da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin<!DOCTYPE book [

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin<!ENTITY mdash "&#8212;">]>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin<refentry xmlns="http://docbook.org/ns/docbook" version="5.0" xml:id="man.host">

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <info>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <date>2009-01-20</date>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin </info>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <refentryinfo>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <corpname>ISC</corpname>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <corpauthor>Internet Systems Consortium, Inc.</corpauthor>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin </refentryinfo>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <refmeta>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <refentrytitle>host</refentrytitle>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <manvolnum>1</manvolnum>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <refmiscinfo>BIND9</refmiscinfo>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin </refmeta>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <refnamediv>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <refname>host</refname>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <refpurpose>DNS lookup utility</refpurpose>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin </refnamediv>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <docinfo>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <copyright>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <year>2004</year>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <year>2005</year>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <year>2007</year>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <year>2008</year>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <year>2009</year>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <year>2014</year>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <year>2015</year>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <holder>Internet Systems Consortium, Inc. ("ISC")</holder>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin </copyright>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <copyright>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <year>2000</year>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <year>2001</year>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <year>2002</year>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <holder>Internet Software Consortium.</holder>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin </copyright>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin </docinfo>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <refsynopsisdiv>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <cmdsynopsis sepchar=" ">

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <command>host</command>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <arg choice="opt" rep="norepeat"><option>-aCdlnrsTwv</option></arg>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <arg choice="opt" rep="norepeat"><option>-c <replaceable class="parameter">class</replaceable></option></arg>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <arg choice="opt" rep="norepeat"><option>-N <replaceable class="parameter">ndots</replaceable></option></arg>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <arg choice="opt" rep="norepeat"><option>-R <replaceable class="parameter">number</replaceable></option></arg>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <arg choice="opt" rep="norepeat"><option>-t <replaceable class="parameter">type</replaceable></option></arg>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <arg choice="opt" rep="norepeat"><option>-W <replaceable class="parameter">wait</replaceable></option></arg>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <arg choice="opt" rep="norepeat"><option>-m <replaceable class="parameter">flag</replaceable></option></arg>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <arg choice="opt" rep="norepeat"><option>-4</option></arg>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <arg choice="opt" rep="norepeat"><option>-6</option></arg>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <arg choice="opt" rep="norepeat"><option>-v</option></arg>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <arg choice="opt" rep="norepeat"><option>-V</option></arg>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <arg choice="req" rep="norepeat">name</arg>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <arg choice="opt" rep="norepeat">server</arg>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin </cmdsynopsis>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin </refsynopsisdiv>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <refsection><info><title>DESCRIPTION</title></info>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <para><command>host</command>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin is a simple utility for performing DNS lookups.

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin It is normally used to convert names to IP addresses and vice versa.

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin When no arguments or options are given,

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <command>host</command>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin prints a short summary of its command line arguments and options.

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin </para>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <para><parameter>name</parameter> is the domain name that is to be

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin looked

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin up. It can also be a dotted-decimal IPv4 address or a colon-delimited

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin IPv6 address, in which case <command>host</command> will by

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin default

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin perform a reverse lookup for that address.

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <parameter>server</parameter> is an optional argument which

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin is either

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin the name or IP address of the name server that <command>host</command>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin should query instead of the server or servers listed in

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <filename>/etc/resolv.conf</filename>.

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin </para>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <para>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin The <option>-a</option> (all) option is equivalent to setting the

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <option>-v</option> option and asking <command>host</command> to make

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin a query of type ANY.

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin </para>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <para>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin When the <option>-C</option> option is used, <command>host</command>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin will attempt to display the SOA records for zone

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <parameter>name</parameter> from all the listed

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin authoritative name

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin servers for that zone. The list of name servers is defined by the NS

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin records that are found for the zone.

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin </para>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <para>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin The <option>-c</option> option instructs to make a DNS query of class

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <parameter>class</parameter>. This can be used to lookup

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin Hesiod or

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin Chaosnet class resource records. The default class is IN (Internet).

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin </para>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <para>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin Verbose output is generated by <command>host</command> when

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin the

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <option>-d</option> or <option>-v</option> option is used. The two

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin options are equivalent. They have been provided for backwards

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin compatibility. In previous versions, the <option>-d</option> option

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin switched on debugging traces and <option>-v</option> enabled verbose

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin output. Verbose output can also be enabled by setting the

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <parameter>debug</parameter> option in

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <filename>/etc/resolv.conf</filename>.

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin </para>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <para>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin List mode is selected by the <option>-l</option> option. This makes

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <command>host</command> perform a zone transfer for zone

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <parameter>name</parameter>. Transfer the zone printing out

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin the NS, PTR

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin and address records (A/AAAA). If combined with <option>-a</option>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin all records will be printed.

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin </para>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <para>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin The <option>-i</option>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin option specifies that reverse lookups of IPv6 addresses should

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin use the IP6.INT domain as defined in RFC1886.

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin The default is to use IP6.ARPA.

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin </para>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <para>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin The <option>-N</option> option sets the number of dots that have to be

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin in <parameter>name</parameter> for it to be considered

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin absolute. The

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin default value is that defined using the ndots statement in

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <filename>/etc/resolv.conf</filename>, or 1 if no ndots

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin statement is

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin present. Names with fewer dots are interpreted as relative names and

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin will be searched for in the domains listed in the <type>search</type>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin or <type>domain</type> directive in

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <filename>/etc/resolv.conf</filename>.

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin </para>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <para>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin The number of UDP retries for a lookup can be changed with the

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <option>-R</option> option. <parameter>number</parameter>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin indicates

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin how many times <command>host</command> will repeat a query

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin that does

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin not get answered. If

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <parameter>number</parameter> is negative or zero, the

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin number of

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin retries will default to 1. The default value is 1, or

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin the value of the <parameter>attempts</parameter> option in

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <filename>/etc/resolv.conf</filename>, if set.

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin </para>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <para>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin Non-recursive queries can be made via the <option>-r</option> option.

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin Setting this option clears the <type>RD</type> &mdash; recursion

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin desired &mdash; bit in the query which <command>host</command> makes.

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin This should mean that the name server receiving the query will not

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin attempt to resolve <parameter>name</parameter>. The

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <option>-r</option> option enables <command>host</command>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin to mimic

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin the behavior of a name server by making non-recursive queries and

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin expecting to receive answers to those queries that are usually

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin referrals to other name servers.

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin </para>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <para>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin By default, <command>host</command> uses UDP when making

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin queries. The

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <option>-T</option> option makes it use a TCP connection when querying

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin the name server. TCP will be automatically selected for queries that

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin require it, such as zone transfer (AXFR) requests.

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin </para>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <para>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin The <option>-4</option> option forces <command>host</command> to only

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin use IPv4 query transport. The <option>-6</option> option forces

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <command>host</command> to only use IPv6 query transport.

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin </para>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <para>

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin The <option>-t</option> option is used to select the query type.

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <parameter>type</parameter> can be any recognized query

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin type: CNAME,

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin NS, SOA, SIG, KEY, AXFR, etc. When no query type is specified,

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <command>host</command> automatically selects an appropriate

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin query

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin type. By default, it looks for A, AAAA, and MX records, but if the

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin <option>-C</option> option was given, queries will be made for SOA

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin records, and if <parameter>name</parameter> is a

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin dotted-decimal IPv4

address or colon-delimited IPv6 address, <command>host</command> 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).

</para>

<para>

The time to wait for a reply can be controlled through the

<option>-W</option> and <option>-w</option> options. The

<option>-W</option> option makes <command>host</command>

wait for

<parameter>wait</parameter> seconds. If <parameter>wait</parameter>

is less than one, the wait interval is set to one second. When the

<option>-w</option> option is used, <command>host</command>

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. By default, <command>host</command>

will wait for 5 seconds for UDP responses and 10 seconds for TCP

connections. These defaults can be overridden by the

<parameter>timeout</parameter> option in

<filename>/etc/resolv.conf</filename>.

</para>

<para>

The <option>-s</option> option tells <command>host</command>

<emphasis>not</emphasis> to send the query to the next nameserver

if any server responds with a SERVFAIL response, which is the

reverse of normal stub resolver behavior.

</para>

<para>

The <option>-m</option> can be used to set the memory usage debugging

flags

<parameter>record</parameter>, <parameter>usage</parameter> and

<parameter>trace</parameter>.

</para>

<para>

The <option>-V</option> option causes <command>host</command>

to print the version number and exit.

</para>

</refsection>

<refsection><info><title>IDN SUPPORT</title></info>

<para>

If <command>host</command> has been built with IDN (internationalized

domain name) support, it can accept and display non-ASCII domain names.

<command>host</command> 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 <envar>IDN_DISABLE</envar> environment variable.

The IDN support is disabled if the variable is set when

<command>host</command> runs.

</para>

</refsection>

<refsection><info><title>FILES</title></info>

<para><filename>/etc/resolv.conf</filename>

</para>

</refsection>

<refsection><info><title>SEE ALSO</title></info>

<para><citerefentry>

<refentrytitle>dig</refentrytitle><manvolnum>1</manvolnum>

</citerefentry>,

<citerefentry>

<refentrytitle>named</refentrytitle><manvolnum>8</manvolnum>

</citerefentry>.

</para>

</refsection>

</refentry>