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<?xml version="1.0" encoding="latin1" ?>
<!DOCTYPE comref SYSTEM "comref.dtd">
<comref>
<header>
<copyright>
<year>1996</year><year>2009</year>
<holder>Ericsson AB. All Rights Reserved.</holder>
</copyright>
<legalnotice>
The contents of this file are subject to the Erlang Public License,
Version 1.1, (the "License"); you may not use this file except in
compliance with the License. You should have received a copy of the
Erlang Public License along with this software. If not, it can be
retrieved online at http://www.erlang.org/.
Software distributed under the License is distributed on an "AS IS"
basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
the License for the specific language governing rights and limitations
under the License.
</legalnotice>
<title>epmd</title>
<prepared>Claes Wikström</prepared>
<responsible></responsible>
<docno>1</docno>
<approved></approved>
<checked></checked>
<date>98-01-05</date>
<rev>A</rev>
<file>epmd.xml</file>
</header>
<com>epmd</com>
<comsummary>Erlang Port Mapper Daemon </comsummary>
<description>
<p>This daemon acts as a name server on all hosts involved in
distributed Erlang computations. When an Erlang node
starts, the node has a name and it obtains an address from the host
OS kernel.
The name and the address are sent to the
<c><![CDATA[epmd]]></c> daemon running on the local host.
In a TCP/IP environment, the address consists
of the IP address and a port number. The name of the node is
an atom on the form of <c><![CDATA[Name@Node]]></c>.
The job of the <c><![CDATA[epmd]]></c> daemon is to keep track of which
node name listens on which address. Hence, <c><![CDATA[epmd]]></c> map
symbolic node names to machine addresses.</p>
<p>The daemon is started automatically by the Erlang start-up script.</p>
<p>The program <c><![CDATA[epmd]]></c> can also be used for a variety of other
purposes, for example checking the DNS (Domain Name System)
configuration of a host.</p>
</description>
<funcs>
<func>
<name>epmd [-daemon] </name>
<fsummary>Start a name server as a daemon</fsummary>
<desc>
<p>Starts a name server as a daemon. If it has no argument, the
<c><![CDATA[epmd]]></c> runs as a normal program with the controlling terminal
of the shell in which it is started. Normally, it should run as a
daemon.</p>
</desc>
</func>
<func>
<name>epmd -names</name>
<fsummary>Request the names of the registered Erlang nodes on this host</fsummary>
<desc>
<p>Requests the names of the local Erlang nodes <c><![CDATA[epmd]]></c> has
registered.</p>
</desc>
</func>
<func>
<name>epmd -kill</name>
<fsummary>Kill the <c><![CDATA[epmd]]></c>process</fsummary>
<desc>
<p>Kills the <c><![CDATA[epmd]]></c> process.</p>
</desc>
</func>
<func>
<name>epmd -help</name>
<fsummary>List options</fsummary>
<desc>
<p>Write short info about the usage including some debugging
options not listed here.</p>
</desc>
</func>
</funcs>
<section>
<marker id="environment_variables"></marker>
<title>Environment variables</title>
<taglist>
<tag><c><![CDATA[ERL_EPMD_PORT]]></c></tag>
<item>
<p>This environment variable can contain the port number epmd will use.
The default port will work fine in most cases. A different port can
be specified to allow several instances of epmd, representing
independent clusters of nodes, to co-exist on the same host.
All nodes in a cluster must use the same epmd port number.</p>
</item>
</taglist>
</section>
<section>
<title>Logging</title>
<p>On some operating systems <em>syslog</em> will be used for
error reporting when epmd runs as an daemon. To enable
the error logging you have to edit <path unix="" windows="">/etc/syslog.conf</path>
file and add an entry</p>
<code type="none"><![CDATA[
!epmd
*.*<TABs>/var/log/epmd.log
]]></code>
<p>where <TABs> are at least one real tab character. Spaces will
silently be ignored.
</p>
</section>
</comref>
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