<!DOCTYPE book [

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

<info>

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

</info>

<refentryinfo>

<corpname>ISC</corpname>

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

</refentryinfo>

<refmeta>

<refentrytitle>host</refentrytitle>

<manvolnum>1</manvolnum>

<refmiscinfo>BIND9</refmiscinfo>

</refmeta>

<refnamediv>

<refname>host</refname>

<refpurpose>DNS lookup utility</refpurpose>

</refnamediv>

<docinfo>

<copyright>

<year>2004</year>

<year>2005</year>

<year>2007</year>

<year>2008</year>

<year>2009</year>

<year>2014</year>

<year>2015</year>

<year>2016</year>

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

</copyright>

<copyright>

<year>2000</year>

<year>2001</year>

<year>2002</year>

<holder>Internet Software Consortium.</holder>

</copyright>

</docinfo>

<refsynopsisdiv>

<cmdsynopsis sepchar=" ">

<command>host</command>

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

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

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

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

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

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

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

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

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

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

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

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

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

</cmdsynopsis>

</refsynopsisdiv>

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

<para><command>host</command>

is a simple utility for performing DNS lookups.

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

When no arguments or options are given,

<command>host</command>

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

</para>

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

looked

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

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

default

perform a reverse lookup for that address.

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

is either

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

should query instead of the server or servers listed in

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

</para>

</refsection>

<refsection><info><title>OPTIONS</title></info>

<variablelist>

<varlistentry>

<term>-4</term>

<listitem>

<para>

Use IPv4 only for query transport.

See also the <option>-6</option> option.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term>-6</term>

<listitem>

<para>

Use IPv6 only for query transport.

See also the <option>-4</option> option.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term>-a</term>

<listitem>

<para>

"All". The <option>-a</option> option is normally equivalent

to <option>-v -t <literal>ANY</literal></option>.

It also affects the behaviour of the <option>-l</option>

list zone option.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term>-c <replaceable class="parameter">class</replaceable></term>

<listitem>

<para>

Query class: This can be used to lookup HS (Hesiod) or CH

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

(Internet).

</para>

</listitem>

</varlistentry>

<varlistentry>

<term>-C</term>

<listitem>

<para>

Check consistency: <command>host</command> will query the

SOA records for zone <parameter>name</parameter> 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.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term>-d</term>

<listitem>

<para>

Print debugging traces.

Equivalent to the <option>-v</option> verbose option.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term>-i</term>

<listitem>

<para>

Obsolete.

Use the IP6.INT domain for reverse lookups of IPv6

addresses as defined in RFC1886 and deprecated in RFC4159.

The default is to use IP6.ARPA as specified in RFC3596.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term>-l</term>

<listitem>

<para>

List zone:

The <command>host</command> command performs a zone transfer of

zone <parameter>name</parameter> and prints out the NS,

PTR and address records (A/AAAA).

</para>

<para>

Together, the <option>-l -a</option>

options print all records in the zone.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term>-N <replaceable class="parameter">ndots</replaceable></term>

<listitem>

<para>

The number of dots that have to be

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

absolute. The default value is that defined using the

ndots statement in <filename>/etc/resolv.conf</filename>,

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 <type>search</type> or <type>domain</type> directive

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

</para>

</listitem>

</varlistentry>

<varlistentry>

<term>-r</term>

<listitem>

<para>

Non-recursive query:

Setting this option clears the RD (recursion desired) bit

in the query. This should mean that the name server

receiving the query will not attempt to

resolve <parameter>name</parameter>.

The <option>-r</option> option

enables <command>host</command> 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.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term>-R <replaceable class="parameter">number</replaceable></term>

<listitem>

<para>

Number of retries for UDP queries:

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

number of retries will default to 1. The default value is

1, or the value of the <parameter>attempts</parameter>

option in <filename>/etc/resolv.conf</filename>, if set.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term>-s</term>

<listitem>

<para>

Do <emphasis>not</emphasis> 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>

</listitem>

</varlistentry>

<varlistentry>

<term>-t <replaceable class="parameter">type</replaceable></term>

<listitem>

<para>

Query type:

The <parameter>type</parameter> argument can be any

recognized query type: CNAME, NS, SOA, TXT, DNSKEY, AXFR, etc.

</para>

<para>

When no query type is specified, <command>host</command>

automatically selects an appropriate query type. By default, it

looks for A, AAAA, and MX records.

If the <option>-C</option> option is given, queries will

be made for SOA records.

If <parameter>name</parameter> is a dotted-decimal IPv4

address or colon-delimited IPv6

address, <command>host</command> will query for PTR

records.

</para>

<para>

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 <option>-t <literal>IXFR=12345678</literal></option>).

</para>

</listitem>

</varlistentry>

<varlistentry>

<term>-T</term>

<listitem>

<para>

TCP:

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

queries. The <option>-T</option> 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.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term>-m <replaceable class="parameter">flag</replaceable></term>

<listitem>

<para>

Memory usage debugging: the flag can

be <parameter>record</parameter>, <parameter>usage</parameter>,

or <parameter>trace</parameter>. You can specify

the <option>-m</option> option more than once to set

multiple flags.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term>-v</term>

<listitem>

<para>

Verbose output.

Equivalent to the <option>-d</option> debug option.

Verbose output can also be enabled by setting

the <parameter>debug</parameter> option

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

</para>

</listitem>

</varlistentry>

<varlistentry>

<term>-V</term>

<listitem>

<para>

Print the version number and exit.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term>-w</term>

<listitem>

<para>

Wait forever: The query timeout is set to the maximum possible.

See also the <option>-W</option> option.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term>-W <replaceable class="parameter">wait</replaceable></term>

<listitem>

<para>

Timeout: Wait for up to <parameter>wait</parameter>

seconds for a reply. If <parameter>wait</parameter> is

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

</para>

<para>

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>

See also the <option>-w</option> option.

</para>

</listitem>

</varlistentry>

</variablelist>

</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>