esmd(8)esmd(8)NAMEesmd - Essential Services Monitor daemon
SYNOPSIS
/usr/sbin/esmd [-a] [-r retry_seconds]
OPTIONS
Limits the priority of any syslog messages posted by the ESM daemon to
“alert.” If this option is not specified, esmd will post an “emergency”
message if it cannot restart a failed daemon, which may result in a
message being 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. Specifies 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.
OPERANDS
None.
DESCRIPTION
The Essential Services Monitor (ESM) daemon, esmd, maintains the avail‐
ability of essential system daemons by automatically restarting them if
they terminate. The ESM daemon monitors the Event Manager daemon, evmd,
and, in a cluster environment, the Cluster Application Availability
(CAA) daemon, caad.
The ESM daemon is started by the init process when the system is ini‐
tialized to run level 2 and continues to run until the system is shut
down or returned to single user mode. If the daemon terminates, it is
restarted automatically by init.
Configuration information is sent to the ESM daemon by a control pro‐
gram, /sbin/init.d/esm, which is run at key points in the startup and
shutdown procedures. As startup or shutdown progresses, the control
program updates the ESM state file, /var/run/esm.state and signals the
daemon to reconfigure itself.
On startup, state transitions occur after evmd has started and, in a
cluster environment, after caad 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 sys‐
logd is not running. See syslogd(8) 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. ESM 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, ESM will again make one attempt to restart it.
ESM can be forced to restart a failed daemon by sending a SIGHUP signal
to the esmd process.
If there is a need to temporarily disable the ESM daemon for test pur‐
poses, to prevent the monitored daemons from being restarted automati‐
cally, send a SIGSTOP signal to esmd. To reactivate it, send a SIGCONT
signal. The daemon should never be disabled on a production system.
NOTES
If you want to use start options, you must add them to the esmd startup
command in the /etc/inittab 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.
EXIT STATUS
Success. An error occurred.
FILES
Executable file Configuration control script Initialization process
control file Monitoring state file Receives esmd status messages
SEE ALSO
Commands: kill(1), caad(8), evmd(8), init(8), syslogd(8)
Files: inittab(4)esmd(8)