watchdog is a daemon that periodically pokes a hardware chip,
and if it fails to do so (presumaby because the system got stuck),
the chip would reboot the system. A somehow working software
emulation of this chip, called "softdog" also exists in Linux.
A reboot can be triggered by some other criteria too.
This script installs a RedHat-style initscript, but you can run it from
/etc/rc.d/rc.local too.
This daemon needs a proper kernel driver to work.
Some machines, such as raspberry pi 4b, provide /dev/wachdog by default.
Intel systems might require editing /etc/sysconfig/watchdog to have
START_MOD_CMD="modprobe iTCO_wdt" and
You can try "softdog" if nothing better is available.
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