Watchdog (watchdog) in Linux (Armbian/Ubuntu/Debian)

Watchdog (watchdog) - a hardware-implemented circuit for monitoring system hang. Watchdog timers are used in systems that must operate without human supervision. Such systems should be self-healing without operator intervention.

In controllers  JetHub D1 and  ; JetHub H1 meson_wdt hardware watchdog driver supported.

With the watchdog modules running correctly on /dev, the /dev/watchdog and /dev/watchdog0 devices should be visible:

root@jethubj100:~# ls -la /dev/watchdog*
crw------- 1 root root 10, 130 Feb 21 17:29 /dev/watchdog
crw------- 1 root root 246, 0 Feb 21 17:29 /dev/watchdog0
root@jethubj100:~#

Create a folder for the watchdog log files:

sudo mkdir -p /var/log/watchdog

Check the settings for the service in /etc/default/watchdog:

# Start watchdog at boot time? 0 or 1
run_watchdog= 1
# Start wd_keepalive after stopping watchdog? 0 or 1
run_wd_keepalive= 1
# Load module before starting watchdog
watchdog_module="none"
# Specify additional watchdog options here (see manpage).
watchdog_options="-s -v -c /etc/watchdog.conf"

Make the necessary changes to the configuration file /etc/watchdog.conf: * uncomment the use of the /dev/watchdog device (otherwise the watchdog service will not use the hardware timer to restart the controller) * set the necessary checks and timeouts

The following is an example of a config file, with a 15 second timeout set to hang:

$ cat /etc/watchdog.conf
#ping = 172.31.14.1
#ping = 172.26.1.255
#interface=eth0
#file = /var/log/messages
#change = 1407

# Uncomment to enable test. Setting one of these values to '0' disables it.
# These values will hopefully never reboot your machine during normal use
# (if your machine is really hung, the loadavg will go much higher than 25)
#max-load- 1 = 24
#max-load-5 = 18
#max-load- 15 = 12

# Note that this is the number of pages!
# To get the real size, check how large the pagesize is on your machine.
#min-memory = 1
#allocatable-memory = 1

#repair-binary = /usr/sbin/repair
#repair-timeout = 60
#test-binary=
#test-timeout = 60

# The retry-timeout and repair limit are used to handle errors in a more robust
# style. Errors must persist for longer than retry-timeout to action a repair
# or reboot, and if repair-maximum attempts are made without the test passing a
# reboot is initiated anyway.
#retry-timeout = 60
#repair-maximum = 1

watchdog-device=/dev/watchdog

# Defaults compiled into the binary
#temperature-sensor =
#max-temperature = 90

# Defaults compiled into the binary
#admin = root
#interval = 1
#logstick = 1
#log-dir = /var/log/watchdog

# This greatly decreases the chance that watchdog won't be scheduled before
#your machine is really loaded
realtime = yes
priority= 1

# Check if rsyslogd is still running by enabling the following line
#pidfile = /var/run/rsyslogd.pid

watchdog-timeout = 15

To enable autostart of the service, run the following commands:

sudo systemctl enable watchdog.service
sudo systemctl start watchdog.service

Check if service is running:

root@jethubj100:~# service watchdog status
● watchdog.service - watchdog daemon
Loaded: loaded (/lib/systemd/system/watchdog.service; enabled; vendor pres>
Active: active (running) since Mon 2022-02-21 17:29:24 UTC; 17 hours ago
Process: 2718 ExecStartPre=/bin/sh -c [ -z "${watchdog_module}" ] || [ "${w>
Process: 2720 ExecStart=/bin/sh -c [ $run_watchdog != 1 ] || exec /usr/sbin>
Main PID: 2722 (watchdog)
Tasks: 1 (limit: 977)
Memory: 516.0K
CPU: 3min 33.528s
CGroup: /system.slice/watchdog.service
└─2722 /usr/sbin/watchdog -s -v -c /etc/watchdog.conf

Feb 22 10 jethubj100 watchdog[2722]: still alive after 62076 interval(s)
Feb 22 10 jethubj100 watchdog[2722]: still alive after 62077 interval(s)
Feb 22 10 jethubj100 watchdog[2722]: still alive after 62078 interval(s)
Feb 22 10 jethubj100 watchdog[2722]: still alive after 62079 interval(s)
Feb 22 10 jethubj100 watchdog[2722]: still alive after 62080 interval(s)
Feb 22 10 jethubj100 watchdog[2722]: still alive after 62081 interval(s)
Feb 22 10 jethubj100 watchdog[2722]: still alive after 62082 interval(s)

A configured and running watchdog service constantly resets the hardware watchdog. If it fails to do this (for example, if the system freezes or any other condition configured in the config occurs), the timer will work and restart the controller.