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IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT, - INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM - LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE - OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR - PERFORMANCE OF THIS SOFTWARE. --> <!-- $Id$ --> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> <title>host</title> <meta name="generator" content="DocBook XSL Stylesheets V1.71.1"> </head> <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="refentry" lang="en"> <a name="man.host"></a><div class="titlepage"></div> <div class="refnamediv"> <h2>Name</h2> <p>host — DNS lookup utility</p> </div> <div class="refsynopsisdiv"> <h2>Synopsis</h2> <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> </div> <div class="refsect1" lang="en"> <a name="id2543436"></a><h2>DESCRIPTION</h2> <p><span><strong class="command">host</strong></span> 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, <span><strong class="command">host</strong></span> prints a short summary of its command line arguments and options. </p> <p><em class="parameter"><code>name</code></em> 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 <span><strong class="command">host</strong></span> will by default perform a reverse lookup for that address. <em class="parameter"><code>server</code></em> is an optional argument which is either the name or IP address of the name server that <span><strong class="command">host</strong></span> should query instead of the server or servers listed in <code class="filename">/etc/resolv.conf</code>. </p> <p> The <code class="option">-a</code> (all) option is equivalent to setting the <code class="option">-v</code> option and asking <span><strong class="command">host</strong></span> to make a query of type ANY. </p> <p> When the <code class="option">-C</code> option is used, <span><strong class="command">host</strong></span> will attempt to display the SOA records for zone <em class="parameter"><code>name</code></em> 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. </p> <p> The <code class="option">-c</code> option instructs to make a DNS query of class <em class="parameter"><code>class</code></em>. This can be used to lookup Hesiod or Chaosnet class resource records. The default class is IN (Internet). </p> <p> Verbose output is generated by <span><strong class="command">host</strong></span> when the <code class="option">-d</code> or <code class="option">-v</code> option is used. The two options are equivalent. They have been provided for backwards compatibility. In previous versions, the <code class="option">-d</code> option switched on debugging traces and <code class="option">-v</code> enabled verbose output. </p> <p> List mode is selected by the <code class="option">-l</code> option. This makes <span><strong class="command">host</strong></span> perform a zone transfer for zone <em class="parameter"><code>name</code></em>. Transfer the zone printing out the NS, PTR and address records (A/AAAA). If combined with <code class="option">-a</code> all records will be printed. </p> <p> The <code class="option">-i</code> option specifies that reverse lookups of IPv6 addresses should use the IP6.INT domain as defined in RFC1886. The default is to use IP6.ARPA. </p> <p> The <code class="option">-N</code> option sets the number of dots that have to be in <em class="parameter"><code>name</code></em> for it to be considered absolute. The default value is that defined using the ndots statement in <code class="filename">/etc/resolv.conf</code>, 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 <span class="type">search</span> or <span class="type">domain</span> directive in <code class="filename">/etc/resolv.conf</code>. </p> <p> The number of UDP retries for a lookup can be changed with the <code class="option">-R</code> option. <em class="parameter"><code>number</code></em> indicates how many times <span><strong class="command">host</strong></span> will repeat a query that does not get answered. The default number of retries is 1. If <em class="parameter"><code>number</code></em> is negative or zero, the number of retries will default to 1. </p> <p> Non-recursive queries can be made via the <code class="option">-r</code> option. Setting this option clears the <span class="type">RD</span> — recursion desired — bit in the query which <span><strong class="command">host</strong></span> makes. This should mean that the name server receiving the query will not attempt to resolve <em class="parameter"><code>name</code></em>. The <code class="option">-r</code> option enables <span><strong class="command">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 are usually referrals to other name servers. </p> <p> By default, <span><strong class="command">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> <p> The <code class="option">-4</code> option forces <span><strong class="command">host</strong></span> to only use IPv4 query transport. The <code class="option">-6</code> option forces <span><strong class="command">host</strong></span> to only use IPv6 query transport. </p> <p> The <code class="option">-t</code> option is used to select the query type. <em class="parameter"><code>type</code></em> can be any recognized query type: CNAME, NS, SOA, SIG, KEY, AXFR, etc. When no query type is specified, <span><strong class="command">host</strong></span> automatically selects an appropriate query type. By default, it looks for A, AAAA, and MX records, but if the <code class="option">-C</code> option was given, queries will be made for SOA records, and if <em class="parameter"><code>name</code></em> is a dotted-decimal IPv4 address or colon-delimited IPv6 address, <span><strong class="command">host</strong></span> 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). </p> <p> The time to wait for a reply can be controlled through the <code class="option">-W</code> and <code class="option">-w</code> options. The <code class="option">-W</code> option makes <span><strong class="command">host</strong></span> wait for <em class="parameter"><code>wait</code></em> seconds. If <em class="parameter"><code>wait</code></em> is less than one, the wait interval is set to one second. When the <code class="option">-w</code> option is used, <span><strong class="command">host</strong></span> 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. </p> <p> The <code class="option">-s</code> option tells <span><strong class="command">host</strong></span> <span class="emphasis"><em>not</em></span> 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. </p> <p> The <code class="option">-m</code> can be used to set the memory usage debugging flags <em class="parameter"><code>record</code></em>, <em class="parameter"><code>usage</code></em> and <em class="parameter"><code>trace</code></em>. </p> </div> <div class="refsect1" lang="en"> <a name="id2543802"></a><h2>IDN SUPPORT</h2> <p> If <span><strong class="command">host</strong></span> has been built with IDN (internationalized domain name) support, it can accept and display non-ASCII domain names. <span><strong class="command">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><strong class="command">host</strong></span> runs. </p> </div> <div class="refsect1" lang="en"> <a name="id2543825"></a><h2>FILES</h2> <p><code class="filename">/etc/resolv.conf</code> </p> </div> <div class="refsect1" lang="en"> <a name="id2543836"></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> </div> </div></body> </html>