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60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<div class="refentry">
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<a name="man.host"></a><div class="titlepage"></div>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<div class="refnamediv">
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<h2>Name</h2>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<p>host &#8212; DNS lookup utility</p>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein</div>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<div class="refsynopsisdiv">
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<h2>Synopsis</h2>
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>] [<code class="option">-v</code>] [<code class="option">-V</code>] {name} [server]</p></div>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein</div>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<div class="refsection">
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<a name="id-1.14.4.7"></a><h2>DESCRIPTION</h2>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<p><span class="command"><strong>host</strong></span>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein is a simple utility for performing DNS lookups.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein It is normally used to convert names to IP addresses and vice versa.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein When no arguments or options are given,
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <span class="command"><strong>host</strong></span>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein prints a short summary of its command line arguments and options.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein </p>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<p><em class="parameter"><code>name</code></em> is the domain name that is to be
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein looked
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein up. It can also be a dotted-decimal IPv4 address or a colon-delimited
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein IPv6 address, in which case <span class="command"><strong>host</strong></span> will by
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein default
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein perform a reverse lookup for that address.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <em class="parameter"><code>server</code></em> is an optional argument which
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein is either
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein the name or IP address of the name server that <span class="command"><strong>host</strong></span>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein should query instead of the server or servers listed in
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <code class="filename">/etc/resolv.conf</code>.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein </p>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein</div>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<div class="refsection">
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<a name="id-1.14.4.8"></a><h2>OPTIONS</h2>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<div class="variablelist"><dl class="variablelist">
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<dt><span class="term">-4</span></dt>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<dd><p>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein Use IPv4 only for query transport.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein See also the <code class="option">-6</code> option.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein </p></dd>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<dt><span class="term">-6</span></dt>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<dd><p>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein Use IPv6 only for query transport.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein See also the <code class="option">-4</code> option.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein </p></dd>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<dt><span class="term">-a</span></dt>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<dd><p>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein "All". The <code class="option">-a</code> option is normally equivalent
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein to <code class="option">-v -t <code class="literal">ANY</code></code>.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein It also affects the behaviour of the <code class="option">-l</code>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein list zone option.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein </p></dd>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<dt><span class="term">-c <em class="replaceable"><code>class</code></em></span></dt>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<dd><p>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein Query class: This can be used to lookup HS (Hesiod) or CH
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein (Chaosnet) class resource records. The default class is IN
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein (Internet).
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein </p></dd>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<dt><span class="term">-C</span></dt>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<dd><p>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein Check consistency: <span class="command"><strong>host</strong></span> will query the
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein SOA records for zone <em class="parameter"><code>name</code></em> from all
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein the listed authoritative name servers for that zone. The
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein list of name servers is defined by the NS records that are
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein found for the zone.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein </p></dd>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<dt><span class="term">-d</span></dt>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<dd><p>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein Print debugging traces.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein Equivalent to the <code class="option">-v</code> verbose option.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein </p></dd>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<dt><span class="term">-i</span></dt>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<dd><p>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein Obsolete.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein Use the IP6.INT domain for reverse lookups of IPv6
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein addresses as defined in RFC1886 and deprecated in RFC4159.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein The default is to use IP6.ARPA as specified in RFC3596.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein </p></dd>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<dt><span class="term">-l</span></dt>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<dd>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<p>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein List zone:
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein The <span class="command"><strong>host</strong></span> command performs a zone transfer of
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein zone <em class="parameter"><code>name</code></em> and prints out the NS,
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein PTR and address records (A/AAAA).
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein </p>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<p>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein Together, the <code class="option">-l -a</code>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein options print all records in the zone.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein </p>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein</dd>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<dt><span class="term">-N <em class="replaceable"><code>ndots</code></em></span></dt>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<dd><p>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein The number of dots that have to be
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein in <em class="parameter"><code>name</code></em> for it to be considered
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein absolute. The default value is that defined using the
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein ndots statement in <code class="filename">/etc/resolv.conf</code>,
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein or 1 if no ndots statement is present. Names with fewer
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein dots are interpreted as relative names and will be
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein searched for in the domains listed in
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein the <span class="type">search</span> or <span class="type">domain</span> directive
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein in <code class="filename">/etc/resolv.conf</code>.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein </p></dd>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<dt><span class="term">-r</span></dt>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<dd><p>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein Non-recursive query:
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein Setting this option clears the RD (recursion desired) bit
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein in the query. This should mean that the name server
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein receiving the query will not attempt to
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein resolve <em class="parameter"><code>name</code></em>.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein The <code class="option">-r</code> option
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein enables <span class="command"><strong>host</strong></span> to mimic the behavior of a
name server by making non-recursive queries and expecting
to receive answers to those queries that can be
referrals to other name servers.
</p></dd>
<dt><span class="term">-R <em class="replaceable"><code>number</code></em></span></dt>
<dd><p>
Number of retries for UDP queries:
If <em class="parameter"><code>number</code></em> is negative or zero, the
number of retries will default to 1. The default value is
1, or the value of the <em class="parameter"><code>attempts</code></em>
option in <code class="filename">/etc/resolv.conf</code>, if set.
</p></dd>
<dt><span class="term">-s</span></dt>
<dd><p>
Do <span class="emphasis"><em>not</em></span> send the query to the next
nameserver if any server responds with a SERVFAIL
response, which is the reverse of normal stub resolver
behavior.
</p></dd>
<dt><span class="term">-t <em class="replaceable"><code>type</code></em></span></dt>
<dd>
<p>
Query type:
The <em class="parameter"><code>type</code></em> argument can be any
recognized query type: CNAME, NS, SOA, TXT, DNSKEY, AXFR, etc.
</p>
<p>
When no query type is specified, <span class="command"><strong>host</strong></span>
automatically selects an appropriate query type. By default, it
looks for A, AAAA, and MX records.
If the <code class="option">-C</code> option is given, queries will
be made for SOA records.
If <em class="parameter"><code>name</code></em> is a dotted-decimal IPv4
address or colon-delimited IPv6
address, <span class="command"><strong>host</strong></span> will query for PTR
records.
</p>
<p>
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
(like <code class="option">-t <code class="literal">IXFR=12345678</code></code>).
</p>
</dd>
<dt><span class="term">-T</span></dt>
<dd><p>
TCP:
By default, <span class="command"><strong>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></dd>
<dt><span class="term">-m <em class="replaceable"><code>flag</code></em></span></dt>
<dd><p>
Memory usage debugging: the flag can
be <em class="parameter"><code>record</code></em>, <em class="parameter"><code>usage</code></em>,
or <em class="parameter"><code>trace</code></em>. You can specify
the <code class="option">-m</code> option more than once to set
multiple flags.
</p></dd>
<dt><span class="term">-v</span></dt>
<dd><p>
Verbose output.
Equivalent to the <code class="option">-d</code> debug option.
Verbose output can also be enabled by setting
the <em class="parameter"><code>debug</code></em> option
in <code class="filename">/etc/resolv.conf</code>.
</p></dd>
<dt><span class="term">-V</span></dt>
<dd><p>
Print the version number and exit.
</p></dd>
<dt><span class="term">-w</span></dt>
<dd><p>
Wait forever: The query timeout is set to the maximum possible.
See also the <code class="option">-W</code> option.
</p></dd>
<dt><span class="term">-W <em class="replaceable"><code>wait</code></em></span></dt>
<dd>
<p>
Timeout: Wait for up to <em class="parameter"><code>wait</code></em>
seconds for a reply. If <em class="parameter"><code>wait</code></em> is
less than one, the wait interval is set to one second.
</p>
<p>
By default, <span class="command"><strong>host</strong></span> will wait for 5
seconds for UDP responses and 10 seconds for TCP
connections. These defaults can be overridden by
the <em class="parameter"><code>timeout</code></em> option
in <code class="filename">/etc/resolv.conf</code>.
</p>
<p>
See also the <code class="option">-w</code> option.
</p>
</dd>
</dl></div>
</div>
<div class="refsection">
<a name="id-1.14.4.9"></a><h2>IDN SUPPORT</h2>
<p>
If <span class="command"><strong>host</strong></span> has been built with IDN (internationalized
domain name) support, it can accept and display non-ASCII domain names.
<span class="command"><strong>host</strong></span> appropriately converts character encoding of
domain name before sending a request to DNS server or displaying a
reply from the server.
If you'd like to turn off the IDN support for some reason, defines
the <code class="envar">IDN_DISABLE</code> environment variable.
The IDN support is disabled if the variable is set when
<span class="command"><strong>host</strong></span> runs.
</p>
</div>
<div class="refsection">
<a name="id-1.14.4.10"></a><h2>FILES</h2>
<p><code class="filename">/etc/resolv.conf</code>
</p>
</div>
<div class="refsection">
<a name="id-1.14.4.11"></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>
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