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42 <div class="refentry" lang="en">
43 <a name="man.host"></a><div class="titlepage"></div>
44 <div class="refnamediv">
46 <p>host — DNS lookup utility</p>
48 <div class="refsynopsisdiv">
50 <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>
52 <div class="refsect1" lang="en">
53 <a name="id2597000"></a><h2>DESCRIPTION</h2>
54 <p><span><strong class="command">host</strong></span>
55 is a simple utility for performing DNS lookups.
56 It is normally used to convert names to IP addresses and vice versa.
57 When no arguments or options are given,
58 <span><strong class="command">host</strong></span>
59 prints a short summary of its command line arguments and options.
61 <p><em class="parameter"><code>name</code></em> is the domain name that is to be
63 up. It can also be a dotted-decimal IPv4 address or a colon-delimited
64 IPv6 address, in which case <span><strong class="command">host</strong></span> will by
66 perform a reverse lookup for that address.
67 <em class="parameter"><code>server</code></em> is an optional argument which
69 the name or IP address of the name server that <span><strong class="command">host</strong></span>
70 should query instead of the server or servers listed in
71 <code class="filename">/etc/resolv.conf</code>.
74 The <code class="option">-a</code> (all) option is equivalent to setting the
75 <code class="option">-v</code> option and asking <span><strong class="command">host</strong></span> to make
79 When the <code class="option">-C</code> option is used, <span><strong class="command">host</strong></span>
80 will attempt to display the SOA records for zone
81 <em class="parameter"><code>name</code></em> from all the listed
83 servers for that zone. The list of name servers is defined by the NS
84 records that are found for the zone.
87 The <code class="option">-c</code> option instructs to make a DNS query of class
88 <em class="parameter"><code>class</code></em>. This can be used to lookup
90 Chaosnet class resource records. The default class is IN (Internet).
93 Verbose output is generated by <span><strong class="command">host</strong></span> when
95 <code class="option">-d</code> or <code class="option">-v</code> option is used. The two
96 options are equivalent. They have been provided for backwards
97 compatibility. In previous versions, the <code class="option">-d</code> option
98 switched on debugging traces and <code class="option">-v</code> enabled verbose
102 List mode is selected by the <code class="option">-l</code> option. This makes
103 <span><strong class="command">host</strong></span> perform a zone transfer for zone
104 <em class="parameter"><code>name</code></em>. Transfer the zone printing out
106 and address records (A/AAAA). If combined with <code class="option">-a</code>
107 all records will be printed.
110 The <code class="option">-i</code>
111 option specifies that reverse lookups of IPv6 addresses should
112 use the IP6.INT domain as defined in RFC1886.
113 The default is to use IP6.ARPA.
116 The <code class="option">-N</code> option sets the number of dots that have to be
117 in <em class="parameter"><code>name</code></em> for it to be considered
119 default value is that defined using the ndots statement in
120 <code class="filename">/etc/resolv.conf</code>, or 1 if no ndots
122 present. Names with fewer dots are interpreted as relative names and
123 will be searched for in the domains listed in the <span class="type">search</span>
124 or <span class="type">domain</span> directive in
125 <code class="filename">/etc/resolv.conf</code>.
128 The number of UDP retries for a lookup can be changed with the
129 <code class="option">-R</code> option. <em class="parameter"><code>number</code></em>
131 how many times <span><strong class="command">host</strong></span> will repeat a query
133 not get answered. The default number of retries is 1. If
134 <em class="parameter"><code>number</code></em> is negative or zero, the
136 retries will default to 1.
139 Non-recursive queries can be made via the <code class="option">-r</code> option.
140 Setting this option clears the <span class="type">RD</span> — recursion
141 desired — bit in the query which <span><strong class="command">host</strong></span> makes.
142 This should mean that the name server receiving the query will not
143 attempt to resolve <em class="parameter"><code>name</code></em>. The
144 <code class="option">-r</code> option enables <span><strong class="command">host</strong></span>
146 the behavior of a name server by making non-recursive queries and
147 expecting to receive answers to those queries that are usually
148 referrals to other name servers.
151 By default <span><strong class="command">host</strong></span> uses UDP when making
153 <code class="option">-T</code> option makes it use a TCP connection when querying
154 the name server. TCP will be automatically selected for queries that
155 require it, such as zone transfer (AXFR) requests.
158 The <code class="option">-4</code> option forces <span><strong class="command">host</strong></span> to only
159 use IPv4 query transport. The <code class="option">-6</code> option forces
160 <span><strong class="command">host</strong></span> to only use IPv6 query transport.
163 The <code class="option">-t</code> option is used to select the query type.
164 <em class="parameter"><code>type</code></em> can be any recognized query
166 NS, SOA, SIG, KEY, AXFR, etc. When no query type is specified,
167 <span><strong class="command">host</strong></span> automatically selects an appropriate
169 type. By default it looks for A records, but if the
170 <code class="option">-C</code> option was given, queries will be made for SOA
171 records, and if <em class="parameter"><code>name</code></em> is a
173 address or colon-delimited IPv6 address, <span><strong class="command">host</strong></span> will
174 query for PTR records. If a query type of IXFR is chosen the starting
175 serial number can be specified by appending an equal followed by the
176 starting serial number (e.g. -t IXFR=12345678).
179 The time to wait for a reply can be controlled through the
180 <code class="option">-W</code> and <code class="option">-w</code> options. The
181 <code class="option">-W</code> option makes <span><strong class="command">host</strong></span>
183 <em class="parameter"><code>wait</code></em> seconds. If <em class="parameter"><code>wait</code></em>
184 is less than one, the wait interval is set to one second. When the
185 <code class="option">-w</code> option is used, <span><strong class="command">host</strong></span>
187 effectively wait forever for a reply. The time to wait for a response
188 will be set to the number of seconds given by the hardware's maximum
189 value for an integer quantity.
192 The <code class="option">-s</code> option tells <span><strong class="command">host</strong></span>
193 <span class="emphasis"><em>not</em></span> to send the query to the next nameserver
194 if any server responds with a SERVFAIL response, which is the
195 reverse of normal stub resolver behavior.
198 The <code class="option">-m</code> can be used to set the memory usage debugging
200 <em class="parameter"><code>record</code></em>, <em class="parameter"><code>usage</code></em> and
201 <em class="parameter"><code>trace</code></em>.
204 <div class="refsect1" lang="en">
205 <a name="id2597514"></a><h2>IDN SUPPORT</h2>
207 If <span><strong class="command">host</strong></span> has been built with IDN (internationalized
208 domain name) support, it can accept and display non-ASCII domain names.
209 <span><strong class="command">host</strong></span> appropriately converts character encoding of
210 domain name before sending a request to DNS server or displaying a
211 reply from the server.
212 If you'd like to turn off the IDN support for some reason, defines
213 the <code class="envar">IDN_DISABLE</code> environment variable.
214 The IDN support is disabled if the variable is set when
215 <span><strong class="command">host</strong></span> runs.
218 <div class="refsect1" lang="en">
219 <a name="id2597543"></a><h2>FILES</h2>
220 <p><code class="filename">/etc/resolv.conf</code>
223 <div class="refsect1" lang="en">
224 <a name="id2597557"></a><h2>SEE ALSO</h2>
225 <p><span class="citerefentry"><span class="refentrytitle">dig</span>(1)</span>,
226 <span class="citerefentry"><span class="refentrytitle">named</span>(8)</span>.
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