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03831d35f7499c87d51205817c93e9a8d42c4baestevel<title>host</title>
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03831d35f7499c87d51205817c93e9a8d42c4baestevel<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="refentry" lang="en">
03831d35f7499c87d51205817c93e9a8d42c4baestevel<a name="id2456836"></a><div class="titlepage"></div>
03831d35f7499c87d51205817c93e9a8d42c4baestevel<div class="refnamediv">
03831d35f7499c87d51205817c93e9a8d42c4baestevel<h2>Name</h2>
03831d35f7499c87d51205817c93e9a8d42c4baestevel<p>host &#8212; DNS lookup utility</p>
03831d35f7499c87d51205817c93e9a8d42c4baestevel</div>
03831d35f7499c87d51205817c93e9a8d42c4baestevel<div class="refsynopsisdiv">
03831d35f7499c87d51205817c93e9a8d42c4baestevel<h2>Synopsis</h2>
03831d35f7499c87d51205817c93e9a8d42c4baestevel<div class="cmdsynopsis"><p><code class="command">host</code>  [<code class="option">-aCdlnrTwv</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>
03831d35f7499c87d51205817c93e9a8d42c4baestevel</div>
03831d35f7499c87d51205817c93e9a8d42c4baestevel<div class="refsect1" lang="en">
03831d35f7499c87d51205817c93e9a8d42c4baestevel<a name="id2514251"></a><h2>DESCRIPTION</h2>
03831d35f7499c87d51205817c93e9a8d42c4baestevel<p><span><strong class="command">host</strong></span>
03831d35f7499c87d51205817c93e9a8d42c4baestevel      is a simple utility for performing DNS lookups.
03831d35f7499c87d51205817c93e9a8d42c4baestevel      It is normally used to convert names to IP addresses and vice versa.
03831d35f7499c87d51205817c93e9a8d42c4baestevel      When no arguments or options are given,
03831d35f7499c87d51205817c93e9a8d42c4baestevel      <span><strong class="command">host</strong></span>
03831d35f7499c87d51205817c93e9a8d42c4baestevel      prints a short summary of its command line arguments and options.
03831d35f7499c87d51205817c93e9a8d42c4baestevel    </p>
03831d35f7499c87d51205817c93e9a8d42c4baestevel<p><em class="parameter"><code>name</code></em> is the domain name that is to be
03831d35f7499c87d51205817c93e9a8d42c4baestevel      looked
03831d35f7499c87d51205817c93e9a8d42c4baestevel      up.  It can also be a dotted-decimal IPv4 address or a colon-delimited
03831d35f7499c87d51205817c93e9a8d42c4baestevel      IPv6 address, in which case <span><strong class="command">host</strong></span> will by
      default
      perform a reverse lookup for that address.
      <em class="parameter"><code>server</code></em> is an optional argument which
      is either
      the name or IP address of the name server that <span><strong class="command">host</strong></span>
      should query instead of the server or servers listed in
      <code class="filename">/etc/resolv.conf</code>.
    </p>
<p>
      The <code class="option">-a</code> (all) option is equivalent to setting the
      <code class="option">-v</code> option and asking <span><strong class="command">host</strong></span> to make
      a query of type ANY.
    </p>
<p>
      When the <code class="option">-C</code> option is used, <span><strong class="command">host</strong></span>
      will attempt to display the SOA records for zone
      <em class="parameter"><code>name</code></em> from all the listed
      authoritative name
      servers for that zone.  The list of name servers is defined by the NS
      records that are found for the zone.
    </p>
<p>
      The <code class="option">-c</code> option instructs to make a DNS query of class
      <em class="parameter"><code>class</code></em>.  This can be used to lookup
      Hesiod or
      Chaosnet class resource records.  The default class is IN (Internet).
    </p>
<p>
      Verbose output is generated by <span><strong class="command">host</strong></span> when
      the
      <code class="option">-d</code> or <code class="option">-v</code> option is used.  The two
      options are equivalent.  They have been provided for backwards
      compatibility.  In previous versions, the <code class="option">-d</code> option
      switched on debugging traces and <code class="option">-v</code> enabled verbose
      output.
    </p>
<p>
      List mode is selected by the <code class="option">-l</code> option.  This makes
      <span><strong class="command">host</strong></span> perform a zone transfer for zone
      <em class="parameter"><code>name</code></em>.  Transfer the zone printing out
      the NS, PTR
      and address records (A/AAAA).  If combined with <code class="option">-a</code>
      all records will be printed.
    </p>
<p>
      The <code class="option">-i</code>
      option specifies that reverse lookups of IPv6 addresses should
      use the IP6.INT domain as defined in RFC1886.
      The default is to use IP6.ARPA.
    </p>
<p>
      The <code class="option">-N</code> option sets the number of dots that have to be
      in <em class="parameter"><code>name</code></em> for it to be considered
      absolute.  The
      default value is that defined using the ndots statement in
      <code class="filename">/etc/resolv.conf</code>, or 1 if no ndots
      statement is
      present.  Names with fewer dots are interpreted as relative names and
      will be searched for in the domains listed in the <span class="type">search</span>
      or <span class="type">domain</span> directive in
      <code class="filename">/etc/resolv.conf</code>.
    </p>
<p>
      The number of UDP retries for a lookup can be changed with the
      <code class="option">-R</code> option.  <em class="parameter"><code>number</code></em>
      indicates
      how many times <span><strong class="command">host</strong></span> will repeat a query
      that does
      not get answered.  The default number of retries is 1.  If
      <em class="parameter"><code>number</code></em> is negative or zero, the
      number of
      retries will default to 1.
    </p>
<p>
      Non-recursive queries can be made via the <code class="option">-r</code> option.
      Setting this option clears the <span class="type">RD</span> &#8212; recursion
      desired &#8212; bit in the query which <span><strong class="command">host</strong></span> makes.
      This should mean that the name server receiving the query will not
      attempt to resolve <em class="parameter"><code>name</code></em>.  The
      <code class="option">-r</code> option enables <span><strong class="command">host</strong></span>
      to mimic
      the behaviour of a name server by making non-recursive queries and
      expecting to receive answers to those queries that are usually
      referrals to other name servers.
    </p>
<p>
      By default <span><strong class="command">host</strong></span> uses UDP when making
      queries.  The
      <code class="option">-T</code> option makes it use a TCP connection when querying
      the name server.  TCP will be automatically selected for queries that
      require it, such as zone transfer (AXFR) requests.
    </p>
<p>
      The <code class="option">-4</code> option forces <span><strong class="command">host</strong></span> to only
      use IPv4 query transport.  The <code class="option">-6</code> option forces
      <span><strong class="command">host</strong></span> to only use IPv6 query transport.
    </p>
<p>
      The <code class="option">-t</code> option is used to select the query type.
      <em class="parameter"><code>type</code></em> can be any recognised query
      type: CNAME,
      NS, SOA, SIG, KEY, AXFR, etc.  When no query type is specified,
      <span><strong class="command">host</strong></span> automatically selects an appropriate
      query
      type.  By default it looks for A records, but if the
      <code class="option">-C</code> option was given, queries will be made for SOA
      records, and if <em class="parameter"><code>name</code></em> is a
      dotted-decimal IPv4
      address or colon-delimited IPv6 address, <span><strong class="command">host</strong></span> will
      query for PTR records.  If a query type of IXFR is chosen the starting
      serial number can be specified by appending an equal followed by the
      starting serial number (e.g. -t IXFR=12345678).
    </p>
<p>
      The time to wait for a reply can be controlled through the
      <code class="option">-W</code> and <code class="option">-w</code> options.  The
      <code class="option">-W</code> option makes <span><strong class="command">host</strong></span>
      wait for
      <em class="parameter"><code>wait</code></em> seconds.  If <em class="parameter"><code>wait</code></em>
      is less than one, the wait interval is set to one second.  When the
      <code class="option">-w</code> option is used, <span><strong class="command">host</strong></span>
      will
      effectively wait forever for a reply.  The time to wait for a response
      will be set to the number of seconds given by the hardware's maximum
      value for an integer quantity.
    </p>
<p>
      The <code class="option">-m</code> can be used to set the memory usage debugging
      flags
      <em class="parameter"><code>record</code></em>, <em class="parameter"><code>usage</code></em> and
      <em class="parameter"><code>trace</code></em>.
    </p>
</div>
<div class="refsect1" lang="en">
<a name="id2514604"></a><h2>FILES</h2>
<p><code class="filename">/etc/resolv.conf</code>
    </p>
</div>
<div class="refsect1" lang="en">
<a name="id2514616"></a><h2>SEE ALSO</h2>
<p><span class="citerefentry"><span class="refentrytitle">dig</span>(1)</span>,
      <span class="citerefentry"><span class="refentrytitle">named</span>(8)</span>.
    </p>
</div>
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