WD(3)WD(3)NAMEwd - hardware watchdog timer
bind -a #w /dev
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:
enabled 3 restarts
disabled 3 restarts
Control messages may be written to wdctl and include and
The watchdog is disabled at system shutdown, and when the last open
file descriptor for wdctl is closed.
SEE ALSOproc(3), watchdog(8)BUGS
On PCs, to ensure consistent use of one CPU's timers, an 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.