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c4958494a98a59ce25e9fecad76a9ab0e36cc59fDanny Mayer<tr><th colspan="3" align="center">host</th></tr>
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ab023a65562e62b85a824509d829b6fad87e00b1Rob Austein<a name="man.host"></a><div class="titlepage"></div>
ab023a65562e62b85a824509d829b6fad87e00b1Rob 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>] [<code class="option">-v</code>] [<code class="option">-V</code>] {name} [server]</p></div>
ab023a65562e62b85a824509d829b6fad87e00b1Rob Austein<p><span><strong class="command">host</strong></span>
fc80027fb54b501cdd88461bf879d078259e0226David Lawrence is a simple utility for performing DNS lookups.
fc80027fb54b501cdd88461bf879d078259e0226David Lawrence It is normally used to convert names to IP addresses and vice versa.
fc80027fb54b501cdd88461bf879d078259e0226David Lawrence When no arguments or options are given,
fc80027fb54b501cdd88461bf879d078259e0226David Lawrence <span><strong class="command">host</strong></span>
fc80027fb54b501cdd88461bf879d078259e0226David Lawrence prints a short summary of its command line arguments and options.
fc80027fb54b501cdd88461bf879d078259e0226David Lawrence<p><em class="parameter"><code>name</code></em> is the domain name that is to be
ab023a65562e62b85a824509d829b6fad87e00b1Rob Austein up. It can also be a dotted-decimal IPv4 address or a colon-delimited
fc80027fb54b501cdd88461bf879d078259e0226David Lawrence IPv6 address, in which case <span><strong class="command">host</strong></span> will by
fc80027fb54b501cdd88461bf879d078259e0226David Lawrence perform a reverse lookup for that address.
fc80027fb54b501cdd88461bf879d078259e0226David Lawrence <em class="parameter"><code>server</code></em> is an optional argument which
fc80027fb54b501cdd88461bf879d078259e0226David Lawrence the name or IP address of the name server that <span><strong class="command">host</strong></span>
2918b5bda6a55c301eb87992b5f2acd7176d0737David Lawrence should query instead of the server or servers listed in
2918b5bda6a55c301eb87992b5f2acd7176d0737David Lawrence <code class="filename">/etc/resolv.conf</code>.
ab023a65562e62b85a824509d829b6fad87e00b1Rob Austein The <code class="option">-a</code> (all) option is equivalent to setting the
fc80027fb54b501cdd88461bf879d078259e0226David Lawrence <code class="option">-v</code> option and asking <span><strong class="command">host</strong></span> to make
ab023a65562e62b85a824509d829b6fad87e00b1Rob Austein a query of type ANY.
ab023a65562e62b85a824509d829b6fad87e00b1Rob Austein When the <code class="option">-C</code> option is used, <span><strong class="command">host</strong></span>
fc80027fb54b501cdd88461bf879d078259e0226David Lawrence will attempt to display the SOA records for zone
fc80027fb54b501cdd88461bf879d078259e0226David Lawrence <em class="parameter"><code>name</code></em> from all the listed
fc80027fb54b501cdd88461bf879d078259e0226David Lawrence authoritative name
fc80027fb54b501cdd88461bf879d078259e0226David Lawrence servers for that zone. The list of name servers is defined by the NS
fc80027fb54b501cdd88461bf879d078259e0226David Lawrence records that are found for the zone.
fc80027fb54b501cdd88461bf879d078259e0226David Lawrence The <code class="option">-c</code> option instructs to make a DNS query of class
ab023a65562e62b85a824509d829b6fad87e00b1Rob Austein <em class="parameter"><code>class</code></em>. This can be used to lookup
ab023a65562e62b85a824509d829b6fad87e00b1Rob Austein Chaosnet class resource records. The default class is IN (Internet).
d409ceeda41a256e8114423674d844d5f5035ee8Bob Halley Verbose output is generated by <span><strong class="command">host</strong></span> when
8f804834e2b537da5c8bc81f986143a46147b490Andreas Gustafsson <code class="option">-d</code> or <code class="option">-v</code> option is used. The two
fc80027fb54b501cdd88461bf879d078259e0226David Lawrence options are equivalent. They have been provided for backwards
fc80027fb54b501cdd88461bf879d078259e0226David Lawrence compatibility. In previous versions, the <code class="option">-d</code> option
8f804834e2b537da5c8bc81f986143a46147b490Andreas Gustafsson switched on debugging traces and <code class="option">-v</code> enabled verbose
fc80027fb54b501cdd88461bf879d078259e0226David Lawrence output. Verbose output can also be enabled by setting the
ab023a65562e62b85a824509d829b6fad87e00b1Rob Austein <em class="parameter"><code>debug</code></em> option in
fc80027fb54b501cdd88461bf879d078259e0226David Lawrence List mode is selected by the <code class="option">-l</code> option. This makes
fc80027fb54b501cdd88461bf879d078259e0226David Lawrence <span><strong class="command">host</strong></span> perform a zone transfer for zone
8f804834e2b537da5c8bc81f986143a46147b490Andreas Gustafsson <em class="parameter"><code>name</code></em>. Transfer the zone printing out
ab023a65562e62b85a824509d829b6fad87e00b1Rob Austein and address records (A/AAAA). If combined with <code class="option">-a</code>
fc80027fb54b501cdd88461bf879d078259e0226David Lawrence all records will be printed.
fc80027fb54b501cdd88461bf879d078259e0226David Lawrence option specifies that reverse lookups of IPv6 addresses should
ab023a65562e62b85a824509d829b6fad87e00b1Rob Austein use the IP6.INT domain as defined in RFC1886.
fc80027fb54b501cdd88461bf879d078259e0226David Lawrence The default is to use IP6.ARPA.
fc80027fb54b501cdd88461bf879d078259e0226David Lawrence The <code class="option">-N</code> option sets the number of dots that have to be
fc80027fb54b501cdd88461bf879d078259e0226David Lawrence in <em class="parameter"><code>name</code></em> for it to be considered
ab023a65562e62b85a824509d829b6fad87e00b1Rob Austein absolute. The
ab023a65562e62b85a824509d829b6fad87e00b1Rob Austein default value is that defined using the ndots statement in
ab023a65562e62b85a824509d829b6fad87e00b1Rob Austein <code class="filename">/etc/resolv.conf</code>, or 1 if no ndots
ab023a65562e62b85a824509d829b6fad87e00b1Rob Austein statement is
fc80027fb54b501cdd88461bf879d078259e0226David Lawrence present. Names with fewer dots are interpreted as relative names and
fc80027fb54b501cdd88461bf879d078259e0226David Lawrence will be searched for in the domains listed in the <span class="type">search</span>
fc80027fb54b501cdd88461bf879d078259e0226David Lawrence or <span class="type">domain</span> directive in
fc80027fb54b501cdd88461bf879d078259e0226David Lawrence <code class="filename">/etc/resolv.conf</code>.
61e9c1cdbe29683bb2db388e4fc6a6fd59315cefDavid Lawrence The number of UDP retries for a lookup can be changed with the
ab023a65562e62b85a824509d829b6fad87e00b1Rob Austein <code class="option">-R</code> option. <em class="parameter"><code>number</code></em>
fc80027fb54b501cdd88461bf879d078259e0226David Lawrence how many times <span><strong class="command">host</strong></span> will repeat a query
fc80027fb54b501cdd88461bf879d078259e0226David Lawrence not get answered. If
fc80027fb54b501cdd88461bf879d078259e0226David Lawrence <em class="parameter"><code>number</code></em> is negative or zero, the
fc80027fb54b501cdd88461bf879d078259e0226David Lawrence retries will default to 1. The default value is 1, or
fc80027fb54b501cdd88461bf879d078259e0226David Lawrence the value of the <em class="parameter"><code>attempts</code></em> option in
fc80027fb54b501cdd88461bf879d078259e0226David Lawrence <code class="filename">/etc/resolv.conf</code>, if set.
ab023a65562e62b85a824509d829b6fad87e00b1Rob Austein Non-recursive queries can be made via the <code class="option">-r</code> option.
ab023a65562e62b85a824509d829b6fad87e00b1Rob Austein Setting this option clears the <span class="type">RD</span> — recursion
1a487fb7d230403bf1b5d6628542134f52c80653Michael Graff desired — bit in the query which <span><strong class="command">host</strong></span> makes.
fc80027fb54b501cdd88461bf879d078259e0226David Lawrence This should mean that the name server receiving the query will not
fc80027fb54b501cdd88461bf879d078259e0226David Lawrence attempt to resolve <em class="parameter"><code>name</code></em>. The
fc80027fb54b501cdd88461bf879d078259e0226David Lawrence <code class="option">-r</code> option enables <span><strong class="command">host</strong></span>
fc80027fb54b501cdd88461bf879d078259e0226David Lawrence the behavior of a name server by making non-recursive queries and
c4958494a98a59ce25e9fecad76a9ab0e36cc59fDanny Mayer expecting to receive answers to those queries that are usually
c4958494a98a59ce25e9fecad76a9ab0e36cc59fDanny Mayer referrals to other name servers.
fc80027fb54b501cdd88461bf879d078259e0226David Lawrence By default, <span><strong class="command">host</strong></span> uses UDP when making
ab023a65562e62b85a824509d829b6fad87e00b1Rob Austein queries. The
ab023a65562e62b85a824509d829b6fad87e00b1Rob Austein <code class="option">-T</code> option makes it use a TCP connection when querying
1a487fb7d230403bf1b5d6628542134f52c80653Michael Graff the name server. TCP will be automatically selected for queries that
1a487fb7d230403bf1b5d6628542134f52c80653Michael Graff require it, such as zone transfer (AXFR) requests.
5fe5a0c02634eaadfcbc3528bf2c184557110a3bAndreas Gustafsson The <code class="option">-4</code> option forces <span><strong class="command">host</strong></span> to only
ab023a65562e62b85a824509d829b6fad87e00b1Rob Austein use IPv4 query transport. The <code class="option">-6</code> option forces
fc80027fb54b501cdd88461bf879d078259e0226David Lawrence <span><strong class="command">host</strong></span> to only use IPv6 query transport.
ecf7a1812527d5557564b71363dabec491980246Mark Andrews The <code class="option">-t</code> option is used to select the query type.
88f7da46901f5d1218e354768674e72e9190d05aMichael Graff <em class="parameter"><code>type</code></em> can be any recognized query
b161f87be81548d1b6d0210a7e138a08fbb2d3e5David Lawrence NS, SOA, SIG, KEY, AXFR, etc. When no query type is specified,
b161f87be81548d1b6d0210a7e138a08fbb2d3e5David Lawrence <span><strong class="command">host</strong></span> automatically selects an appropriate
edcd1247ad7e81bb8b430e610d9718f64c70f05dDavid Lawrence type. By default, it looks for A, AAAA, and MX records, but if the
ab023a65562e62b85a824509d829b6fad87e00b1Rob Austein <code class="option">-C</code> option was given, queries will be made for SOA
fc80027fb54b501cdd88461bf879d078259e0226David Lawrence records, and if <em class="parameter"><code>name</code></em> is a
fc80027fb54b501cdd88461bf879d078259e0226David Lawrence dotted-decimal IPv4
fc80027fb54b501cdd88461bf879d078259e0226David Lawrence address or colon-delimited IPv6 address, <span><strong class="command">host</strong></span> will
ab023a65562e62b85a824509d829b6fad87e00b1Rob Austein query for PTR records. If a query type of IXFR is chosen the starting
863ac191b448a13ae1a3a8ee3458344e11602737David Lawrence serial number can be specified by appending an equal followed by the
863ac191b448a13ae1a3a8ee3458344e11602737David Lawrence starting serial number (e.g. -t IXFR=12345678).
ab023a65562e62b85a824509d829b6fad87e00b1Rob Austein The time to wait for a reply can be controlled through the
ab023a65562e62b85a824509d829b6fad87e00b1Rob Austein <code class="option">-W</code> and <code class="option">-w</code> options. The
863ac191b448a13ae1a3a8ee3458344e11602737David Lawrence <code class="option">-W</code> option makes <span><strong class="command">host</strong></span>
ab023a65562e62b85a824509d829b6fad87e00b1Rob Austein <em class="parameter"><code>wait</code></em> seconds. If <em class="parameter"><code>wait</code></em>
863ac191b448a13ae1a3a8ee3458344e11602737David Lawrence is less than one, the wait interval is set to one second. When the
ab023a65562e62b85a824509d829b6fad87e00b1Rob Austein <code class="option">-w</code> option is used, <span><strong class="command">host</strong></span>
ab023a65562e62b85a824509d829b6fad87e00b1Rob Austein effectively wait forever for a reply. The time to wait for a response
863ac191b448a13ae1a3a8ee3458344e11602737David Lawrence will be set to the number of seconds given by the hardware's maximum
863ac191b448a13ae1a3a8ee3458344e11602737David Lawrence value for an integer quantity. By default, <span><strong class="command">host</strong></span>
ab023a65562e62b85a824509d829b6fad87e00b1Rob Austein will wait for 5 seconds for UDP responses and 10 seconds for TCP
ab023a65562e62b85a824509d829b6fad87e00b1Rob Austein connections. These defaults can be overridden by the
863ac191b448a13ae1a3a8ee3458344e11602737David Lawrence <em class="parameter"><code>timeout</code></em> option in
863ac191b448a13ae1a3a8ee3458344e11602737David Lawrence <code class="filename">/etc/resolv.conf</code>.
ab023a65562e62b85a824509d829b6fad87e00b1Rob Austein The <code class="option">-s</code> option tells <span><strong class="command">host</strong></span>
863ac191b448a13ae1a3a8ee3458344e11602737David Lawrence <span class="emphasis"><em>not</em></span> to send the query to the next nameserver
863ac191b448a13ae1a3a8ee3458344e11602737David Lawrence if any server responds with a SERVFAIL response, which is the
863ac191b448a13ae1a3a8ee3458344e11602737David Lawrence reverse of normal stub resolver behavior.
863ac191b448a13ae1a3a8ee3458344e11602737David Lawrence The <code class="option">-m</code> can be used to set the memory usage debugging
ab023a65562e62b85a824509d829b6fad87e00b1Rob Austein <em class="parameter"><code>record</code></em>, <em class="parameter"><code>usage</code></em> and
863ac191b448a13ae1a3a8ee3458344e11602737David Lawrence <em class="parameter"><code>trace</code></em>.
863ac191b448a13ae1a3a8ee3458344e11602737David Lawrence The <code class="option">-V</code> option causes <span><strong class="command">host</strong></span>
863ac191b448a13ae1a3a8ee3458344e11602737David Lawrence to print the version number and exit.
ab023a65562e62b85a824509d829b6fad87e00b1Rob Austein If <span><strong class="command">host</strong></span> has been built with IDN (internationalized
fc80027fb54b501cdd88461bf879d078259e0226David Lawrence domain name) support, it can accept and display non-ASCII domain names.
ab023a65562e62b85a824509d829b6fad87e00b1Rob Austein <span><strong class="command">host</strong></span> appropriately converts character encoding of
fc80027fb54b501cdd88461bf879d078259e0226David Lawrence domain name before sending a request to DNS server or displaying a
ab023a65562e62b85a824509d829b6fad87e00b1Rob Austein reply from the server.
fc80027fb54b501cdd88461bf879d078259e0226David Lawrence If you'd like to turn off the IDN support for some reason, defines
ab023a65562e62b85a824509d829b6fad87e00b1Rob Austein the <code class="envar">IDN_DISABLE</code> environment variable.
fc80027fb54b501cdd88461bf879d078259e0226David Lawrence The IDN support is disabled if the variable is set when
fc80027fb54b501cdd88461bf879d078259e0226David Lawrence <span><strong class="command">host</strong></span> runs.
ab023a65562e62b85a824509d829b6fad87e00b1Rob Austein<p><code class="filename">/etc/resolv.conf</code>
ab023a65562e62b85a824509d829b6fad87e00b1Rob Austein<p><span class="citerefentry"><span class="refentrytitle">dig</span>(1)</span>,
fc80027fb54b501cdd88461bf879d078259e0226David Lawrence <span class="citerefentry"><span class="refentrytitle">named</span>(8)</span>.
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edcd1247ad7e81bb8b430e610d9718f64c70f05dDavid Lawrence<p style="text-align: center;">BIND 9.11.0pre-alpha</p>