Zdog - HP bh5700 User Manual

zdog

NAME
zdog - Configure and send heartbeats to watch dog 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 Ethernet Switch Blade watchdog timer functions and to send
heartbeats to the Ethernet Switch Blade watchdog drivers. There are two components to the
Ethernet Switch Blade 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 Ethernet Switch Blade 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:
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
Ethernet Switch Blade User's Guide
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zdog -i 5000 -n 3
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release 3.2.2j page 211