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EVM(5)								       EVM(5)



NAME

  EVM, evm - Event Management

DESCRIPTION

  Introduction to Events and Event Management


  The purpose of an event management system is to provide a means for any
  system component or application to indicate that something has happened
  that may be of interest to some other	entity.	 The indication	is known as
  an event, and	the component posting the event	is known as an event genera-
  tor or event poster.	The entity interested in the indication	is known as
  an event subscriber.

  When a system	component has something	interesting to report, it makes	the
  information available	through	an event channel.  The term event channel
  describes any	facility used to publish or retrieve event information,	and
  might	refer to any of	the following:

    +  A simple	log file

    +  An event	management system

    +  A program that can be run to obtain a snapshot of status	information

  An event management system is	an active event	channel, and as	such it	pro-
  vides	services for distributing, storing and retrieving event	information.

  The UNIX system logger, syslog, and the binary error logger, binlog, are
  familiar examples of event management	systems.  They provide simple event
  distribution facilities for other components to use, and their daemons
  actively manage the event information	they receive.  By contrast, the	cron
  daemon's log file, /var/adm/cron/log,	is an example of a passive event
  channel.  The	cron daemon simply writes new event information	to the end of
  its file, and	takes no special action	to notify interested entities when it
  does so.

  In general, an event poster is unaware of any	entities that might be
  interested in	its event information; it simply uses an available event
  channel to post the event.  It is the	responsibility of the event channel
  to decide how	to make	the event available, and to whom.  The event sub-
  scriber is responsible for identifying an interest in	events to the event
  channel.  A subscriber might be a user-level process,	a kernel subsystem,
  or (through some utility program) a user.








  About	EVM


  The Tru64 UNIX Event Manager (EVM) is	a comprehensive	event management sys-
  tem that, in addition	to providing traditional event handling	facilities,
  unifies events from many channels to provide a system-wide source of infor-
  mation.  For information about using EVM as an aid to	system administra-
  tion,	see the	System Administration guide.

  The EVM Event


  An EVM event is a package of information that	can be passed between pro-
  grams	and stored in files.  The underlying format of an event	package	is
  binary, but supplied commands	and programming	interfaces can be used to
  extract and display the information contained	in an event.  The term raw
  event	is used	to refer to an event in	its binary state, while	an event that
  has been converted to	text form for display is said to be formatted.

  An EVM event may contain any or all of a set of standard event data items,
  including (but not limited to) an event name,	a timestamp, a priority	value
  and some message text.  An event may also carry any number of	named vari-
  able data items, each	of which can hold further information about the
  event.  EVM events can carry events from other channels, such	as the binary
  error	logger,	by holding them	in variable data items.

  Full details of the EVM event	are provided in	the EvmEvent(5)	reference
  page.

  The EVM Daemon


  The EVM daemon, evmd,	is started automatically when the system is initial-
  ized to level	2.  The	daemon provides	posting	and notification services for
  system and application clients running on the	local system and, in a clus-
  ter environment, on other nodes of the cluster. The daemon also can be con-
  figured to provide services to remote	systems.  Refer	to the evmd(8) and
  evmdaemon.conf(4) reference pages for	more information.

  The EVM Logger


  The EVM logger, evmlogger, is	an event subscriber that is started automati-
  cally	by the daemon.	The logger reads its configuration file	to establish
  the set of events to be logged, subscribes for those events, and stores
  them in managed logfiles as they arrive.  By default,	the logger also
  displays high	priority events	on the system console, and mails information
  about	them to	the root user.	The logger can be configured to	manage any
  number of logfiles, each with	its own	selection of events, and to execute
  user-supplied	commands on receipt of selected	events.

  For more information refer to	the evmlogger(8) and evmlogger.conf(4) refer-
  ence pages.

  The EVM Channel Manager


  The EVM channel manager, evmchmgr, is	started	automatically by the daemon,
  and is responsible for managing time-based event channel functions.  The
  channel manager reads	the EVM	channel	configuration file and periodically
  runs event monitoring	commands for any configured passive channels.  The
  program also is responsible for running daily	logfile	cleanup	commands.

  The channel manager and the channel configuration file are described in the
  evmchmgr(8) and evmchannel.conf(4) reference pages.







  Command Line Utilities


  EVM's	system administration facilities include a set of command line utili-
  ties that can	be used	from the command line or in shell scripts to post
  events, to monitor event activity, to	retrieve stored	events from log
  files, and to	sort and view events in	a variety of ways.  The	utilities are
  designed to be used together in shell	pipelines.  For	more information
  refer	to the evmpost(1), evmwatch(1),	evmget(1), evmsort(1) and evmshow(1)
  reference pages.

  The Event Viewer


  The event viewer provides a graphical	view of	historical events through the
  common system	management interface.  The viewer can be launched through the
  SysMan Menu or through the SysMan Station.  Refer to the sysman(8) refer-
  ence page for	more information.

  Filtering Events


  Because a system may generate	many events over the course of a day, it is
  often	desirable to limit your	view to	the particular set in which you	are
  interested.  For example, you	may want to see	the events posted by one par-
  ticular subsystem, or	all events with	a high priority	value. EVM events can
  be selected by using an event	filter - a character string that describes
  the selection	using a	predefined filter syntax. You can use a	filter to
  select events	according to several different criteria, including event
  name,	timestamp, priority and	the name of the	posting	system.

  You can use an event filter by specifying the	-f option to several of	the
  EVM command line utilities, and the event viewer provides a graphical
  filter builder window.  The EVM logger uses event filters in its configura-
  tion file to select the actions to be	taken when specific events occur.
  Frequently-used event	filters	can be stored in filter	files for easy refer-
  ence.

  For details of the event filter syntax and the use of	filter files, refer
  to the EvmFilter(5) and evmfilterfile(4) reference pages.

  Event	Template Files


  Event	template files are used	to control the set of events that can be
  posted on a given system, and	to provide a central source for	much of	the
  information that is carried in a given event.	 For example, the priority
  and message text for a given event are likely	to be the same each time the
  event	is posted, and centralizing this information makes it much easier to
  see and maintain than	if the information was held in the posting program or
  the UNIX kernel.

  An event template file is a text file	that holds template information	for
  one or more named events.  A template	file must be installed before the
  events it describes can be posted, and is read by the	EVM daemon each	time
  the daemon starts or reloads its configuration.  When	an event is posted,
  the daemon adds the information held in the template to the posted event
  before distributing it to subscribers.

  For more information about the purpose and the syntax	of template files see
  the evmtemplate(4) reference page.





  Event	Authorization


  Because the unrestricted ability to monitor or post certain events could
  compromise security in some environments, EVM	provides a means of restrict-
  ing the ability to post and access selected events to	specific authorized
  users.  Refer	to the evm.auth(4) reference page for more information.

  The EVM Programming Interface


  The EVM application programming interface (API) library, libevm.so, pro-
  vides	all the	functions required for an application program to create, post
  and subscribe	for events, to read and	write them from	and to standard	file
  descriptors, and to manipulate their contents.  For a	full discussion	of
  programming with EVM,	refer to the Programmer's Guide	and the	reference
  pages	for the	routines listed	in the SEE ALSO	section.

SEE ALSO

  Commands: evmchmgr(8), evmd(8), evmget(1), evminfo(1), evmlogger(8),
  evmpost(1), evmreload(8), evmshow(1),	evmsort(1), evmstart(8), evmstop(8),
  evmwatch(1) sysman(8)	sysman_menu(8) sysman_station(8)

  Routines: EvmConnControl(3), EvmConnCreate(3), EvmConnSubscribe(3),
  EvmConnWait(3), EvmEventCreate(3), EvmEventDump(3), EvmEventFormat(3),
  EvmEventPost(3), EvmEventRead(3), EvmEventValidate(3), EvmFilterCreate(3),
  EvmItemSet(3), EvmSrvStart(3), EvmStatusTextGet(3), EvmVarSet(3)

  Files: evm.auth(4), evmchannel.conf(4), evmdaemon.conf(4), evmfilter-
  file(4), evmlogger.conf(4), evmtemplate(4)

  Misc:	sys_attrs_kevm(5)

  Event	Callback: EvmCallback(5)

  Event	Connection: EvmConnection(5)

  EVM Events: EvmEvent(5)

  Event	Filter:	EvmFilter(5)

  Programmer's Guide, System Administration