EVM(5) File Formats Manual 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 hap-
pened 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 sim-
ple 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
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
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 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
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
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 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 events.
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 daemon, 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
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 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), evm-
sort(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
graphical filter builder window. The EVM logger uses event filters in its configuration file to select the actions to be taken when spe-
cific 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
information.
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 Common Desktop Environment: Programmer's Guide and the reference pages for the rou-
tines 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), 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), EvmFilterCreate(3), EvmItemSet(3), EvmSrvStart(3), EvmStatusTextGet(3), Evm-
VarSet(3)
Files: evm.auth(4), evmchannel.conf(4), evmdaemon.conf(4), evmfilterfile(4), evmlogger.conf(4), evmtemplate(4)
Event Callback: EvmCallback(5)
Event Connection: EvmConnection(5)
EVM Events: EvmEvent(5)
Event Filter: EvmFilter(5)
Common Desktop Environment: Programmer's Guide System Administration Programmer's Guide delim off
EVM(5)