system/doc/embedded/embedded_solaris.xml

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<!DOCTYPE chapter SYSTEM "chapter.dtd">

<chapter>
  <header>
    <copyright>
      <year>1997</year><year>2016</year>
      <holder>Ericsson AB. All Rights Reserved.</holder>
    </copyright>
    <legalnotice>
      Licensed under the Apache License, Version 2.0 (the "License");
      you may not use this file except in compliance with the License.
      You may obtain a copy of the License at
 
          http://www.apache.org/licenses/LICENSE-2.0

      Unless required by applicable law or agreed to in writing, software
      distributed under the License is distributed on an "AS IS" BASIS,
      WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
      See the License for the specific language governing permissions and
      limitations under the License.
    
    </legalnotice>

    <title>Embedded Solaris</title>
    <prepared>Fredrik Tillman</prepared>
    <responsible></responsible>
    <docno>ETX/B/SFP/TILLMAN:96-001</docno>
    <approved></approved>
    <checked></checked>
    <date>2000-10-17</date>
    <rev>B</rev>
    <file>embedded_solaris.xml</file>
  </header>
  <marker id="embedded solaris"></marker>

  <p>This section describes the operating system-specific parts
  of OTP that relate to Solaris.</p>

  <section>
    <title>Memory Use</title>
    <p>Solaris takes about 17 MB of RAM on a system with 64 MB of
      total RAM. This leaves about 47 MB for the applications. If
      the system uses swapping, these figures cannot be improved
      because unnecessary daemon processes are swapped out. However,
      if swapping is disabled, or if the swap space is of limited
      resource in the system, it becomes necessary to kill off
      unnecessary daemon processes.</p>
  </section>

  <section>
    <title>Disk Space Use</title>
    <p>The disk space required by Solaris can be minimized by using the
      Core User support installation. It requires about 80 MB of
      disk space. This installs only the minimum software required to
      boot and run Solaris. The disk space can be further reduced by
      deleting unnecessary individual files. However, unless disk
      space is a critical resource the effort required and the risks
      involved cannot be justified.</p>
  </section>

  <section>
    <title>Installing an Embedded System</title>
    <p>This section is about installing an embedded system.
      The following topics are considered:
    </p>
    <list type="bulleted">
      <item>Creating user and installation directory</item>
      <item>Installing an embedded system</item>
      <item>Configuring automatic start at boot</item>
      <item>Making a hardware watchdog available</item>
      <item>Changing permission for reboot</item>
      <item>Setting TERM environment variable</item>
      <item>Adding patches</item>
      <item>Installing module os_sup in application os_mon</item>
    </list>
    <p>Several of the procedures in this section require expert
      knowledge of the Solaris operating system. For most of them
      super user privilege is needed.</p>

    <section>
      <title>Creating User and Installation Directory</title>
      <p>It is recommended that the embedded environment is run by an
        ordinary user, that is, a user who does not have super user
        privileges.</p>
      <p>In this section, it is assumed that the username is
        <c>otpuser</c> and that the home directory of that user is:</p>
      <pre>
        /export/home/otpuser</pre>
      <p>It is also assumed that in the home directory of
        <c>otpuser</c>, there is a directory named <c>otp</c>, the
        full path of which is:</p>
      <pre>
        /export/home/otpuser/otp</pre>
      <p>This directory is the <em>installation directory</em> of the
        embedded environment.</p>
    </section>

    <section>
      <title>Installing an Embedded System</title>
      <p>The procedure for installing an embedded system
        is the same as for an ordinary system (see
	Installation Guide), except for the following:</p>
      <list type="bulleted">
        <item>The (compressed) tape archive file is to be extracted in
	the installation directory defined above.</item>
        <item>It is not needed to link the start script to a standard
	directory like <c>/usr/local/bin</c>.</item>
      </list>
    </section>

    <section>
      <title>Configuring Automatic Start at Boot</title>
      <p>A true embedded system must start when the system boots.
        This section accounts for the necessary configurations
        needed to achieve that.</p>
      <p>The embedded system and all the applications start
        automatically if the script file shown below is added to
        directory <c>/etc/rc3.d</c>. The file must be owned and
        readable by <c>root</c>. Its name cannot be arbitrarily
        assigned; the following name is recommended:</p>
      <pre>
        S75otp.system</pre>
      <p>For more details on initialization (and termination)
        scripts, and naming thereof, see the Solaris documentation.</p>
      <pre>
#!/bin/sh
#  
#  File name:  S75otp.system
#  Purpose:    Automatically starts Erlang and applications when the 
#              system starts
#  Author:     janne@erlang.ericsson.se
#  Resides in: /etc/rc3.d
#

if [ ! -d /usr/bin ]
then                    # /usr not mounted
        exit
fi

killproc() {            # kill the named process(es)
        pid=`/usr/bin/ps -e |
             /usr/bin/grep -w $1 |
             /usr/bin/sed -e 's/^  *//' -e 's/ .*//'`
        [ "$pid" != "" ] &amp;&amp; kill $pid
}

# Start/stop processes required for Erlang

case "$1" in
'start')
        # Start the Erlang emulator
        #
        su - otpuser -c "/export/home/otpuser/otp/bin/start" &amp;
        ;;
'stop')
        killproc beam
        ;;
*)
        echo "Usage: $0 { start | stop }"
        ;;
esac</pre>
      <p>File <c>/export/home/otpuser/otp/bin/start</c> referred to
        in the above script is precisely the <c>start</c> script
        described in <em>Starting Erlang</em>. The
        script variable <c>OTP_ROOT</c> in that <c>start</c> script
        corresponds to the following example path used in this
	section:</p>
      <pre>
        /export/home/otpuser/otp</pre>
      <p>The <c>start</c> script is to be edited accordingly.</p>
      <p>Use of the <c>killproc</c> procedure in the above script can
        be combined with a call to <c>erl_call</c>, for example:</p>
      <pre>
        $SOME_PATH/erl_call -n Node init stop</pre>
      <p>To take Erlang down gracefully, see the <c>erl_call(1)</c>
        manual page in <c>erl_interface</c> for details on the use
	of <c>erl_call</c>. However,
	that requires that Erlang runs as a distributed node, which is
        not always the case.</p>
      <p>The <c>killproc</c> procedure is not to be removed. The
        purpose is here to move from run level 3 (multi-user mode with
        networking resources) to run level 2 (multi-user mode without
        such resources), in which Erlang is not to run.</p>
    </section>

    <section>
      <title>Making Hardware Watchdog Available</title>
      <p>For Solaris running on VME boards from Force Computers,
        the onboard hardware watchdog can be activated,
	provided a VME bus driver is added to the operating system
        (see also Installation Problems).</p>
      <p>See also the <c>heart(3)</c> manual page in Kernel.</p>
    </section>

    <section>
      <title>Changing Permissions for Reboot</title>
      <p>If the <c>HEART_COMMAND</c> environment variable is to be set
        in the <c>start</c> script in
	<em>Starting Erlang</em>, and if the value is to be set to the
        path of the Solaris <c>reboot</c> command, that is:</p>
      <pre>
        HEART_COMMAND=/usr/sbin/reboot</pre>
      <p>then the ownership and file permissions for
      <c>/usr/sbin/reboot</c> must be changed as follows:</p>
      <pre>
        chown 0 /usr/sbin/reboot
        chmod 4755 /usr/sbin/reboot</pre>
      <p>See also the <c>heart(3)</c> manual page in Kernel.</p>
    </section>

    <section>
      <title>Setting TERM Environment Variable</title>
      <p>When the Erlang runtime system is automatically started from
        the <c>S75otp.system</c> script, the <c>TERM</c> environment
        variable must be set. The following is a minimal setting:</p>
      <pre>
        TERM=sun</pre>
      <p>This is to be added to the <c>start</c> script.</p>
    </section>

    <section>
      <title>Adding Patches</title>
      <p>For proper functioning of flushing file system data to disk on
        Solaris 2.5.1, the version-specific patch with number
        103640-02 must be added to the operating system. Other
	patches might be needed, see the release README file
        <c><![CDATA[<ERL_INSTALL_DIR>/README]]></c>.</p>
    </section>

    <section>
      <title>Installing Module os_sup in Application os_mon</title>
      <p>The following four installation procedures require super user
        privilege:</p>

	<section>
	  <title>Installation</title>
	  <list type="bulleted">
	    <item><em>Make a copy of the Solaris standard configuration
	    file for <c>syslogd</c>:</em>
	    <list type="bulleted">
	      <item>Make a copy of the Solaris standard configuration
	      file for <c>syslogd</c>. This file is usually named
	      <c>syslog.conf</c> and found in directory <c>/etc</c>.</item>
              <item>The filename of the copy must be <c>syslog.conf.ORIG</c>.
	      The directory location is optional; usually it is <c>/etc</c>.
	      A simple way to do this is to issue the following command:
	      <code type="none">
cp /etc/syslog.conf /etc/syslog.conf.ORIG</code>
              </item>
	    </list>
	    </item>
	    <item><em>Make an Erlang-specific configuration file for
	    <c>syslogd</c>:</em>
	    <list type="bulleted">
	      <item>Make an edited copy of the backup copy previously
	      made.</item>
              <item>The filename must be <c>syslog.conf.OTP</c>. The
	      path must be the same as the backup copy.</item>
              <item>The format of the configuration file is found in the
	      <c>syslog.conf(5)</c> manual page, by issuing the command
	      <c>man syslog.conf</c>.</item>
              <item>Usually a line is added that is to state:
	      <list type="bulleted">
		<item>Which types of information that is to be
		supervised by Erlang</item>
		<item>The name of the file (actually a named pipe) that
		is to receive the information</item>
	      </list>
	      </item>
	      <item>If, for example, only information originating from
	      the UNIX kernel is to be supervised, the line is to
	      begin with <c>kern.LEVEL</c>. For the possible
	      values of <c>LEVEL</c>, see <c>syslog.conf(5)</c>.</item>
	      <item>After at least one tab-character, the line added is to
	      contain the full name of the named pipe where <c>syslogd</c>
	      writes its information. The path must be the same as for the
	      files <c>syslog.conf.ORIG</c> and <c>syslog.conf.OTP</c>.
	      The filename must be <c>syslog.otp</c>.</item>
	      <item>If the directory for the files <c>syslog.conf.ORIG</c>
	      and <c>syslog.conf.OTP</c> is <c>/etc</c>, the line in
	      <c>syslog.conf.OTP</c> is as follows:
	      <code type="none">
kern.LEVEL                /etc/syslog.otp</code>
	      </item>
	    </list>
	    </item>
	    <item><em>Check the file privileges of the configuration
	    files:</em>
	    <list type="bulleted">
	      <item>The configuration files is to have <c>rw-r--r--</c>
	      file privileges and be owned by root.</item>
              <item>A simple way to do this is to issue these commands:
	      <code type="none">
chmod 644 /etc/syslog.conf
chmod 644 /etc/syslog.conf.ORIG
chmod 644 /etc/syslog.conf.OTP</code>
	      </item>
              <item>Notice that if the files <c>syslog.conf.ORIG</c> and
	      <c>syslog.conf.OTP</c> are not in directory <c>/etc</c>,
	      the file path in the second and third command must be
	      modified.</item>
	    </list>
	    </item>
	    <item><em>Modify file privileges and ownership of the
	    <c>mod_syslog</c> utility:</em>
	    <list type="bulleted">
	      <item>The file privileges and ownership of the
	      <c>mod_syslog</c> utility must be modified.</item>
              <item><p>The full name of the binary executable file is
	      derived from the position of application <c>os_mon</c>
	      in the file system by adding
	      <c>/priv/bin/mod_syslog</c>. The generic full name
	      of the binary executable file is thus:</p>
	      <code type="none"><![CDATA[
<OTP_ROOT>/lib/os_mon-<REV>/priv/bin/mod_syslog]]></code>
	      <p><em>Example:</em> If the path to <c>otp-root</c> is
	      <c>/usr/otp</c>, then the path to the <c>os_mon</c>
	      application is <c>/usr/otp/lib/os_mon-1.0</c>
	      (assuming revision 1.0) and the full name of the
	      binary executable file is
	      <c>/usr/otp/lib/os_mon-1.0/priv/bin/mod_syslog</c>.</p>
	      </item>
	      <item>The binary executable file must be owned by root,
	      have <c>rwsr-xr-x</c> file privileges, in particular
	      the <c>setuid</c> bit of the user must be set.</item>
              <item><p>A simple way to do this is to issue the following
	      commands:</p>
	      <code type="none"><![CDATA[
cd <OTP_ROOT>/lib/os_mon-<REV>/priv/bin/mod_syslog
chmod 4755 mod_syslog
chown root mod_syslog]]></code>
	    </item>
	  </list>
	</item>
      </list>
    </section>

    <section>
      <title>Testing the Application Configuration File</title>
      <p>The following procedure does not require root privilege:</p>
      <list type="bulleted">
	<item>Ensure that the configuration parameters for the
	<c>os_sup</c> module in the <c>os_mon</c> application
	are correct.</item>
	<item><p>Browse the application configuration file (do
	<em>not</em> edit it). The full name of the application
	configuration file is derived from the position of the
	<c>os_mon</c> application in the file system by adding
	<c>/ebin/os_mon.app</c>.</p>
	<p>The generic full name of the file is thus:</p>
	<code type="none"><![CDATA[
<OTP_ROOT>/lib/os_mon-<REV>/ebin/os_mon.app.]]></code>
	<p><em>Example:</em> If the path to <c>otp-root</c> is
	<c>/usr/otp</c>, then the path to the <c>os_mon</c> application
	is <c>/usr/otp/lib/os_mon-1.0 </c> (assuming revision 1.0) and
	the full name of the binary executable file is
	<c>/usr/otp/lib/os_mon-1.0/ebin/os_mon.app</c>.</p>
	</item>
	<item>Ensure that the following configuration parameters have
	correct values:</item>
        </list>

	<table>
          <row>
            <cell align="left" valign="top"><em>Parameter</em></cell>
            <cell align="left" valign="top"><em>Function</em></cell>
            <cell align="left" valign="top"><em>Standard value</em></cell>
          </row>
          <row>
            <cell align="left" valign="middle"><c>start_os_sup</c></cell>
            <cell align="left" valign="middle">Specifies if <c>os_sup</c>
	    is to be started or not.</cell>
            <cell align="left" valign="middle"><c>true</c> for the
	    first instance on the hardware; <c>false</c> for the
	    other instances</cell>
          </row>
          <row>
            <cell align="left" valign="middle"><c>os_sup_own</c></cell>
            <cell align="left" valign="middle">The directory for
	    (1) back-up copy and (2) Erlang-specific configuration
	    file for <c>syslogd</c></cell>
            <cell align="left" valign="middle"><c>"/etc"</c></cell>
          </row>
          <row>
            <cell align="left" valign="middle"><c>os_sup_syslogconf</c></cell>
            <cell align="left" valign="middle">The full name for the
	    Solaris standard configuration file for <c>syslogd</c></cell>
            <cell align="left" valign="middle"><c>"/etc/syslog.conf"</c></cell>
          </row>
          <row>
            <cell align="left" valign="middle"><c>error_tag</c></cell>
            <cell align="left" valign="middle">The tag for the
	    messages that are sent to the error logger in the Erlang
	    runtime system</cell>
            <cell align="left" valign="middle"><c>std_error</c></cell>
          </row>
          <tcaption>Configuration Parameters</tcaption>
        </table>

        <p>If the values listed in <c>os_mon.app</c> do not suit
          your needs, do <em>not</em> edit that file. Instead
          <em>override</em> the values in a <em>system configuration
	  file</em>, the full pathname of which is given
          on the command line to <c>erl</c>.</p>
        <p><em>Example:</em> Contents of an application configuration
	  file:</p>
	  <pre>
          [{os_mon, [{start_os_sup, true}, {os_sup_own, "/etc"}, 
          {os_sup_syslogconf, "/etc/syslog.conf"}, {os_sup_errortag, std_error}]}].</pre>
    </section>

    <section>
      <title>Related Documents</title>
      <p>See the <c>os_mon(3)</c> application,
      the <c>application(3)</c> manual page in Kernel,
      and the <c>erl(1)</c> manual page in ERTS.</p>
    </section>
  </section>

  <section>
    <title>Installation Problems</title>
      <p>The hardware watchdog timer, which is controlled by the
        <c>heart</c> port program, requires package <c>FORCEvme</c>,
        which contains the VME bus driver, to be
        installed. However, this driver can clash with the Sun
        <c>mcp</c> driver and cause the system to refuse to
        boot. To cure this problem, the following lines are
	to be added to <c>/etc/system</c>:</p>
      <list type="bulleted">
        <item><c>exclude: drv/mcp</c></item>
        <item><c>exclude: drv/mcpzsa</c></item>
        <item><c>exclude: drv/mcpp</c></item>
      </list>
      <warning>
        <p>It is recommended to add these lines to avoid a clash.
	The clash can make it impossible to boot the system.</p>
      </warning>
    </section>
  </section>

  <section>
    <title>Starting Erlang</title>
    <p>This section describes how an embedded system is started. Four
      programs are involved and they normally reside in the directory
      <c><![CDATA[<ERL_INSTALL_DIR>/bin]]></c>. The only exception is
      the <c>start</c> program, which can be located anywhere, and
      is also the only program that must be modified by the user.</p>
    <p>In an embedded system, there is usually no interactive shell.
      However, an operator can attach to the Erlang
      system by command <c>to_erl</c>. The operator is then
      connected to the Erlang shell and can give ordinary Erlang
      commands. All interaction with the system through this shell is
      logged in a special directory.</p>
    <p>Basically, the procedure is as follows:</p>
    <list type="bulleted">
      <item>The <c>start</c> program is called when the machine
      is started.</item>
      <item>It calls <c>run_erl</c>, which sets up things so the
      operator can attach to the system.</item>
      <item>It calls <c>start_erl</c>, which calls the correct
      version of <c>erlexec</c> (which is located in
      <c><![CDATA[<ERL_INSTALL_DIR>/erts-EVsn/bin]]></c>) with the
      correct <c>boot</c> and <c>config</c> files.</item>
    </list>
  </section>

  <section>
    <title>Programs</title>
    <section>
      <title>start</title>
      <p>This program is called when the machine is started. It can
        be modified or rewritten to suit a special system. By
        default, it must be called <c>start</c> and reside in
        <c><![CDATA[<ERL_INSTALL_DIR>/bin]]></c>. Another start
	program can be used, by using configuration parameter
	<c>start_prg</c> in application SASL.</p>
      <p>The start program must call <c>run_erl</c> as shown below.
        It must also take an optional parameter, which defaults to
        <c><![CDATA[<ERL_INSTALL_DIR>/releases/start_erl.data]]></c>.</p>
      <p>This program is to set static parameters and environment
        variables such as <c>-sname Name</c> and <c>HEART_COMMAND</c>
        to reboot the machine.</p>
      <p>The <c><![CDATA[<RELDIR>]]></c> directory is where new release
        packets are installed, and where the release handler keeps
	information about releases. For more information, see the
	<c>release_handler(3)</c> manual page in SASL.</p>
      <p>The following script illustrates the default behaviour of the
        program:</p>
      <code type="none"><![CDATA[
#!/bin/sh
# Usage: start [DataFile]
#
ROOTDIR=/usr/local/otp

if [ -z "$RELDIR" ]
then
   RELDIR=$ROOTDIR/releases
fi

START_ERL_DATA=${1:-$RELDIR/start_erl.data}

$ROOTDIR/bin/run_erl /tmp/ $ROOTDIR/log "exec $ROOTDIR/bin/start_erl \ 
                     $ROOTDIR $RELDIR $START_ERL_DATA" > /dev/null 2>&1 &]]></code>
      <p>The following script illustrates a modification where the node
        is given the name <c>cp1</c>, and where the environment variables
        <c>HEART_COMMAND</c> and <c>TERM</c> have been added to the
        previous script:</p>
      <code type="none"><![CDATA[
#!/bin/sh
# Usage: start [DataFile]
#
HEART_COMMAND=/usr/sbin/reboot
TERM=sun
export HEART_COMMAND TERM

ROOTDIR=/usr/local/otp

if [ -z "$RELDIR" ]
then
   RELDIR=$ROOTDIR/releases
fi

START_ERL_DATA=${1:-$RELDIR/start_erl.data}

$ROOTDIR/bin/run_erl /tmp/ $ROOTDIR/log "exec $ROOTDIR/bin/start_erl \ 
      $ROOTDIR $RELDIR $START_ERL_DATA -heart -sname cp1" > /dev/null 2>&1 &]]></code>
      <p>If a diskless and/or read-only client node is about to start,
        file <c>start_erl.data</c> is located in the client directory at
        the master node. Thus, the <c>START_ERL_DATA</c> line is to look
        like:</p>
      <code type="none">
CLIENTDIR=$ROOTDIR/clients/clientname
START_ERL_DATA=${1:-$CLIENTDIR/bin/start_erl.data}</code>
    </section>

    <section>
      <title>run_erl</title>
      <p>This program is used to start the emulator, but you will not
        be connected to the shell. <c>to_erl</c> is used to connect to
        the Erlang shell.</p>
      <code type="none">
Usage: run_erl pipe_dir/ log_dir "exec command [parameters ...]"</code>
<p>Here:</p>
     <list type="bulleted">
       <item><c>pipe_dir/</c> is to be <c>/tmp/</c> (<c>to_erl</c>
       uses this name by default).</item>
       <item><c>log_dir</c> is where the log files are written.</item>
       <item><c>command [parameters]</c> is executed.</item>
       <item>Everything written to <c>stdin</c> and <c>stdout</c>
       is logged in <c>log_dir</c>.</item>
     </list>
     <p>Log files are written in <c>log_dir</c>. Each log file
       has a name of the form <c>erlang.log.N</c>, where N is a
       generation number, ranging from 1 to 5. Each log file holds up
       to 100 kB text. As time goes by, the following log files are
       found in the log file directory:</p>
       <code type="none">
erlang.log.1
erlang.log.1, erlang.log.2
erlang.log.1, erlang.log.2, erlang.log.3
erlang.log.1, erlang.log.2, erlang.log.3, erlang.log.4
erlang.log.2, erlang.log.3, erlang.log.4, erlang.log.5
erlang.log.3, erlang.log.4, erlang.log.5, erlang.log.1
...</code>
      <p>The most recent log file is the rightmost in each row. That
      is, the most recent file is the one with the highest number, or
      if there are already four files, the one before the skip.</p>
      <p>When a log file is opened (for appending or created), a time
        stamp is written to the file. If nothing has been written to
        the log files for 15 minutes, a record is inserted that says
        that we are still alive.</p>
    </section>

    <section>
      <title>to_erl</title>
      <p>This program is used to attach to a running Erlang runtime
        system, started with <c>run_erl</c>.</p>
      <code type="none">
Usage: to_erl [pipe_name | pipe_dir]</code>
      <p>Here <c>pipe_name</c> defaults to <c>/tmp/erlang.pipe.N</c>.</p>
      <p>To disconnect from the shell without exiting the Erlang
        system, type <c>Ctrl-D</c>.</p>
    </section>

    <section>
      <title>start_erl</title>
      <p>This program starts the Erlang emulator with parameters
        <c>-boot</c> and <c>-config</c> set. It reads data about
        where these files are located from a file named
        <c>start_erl.data</c>, which is located in
	<c><![CDATA[<RELDIR>]]></c>.
        Each new release introduces a new data file. This file is
        automatically generated by the release handler in Erlang.</p>
      <p>The following script illustrates the behaviour of the program:</p>
      <code type="none">
#!/bin/sh
#
# This program is called by run_erl. It starts
# the Erlang emulator and sets -boot and -config parameters.
# It should only be used at an embedded target system.
#
# Usage: start_erl RootDir RelDir DataFile [ErlFlags ...]
#
ROOTDIR=$1
shift
RELDIR=$1
shift
DataFile=$1
shift

ERTS_VSN=`awk '{print $1}' $DataFile`
VSN=`awk '{print $2}' $DataFile`

BINDIR=$ROOTDIR/erts-$ERTS_VSN/bin
EMU=beam
PROGNAME=`echo $0 | sed 's/.*\///'`
export EMU
export ROOTDIR
export BINDIR
export PROGNAME
export RELDIR

exec $BINDIR/erlexec -boot $RELDIR/$VSN/start -config $RELDIR/$VSN/sys $*</code>

      <p>If a diskless and/or read-only client node with the
        SASL configuration parameter <c>static_emulator</c> set
        to <c>true</c> is about to start, the <c>-boot</c> and
        <c>-config</c> flags must be changed.</p>
	<p>As such a client cannot
        read a new <c>start_erl.data</c> file (the file cannot
        be changed dynamically). The boot and config files are
        always fetched from the same place (but with new contents if
        a new release has been installed).</p>
	<p>The <c>release_handler</c>
        copies these files to the <c>bin</c> directory in the client
        directory at the master nodes whenever a new release is made
        permanent.</p>
	<p>Assuming the same <c>CLIENTDIR</c> as above, the last line
        is to look like:</p>
	<code type="none">
exec $BINDIR/erlexec -boot $CLIENTDIR/bin/start \ 
     -config $CLIENTDIR/bin/sys $*</code>
    </section>
  </section>
</chapter>