esmd(1M)esmd(1M)NAMEesmd - Essential Services Monitor (ESM) Daemon
SYNOPSIS
retry_seconds]
DESCRIPTION
The Essential Services Monitor (ESM) daemon, maintains the availability
of essential system daemons by automatically restarting them if they
terminate. The ESM daemon monitors the Event Manager daemon, The ESM
daemon is started by the init process when the system is initialized to
run level 2 and continues to run until the system is shut down or
returned to single user mode. Only one instance of can run at a time.
Configuration information is sent to the ESM daemon by a control pro‐
gram, which is run at key points in the startup and shutdown proce‐
dures. As startup or shutdown progresses, the control program updates
the ESM state file, The control program then signals the daemon to
reconfigure itself.
On startup, state transitions occur after has started. On shutdown,
transitions occur after each of these monitored daemons has terminated.
After each transition, the ESM daemon determines which of the monitored
daemons should be running and adjusts its monitoring activities accord‐
ingly.
The ESM daemon reports all state change information, including notice
of failures and restarts, through the system logging daemon, syslogd.
Messages are displayed on the system console during periods when sys‐
logd is not running. See syslogd(1M) for more information.
If the ESM daemon fails to restart a monitored daemon, it reports the
error by posting a high priority message through syslogd, and makes no
further restart attempts. The system administrator should investigate
the problem and restart the failed daemon. The ESM daemon periodically
attempts to resume monitoring of the daemon, and posts an informational
message when it succeeds. If the monitored daemon fails again once
monitoring has resumed, the ESM daemon again attempts to restart it.
The ESM daemon can be forced to restart a failed daemon by sending a
SIGHUP signal to the process.
If there is a need to temporarily disable the ESM daemon for test pur‐
poses, in order to prevent the monitored daemons from being restarted
automatically, send a SIGSTOP signal to the process. To reactivate the
ESM daemon, send a SIGCONT signal to the process. The ESM daemon
should never be disabled on a production system.
If the ESM daemon is terminated unexpectedly, it is restarted automati‐
cally by init.
Options
The command recognizes the following options:
Limit the priority of any syslog messages posted by the ESM daemon to
"alert."
If this option is not specified, posts an "emergency" message if
it cannot restart a failed daemon. A message may be sent to all
users currently logged in to the system. The option should only
be used if the system administrator is actively monitoring syslogd
messages.
Specify the interval between attempts to begin monitoring a daemon
that has failed, and which has been unable to restart automati‐
cally. The default period is 30 seconds. Specifying a period of
zero disables retrying.
Notes
To use the start options, you must add them to the startup command in
the file. The daemon reports any invalid start options with a single
generic message through syslogd.
Restrictions
The daemon terminates with an error message if it is started by any
process other than init.
The /sbin/init.d/esm program is intended to be run by the system
startup and shutdown process and should not be run from the command
line. Only one instance of can run at a time.
RETURN VALUE
The following exit values are returned:
0 (Zero) Successful completion.
not 0 An error occurred.
FILES
Executable file
Configuration control script
Initialization process control file
dispatched by boot init
Monitoring state file
Receives esmd status messages
AUTHOR
was developed by Hewlett Packard Company.
SEE ALSO
Commands
kill(1), evmd(1M), init(1M), syslogd(1M).
Files
inittab(4).
esmd(1M)
