f3bb636e7d7f7aTimo Sirainen<div class="cmdsynopsis"><p><code class="command">host</code> [<code class="option">-aCdlnrTwv</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>
83879fb63453dc3b96269d2217339e14dca753b4Timo Sirainen</div>
83942ac160cdfb922c3a2f29ddfae2a13ebf8b5dTimo Sirainen<div class="refsect1" lang="en">
83942ac160cdfb922c3a2f29ddfae2a13ebf8b5dTimo Sirainen<a name="id2514112"></a><h2>DESCRIPTION</h2>
d176f84ce5ca2073f4dfbafb457b9c74f6bf0d76Timo Sirainen<p><span><strong class="command">host</strong></span>
d47a87c927ca77e780480f4eaf575511698d42c8Timo Sirainen is a simple utility for performing DNS lookups.
d176f84ce5ca2073f4dfbafb457b9c74f6bf0d76Timo Sirainen It is normally used to convert names to IP addresses and vice versa.
cf0ad1a0bddb0787f3d7b408a96d721a8b2a98a3Timo Sirainen When no arguments or options are given,
cf0ad1a0bddb0787f3d7b408a96d721a8b2a98a3Timo Sirainen <span><strong class="command">host</strong></span>
8d3278a82b964217d95c340ec6f82037cdc59d19Timo Sirainen prints a short summary of its command line arguments and options.
8d3278a82b964217d95c340ec6f82037cdc59d19Timo Sirainen </p>
8d3278a82b964217d95c340ec6f82037cdc59d19Timo Sirainen<p><em class="parameter"><code>name</code></em> is the domain name that is to be
2710604bdf77c8db98ef3837223edc81a24a52f0Timo Sirainen looked
cf3894a2a22dc76247275e7ad7a5417fa5f27a28Timo Sirainen up. It can also be a dotted-decimal IPv4 address or a colon-delimited
f29756821a4c6b12b73e4a2a3e1c230117a43773Timo Sirainen IPv6 address, in which case <span><strong class="command">host</strong></span> will by
9f0f2de10e4ea0c99052bf4b2bef8179f2536228Timo Sirainen default
b63e20ea9bc84f1aa90a551f217d01385e070b73Timo Sirainen perform a reverse lookup for that address.
8d3278a82b964217d95c340ec6f82037cdc59d19Timo Sirainen <em class="parameter"><code>server</code></em> is an optional argument which
9874b30b34224c1372800be017f3bb636e7d7f7aTimo Sirainen is either
53f37d41e1abb068131320f39f870fc92e81f560Timo Sirainen the name or IP address of the name server that <span><strong class="command">host</strong></span>
53f37d41e1abb068131320f39f870fc92e81f560Timo Sirainen should query instead of the server or servers listed in
e479250007aaa49c9f38aa294f5cfb024cbcec73Timo Sirainen <code class="filename">/etc/resolv.conf</code>.
e479250007aaa49c9f38aa294f5cfb024cbcec73Timo Sirainen </p>
e479250007aaa49c9f38aa294f5cfb024cbcec73Timo Sirainen<p>
e479250007aaa49c9f38aa294f5cfb024cbcec73Timo Sirainen The <code class="option">-a</code> (all) option is equivalent to setting the
e479250007aaa49c9f38aa294f5cfb024cbcec73Timo Sirainen <code class="option">-v</code> option and asking <span><strong class="command">host</strong></span> to make
e479250007aaa49c9f38aa294f5cfb024cbcec73Timo Sirainen a query of type ANY.
e479250007aaa49c9f38aa294f5cfb024cbcec73Timo Sirainen </p>
e479250007aaa49c9f38aa294f5cfb024cbcec73Timo Sirainen<p>
e479250007aaa49c9f38aa294f5cfb024cbcec73Timo Sirainen When the <code class="option">-C</code> option is used, <span><strong class="command">host</strong></span>
e479250007aaa49c9f38aa294f5cfb024cbcec73Timo Sirainen will attempt to display the SOA records for zone
e479250007aaa49c9f38aa294f5cfb024cbcec73Timo Sirainen <em class="parameter"><code>name</code></em> from all the listed
e479250007aaa49c9f38aa294f5cfb024cbcec73Timo Sirainen authoritative name
e479250007aaa49c9f38aa294f5cfb024cbcec73Timo Sirainen servers for that zone. The list of name servers is defined by the NS
e479250007aaa49c9f38aa294f5cfb024cbcec73Timo Sirainen records that are found for the zone.
e479250007aaa49c9f38aa294f5cfb024cbcec73Timo Sirainen </p>
e479250007aaa49c9f38aa294f5cfb024cbcec73Timo Sirainen<p>
149299c7d5136a8fb425ef3cf8953026a1358002Timo Sirainen The <code class="option">-c</code> option instructs to make a DNS query of class
e479250007aaa49c9f38aa294f5cfb024cbcec73Timo Sirainen <em class="parameter"><code>class</code></em>. This can be used to lookup
e479250007aaa49c9f38aa294f5cfb024cbcec73Timo Sirainen Hesiod or
e479250007aaa49c9f38aa294f5cfb024cbcec73Timo Sirainen Chaosnet class resource records. The default class is IN (Internet).
</p>
<p>
Verbose output is generated by <span><strong class="command">host</strong></span> when
the
<code class="option">-d</code> or <code class="option">-v</code> option is used. The two
options are equivalent. They have been provided for backwards
compatibility. In previous versions, the <code class="option">-d</code> option
switched on debugging traces and <code class="option">-v</code> enabled verbose
output.
</p>
<p>
List mode is selected by the <code class="option">-l</code> option. This makes
<span><strong class="command">host</strong></span> perform a zone transfer for zone
<em class="parameter"><code>name</code></em>. Transfer the zone printing out
the NS, PTR
and address records (A/AAAA). If combined with <code class="option">-a</code>
all records will be printed.
</p>
<p>
The <code class="option">-i</code>
option specifies that reverse lookups of IPv6 addresses should
use the IP6.INT domain as defined in RFC1886.
The default is to use IP6.ARPA.
</p>
<p>
The <code class="option">-N</code> option sets the number of dots that have to be
in <em class="parameter"><code>name</code></em> for it to be considered
absolute. The
default value is that defined using the ndots statement in
<code class="filename">/etc/resolv.conf</code>, or 1 if no ndots
statement is
present. Names with fewer dots are interpreted as relative names and
will be searched for in the domains listed in the <span class="type">search</span>
or <span class="type">domain</span> directive in
<code class="filename">/etc/resolv.conf</code>.
</p>
<p>
The number of UDP retries for a lookup can be changed with the
<code class="option">-R</code> option. <em class="parameter"><code>number</code></em>
indicates
how many times <span><strong class="command">host</strong></span> will repeat a query
that does
not get answered. The default number of retries is 1. If
<em class="parameter"><code>number</code></em> is negative or zero, the
number of
retries will default to 1.
</p>
<p>
Non-recursive queries can be made via the <code class="option">-r</code> option.
Setting this option clears the <span class="type">RD</span> &#8212; recursion
desired &#8212; bit in the query which <span><strong class="command">host</strong></span> makes.
This should mean that the name server receiving the query will not
attempt to resolve <em class="parameter"><code>name</code></em>. The
<code class="option">-r</code> option enables <span><strong class="command">host</strong></span>
to mimic
the behaviour of a name server by making non-recursive queries and
expecting to receive answers to those queries that are usually
referrals to other name servers.
</p>
<p>
By default <span><strong class="command">host</strong></span> uses UDP when making
queries. The
<code class="option">-T</code> option makes it use a TCP connection when querying
the name server. TCP will be automatically selected for queries that
require it, such as zone transfer (AXFR) requests.
</p>
<p>
The <code class="option">-4</code> option forces <span><strong class="command">host</strong></span> to only
use IPv4 query transport. The <code class="option">-6</code> option forces
<span><strong class="command">host</strong></span> to only use IPv6 query transport.
</p>
<p>
The <code class="option">-t</code> option is used to select the query type.
<em class="parameter"><code>type</code></em> can be any recognised query
type: CNAME,
NS, SOA, SIG, KEY, AXFR, etc. When no query type is specified,
<span><strong class="command">host</strong></span> automatically selects an appropriate
query
type. By default it looks for A records, but if the
<code class="option">-C</code> option was given, queries will be made for SOA
records, and if <em class="parameter"><code>name</code></em> is a
dotted-decimal IPv4
address or colon-delimited IPv6 address, <span><strong class="command">host</strong></span> will
query for PTR records. If a query type of IXFR is chosen the starting
serial number can be specified by appending an equal followed by the
starting serial number (e.g. -t IXFR=12345678).
</p>
<p>
The time to wait for a reply can be controlled through the
<code class="option">-W</code> and <code class="option">-w</code> options. The
<code class="option">-W</code> option makes <span><strong class="command">host</strong></span>
wait for
<em class="parameter"><code>wait</code></em> seconds. If <em class="parameter"><code>wait</code></em>
is less than one, the wait interval is set to one second. When the
<code class="option">-w</code> option is used, <span><strong class="command">host</strong></span>
will
effectively wait forever for a reply. The time to wait for a response
will be set to the number of seconds given by the hardware's maximum
value for an integer quantity.
</p>
<p>
The <code class="option">-m</code> can be used to set the memory usage debugging
flags
<em class="parameter"><code>record</code></em>, <em class="parameter"><code>usage</code></em> and
<em class="parameter"><code>trace</code></em>.
</p>
</div>
<div class="refsect1" lang="en">
<a name="id2514465"></a><h2>FILES</h2>
<p><code class="filename">/etc/resolv.conf</code>
</p>
</div>
<div class="refsect1" lang="en">
<a name="id2514476"></a><h2>SEE ALSO</h2>
<p><span class="citerefentry"><span class="refentrytitle">dig</span>(1)</span>,
<span class="citerefentry"><span class="refentrytitle">named</span>(8)</span>.
</p>
</div>
</div></body>
</html>