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60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein - Copyright (C) 2004-2009 Internet Systems Consortium, Inc. ("ISC")
32098293b78922a5fbd10906afa28624820d3756Tinderbox User - Copyright (C) 2000-2003 Internet Software Consortium.
5347c0fcb04eaea19d9f39795646239f487c6207Tinderbox User - Permission to use, copy, modify, and distribute this software for any
5347c0fcb04eaea19d9f39795646239f487c6207Tinderbox User - purpose with or without fee is hereby granted, provided that the above
5347c0fcb04eaea19d9f39795646239f487c6207Tinderbox User - copyright notice and this permission notice appear in all copies.
d6fa26d0adaec6c910115be34fe7a5a5f402c14fMark Andrews - THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein - REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein - AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
cd32f419a8a5432fbb139f56ee73cbf68b9350ccTinderbox User - INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User - LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt - OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein - PERFORMANCE OF THIS SOFTWARE.
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33c9436ef1a43d3c0fc3d9be9b4b0509daa83223Tinderbox User<a name="man.host"></a><div class="titlepage"></div>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt<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>
f9ce6280cec79deb16ff6d9807aa493ff23e10d9Tinderbox User<p><span><strong class="command">host</strong></span>
164ade1482251e1da962b42e5bf0d3aa02a11e03Tinderbox User is a simple utility for performing DNS lookups.
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User It is normally used to convert names to IP addresses and vice versa.
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User When no arguments or options are given,
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt <span><strong class="command">host</strong></span>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt prints a short summary of its command line arguments and options.
0da02c26a6631c25f075a8e4ac6de9e58f49a0c2Tinderbox User<p><em class="parameter"><code>name</code></em> is the domain name that is to be
0da02c26a6631c25f075a8e4ac6de9e58f49a0c2Tinderbox User up. It can also be a dotted-decimal IPv4 address or a colon-delimited
0da02c26a6631c25f075a8e4ac6de9e58f49a0c2Tinderbox User IPv6 address, in which case <span><strong class="command">host</strong></span> will by
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User perform a reverse lookup for that address.
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User <em class="parameter"><code>server</code></em> is an optional argument which
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt the name or IP address of the name server that <span><strong class="command">host</strong></span>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt should query instead of the server or servers listed in
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User <code class="filename">/etc/resolv.conf</code>.
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt The <code class="option">-a</code> (all) option is equivalent to setting the
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt <code class="option">-v</code> option and asking <span><strong class="command">host</strong></span> to make
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt a query of type ANY.
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User When the <code class="option">-C</code> option is used, <span><strong class="command">host</strong></span>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User will attempt to display the SOA records for zone
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt <em class="parameter"><code>name</code></em> from all the listed
33c9436ef1a43d3c0fc3d9be9b4b0509daa83223Tinderbox User authoritative name
33c9436ef1a43d3c0fc3d9be9b4b0509daa83223Tinderbox User servers for that zone. The list of name servers is defined by the NS
33c9436ef1a43d3c0fc3d9be9b4b0509daa83223Tinderbox User records that are found for the zone.
33c9436ef1a43d3c0fc3d9be9b4b0509daa83223Tinderbox User The <code class="option">-c</code> option instructs to make a DNS query of class
33c9436ef1a43d3c0fc3d9be9b4b0509daa83223Tinderbox User <em class="parameter"><code>class</code></em>. This can be used to lookup
33c9436ef1a43d3c0fc3d9be9b4b0509daa83223Tinderbox User Chaosnet class resource records. The default class is IN (Internet).
33c9436ef1a43d3c0fc3d9be9b4b0509daa83223Tinderbox User Verbose output is generated by <span><strong class="command">host</strong></span> when
33c9436ef1a43d3c0fc3d9be9b4b0509daa83223Tinderbox User <code class="option">-d</code> or <code class="option">-v</code> option is used. The two
33c9436ef1a43d3c0fc3d9be9b4b0509daa83223Tinderbox User options are equivalent. They have been provided for backwards
33c9436ef1a43d3c0fc3d9be9b4b0509daa83223Tinderbox User compatibility. In previous versions, the <code class="option">-d</code> option
33c9436ef1a43d3c0fc3d9be9b4b0509daa83223Tinderbox User switched on debugging traces and <code class="option">-v</code> enabled verbose
33c9436ef1a43d3c0fc3d9be9b4b0509daa83223Tinderbox User List mode is selected by the <code class="option">-l</code> option. This makes
33c9436ef1a43d3c0fc3d9be9b4b0509daa83223Tinderbox User <span><strong class="command">host</strong></span> perform a zone transfer for zone
33c9436ef1a43d3c0fc3d9be9b4b0509daa83223Tinderbox User <em class="parameter"><code>name</code></em>. Transfer the zone printing out
33c9436ef1a43d3c0fc3d9be9b4b0509daa83223Tinderbox User and address records (A/AAAA). If combined with <code class="option">-a</code>
33c9436ef1a43d3c0fc3d9be9b4b0509daa83223Tinderbox User all records will be printed.
33c9436ef1a43d3c0fc3d9be9b4b0509daa83223Tinderbox User option specifies that reverse lookups of IPv6 addresses should
a1ff871f78b7d907d6fc3a382beea2a640fe8423Tinderbox User use the IP6.INT domain as defined in RFC1886.
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User The default is to use IP6.ARPA.
0da02c26a6631c25f075a8e4ac6de9e58f49a0c2Tinderbox User The <code class="option">-N</code> option sets the number of dots that have to be
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox User in <em class="parameter"><code>name</code></em> for it to be considered
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User absolute. The
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox User default value is that defined using the ndots statement in
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox User <code class="filename">/etc/resolv.conf</code>, or 1 if no ndots
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox User present. Names with fewer dots are interpreted as relative names and
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox User will be searched for in the domains listed in the <span class="type">search</span>
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox User or <span class="type">domain</span> directive in
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User <code class="filename">/etc/resolv.conf</code>.
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox User The number of UDP retries for a lookup can be changed with the
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox User <code class="option">-R</code> option. <em class="parameter"><code>number</code></em>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User how many times <span><strong class="command">host</strong></span> will repeat a query
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox User not get answered. The default number of retries is 1. If
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox User <em class="parameter"><code>number</code></em> is negative or zero, the
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox User retries will default to 1.
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User Non-recursive queries can be made via the <code class="option">-r</code> option.
a1ff871f78b7d907d6fc3a382beea2a640fe8423Tinderbox User Setting this option clears the <span class="type">RD</span> — recursion
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt desired — bit in the query which <span><strong class="command">host</strong></span> makes.
164ade1482251e1da962b42e5bf0d3aa02a11e03Tinderbox User This should mean that the name server receiving the query will not
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User attempt to resolve <em class="parameter"><code>name</code></em>. The
164ade1482251e1da962b42e5bf0d3aa02a11e03Tinderbox User <code class="option">-r</code> option enables <span><strong class="command">host</strong></span>
164ade1482251e1da962b42e5bf0d3aa02a11e03Tinderbox User the behavior of a name server by making non-recursive queries and
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User expecting to receive answers to those queries that are usually
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User referrals to other name servers.
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt By default, <span><strong class="command">host</strong></span> uses UDP when making
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User <code class="option">-T</code> option makes it use a TCP connection when querying
164ade1482251e1da962b42e5bf0d3aa02a11e03Tinderbox User the name server. TCP will be automatically selected for queries that
164ade1482251e1da962b42e5bf0d3aa02a11e03Tinderbox User require it, such as zone transfer (AXFR) requests.
164ade1482251e1da962b42e5bf0d3aa02a11e03Tinderbox User The <code class="option">-4</code> option forces <span><strong class="command">host</strong></span> to only
164ade1482251e1da962b42e5bf0d3aa02a11e03Tinderbox User use IPv4 query transport. The <code class="option">-6</code> option forces
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User <span><strong class="command">host</strong></span> to only use IPv6 query transport.
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User The <code class="option">-t</code> option is used to select the query type.
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User <em class="parameter"><code>type</code></em> can be any recognized query
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt type: CNAME,
164ade1482251e1da962b42e5bf0d3aa02a11e03Tinderbox User NS, SOA, SIG, KEY, AXFR, etc. When no query type is specified,
ffe29868b4bbc64953fc5d0de51f988c20158967Tinderbox User <span><strong class="command">host</strong></span> automatically selects an appropriate
3b15473cedf41d48904f5b07bdc5e87afff6b58cTinderbox User type. By default, it looks for A, AAAA, and MX records, but if the
3b15473cedf41d48904f5b07bdc5e87afff6b58cTinderbox User <code class="option">-C</code> option was given, queries will be made for SOA
3b15473cedf41d48904f5b07bdc5e87afff6b58cTinderbox User records, and if <em class="parameter"><code>name</code></em> is a
3b15473cedf41d48904f5b07bdc5e87afff6b58cTinderbox User dotted-decimal IPv4
3b15473cedf41d48904f5b07bdc5e87afff6b58cTinderbox User address or colon-delimited IPv6 address, <span><strong class="command">host</strong></span> will
3b15473cedf41d48904f5b07bdc5e87afff6b58cTinderbox User query for PTR records. If a query type of IXFR is chosen the starting
ffe29868b4bbc64953fc5d0de51f988c20158967Tinderbox User serial number can be specified by appending an equal followed by the
ffe29868b4bbc64953fc5d0de51f988c20158967Tinderbox User starting serial number (e.g. -t IXFR=12345678).
ffe29868b4bbc64953fc5d0de51f988c20158967Tinderbox User The time to wait for a reply can be controlled through the
ffe29868b4bbc64953fc5d0de51f988c20158967Tinderbox User <code class="option">-W</code> and <code class="option">-w</code> options. The
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt <code class="option">-W</code> option makes <span><strong class="command">host</strong></span>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt <em class="parameter"><code>wait</code></em> seconds. If <em class="parameter"><code>wait</code></em>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt is less than one, the wait interval is set to one second. When the
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User <code class="option">-w</code> option is used, <span><strong class="command">host</strong></span>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User effectively wait forever for a reply. The time to wait for a response
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User will be set to the number of seconds given by the hardware's maximum
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt value for an integer quantity.
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User The <code class="option">-s</code> option tells <span><strong class="command">host</strong></span>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt <span class="emphasis"><em>not</em></span> to send the query to the next nameserver
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt if any server responds with a SERVFAIL response, which is the
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt reverse of normal stub resolver behavior.
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User The <code class="option">-m</code> can be used to set the memory usage debugging
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User <em class="parameter"><code>record</code></em>, <em class="parameter"><code>usage</code></em> and
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein If <span><strong class="command">host</strong></span> has been built with IDN (internationalized
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrews domain name) support, it can accept and display non-ASCII domain names.
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrews <span><strong class="command">host</strong></span> appropriately converts character encoding of
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein domain name before sending a request to DNS server or displaying a
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein reply from the server.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein If you'd like to turn off the IDN support for some reason, defines
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein the <code class="envar">IDN_DISABLE</code> environment variable.
cd32f419a8a5432fbb139f56ee73cbf68b9350ccTinderbox User The IDN support is disabled if the variable is set when
cd32f419a8a5432fbb139f56ee73cbf68b9350ccTinderbox User <span><strong class="command">host</strong></span> runs.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<p><code class="filename">/etc/resolv.conf</code>