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NAME
os_sup - Interface to OS System Messages
DESCRIPTION
os_sup 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 os_mon(7). Available for Solaris and
Windows.
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.
SOLARIS OPERATION
The Solaris (SunOS 5.x) messages are retrieved from the syslog daemon, syslogd.
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
syslogd. When os_sup is terminated, the service must be disabled, meaning the original configuration must
be restored. Enabling/disabling can be done either outside or inside os_sup. See Configuration below.
Warning:
This process cannot run in multiple instances on the same hardware. OS_Mon must be configured to start
os_sup on one node only if two or more Erlang nodes execute on the same machine.
The format of received events is not defined.
WINDOWS OPERATION
The Windows messages are retrieved from the eventlog file.
The nteventlog module is used to implement os_sup. See nteventlog(3erl). Note that the start functions of
nteventlog does not need to be used, as in this case the process is started automatically as part of the
OS_Mon supervision tree.
OS messages are formatted as a tuple {Time, Category, Facility, Severity, Message}:
Time = {MegaSecs, Secs, MicroSecs}:
A time stamp as returned by the BIF now().
Category = string():
Usually one of "System", "Application" or "Security". 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.
Facility = string():
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".
Severity = string():
One of "Error", "Warning", "Informational", "Audit_Success", "Audit_Faulure" or, in case of a
currently unknown Windows NT version "Severity_Unknown".
Message = string():
Formatted exactly as it would be in the NT eventlog viewer. Binary data is not imported into Erlang.
CONFIGURATION
os_sup_mfa = {Module, Function, Args}:
The callback function to use. Module and Function are atoms and Args is a list of terms. When an OS
message Msg is received, this function is called as apply(Module, Function, [Msg | Args]).
Default is {os_sup, error_report, [Tag]} which will send the event to the error logger using
error_logger:error_report(Tag, Msg). Tag is the value of os_sup_errortag, see below.
os_sup_errortag = atom():
This parameter defines the error report type used when messages are sent to error logger using the
default callback function. Default is std_error, which means the events are handled by the standard
event handler.
os_sup_enable = bool():
Solaris only. Defines if the service should be enabled (and disabled) inside (true) or outside
(false) os_sup. For backwards compatibility reasons, the default is true. The recommended value is
false, as the Erlang emulator should normally not be run with root privileges, as is required for
enabling the service.
os_sup_own = string():
Solaris only. Defines the directory which contains the backup copy and the Erlang specific
configuration files for syslogd, and a named pipe to receive the messages from syslogd. Default is
"/etc".
os_sup_syslogconf = string():
Solaris only. Defines the full name of the configuration file for syslogd. Default is
"/etc/syslog.conf".
EXPORTS
enable() -> ok | {error, Res}
enable(Dir, Conf) -> ok | {error, Error}
Types:
Dir = Conf = Res = string()
Enables the os_sup service. Needed on Solaris only.
If the configuration parameter os_sup_enable is false, this function is called automatically by
os_sup, using the values of os_sup_own and os_sup_syslogconf as arguments.
If os_sup_enable is true, this function must be called before OS_Mon/os_sup is started. Dir
defines the directory which contains the backup copy and the Erlang specific configuration files
for syslogd, and a named pipe to receive the messages from syslogd. Defaults to "/etc". Conf
defines the full name of the configuration file for syslogd. Default is "/etc/syslog.conf".
Results in a OS call to:
<PRIVDIR>/bin/mod_syslog otp Dir Conf
where <PRIVDIR> is the priv directory of OS_Mon, code:priv_dir(os_mon).
Returns ok if this yields the expected result "0", and {error, Res} if it yields anything else.
Note:
This function requires root privileges to succeed.
disable() -> ok | {error, Res}
disable(Dir, Conf) -> ok | {error, Error}
Types:
Dir = Conf = Res = string()
Disables the os_sup service. Needed on Solaris only.
If the configuration parameter os_sup_enable is false, this function is called automatically by
os_sup, using the same arguments as when enable/2 was called.
If os_sup_enable is true, this function must be called after OS_Mon/os_sup is stopped. Dir defines
the directory which contains the backup copy and the Erlang specific configuration files for
syslogd, and a named pipe to receive the messages from syslogd. Defaults to "/etc". Conf defines
the full name of the configuration file for syslogd. Default is "/etc/syslog.conf".
Results in a OS call to:
<PRIVDIR>/bin/mod_syslog nootp Dir Conf
where <PRIVDIR> is the priv directory of OS_Mon, code:priv_dir(os_mon).
Returns ok if this yields the expected result "0", and {error, Res} if it yields anything else.
Note:
This function requires root privileges to succeed.
SEE ALSO
error_logger(3erl), os_mon(3erl) syslogd(1M), syslog.conf(5) in the Solaris documentation.