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<?xml version="1.0" encoding="utf-8" ?>
<!DOCTYPE erlref SYSTEM "erlref.dtd">
<erlref>
<header>
<copyright>
<year>1996</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>os_sup</title>
<prepared></prepared>
<docno></docno>
<date></date>
<rev></rev>
</header>
<module>os_sup</module>
<modulesummary>Interface to OS System Messages</modulesummary>
<description>
<p><c>os_sup</c> is a process providing a message passing service
from the operating system to the error logger in the Erlang
runtime system. It is part of the OS_Mon application, see
<seealso marker="os_mon_app">os_mon(6)</seealso>. Available for
Solaris and Windows.</p>
<p>Messages received from the operating system results in an
user defined callback function being called. This function can do
whatever filtering and formatting is necessary and then deploy any
type of logging suitable for the user's application.</p>
</description>
<section>
<title>Solaris Operation</title>
<p>The Solaris (SunOS 5.x) messages are retrieved from
the syslog-daemon, <c>syslogd</c>.</p>
<p>Enabling the service includes actions which require root
privileges, such as change of ownership and file privileges of an
executable binary file, and creating a modified copy of
the configuration file for <c>syslogd</c>. When <c>os_sup</c> is
terminated, the service must be disabled, meaning the original
configuration must be restored. Enabling/disabling can be done
either outside or inside <c>os_sup</c>, see
<seealso marker="#config">Configuration</seealso> below.</p>
<warning>
<p>This process cannot run in multiple instances on the same
hardware. OS_Mon must be configured to start <c>os_sup</c> on
one node only if two or more Erlang nodes execute on the same
machine.</p>
</warning>
<p>The format of received events is not defined.</p>
</section>
<section>
<title>Windows Operation</title>
<p>The Windows messages are retrieved from the eventlog file.</p>
<p>The <c>nteventlog</c> module is used to implement <c>os_sup</c>.
See <seealso marker="nteventlog">nteventlog(3)</seealso>. Note
that the start functions of <c>nteventlog</c> does not need to be
used, in this case the process is started automatically as part of
the OS_Mon supervision tree.</p>
<p>OS messages are formatted as a tuple
<c>{Time, Category, Facility, Severity, Message}</c>:</p>
<taglist>
<tag><c>Time = {MegaSecs, Secs, MicroSecs}</c></tag>
<item>
<p>A time stamp as returned by the BIF <c>now()</c>.</p>
</item>
<tag><c>Category = string()</c></tag>
<item>
<p>Usually one of <c>"System"</c>, <c>"Application"</c> or
<c>"Security"</c>. Note that the NT eventlog viewer has
another notion of category, which in most cases is totally
meaningless and therefore not imported into Erlang. What is
called a category here is one of the main three types of
events occurring in a normal NT system.</p>
</item>
<tag><c>Facility = string()</c></tag>
<item>
<p>The source of the message, usually the name of
the application that generated it. This could be almost any
string. When matching messages from certain applications,
the version number of the application may have to be
accounted for. This is what the NT event viewer calls
"source".</p>
</item>
<tag><c>Severity = string()</c></tag>
<item>
<p>One of <c>"Error"</c>, <c>"Warning"</c>,
<c>"Informational"</c>, <c>"Audit_Success"</c>,
<c>"Audit_Faulure"</c> or, in case of a currently unknown
Windows NT version <c>"Severity_Unknown"</c>.</p>
</item>
<tag><c>Message = string()</c></tag>
<item>
<p>Formatted exactly as it would be in the NT eventlog viewer.
Binary data is not imported into Erlang.</p>
</item>
</taglist>
</section>
<section>
<marker id="config"></marker>
<title>Configuration</title>
<taglist>
<tag><c>os_sup_mfa = {Module, Function, Args}</c></tag>
<item>
<p>The callback function to use. <c>Module</c> and
<c>Function</c> are atoms and <c>Args</c> is a list of terms.
When an OS message <c>Msg</c> is received, this function is
called as <c>apply(Module, Function, [Msg | Args])</c>.</p>
<p>Default is <c>{os_sup, error_report, [Tag]}</c> which will
send the event to the error logger using
<seealso marker="kernel:error_logger#error_report/2">error_logger:error_report(Tag, Msg)</seealso>. <c>Tag</c> is the value of
<c>os_sup_errortag</c>, see below.</p>
</item>
<tag><c>os_sup_errortag = atom()</c></tag>
<item>
<p>This parameter defines the error report type used when
messages are sent to error logger using the default callback
function. Default is <c>std_error</c>, which means the events
are handled by the standard event handler.</p>
</item>
<tag><c>os_sup_enable = bool()</c></tag>
<item>
<p>Solaris only. Defines if the service should be enabled (and
disabled) inside (<c>true</c>) or outside (<c>false</c>)
<c>os_sup</c>. For backwards compatibility reasons,
the default is <c>true</c>. The recommended value is
<c>false</c>, as the Erlang emulator should normally not be
run with <c>root</c> privileges, as is required for enabling
the service.</p>
</item>
<tag><c>os_sup_own = string()</c></tag>
<item>
<p>Solaris only. Defines the directory which contains
the backup copy and the Erlang specific configuration files
for <c>syslogd</c>, and a named pipe to receive the messages
from <c>syslogd</c>. Default is <c>"/etc"</c>.</p>
</item>
<tag><c>os_sup_syslogconf = string()</c></tag>
<item>
<p>Solaris only. Defines the full name of the configuration file
for <c>syslogd</c>. Default is <c>"/etc/syslog.conf"</c>.</p>
</item>
</taglist>
</section>
<funcs>
<func>
<name>enable() -> ok | {error, Res}</name>
<name>enable(Dir, Conf) -> ok | {error, Error}</name>
<fsummary>Enable the service (Solaris only)</fsummary>
<type>
<v>Dir = Conf = Res = string()</v>
</type>
<desc>
<p>Enables the <c>os_sup</c> service. Needed on Solaris only.</p>
<p>If the configuration parameter <c>os_sup_enable</c> is
<c>false</c>, this function is called automatically by
<c>os_sup</c>, using the values of <c>os_sup_own</c> and
<c>os_sup_syslogconf</c> as arguments.</p>
<p>If <c>os_sup_enable</c> is <c>true</c>, this function must
be called <em>before</em> OS_Mon/<c>os_sup</c> is started.
<c>Dir</c> defines the directory which contains the backup
copy and the Erlang specific configuration files for
<c>syslogd</c>, and a named pipe to receive the messages
from <c>syslogd</c>. Defaults to <c>"/etc"</c>. <c>Conf</c>
defines the full name of the configuration file for
<c>syslogd</c>. Default is <c>"/etc/syslog.conf"</c>.</p>
<p>Results in a OS call to:</p>
<code type="none"><![CDATA[
<PRIVDIR>/bin/mod_syslog otp Dir Conf
]]></code>
<p>where <c><![CDATA[<PRIVDIR>]]></c> is the <c>priv</c> directory of
OS_Mon, <c>code:priv_dir(os_mon)</c>.</p>
<p>Returns <c>ok</c> if this yields the expected result
<c>"0"</c>, and <c>{error, Res}</c> if it yields anything
else.</p>
<note>
<p>This function requires root privileges to succeed.</p>
</note>
</desc>
</func>
<func>
<name>disable() -> ok | {error, Res}</name>
<name>disable(Dir, Conf) -> ok | {error, Error}</name>
<fsummary>Disable the service (Solaris only)</fsummary>
<type>
<v>Dir = Conf = Res = string()</v>
</type>
<desc>
<p>Disables the <c>os_sup</c> service. Needed on Solaris only.</p>
<p>If the configuration parameter <c>os_sup_enable</c> is
<c>false</c>, this function is called automatically by
<c>os_sup</c>, using the same arguments as when
<c>enable/2</c> was called.</p>
<p>If <c>os_sup_enable</c> is <c>true</c>, this function must
be called <em>after</em> OS_Mon/<c>os_sup</c> is stopped.
<c>Dir</c> defines the directory which contains the backup
copy and the Erlang specific configuration files for
<c>syslogd</c>, and a named pipe to receive the messages
from <c>syslogd</c>. Defaults to <c>"/etc"</c>. <c>Conf</c>
defines the full name of the configuration file for
<c>syslogd</c>. Default is <c>"/etc/syslog.conf"</c>.</p>
<p>Results in a OS call to:</p>
<code type="none"><![CDATA[
<PRIVDIR>/bin/mod_syslog nootp Dir Conf
]]></code>
<p>where <c><![CDATA[<PRIVDIR>]]></c> is the <c>priv</c> directory of
OS_Mon, <c>code:priv_dir(os_mon)</c>.</p>
<p>Returns <c>ok</c> if this yields the expected result
<c>"0"</c>, and <c>{error, Res}</c> if it yields anything
else.</p>
<note>
<p>This function requires root privileges to succeed.</p>
</note>
</desc>
</func>
</funcs>
<section>
<title>See also</title>
<p><seealso marker="kernel:error_logger">error_logger(3)</seealso>,
<seealso marker="os_mon_app">os_mon(3)</seealso></p>
<p><c>syslogd(1M)</c>, <c>syslog.conf(4)</c> in the Solaris
documentation.</p>
<p></p>
</section>
</erlref>
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