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EVM(5)									EVM(5)

       EVM, evm - Event Management

   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
       generator  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 infor‐
       mation,	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
       provides services for distributing, storing and retrieving event infor‐

       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  con‐
       trast,  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 chan‐
       nel  to decide how to make the event available, and to whom.  The event
       subscriber 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
       system that, in addition to providing traditional event handling facil‐
       ities, unifies events from  many	 channels  to  provide	a  system-wide
       source  of  information.	  For information about using EVM as an aid to
       system administration, see the System Administration guide.

   The EVM Event
       An EVM event is a package of information that  can  be  passed  between
       programs	 and stored in files.  The underlying format of an event pack‐
       age 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

       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 num‐
       ber of named variable data items, each of which can hold further infor‐
       mation about the event.	EVM events can carry events from  other	 chan‐
       nels, such as the binary error logger, by holding them in variable data

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

   The EVM Daemon
       The  EVM daemon, evmd, is started automatically when the system is ini‐
       tialized to level 2.  The daemon provides posting and notification ser‐
       vices  for  system  and application clients running on the local system
       and, in a cluster environment, on other nodes of the cluster. The  dae‐
       mon  also  can  be  configured  to  provide services to remote systems.
       Refer to the evmd(8) and evmdaemon.conf(4)  reference  pages  for  more

   The EVM Logger
       The EVM logger, evmlogger, is an event subscriber that is started auto‐
       matically 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  con‐
       figured	to  manage any number of logfiles, each with its own selection
       of events, and to execute user-supplied commands on receipt of selected

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

   The EVM Channel Manager
       The EVM channel manager, evmchmgr, is started automatically by the dae‐
       mon,  and  is  responsible  for managing time-based event channel func‐
       tions.  The channel manager reads the EVM  channel  configuration  file
       and periodically runs event monitoring commands for any configured pas‐
       sive channels.  The program also is responsible for running daily  log‐
       file 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
       utilities 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 util‐
       ities 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) reference 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 particular 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 graphi‐
       cal  filter  builder  window.  The EVM logger uses event filters in its
       configuration file to select the actions	 to  be	 taken	when  specific
       events  occur.	Frequently-used	 event filters can be stored in filter
       files for easy reference.

       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
       restricting  the ability to post and access selected events to specific
       authorized users.  Refer to the evm.auth(4)  reference  page  for  more

   The EVM Programming Interface
       The  EVM	 application  programming  interface (API) library, libevm.so,
       provides all the functions required for an application program to  cre‐
       ate,  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

       EVM supports event posting and subscription in kernel space through the
       pseudo-device driver /dev/kevm. See kevm(7) for more information.

       Commands: evmchmgr(8), evmd(8),	evmget(1),  evminfo(1),	 evmlogger(8),
       evmpost(1),  evmreload(8),  evmshow(1),	evmsort(1),  evmstart(8), evm‐
       stop(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),	 EvmFilterCre‐
       ate(3),	 EvmItemSet(3),	  EvmSrvStart(3),   EvmStatusTextGet(3),  Evm‐

       Files: evm.auth(4), evmchannel.conf(4),	evmdaemon.conf(4),  evmfilter‐
       file(4), evmlogger.conf(4), evmtemplate(4), kevm(7)

       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


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