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  <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>os_mon</title>
    <prepared></prepared>
    <docno></docno>
    <date></date>
    <rev></rev>
  </header>
  <app>os_mon</app>
  <appsummary>OS Monitoring Application</appsummary>
  <description>
    <p>The operating system monitor, OS_Mon, provides the following
      services:</p>
    <list type="bulleted">
      <item><seealso marker="cpu_sup">cpu_sup</seealso>
       CPU load and utilization supervision (Unix)</item>
      <item><seealso marker="disksup">disksup</seealso>
       Disk supervision(Unix, Windows)</item>
      <item><seealso marker="memsup">memsup</seealso>
       Memory supervision (Unix, Windows, VxWorks)</item>
      <item><seealso marker="os_sup">os_sup</seealso>
       Interface to OS system messages (Solaris, Windows)</item>
    </list>
    <p>To simplify usage of OS_Mon on distributed Erlang systems, it is
      not considered an error trying to use a service at a node where it
      is not available (either because OS_Mon is not running, or because
      the service is not available for that OS, or because the service
      is not started). Instead, a warning message is issued via
      <c>error_logger</c> and a dummy value is returned, which one is
      specified in the man pages for the respective services.</p>
  </description>

  <section>
    <title>Configuration</title>
    <p>When OS_Mon is started, by default all services available for
      the OS, except <c>os_sup</c>, are automatically started. This
      configuration can be changed using the following application
      configuration parameters:</p>
    <taglist>
      <tag><c>start_cpu_sup = bool()</c></tag>
      <item>
        <p>Specifies if <c>cpu_sup</c> should be started. Defaults to
          <c>true</c>.</p>
      </item>
      <tag><c>start_disksup = bool()</c></tag>
      <item>
        <p>Specifies if <c>disksup</c> should be started. Defaults to
          <c>true</c>.</p>
      </item>
      <tag><c>start_memsup = bool()</c></tag>
      <item>
        <p>Specifies if <c>memsup</c> should be started. Defaults to
          <c>true</c>.</p>
      </item>
      <tag><c>start_os_sup = bool()</c></tag>
      <item>
        <p>Specifies if <c>os_sup</c> should be started. Defaults to
          <c>false</c>.</p>
      </item>
    </taglist>
    <p>Configuration parameters effecting the different OS_Mon services
      are described in the respective man pages.</p>
    <p>See <seealso marker="kernel:config">config(4)</seealso> for
      information about how to change the value of configuration
      parameters.</p>
  </section>

  <section>
    <title>SNMP MIBs</title>
    <p>The following MIBs are defined in OS_Mon:</p>
    <taglist>
      <tag>OTP-OS-MON-MIB</tag>
      <item>
        <p>This MIB contains objects for instrumentation of disk,
          memory and CPU usage of the nodes in the system.</p>
      </item>
    </taglist>
    <p>The MIB is stored in the <c>mibs</c> directory.  It is defined
      in SNMPv2 SMI syntax. An SNMPv1 version of the MIB is delivered
      in the <c>mibs/v1</c> directory.</p>
    <p>The compiled MIB is located under <c>priv/mibs</c>, and
      the generated <c>.hrl</c> file under the <c>include</c> directory.
      To compile a MIB that IMPORTS the <c>OTP-OS-MON-MIB</c>, give
      the option <c>{il, ["os_mon/priv/mibs"]}</c> to the MIB compiler.</p>
    <p>If the MIB should be used in a system, it should be loaded into
      an agent with a call to <c>os_mon_mib:load(Agent)</c>, where
      <c>Agent</c> is the pid or registered name of an SNMP agent. Use
      <c>os_mon_mib:unload(Agent)</c> to unload the MIB.
      The implementation of this MIB uses Mnesia to store a cache with
      data needed, which implicates that Mnesia must be up and running.
      The MIB also use functions defined for the <c>OTP-MIB</c>, thus
      that MIB must be loaded as well.</p>
  </section>

  <section>
    <title>See Also</title>
    <p><seealso marker="cpu_sup">cpu_sup(3)</seealso>,
      <seealso marker="disksup">disksup(3)</seealso>,
      <seealso marker="memsup">memsup(3)</seealso>,
      <seealso marker="os_sup">os_sup(3)</seealso>,
      <seealso marker="nteventlog">nteventlog(3)</seealso>,
      <seealso marker="snmp:snmp">snmp(3)</seealso>.</p>
  </section>
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