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1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo<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>
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo is a simple utility for performing DNS lookups.
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo It is normally used to convert names to IP addresses and vice versa.
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo When no arguments or options are given,
ba2e4443695ee6a6f420a35cd4fc3d3346d22932seb prints a short summary of its command line arguments and options.
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo<p><em class="parameter"><code>name</code></em> is the domain name that is to be
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo up. It can also be a dotted-decimal IPv4 address or a colon-delimited
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo IPv6 address, in which case <span><strong class="command">host</strong></span> will by
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo perform a reverse lookup for that address.
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo <em class="parameter"><code>server</code></em> is an optional argument which
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo the name or IP address of the name server that <span><strong class="command">host</strong></span>
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo should query instead of the server or servers listed in
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo The <code class="option">-a</code> (all) option is equivalent to setting the
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo <code class="option">-v</code> option and asking <span><strong class="command">host</strong></span> to make
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo a query of type ANY.
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo When the <code class="option">-C</code> option is used, <span><strong class="command">host</strong></span>
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo will attempt to display the SOA records for zone
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo <em class="parameter"><code>name</code></em> from all the listed
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo authoritative name
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo servers for that zone. The list of name servers is defined by the NS
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo records that are found for the zone.
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo The <code class="option">-c</code> option instructs to make a DNS query of class
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo <em class="parameter"><code>class</code></em>. This can be used to lookup
ba2e4443695ee6a6f420a35cd4fc3d3346d22932seb Chaosnet class resource records. The default class is IN (Internet).
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo Verbose output is generated by <span><strong class="command">host</strong></span> when
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo <code class="option">-d</code> or <code class="option">-v</code> option is used. The two
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo options are equivalent. They have been provided for backwards
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo compatibility. In previous versions, the <code class="option">-d</code> option
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo switched on debugging traces and <code class="option">-v</code> enabled verbose
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo List mode is selected by the <code class="option">-l</code> option. This makes
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo <span><strong class="command">host</strong></span> perform a zone transfer for zone
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo <em class="parameter"><code>name</code></em>. Transfer the zone printing out
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo the NS, PTR
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo and address records (A/AAAA). If combined with <code class="option">-a</code>
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo all records will be printed.
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo option specifies that reverse lookups of IPv6 addresses should
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo use the IP6.INT domain as defined in RFC1886.
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo The default is to use IP6.ARPA.
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo The <code class="option">-N</code> option sets the number of dots that have to be
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo in <em class="parameter"><code>name</code></em> for it to be considered
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo absolute. The
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo default value is that defined using the ndots statement in
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo <code class="filename">/etc/resolv.conf</code>, or 1 if no ndots
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo statement is
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo present. Names with fewer dots are interpreted as relative names and
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo will be searched for in the domains listed in the <span class="type">search</span>
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo The number of UDP retries for a lookup can be changed with the
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo <code class="option">-R</code> option. <em class="parameter"><code>number</code></em>
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo how many times <span><strong class="command">host</strong></span> will repeat a query
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo not get answered. The default number of retries is 1. If
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo <em class="parameter"><code>number</code></em> is negative or zero, the
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo retries will default to 1.
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo Non-recursive queries can be made via the <code class="option">-r</code> option.
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo Setting this option clears the <span class="type">RD</span> — recursion
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo desired — bit in the query which <span><strong class="command">host</strong></span> makes.
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo This should mean that the name server receiving the query will not
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo attempt to resolve <em class="parameter"><code>name</code></em>. The
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo <code class="option">-r</code> option enables <span><strong class="command">host</strong></span>
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo the behavior of a name server by making non-recursive queries and
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo expecting to receive answers to those queries that are usually
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo referrals to other name servers.
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo By default, <span><strong class="command">host</strong></span> uses UDP when making
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo queries. The
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo <code class="option">-T</code> option makes it use a TCP connection when querying
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo the name server. TCP will be automatically selected for queries that
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo require it, such as zone transfer (AXFR) requests.
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo The <code class="option">-4</code> option forces <span><strong class="command">host</strong></span> to only
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo use IPv4 query transport. The <code class="option">-6</code> option forces
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo <span><strong class="command">host</strong></span> to only use IPv6 query transport.
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo The <code class="option">-t</code> option is used to select the query type.
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo <em class="parameter"><code>type</code></em> can be any recognized query
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo type: CNAME,
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo NS, SOA, SIG, KEY, AXFR, etc. When no query type is specified,
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo <span><strong class="command">host</strong></span> automatically selects an appropriate
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo type. By default, it looks for A, AAAA, and MX records, but if the
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo <code class="option">-C</code> option was given, queries will be made for SOA
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo records, and if <em class="parameter"><code>name</code></em> is a
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo dotted-decimal IPv4
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo address or colon-delimited IPv6 address, <span><strong class="command">host</strong></span> will
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo query for PTR records. If a query type of IXFR is chosen the starting
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo serial number can be specified by appending an equal followed by the
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo starting serial number (e.g. -t IXFR=12345678).
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo The time to wait for a reply can be controlled through the
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo <code class="option">-W</code> and <code class="option">-w</code> options. The
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo <code class="option">-W</code> option makes <span><strong class="command">host</strong></span>
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo <em class="parameter"><code>wait</code></em> seconds. If <em class="parameter"><code>wait</code></em>
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo is less than one, the wait interval is set to one second. When the
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo <code class="option">-w</code> option is used, <span><strong class="command">host</strong></span>
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo effectively wait forever for a reply. The time to wait for a response
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo will be set to the number of seconds given by the hardware's maximum
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo value for an integer quantity.
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo The <code class="option">-s</code> option tells <span><strong class="command">host</strong></span>
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo <span class="emphasis"><em>not</em></span> to send the query to the next nameserver
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo if any server responds with a SERVFAIL response, which is the
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo reverse of normal stub resolver behavior.
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo The <code class="option">-m</code> can be used to set the memory usage debugging
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo <em class="parameter"><code>record</code></em>, <em class="parameter"><code>usage</code></em> and
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo If <span><strong class="command">host</strong></span> has been built with IDN (internationalized
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo domain name) support, it can accept and display non-ASCII domain names.
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo <span><strong class="command">host</strong></span> appropriately converts character encoding of
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo domain name before sending a request to DNS server or displaying a
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo reply from the server.
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo If you'd like to turn off the IDN support for some reason, defines
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo the <code class="envar">IDN_DISABLE</code> environment variable.
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo The IDN support is disabled if the variable is set when
1ae0874509b6811fdde1dfd46f0d93fd09867a3fheppo <span><strong class="command">host</strong></span> runs.
ba2e4443695ee6a6f420a35cd4fc3d3346d22932seb<p><span class="citerefentry"><span class="refentrytitle">dig</span>(1)</span>,
ba2e4443695ee6a6f420a35cd4fc3d3346d22932seb <span class="citerefentry"><span class="refentrytitle">named</span>(8)</span>.
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