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11e9368a226272085c337e9e74b79808c16fbdbaTinderbox User - Copyright (C) 2004-2013 Internet Systems Consortium, Inc. ("ISC")
75c0816e8295e180f4bc7f10db3d0d880383bc1cMark Andrews - Copyright (C) 2000-2003 Internet Software Consortium.
4a14ce5ba00ab7bc55c99ffdcf59c7a4ab902721Automatic Updater - Permission to use, copy, modify, and/or distribute this software for any
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein - purpose with or without fee is hereby granted, provided that the above
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein - copyright notice and this permission notice appear in all copies.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein - 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,
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein - INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein - LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
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60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<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>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<p><span><strong class="command">host</strong></span>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein is a simple utility for performing DNS lookups.
11e9368a226272085c337e9e74b79808c16fbdbaTinderbox User It is normally used to convert names to IP addresses and vice versa.
11e9368a226272085c337e9e74b79808c16fbdbaTinderbox User When no arguments or options are given,
11e9368a226272085c337e9e74b79808c16fbdbaTinderbox User <span><strong class="command">host</strong></span>
11e9368a226272085c337e9e74b79808c16fbdbaTinderbox User prints a short summary of its command line arguments and options.
11e9368a226272085c337e9e74b79808c16fbdbaTinderbox User<p><em class="parameter"><code>name</code></em> is the domain name that is to be
11e9368a226272085c337e9e74b79808c16fbdbaTinderbox User up. It can also be a dotted-decimal IPv4 address or a colon-delimited
11e9368a226272085c337e9e74b79808c16fbdbaTinderbox User IPv6 address, in which case <span><strong class="command">host</strong></span> will by
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein perform a reverse lookup for that address.
11e9368a226272085c337e9e74b79808c16fbdbaTinderbox User <em class="parameter"><code>server</code></em> is an optional argument which
11e9368a226272085c337e9e74b79808c16fbdbaTinderbox User the name or IP address of the name server that <span><strong class="command">host</strong></span>
44d0f0256fbdce130a18655023c3b06bacacbd61Automatic Updater should query instead of the server or servers listed in
6f64d4ab8e68f9b2333bcbfc755396d29a4a9d7cAutomatic Updater <code class="filename">/etc/resolv.conf</code>.
ef8014e56f35bb36daa5fd2c313f5e7963e97aa1Tinderbox User The <code class="option">-a</code> (all) option is equivalent to setting the
ef8014e56f35bb36daa5fd2c313f5e7963e97aa1Tinderbox User <code class="option">-v</code> option and asking <span><strong class="command">host</strong></span> to make
ef8014e56f35bb36daa5fd2c313f5e7963e97aa1Tinderbox User a query of type ANY.
ef8014e56f35bb36daa5fd2c313f5e7963e97aa1Tinderbox User When the <code class="option">-C</code> option is used, <span><strong class="command">host</strong></span>
ef8014e56f35bb36daa5fd2c313f5e7963e97aa1Tinderbox User will attempt to display the SOA records for zone
ef8014e56f35bb36daa5fd2c313f5e7963e97aa1Tinderbox User <em class="parameter"><code>name</code></em> from all the listed
ef8014e56f35bb36daa5fd2c313f5e7963e97aa1Tinderbox User authoritative name
ef8014e56f35bb36daa5fd2c313f5e7963e97aa1Tinderbox User servers for that zone. The list of name servers is defined by the NS
ef8014e56f35bb36daa5fd2c313f5e7963e97aa1Tinderbox User records that are found for the zone.
44d0f0256fbdce130a18655023c3b06bacacbd61Automatic Updater The <code class="option">-c</code> option instructs to make a DNS query of class
44d0f0256fbdce130a18655023c3b06bacacbd61Automatic Updater <em class="parameter"><code>class</code></em>. This can be used to lookup
ef8014e56f35bb36daa5fd2c313f5e7963e97aa1Tinderbox User Chaosnet class resource records. The default class is IN (Internet).
bbbf2e27d3a981163dab139497d6b2dc85449db0Tinderbox User Verbose output is generated by <span><strong class="command">host</strong></span> when
ef8014e56f35bb36daa5fd2c313f5e7963e97aa1Tinderbox User <code class="option">-d</code> or <code class="option">-v</code> option is used. The two
ef8014e56f35bb36daa5fd2c313f5e7963e97aa1Tinderbox User options are equivalent. They have been provided for backwards
ef8014e56f35bb36daa5fd2c313f5e7963e97aa1Tinderbox User compatibility. In previous versions, the <code class="option">-d</code> option
ef8014e56f35bb36daa5fd2c313f5e7963e97aa1Tinderbox User switched on debugging traces and <code class="option">-v</code> enabled verbose
bcf15a19ae0efa72a22cdfb50666a3c6ce39eb9fTinderbox User List mode is selected by the <code class="option">-l</code> option. This makes
44d0f0256fbdce130a18655023c3b06bacacbd61Automatic Updater <span><strong class="command">host</strong></span> perform a zone transfer for zone
ef8014e56f35bb36daa5fd2c313f5e7963e97aa1Tinderbox User <em class="parameter"><code>name</code></em>. Transfer the zone printing out
bcf15a19ae0efa72a22cdfb50666a3c6ce39eb9fTinderbox User and address records (A/AAAA). If combined with <code class="option">-a</code>
11e9368a226272085c337e9e74b79808c16fbdbaTinderbox User all records will be printed.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein option specifies that reverse lookups of IPv6 addresses should
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein use the IP6.INT domain as defined in RFC1886.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein The default is to use IP6.ARPA.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein The <code class="option">-N</code> option sets the number of dots that have to be
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein in <em class="parameter"><code>name</code></em> for it to be considered
71c66a876ecca77923638d3f94cc0783152b2f03Mark Andrews absolute. The
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein default value is that defined using the ndots statement in
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrews <code class="filename">/etc/resolv.conf</code>, or 1 if no ndots
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein statement is
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein present. Names with fewer dots are interpreted as relative names and
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein will be searched for in the domains listed in the <span class="type">search</span>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein or <span class="type">domain</span> directive in
71c66a876ecca77923638d3f94cc0783152b2f03Mark Andrews <code class="filename">/etc/resolv.conf</code>.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein The number of UDP retries for a lookup can be changed with the
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <code class="option">-R</code> option. <em class="parameter"><code>number</code></em>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein how many times <span><strong class="command">host</strong></span> will repeat a query
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrews not get answered. The default number of retries is 1. If
58d9e9169e7ab4355a0b0bfc13bc616bc5247dfeAutomatic Updater <em class="parameter"><code>number</code></em> is negative or zero, the
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrews retries will default to 1.
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrews Non-recursive queries can be made via the <code class="option">-r</code> option.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein Setting this option clears the <span class="type">RD</span> — recursion
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein desired — bit in the query which <span><strong class="command">host</strong></span> makes.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein This should mean that the name server receiving the query will not
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein attempt to resolve <em class="parameter"><code>name</code></em>. The
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <code class="option">-r</code> option enables <span><strong class="command">host</strong></span>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein the behavior of a name server by making non-recursive queries and
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein expecting to receive answers to those queries that are usually
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein referrals to other name servers.
acb72d5e2c83b597332e3eb0c7d59e1142f1adfdMark Andrews By default, <span><strong class="command">host</strong></span> uses UDP when making
3cddb2c552ee6582e8db0849c28747f6b6ca57feAutomatic Updater <code class="option">-T</code> option makes it use a TCP connection when querying
852ccdd42a71550c974111b49415204ffeca6573Automatic Updater the name server. TCP will be automatically selected for queries that
852ccdd42a71550c974111b49415204ffeca6573Automatic Updater require it, such as zone transfer (AXFR) requests.
3cddb2c552ee6582e8db0849c28747f6b6ca57feAutomatic Updater The <code class="option">-4</code> option forces <span><strong class="command">host</strong></span> to only
ca67ebfe9eef0b8f04179f7e511a19e0337a5422Automatic Updater use IPv4 query transport. The <code class="option">-6</code> option forces
3cddb2c552ee6582e8db0849c28747f6b6ca57feAutomatic Updater <span><strong class="command">host</strong></span> to only use IPv6 query transport.
66f25f2ceeb589e67efe7af2413baaa3426b0042Automatic Updater The <code class="option">-t</code> option is used to select the query type.
66f25f2ceeb589e67efe7af2413baaa3426b0042Automatic Updater <em class="parameter"><code>type</code></em> can be any recognized query
66f25f2ceeb589e67efe7af2413baaa3426b0042Automatic Updater NS, SOA, SIG, KEY, AXFR, etc. When no query type is specified,
66f25f2ceeb589e67efe7af2413baaa3426b0042Automatic Updater <span><strong class="command">host</strong></span> automatically selects an appropriate
66f25f2ceeb589e67efe7af2413baaa3426b0042Automatic Updater type. By default, it looks for A, AAAA, and MX records, but if the
66f25f2ceeb589e67efe7af2413baaa3426b0042Automatic Updater <code class="option">-C</code> option was given, queries will be made for SOA
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein records, and if <em class="parameter"><code>name</code></em> is a
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein dotted-decimal IPv4
38417cbfb1a328c20b5b723b8584a02c57f88897Automatic Updater address or colon-delimited IPv6 address, <span><strong class="command">host</strong></span> will
38417cbfb1a328c20b5b723b8584a02c57f88897Automatic Updater query for PTR records. If a query type of IXFR is chosen the starting
38417cbfb1a328c20b5b723b8584a02c57f88897Automatic Updater serial number can be specified by appending an equal followed by the
38417cbfb1a328c20b5b723b8584a02c57f88897Automatic Updater starting serial number (e.g. -t IXFR=12345678).
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein The time to wait for a reply can be controlled through the
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <code class="option">-W</code> and <code class="option">-w</code> options. The
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <code class="option">-W</code> option makes <span><strong class="command">host</strong></span>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <em class="parameter"><code>wait</code></em> seconds. If <em class="parameter"><code>wait</code></em>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein is less than one, the wait interval is set to one second. When the
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <code class="option">-w</code> option is used, <span><strong class="command">host</strong></span>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein effectively wait forever for a reply. The time to wait for a response
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein will be set to the number of seconds given by the hardware's maximum
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein value for an integer quantity.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein The <code class="option">-s</code> option tells <span><strong class="command">host</strong></span>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <span class="emphasis"><em>not</em></span> to send the query to the next nameserver
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein if any server responds with a SERVFAIL response, which is the
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein reverse of normal stub resolver behavior.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein The <code class="option">-m</code> can be used to set the memory usage debugging
3a5fe5abf08f16b8d31ab8ee9a788063110ef000Automatic Updater <em class="parameter"><code>record</code></em>, <em class="parameter"><code>usage</code></em> and
3a5fe5abf08f16b8d31ab8ee9a788063110ef000Automatic Updater <em class="parameter"><code>trace</code></em>.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein If <span><strong class="command">host</strong></span> has been built with IDN (internationalized
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein domain name) support, it can accept and display non-ASCII domain names.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <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.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein The IDN support is disabled if the variable is set when
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <span><strong class="command">host</strong></span> runs.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<p><code class="filename">/etc/resolv.conf</code>
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