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NAME    [Toc]    [Back]

       EVM, evm - Event Management

DESCRIPTION    [Toc]    [Back]

   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  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 provides 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  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    [Toc]    [Back]
       The Tru64 UNIX Event  Manager  (EVM)  is  a  comprehensive
       event  management  system  that,  in addition to providing
       traditional event handling facilities, 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    [Toc]    [Back]
       An  EVM  event  is  a  package  of information that can be
       passed between programs 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 variable 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    [Toc]    [Back]
       The EVM daemon, evmd, is started  automatically  when  the
       system  is  initialized  to  level 2.  The daemon provides
       posting and notification services for system and  application
 clients running on the local system and, in a cluster
       environment, on other nodes of  the  cluster.  The  daemon
       also  can be configured to provide services to remote systems.
  Refer to the evmd(8) and  evmdaemon.conf(4)  reference
 pages for more information.

   The EVM Logger    [Toc]    [Back]
       The  EVM logger, evmlogger, is an event subscriber that is
       started automatically 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) reference pages.

   The EVM Channel Manager    [Toc]    [Back]
       The  EVM  channel  manager, evmchmgr, is started automatically
 by the daemon, and is responsible for managing timebased
  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

   Command Line Utilities    [Toc]    [Back]
       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 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    [Toc]    [Back]
       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    [Toc]    [Back]
       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 graphical 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    [Toc]    [Back]
       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

       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    [Toc]    [Back]
       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    [Toc]    [Back]
       The  EVM  application programming interface (API) library,
       libevm.so, provides 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.

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

SEE ALSO    [Toc]    [Back]

       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),
       evmfilterfile(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

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