wdogctl
—
Watchdog timer control utility
wdogctl |
-e [-A ]
[-p seconds]
timer |
wdogctl |
-k [-A ]
[-p seconds]
timer |
wdogctl |
-u [-A ]
[-p seconds]
timer |
wdogctl |
-x [-A ]
[-p seconds]
timer |
wdogctl
is used to manipulate watchdog timers. A
watchdog timer is a hardware or software timer that resets the system if it
fails to make progress within a prescribed period. To prevent the system from
being reset, something must refresh the timer to prevent it from expiring.
A hardware watchdog timer asserts system's hardware reset signal
when it expires. A software watchdog timer calls the kernel's s normal
reboot path.
The NetBSD kernel provides three modes in
which watchdog timers may operate: kernel tickle mode, user tickle mode, and
external tickle mode.
- kernel tickle mode
- A timer in the kernel refreshes the watchdog timer. This ensures kernel
threads can make progress within the period of the watchdog timer.
- user tickle mode
wdogctl
runs in the background and refreshes the
watchdog timer. This ensures user programs can make progress within the
period of the watchdog timer.
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 tickle mode
- Similar to user tickle mode, except that the tickle must be done
explicitly by a separate invocation of
wdogctl
-t
. This allows users to determine the activity
whose progress the watchdog timer checks.
In kernel and user tickle modes, an attempt is made to refresh the
watchdog timer in one half the timer's configured period. For example, 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
disabled, 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 seconds. 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.
- /dev/watchdog
- the system monitor watchdog timer device
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/tco(4)
The wdogctl
command first appeared in
NetBSD 1.6.
The wdogctl
command and the
NetBSD watchdog timer framework were written by
Jason R. Thorpe ⟨thorpej@zembu.com⟩, and
contributed by Zembu Labs, Inc.