HP-UX Reference (11i v3 07/02) - 1M System Administration Commands A-M (vol 3)

e
esmd(1M) esmd(1M)
NAME
esmd - Essential Services Monitor (ESM) Daemon
SYNOPSIS
/usr/sbin/esmd
[-a][-r retry_seconds]
DESCRIPTION
The Essential Services Monitor (ESM) daemon,
esmd, maintains the availability of essential system dae-
mons by automatically restarting them if they terminate. The ESM daemon monitors the Event Manager
daemon, evmd. 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
esmd can run at a time.
Configuration information is sent to the ESM daemon by a control program,
/sbin/init.d/esm
, which
is run at key points in the startup and shutdown procedures. As startup or shutdown progresses, the con-
trol program updates the ESM state file,
/var/run/esm.state.
The control program then signals
the
esmd daemon to reconfigure itself.
On startup, state transitions occur after evmd 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 accordingly.
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
syslogd 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 mes-
sage 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
esmd pro-
cess.
If there is a need to temporarily disable the ESM daemon for test purposes, in order to prevent the moni-
tored daemons from being restarted automatically, send a SIGSTOP signal to the
esmd process. To reac-
tivate the ESM daemon, send a SIGCONT signal to the
esmd process. The ESM daemon should never be
disabled on a production system.
If the ESM daemon is terminated unexpectedly, it is restarted automatically by init.
Options
The esmd command recognizes the following options:
-a Limit the priority of any syslog messages posted by the ESM daemon to "alert." If this option is not
specified, esmd 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 -a option should only be used if the system
administrator is actively monitoring syslogd messages.
-r retry_seconds
Specify the interval between attempts to begin monitoring a daemon that has failed, and which esmd
has been unable to restart automatically. 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 esmd startup command in the /etc/inittab file.
The esmd daemon reports any invalid start options with a single generic message through syslogd.
Restrictions
The esmd 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 esmd can run at a time.
192 Hewlett-Packard Company − 1 − HP-UX 11i Version 3: February 2007