1<!-- 2 - Copyright (C) 2004, 2005, 2007-2009, 2014 Internet Systems Consortium, Inc. ("ISC") 3 - Copyright (C) 2000-2002 Internet Software Consortium. 4 - 5 - Permission to use, copy, modify, and/or distribute this software for any 6 - purpose with or without fee is hereby granted, provided that the above 7 - copyright notice and this permission notice appear in all copies. 8 - 9 - THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH 10 - REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY 11 - AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT, 12 - INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM 13 - LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE 14 - OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR 15 - PERFORMANCE OF THIS SOFTWARE. 16--> 17<!-- Id --> 18<html> 19<head> 20<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> 21<title>host</title> 22<meta name="generator" content="DocBook XSL Stylesheets V1.71.1"> 23</head> 24<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="refentry" lang="en"> 25<a name="man.host"></a><div class="titlepage"></div> 26<div class="refnamediv"> 27<h2>Name</h2> 28<p>host — DNS lookup utility</p> 29</div> 30<div class="refsynopsisdiv"> 31<h2>Synopsis</h2> 32<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>] [<code class="option">-v</code>] [<code class="option">-V</code>] {name} [server]</p></div> 33</div> 34<div class="refsect1" lang="en"> 35<a name="id2543454"></a><h2>DESCRIPTION</h2> 36<p><span><strong class="command">host</strong></span> 37 is a simple utility for performing DNS lookups. 38 It is normally used to convert names to IP addresses and vice versa. 39 When no arguments or options are given, 40 <span><strong class="command">host</strong></span> 41 prints a short summary of its command line arguments and options. 42 </p> 43<p><em class="parameter"><code>name</code></em> is the domain name that is to be 44 looked 45 up. It can also be a dotted-decimal IPv4 address or a colon-delimited 46 IPv6 address, in which case <span><strong class="command">host</strong></span> will by 47 default 48 perform a reverse lookup for that address. 49 <em class="parameter"><code>server</code></em> is an optional argument which 50 is either 51 the name or IP address of the name server that <span><strong class="command">host</strong></span> 52 should query instead of the server or servers listed in 53 <code class="filename">/etc/resolv.conf</code>. 54 </p> 55<p> 56 The <code class="option">-a</code> (all) option is equivalent to setting the 57 <code class="option">-v</code> option and asking <span><strong class="command">host</strong></span> to make 58 a query of type ANY. 59 </p> 60<p> 61 When the <code class="option">-C</code> option is used, <span><strong class="command">host</strong></span> 62 will attempt to display the SOA records for zone 63 <em class="parameter"><code>name</code></em> from all the listed 64 authoritative name 65 servers for that zone. The list of name servers is defined by the NS 66 records that are found for the zone. 67 </p> 68<p> 69 The <code class="option">-c</code> option instructs to make a DNS query of class 70 <em class="parameter"><code>class</code></em>. This can be used to lookup 71 Hesiod or 72 Chaosnet class resource records. The default class is IN (Internet). 73 </p> 74<p> 75 Verbose output is generated by <span><strong class="command">host</strong></span> when 76 the 77 <code class="option">-d</code> or <code class="option">-v</code> option is used. The two 78 options are equivalent. They have been provided for backwards 79 compatibility. In previous versions, the <code class="option">-d</code> option 80 switched on debugging traces and <code class="option">-v</code> enabled verbose 81 output. 82 </p> 83<p> 84 List mode is selected by the <code class="option">-l</code> option. This makes 85 <span><strong class="command">host</strong></span> perform a zone transfer for zone 86 <em class="parameter"><code>name</code></em>. Transfer the zone printing out 87 the NS, PTR 88 and address records (A/AAAA). If combined with <code class="option">-a</code> 89 all records will be printed. 90 </p> 91<p> 92 The <code class="option">-i</code> 93 option specifies that reverse lookups of IPv6 addresses should 94 use the IP6.INT domain as defined in RFC1886. 95 The default is to use IP6.ARPA. 96 </p> 97<p> 98 The <code class="option">-N</code> option sets the number of dots that have to be 99 in <em class="parameter"><code>name</code></em> for it to be considered 100 absolute. The 101 default value is that defined using the ndots statement in 102 <code class="filename">/etc/resolv.conf</code>, or 1 if no ndots 103 statement is 104 present. Names with fewer dots are interpreted as relative names and 105 will be searched for in the domains listed in the <span class="type">search</span> 106 or <span class="type">domain</span> directive in 107 <code class="filename">/etc/resolv.conf</code>. 108 </p> 109<p> 110 The number of UDP retries for a lookup can be changed with the 111 <code class="option">-R</code> option. <em class="parameter"><code>number</code></em> 112 indicates 113 how many times <span><strong class="command">host</strong></span> will repeat a query 114 that does 115 not get answered. The default number of retries is 1. If 116 <em class="parameter"><code>number</code></em> is negative or zero, the 117 number of 118 retries will default to 1. 119 </p> 120<p> 121 Non-recursive queries can be made via the <code class="option">-r</code> option. 122 Setting this option clears the <span class="type">RD</span> — recursion 123 desired — bit in the query which <span><strong class="command">host</strong></span> makes. 124 This should mean that the name server receiving the query will not 125 attempt to resolve <em class="parameter"><code>name</code></em>. The 126 <code class="option">-r</code> option enables <span><strong class="command">host</strong></span> 127 to mimic 128 the behavior of a name server by making non-recursive queries and 129 expecting to receive answers to those queries that are usually 130 referrals to other name servers. 131 </p> 132<p> 133 By default, <span><strong class="command">host</strong></span> uses UDP when making 134 queries. The 135 <code class="option">-T</code> option makes it use a TCP connection when querying 136 the name server. TCP will be automatically selected for queries that 137 require it, such as zone transfer (AXFR) requests. 138 </p> 139<p> 140 The <code class="option">-4</code> option forces <span><strong class="command">host</strong></span> to only 141 use IPv4 query transport. The <code class="option">-6</code> option forces 142 <span><strong class="command">host</strong></span> to only use IPv6 query transport. 143 </p> 144<p> 145 The <code class="option">-t</code> option is used to select the query type. 146 <em class="parameter"><code>type</code></em> can be any recognized query 147 type: CNAME, 148 NS, SOA, SIG, KEY, AXFR, etc. When no query type is specified, 149 <span><strong class="command">host</strong></span> automatically selects an appropriate 150 query 151 type. By default, it looks for A, AAAA, and MX records, but if the 152 <code class="option">-C</code> option was given, queries will be made for SOA 153 records, and if <em class="parameter"><code>name</code></em> is a 154 dotted-decimal IPv4 155 address or colon-delimited IPv6 address, <span><strong class="command">host</strong></span> will 156 query for PTR records. If a query type of IXFR is chosen the starting 157 serial number can be specified by appending an equal followed by the 158 starting serial number (e.g. -t IXFR=12345678). 159 </p> 160<p> 161 The time to wait for a reply can be controlled through the 162 <code class="option">-W</code> and <code class="option">-w</code> options. The 163 <code class="option">-W</code> option makes <span><strong class="command">host</strong></span> 164 wait for 165 <em class="parameter"><code>wait</code></em> seconds. If <em class="parameter"><code>wait</code></em> 166 is less than one, the wait interval is set to one second. When the 167 <code class="option">-w</code> option is used, <span><strong class="command">host</strong></span> 168 will 169 effectively wait forever for a reply. The time to wait for a response 170 will be set to the number of seconds given by the hardware's maximum 171 value for an integer quantity. 172 </p> 173<p> 174 The <code class="option">-s</code> option tells <span><strong class="command">host</strong></span> 175 <span class="emphasis"><em>not</em></span> to send the query to the next nameserver 176 if any server responds with a SERVFAIL response, which is the 177 reverse of normal stub resolver behavior. 178 </p> 179<p> 180 The <code class="option">-m</code> can be used to set the memory usage debugging 181 flags 182 <em class="parameter"><code>record</code></em>, <em class="parameter"><code>usage</code></em> and 183 <em class="parameter"><code>trace</code></em>. 184 </p> 185<p> 186 The <code class="option">-V</code> option causes <span><strong class="command">host</strong></span> 187 to print the version number and exit. 188 </p> 189</div> 190<div class="refsect1" lang="en"> 191<a name="id2543831"></a><h2>IDN SUPPORT</h2> 192<p> 193 If <span><strong class="command">host</strong></span> has been built with IDN (internationalized 194 domain name) support, it can accept and display non-ASCII domain names. 195 <span><strong class="command">host</strong></span> appropriately converts character encoding of 196 domain name before sending a request to DNS server or displaying a 197 reply from the server. 198 If you'd like to turn off the IDN support for some reason, defines 199 the <code class="envar">IDN_DISABLE</code> environment variable. 200 The IDN support is disabled if the variable is set when 201 <span><strong class="command">host</strong></span> runs. 202 </p> 203</div> 204<div class="refsect1" lang="en"> 205<a name="id2543853"></a><h2>FILES</h2> 206<p><code class="filename">/etc/resolv.conf</code> 207 </p> 208</div> 209<div class="refsect1" lang="en"> 210<a name="id2543865"></a><h2>SEE ALSO</h2> 211<p><span class="citerefentry"><span class="refentrytitle">dig</span>(1)</span>, 212 <span class="citerefentry"><span class="refentrytitle">named</span>(8)</span>. 213 </p> 214</div> 215</div></body> 216</html> 217