host.html revision 260e8e04b0dc24cb884c789b5d9eb046457f264e
5fbced719b71e659322b4ce3e4a39c9b039674c7Bob Halley - Copyright (C) 2004, 2005, 2007-2009, 2014-2016 Internet Systems Consortium, Inc. ("ISC")
499b34cea04a46823d003d4c0520c8b03e8513cbBrian Wellington - Copyright (C) 2000-2002 Internet Software Consortium.
5fbced719b71e659322b4ce3e4a39c9b039674c7Bob Halley - Permission to use, copy, modify, and/or distribute this software for any
5fbced719b71e659322b4ce3e4a39c9b039674c7Bob Halley - purpose with or without fee is hereby granted, provided that the above
5fbced719b71e659322b4ce3e4a39c9b039674c7Bob Halley - copyright notice and this permission notice appear in all copies.
15a44745412679c30a6d022733925af70a38b715David Lawrence - THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
15a44745412679c30a6d022733925af70a38b715David Lawrence - REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
15a44745412679c30a6d022733925af70a38b715David Lawrence - AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
15a44745412679c30a6d022733925af70a38b715David Lawrence - INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
15a44745412679c30a6d022733925af70a38b715David Lawrence - LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
15a44745412679c30a6d022733925af70a38b715David Lawrence - OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
15a44745412679c30a6d022733925af70a38b715David Lawrence - PERFORMANCE OF THIS SOFTWARE.
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5a6e6c2c9b2f6cf426aa2a682aa800765e26d540Andreas Gustafsson<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="refentry">
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence<a name="man.host"></a><div class="titlepage"></div>
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence<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>
5a6e6c2c9b2f6cf426aa2a682aa800765e26d540Andreas Gustafsson<p><span class="command"><strong>host</strong></span>
5a6e6c2c9b2f6cf426aa2a682aa800765e26d540Andreas Gustafsson is a simple utility for performing DNS lookups.
5a6e6c2c9b2f6cf426aa2a682aa800765e26d540Andreas Gustafsson It is normally used to convert names to IP addresses and vice versa.
5a6e6c2c9b2f6cf426aa2a682aa800765e26d540Andreas Gustafsson When no arguments or options are given,
5a6e6c2c9b2f6cf426aa2a682aa800765e26d540Andreas Gustafsson <span class="command"><strong>host</strong></span>
c968a9ca37964ae0bdc5d452ad784ec93bd04c57David Lawrence prints a short summary of its command line arguments and options.
5a6e6c2c9b2f6cf426aa2a682aa800765e26d540Andreas Gustafsson<p><em class="parameter"><code>name</code></em> is the domain name that is to be
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence up. It can also be a dotted-decimal IPv4 address or a colon-delimited
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence IPv6 address, in which case <span class="command"><strong>host</strong></span> will by
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence perform a reverse lookup for that address.
b897c52f865b2fc4e220e2110b874e59c716456bBob Halley <em class="parameter"><code>server</code></em> is an optional argument which
b897c52f865b2fc4e220e2110b874e59c716456bBob Halley the name or IP address of the name server that <span class="command"><strong>host</strong></span>
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence should query instead of the server or servers listed in
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence <code class="filename">/etc/resolv.conf</code>.
4b598d8ae578861d5f3fc1333c9f84c9c9c8be7cDavid Lawrence<div class="variablelist"><dl class="variablelist">
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence Use IPv4 only for query transport.
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence See also the <code class="option">-6</code> option.
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence Use IPv6 only for query transport.
4b598d8ae578861d5f3fc1333c9f84c9c9c8be7cDavid Lawrence See also the <code class="option">-4</code> option.
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence "All". The <code class="option">-a</code> option is normally equivalent
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence to <code class="option">-v -t <code class="literal">ANY</code></code>.
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence It also affects the behaviour of the <code class="option">-l</code>
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence list zone option.
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence<dt><span class="term">-c <em class="replaceable"><code>class</code></em></span></dt>
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence Query class: This can be used to lookup HS (Hesiod) or CH
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence (Chaosnet) class resource records. The default class is IN
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence Check consistency: <span class="command"><strong>host</strong></span> will query the
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence SOA records for zone <em class="parameter"><code>name</code></em> from all
abfb7fe67fd97adfa4628afa79af5d98c2d9cad0Andreas Gustafsson the listed authoritative name servers for that zone. The
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence list of name servers is defined by the NS records that are
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence found for the zone.
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence Print debugging traces.
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence Equivalent to the <code class="option">-v</code> verbose option.
5a48c9f76003a649e16de34fe6206e3b67b97afbBob Halley Use the IP6.INT domain for reverse lookups of IPv6
5a48c9f76003a649e16de34fe6206e3b67b97afbBob Halley addresses as defined in RFC1886 and deprecated in RFC4159.
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence The default is to use IP6.ARPA as specified in RFC3596.
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence The <span class="command"><strong>host</strong></span> command performs a zone transfer of
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence zone <em class="parameter"><code>name</code></em> and prints out the NS,
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence Together, the <code class="option">-l -a</code>
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence options print all records in the zone.
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence<dt><span class="term">-N <em class="replaceable"><code>ndots</code></em></span></dt>
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence The number of dots that have to be
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence in <em class="parameter"><code>name</code></em> for it to be considered
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence absolute. The default value is that defined using the
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence ndots statement in <code class="filename">/etc/resolv.conf</code>,
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence or 1 if no ndots statement is present. Names with fewer
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence dots are interpreted as relative names and will be
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence searched for in the domains listed in
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence the <span class="type">search</span> or <span class="type">domain</span> directive
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence in <code class="filename">/etc/resolv.conf</code>.
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence Non-recursive query:
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence Setting this option clears the RD (recursion desired) bit
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence in the query. This should mean that the name server
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence receiving the query will not attempt to
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence resolve <em class="parameter"><code>name</code></em>.
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence enables <span class="command"><strong>host</strong></span> to mimic the behavior of a
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence name server by making non-recursive queries and expecting
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence to receive answers to those queries that can be
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence referrals to other name servers.
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence<dt><span class="term">-R <em class="replaceable"><code>number</code></em></span></dt>
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence Number of retries for UDP queries:
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence If <em class="parameter"><code>number</code></em> is negative or zero, the
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence number of retries will default to 1. The default value is
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence 1, or the value of the <em class="parameter"><code>attempts</code></em>
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence option in <code class="filename">/etc/resolv.conf</code>, if set.
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence Do <span class="emphasis"><em>not</em></span> send the query to the next
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence nameserver if any server responds with a SERVFAIL
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence response, which is the reverse of normal stub resolver
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence<dt><span class="term">-t <em class="replaceable"><code>type</code></em></span></dt>
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence The <em class="parameter"><code>type</code></em> argument can be any
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence recognized query type: CNAME, NS, SOA, TXT, DNSKEY, AXFR, etc.
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence When no query type is specified, <span class="command"><strong>host</strong></span>
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence automatically selects an appropriate query type. By default, it
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence looks for A, AAAA, and MX records.
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence If the <code class="option">-C</code> option is given, queries will
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence be made for SOA records.
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence If <em class="parameter"><code>name</code></em> is a dotted-decimal IPv4
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence address or colon-delimited IPv6
c968a9ca37964ae0bdc5d452ad784ec93bd04c57David Lawrence address, <span class="command"><strong>host</strong></span> will query for PTR
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence If a query type of IXFR is chosen the starting serial
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence number can be specified by appending an equal followed by
5a48c9f76003a649e16de34fe6206e3b67b97afbBob Halley the starting serial number
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence (like <code class="option">-t <code class="literal">IXFR=12345678</code></code>).
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence By default, <span class="command"><strong>host</strong></span> uses UDP when making
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence queries. The <code class="option">-T</code> option makes it use a TCP
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence connection when querying the name server. TCP will be
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence automatically selected for queries that require it, such
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence as zone transfer (AXFR) requests.
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence<dt><span class="term">-m <em class="replaceable"><code>flag</code></em></span></dt>
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence Memory usage debugging: the flag can
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence be <em class="parameter"><code>record</code></em>, <em class="parameter"><code>usage</code></em>,
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence or <em class="parameter"><code>trace</code></em>. You can specify
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence the <code class="option">-m</code> option more than once to set
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence multiple flags.
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence Verbose output.
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence Equivalent to the <code class="option">-d</code> debug option.
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence Verbose output can also be enabled by setting
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence the <em class="parameter"><code>debug</code></em> option
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence in <code class="filename">/etc/resolv.conf</code>.
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence Print the version number and exit.
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence Wait forever: The query timeout is set to the maximum possible.
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence See also the <code class="option">-W</code> option.
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence<dt><span class="term">-W <em class="replaceable"><code>wait</code></em></span></dt>
4b598d8ae578861d5f3fc1333c9f84c9c9c8be7cDavid Lawrence Timeout: Wait for up to <em class="parameter"><code>wait</code></em>
4b598d8ae578861d5f3fc1333c9f84c9c9c8be7cDavid Lawrence seconds for a reply. If <em class="parameter"><code>wait</code></em> is
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence less than one, the wait interval is set to one second.
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence By default, <span class="command"><strong>host</strong></span> will wait for 5
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence seconds for UDP responses and 10 seconds for TCP
5a6e6c2c9b2f6cf426aa2a682aa800765e26d540Andreas Gustafsson connections. These defaults can be overridden by
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence the <em class="parameter"><code>timeout</code></em> option
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence in <code class="filename">/etc/resolv.conf</code>.
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence See also the <code class="option">-w</code> option.
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence If <span class="command"><strong>host</strong></span> has been built with IDN (internationalized
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence domain name) support, it can accept and display non-ASCII domain names.
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence <span class="command"><strong>host</strong></span> appropriately converts character encoding of
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence domain name before sending a request to DNS server or displaying a
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence reply from the server.
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence If you'd like to turn off the IDN support for some reason, defines
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence the <code class="envar">IDN_DISABLE</code> environment variable.
5a6e6c2c9b2f6cf426aa2a682aa800765e26d540Andreas Gustafsson The IDN support is disabled if the variable is set when
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence <span class="command"><strong>host</strong></span> runs.
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence<p><code class="filename">/etc/resolv.conf</code>
cb3e854e181373807f7f011e5050c1a8013b4841Brian Wellington<p><span class="citerefentry"><span class="refentrytitle">dig</span>(1)</span>,
f4a7d04843eb62c92f2d4ff338da49ae86e3279bDavid Lawrence <span class="citerefentry"><span class="refentrytitle">named</span>(8)</span>.