Znyx Networks bh5700 - Manual (Page 286)

zdog
NAME
zdog - Configure and send heartbeats to watchdog enabled drivers.
SYNOPSIS
zdog [-d <level>] -h | -i <interval> | -n <heartbeats>
zdog [-d <level>] -b
zdog [-d <level>] -a
DESCRIPTION
zdog is used to configure the base switch watchdog timer functions and to send heartbeats to the
base switch watchdog drivers. There are two components to the base switch watchdog timer: A
hardware component and a software component. The two components are independent from each
other in implementation, but work together to provide safety against zombie hardware and
software. The hardware component requires attention on a predefined 1.5 second interval. The
driver acts on this at interrupt level to ensure that spurious reboots do not occur. The software
component allows for a user programmable interval on which lack of application to driver
communication will cause a reboot. Both components can be turned on with zdog.
The options -i and -n are used to configure the expected interval of heartbeats and the number
of missed heartbeats of the software component before the base switch should be rebooted. If
either the interval or number of heartbeats is 0, the software component is off. The -h option is
used to toggle on and off the hardware component of the watchdog timer. The hardware
component is off by default.
Once the software component of the watchdog timer is turned on, a heartbeat must be sent with
the -b option within that interval or the system will reboot. For example after issuing the
following command:
zdog -i 5000 -n 3
A heartbeat must be sent at least every 3*5000=15000 milliseconds (every 15 seconds). This can
be accomplished with something as simple as a polling script with a sleep, or started with a
higher level function like monit. The driver checks for heartbeat timeout approximately 3 times
per second. So (<heartbeat intervals>*<number of heartbeats>) faster then
330 milliseconds will have diminishing returns.
Combining monit and zdog allows multiple levels of insuring system integrity. The hardware
component of zdog insures that the CPU is functioning well enough to execute something. The
Ethernet Switch Blade User's Guide release 3.2.2j page 286