1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
|
<!--
- Copyright (C) 2004, 2005, 2007, 2008 Internet Systems Consortium, Inc. ("ISC")
- Copyright (C) 2000-2002 Internet Software Consortium.
-
- Permission to use, copy, modify, and distribute this software for any
- purpose with or without fee is hereby granted, provided that the above
- copyright notice and this permission notice appear in all copies.
-
- THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
- REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
- AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
- INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
- LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
- OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
- PERFORMANCE OF THIS SOFTWARE.
-->
<!-- $Id: host.html,v 1.28 2008/04/05 01:09:34 tbox Exp $ -->
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>host</title>
<meta name="generator" content="DocBook XSL Stylesheets V1.71.1">
</head>
<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="refentry" lang="en">
<a name="man.host"></a><div class="titlepage"></div>
<div class="refnamediv">
<h2>Name</h2>
<p>host — DNS lookup utility</p>
</div>
<div class="refsynopsisdiv">
<h2>Synopsis</h2>
<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>
</div>
<div class="refsect1" lang="en">
<a name="id2543431"></a><h2>DESCRIPTION</h2>
<p><span><strong class="command">host</strong></span>
is a simple utility for performing DNS lookups.
It is normally used to convert names to IP addresses and vice versa.
When no arguments or options are given,
<span><strong class="command">host</strong></span>
prints a short summary of its command line arguments and options.
</p>
<p><em class="parameter"><code>name</code></em> is the domain name that is to be
looked
up. It can also be a dotted-decimal IPv4 address or a colon-delimited
IPv6 address, in which case <span><strong class="command">host</strong></span> will by
default
perform a reverse lookup for that address.
<em class="parameter"><code>server</code></em> is an optional argument which
is either
the name or IP address of the name server that <span><strong class="command">host</strong></span>
should query instead of the server or servers listed in
<code class="filename">/etc/resolv.conf</code>.
</p>
<p>
The <code class="option">-a</code> (all) option is equivalent to setting the
<code class="option">-v</code> option and asking <span><strong class="command">host</strong></span> to make
a query of type ANY.
</p>
<p>
When the <code class="option">-C</code> option is used, <span><strong class="command">host</strong></span>
will attempt to display the SOA records for zone
<em class="parameter"><code>name</code></em> from all the listed
authoritative name
servers for that zone. The list of name servers is defined by the NS
records that are found for the zone.
</p>
<p>
The <code class="option">-c</code> option instructs to make a DNS query of class
<em class="parameter"><code>class</code></em>. This can be used to lookup
Hesiod or
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> — recursion
desired — 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 behavior 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 recognized 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, AAAA, and MX 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">-s</code> option tells <span><strong class="command">host</strong></span>
<span class="emphasis"><em>not</em></span> to send the query to the next nameserver
if any server responds with a SERVFAIL response, which is the
reverse of normal stub resolver behavior.
</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="id2543797"></a><h2>IDN SUPPORT</h2>
<p>
If <span><strong class="command">host</strong></span> has been built with IDN (internationalized
domain name) support, it can accept and display non-ASCII domain names.
<span><strong class="command">host</strong></span> appropriately converts character encoding of
domain name before sending a request to DNS server or displaying a
reply from the server.
If you'd like to turn off the IDN support for some reason, defines
the <code class="envar">IDN_DISABLE</code> environment variable.
The IDN support is disabled if the variable is set when
<span><strong class="command">host</strong></span> runs.
</p>
</div>
<div class="refsect1" lang="en">
<a name="id2543819"></a><h2>FILES</h2>
<p><code class="filename">/etc/resolv.conf</code>
</p>
</div>
<div class="refsect1" lang="en">
<a name="id2543831"></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>
|
