raspi-watchdog.txt

grep -q "bcm2835_wdt" /etc/modules || echo "bcm2835_wdt" | sudo tee -a /etc/modules
dpkg -l | grep -q "ii *watchdog" || sudo apt-get install -y watchdog
[ ! -f /etc/watchdog.conf.dist ] && sudo cp /etc/watchdog.conf /etc/watchdog.conf.dist
cat<<EOF | sudo tee /etc/watchdog.conf
max-load-1              = 24
watchdog-device = /dev/watchdog
realtime                = yes
priority                = 1
EOF
sudo update-rc.d watchdog defaults
# sudo update-rc.d watchdog enable 2
sudo /etc/init.d/watchdog start
sudo modprobe bcm2835_wdt

# add: /lib/systemd/system/watchdog.service
[Install]
WantedBy=multi-user.target

# Then
systemctl enable watchdog