WD(3) WD(3) NAME wd - hardware watchdog timer SYNOPSIS 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: enabled 3 restarts or disabled 3 restarts Control messages may be written to wdctl and include `enable', `disable', and `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 `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.