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NetBSD 6.1.5 - man page for wdogctl (netbsd section 8)

WDOGCTL(8)			   BSD System Manager's Manual			       WDOGCTL(8)

NAME
     wdogctl -- Watchdog timer control utility

SYNOPSIS
     wdogctl
     wdogctl -d
     wdogctl -e [-A] [-p seconds] timer
     wdogctl -k [-A] [-p seconds] timer
     wdogctl -t
     wdogctl -u [-A] [-p seconds] timer
     wdogctl -x [-A] [-p seconds] timer

DESCRIPTION
     wdogctl is used to manipulate watchdog timers.  Watchdog timers provide a means of ensuring
     that a system continues to make progress.	This is accomplished by use of a timer, provided
     by either hardware or software; when the timer expires, the watchdog resets the system.  In
     this case of a hardware watchdog timer, this is accomplished by asserting the system's hard-
     ware reset signal.  In the case of a software watchdog timer, this is accomplished by call-
     ing the kernel's normal reboot path.  In order to prevent the system from rebooting, some-
     thing must refresh the timer to prevent it from expiring.

     The NetBSD kernel provides three basic modes in which watchdog timers may operate: kernel
     tickle mode, user tickle mode, and external tickle mode.  In kernel tickle mode, a timer in
     the kernel refreshes the watchdog timer.  In user tickle mode, wdogctl runs in the back-
     ground and refreshes the watchdog timer.  In kernel tickle mode, progress of the kernel is
     ensured.  In user tickle mode, the ability for user programs to run within a known period of
     time is ensured.  Note that user tickle mode must be used with caution; on a heavily loaded
     system, the timer may expire accidentally, even though user programs may be making (very
     slow) progress.  A user-mode timer is disarmed (if possible) when the device is closed,
     unless the timer is activated with the -x option.

     External-mode watchdogs are similar to user-mode watchdogs, except that the tickle must be
     done explicitly by a separate invocation of the program with the -t option.

     In the first two modes, an attempt is made to refresh the watchdog timer in one half the
     timer's configured period.  That is, if the watchdog timer has a period of 30 seconds, a
     refresh attempt is made every 15 seconds.

     If called without arguments, wdogctl will list the timers available on the system.  When
     arming a watchdog timer, the timer argument is the name of the timer to arm.

     Only one timer may be armed at a time; if an attempt is made to arm a timer when one is
     already armed, an error message will be displayed and no action will be taken.

     The options are as follows:

	   -A		When arming a timer, this flag indicates that an audible alarm is to
			sound when the watchdog timer expires and resets the system.  If the
			selected timer does not support an audible alarm, this option will be
			silently ignored.

	   -d		This flag disarms the currently active timer.  Note that not all watchdog
			timers can be disabled once armed.  If the selected timer can not be dis-
			abled, an error message will be displayed and the timer will remain
			armed.

	   -e		Arm timer in external tickle mode.

	   -k		Arm timer in kernel tickle mode.

	   -p period	When arming a timer, this flag configures the timer period to period sec-
			onds.  If the specified period is outside the timer's range, an error
			message will be displayed and no action will be taken.

	   -t		This flag tickles an external mode timer.

	   -u		Arm timer in user tickle mode.

	   -x		Arm timer in a modified user tickle mode: closing the device will not
			disarm the timer.

FILES
     /dev/watchdog -- the system monitor watchdog timer device

SEE ALSO
     acpiwdrt(4), evbarm/iopwdog(4), i386/elansc(4), i386/gcscpcib(4), i386/geodewdog(4),
     ipmi(4), itesio(4), pcweasel(4), pwdog(4), swwdog(4), x86/ichlpcib(4)

HISTORY
     The wdogctl command first appeared in NetBSD 1.6.

AUTHORS
     The wdogctl command and the NetBSD watchdog timer framework were written by Jason R. Thorpe
     <thorpej@zembu.com>, and contributed by Zembu Labs, Inc.

BSD					 August 11, 2011				      BSD


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