bind -a #w /dev  /dev/wdctl 
 DESCRIPTION
This device presents textual information about hardware watchdog timers
on PCs and some other machines,
and allows user-level control of them.
When enabled, a watchdog timer counts to zero in a few seconds;
upon reaching zero, it resets the machine with an NMI or equivalent.
Some process must periodically restart the watchdog to avoid the NMI and
keep the system alive;
 watchdog (8) is one such program.

Reads from
 wdctl yield data of this form:
.EX
enabled 3 restarts


or
.EX
disabled 3 restarts


Control messages may be written to
 wdctl and include
.LR enable ,
.LR disable ,
and
.LR restart .

The watchdog is disabled at system shutdown, and when the last open
file descriptor for
 wdctl is closed.
 SOURCE
 /sys/src/9/port/devwd.c 

 /sys/src/9/*/*watchdog.c 
 SEE ALSO
 proc (3),  watchdog (8) 
 BUGS
On PCs,
to ensure consistent use of one CPU's timers,
an
.L enable
message wires the issuing process
(see
 proc (3)) to a CPU,
and any subsequent control messages will
wire the issuing processes to that same CPU.