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60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein - Copyright (C) 2004-2009 Internet Systems Consortium, Inc. ("ISC")
71cef386fae61275b03e203825680b39fedaa8c6Tinderbox 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,
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein - 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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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>
9c6a5d1f22f972232d7a9fd5c5fa64f10bacbdffAutomatic Updater<p><span><strong class="command">host</strong></span>
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrews is a simple utility for performing DNS lookups.
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrews It is normally used to convert names to IP addresses and vice versa.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein When no arguments or options are given,
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User <span><strong class="command">host</strong></span>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User prints a short summary of its command line arguments and options.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<p><em class="parameter"><code>name</code></em> is the domain name that is to be
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User up. It can also be a dotted-decimal IPv4 address or a colon-delimited
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein 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
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein the name or IP address of the name server that <span><strong class="command">host</strong></span>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein should query instead of the server or servers listed in
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein The <code class="option">-a</code> (all) option is equivalent to setting the
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <code class="option">-v</code> option and asking <span><strong class="command">host</strong></span> to make
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User a query of type ANY.
727f5b8846457a33d06f515a10a7e1aa849ddf18Andreas Gustafsson When the <code class="option">-C</code> option is used, <span><strong class="command">host</strong></span>
f293a69bcd1c1dd7bdac8f4102fc2398b9e475c8Eric Luce will attempt to display the SOA records for zone
ac93437301f55ed69bf85883a497a75598c628f9Automatic Updater <em class="parameter"><code>name</code></em> from all the listed
ac93437301f55ed69bf85883a497a75598c628f9Automatic Updater authoritative name
ac93437301f55ed69bf85883a497a75598c628f9Automatic Updater servers for that zone. The list of name servers is defined by the NS
727f5b8846457a33d06f515a10a7e1aa849ddf18Andreas Gustafsson records that are found for the zone.
ac93437301f55ed69bf85883a497a75598c628f9Automatic Updater The <code class="option">-c</code> option instructs to make a DNS query of class
f293a69bcd1c1dd7bdac8f4102fc2398b9e475c8Eric Luce <em class="parameter"><code>class</code></em>. This can be used to lookup
f293a69bcd1c1dd7bdac8f4102fc2398b9e475c8Eric Luce Chaosnet class resource records. The default class is IN (Internet).
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein Verbose output is generated by <span><strong class="command">host</strong></span> when
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User <code class="option">-d</code> or <code class="option">-v</code> option is used. The two
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User options are equivalent. They have been provided for backwards
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User compatibility. In previous versions, the <code class="option">-d</code> option
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein switched on debugging traces and <code class="option">-v</code> enabled verbose
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein List mode is selected by the <code class="option">-l</code> option. This makes
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <span><strong class="command">host</strong></span> perform a zone transfer for zone
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <em class="parameter"><code>name</code></em>. Transfer the zone printing out
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User and address records (A/AAAA). If combined with <code class="option">-a</code>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein all records will be printed.
ac93437301f55ed69bf85883a497a75598c628f9Automatic Updater option specifies that reverse lookups of IPv6 addresses should
ac93437301f55ed69bf85883a497a75598c628f9Automatic Updater use the IP6.INT domain as defined in RFC1886.
ac93437301f55ed69bf85883a497a75598c628f9Automatic Updater The default is to use IP6.ARPA.
ac93437301f55ed69bf85883a497a75598c628f9Automatic Updater The <code class="option">-N</code> option sets the number of dots that have to be
f293a69bcd1c1dd7bdac8f4102fc2398b9e475c8Eric Luce in <em class="parameter"><code>name</code></em> for it to be considered
f293a69bcd1c1dd7bdac8f4102fc2398b9e475c8Eric Luce absolute. The
ac93437301f55ed69bf85883a497a75598c628f9Automatic Updater default value is that defined using the ndots statement in
ac93437301f55ed69bf85883a497a75598c628f9Automatic Updater <code class="filename">/etc/resolv.conf</code>, or 1 if no ndots
f293a69bcd1c1dd7bdac8f4102fc2398b9e475c8Eric Luce statement is
f293a69bcd1c1dd7bdac8f4102fc2398b9e475c8Eric Luce present. Names with fewer dots are interpreted as relative names and
f293a69bcd1c1dd7bdac8f4102fc2398b9e475c8Eric Luce will be searched for in the domains listed in the <span class="type">search</span>
f293a69bcd1c1dd7bdac8f4102fc2398b9e475c8Eric Luce The number of UDP retries for a lookup can be changed with the
f293a69bcd1c1dd7bdac8f4102fc2398b9e475c8Eric Luce <code class="option">-R</code> option. <em class="parameter"><code>number</code></em>
ac93437301f55ed69bf85883a497a75598c628f9Automatic Updater how many times <span><strong class="command">host</strong></span> will repeat a query
f293a69bcd1c1dd7bdac8f4102fc2398b9e475c8Eric Luce not get answered. The default number of retries is 1. If
f293a69bcd1c1dd7bdac8f4102fc2398b9e475c8Eric Luce <em class="parameter"><code>number</code></em> is negative or zero, the
f293a69bcd1c1dd7bdac8f4102fc2398b9e475c8Eric Luce retries will default to 1.
f293a69bcd1c1dd7bdac8f4102fc2398b9e475c8Eric Luce Non-recursive queries can be made via the <code class="option">-r</code> option.
f293a69bcd1c1dd7bdac8f4102fc2398b9e475c8Eric Luce Setting this option clears the <span class="type">RD</span> — recursion
f293a69bcd1c1dd7bdac8f4102fc2398b9e475c8Eric Luce desired — bit in the query which <span><strong class="command">host</strong></span> makes.
f293a69bcd1c1dd7bdac8f4102fc2398b9e475c8Eric Luce This should mean that the name server receiving the query will not
f293a69bcd1c1dd7bdac8f4102fc2398b9e475c8Eric Luce 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>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox 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.
af40ebed6257e4ac1996144530b3de317cf4da11Tinderbox User 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
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User the name server. TCP will be automatically selected for queries that
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User require it, such as zone transfer (AXFR) requests.
1224c3b69b3d18f7127aa042644936af25a2d679Mark Andrews The <code class="option">-4</code> option forces <span><strong class="command">host</strong></span> to only
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein 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.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein The <code class="option">-t</code> option is used to select the query type.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <em class="parameter"><code>type</code></em> can be any recognized query
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein type: CNAME,
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein NS, SOA, SIG, KEY, AXFR, etc. When no query type is specified,
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User <span><strong class="command">host</strong></span> automatically selects an appropriate
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User type. By default, it looks for A, AAAA, and MX records, but if the
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <code class="option">-C</code> option was given, queries will be made for SOA
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt records, and if <em class="parameter"><code>name</code></em> is a
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt dotted-decimal IPv4
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt address or colon-delimited IPv6 address, <span><strong class="command">host</strong></span> will
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt query for PTR records. If a query type of IXFR is chosen the starting
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt serial number can be specified by appending an equal followed by the
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein 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
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <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
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>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<p><span class="citerefentry"><span class="refentrytitle">dig</span>(1)</span>,
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <span class="citerefentry"><span class="refentrytitle">named</span>(8)</span>.
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