====== Watchdog ======

===== Introduction =====

This page introduces the internal Watchdog. You will learn how to enable the watchdog and test it.

===== Enable Internal Watchdog =====

Watchdog is disabled by default, use the commands below to enable it.

<tabbox Ubuntu 18.04> 
```shell
sudo ln -s  /lib/systemd/system/watchdog.service /etc/systemd/system/multi-user.target.wants/watchdog.service
sudo systemctl enable watchdog.service
sudo systemctl start watchdog.service
```

<WRAP info >
You need to create the service link manually, due to a [[https://unix.stackexchange.com/questions/346224/problem-with-systemd-starting-watchdog?utm_medium=organic&utm_source=google_rich_qa&utm_campaign=google_rich_qa|Debian bug]].
</WRAP>

<tabbox Ubuntu 20.04> 
```shell
sudo systemctl enable watchdog.service
sudo systemctl start watchdog.service
```
</tabbox>

Check watchdog status:

```shell
khadas@Khadas:~$ systemctl status watchdog.service 
● watchdog.service - watchdog daemon
     Loaded: loaded (/lib/systemd/system/watchdog.service; enabled; vendor pres>
     Active: active (running) since Fri 2021-03-26 10:00:38 UTC; 15min ago
    Process: 3381 ExecStartPre=/bin/sh -c [ -z "${watchdog_module}" ] || [ "${w>
    Process: 3382 ExecStart=/bin/sh -c [ $run_watchdog != 1 ] || exec /usr/sbin>
   Main PID: 3385 (watchdog)
      Tasks: 1 (limit: 2932)
     Memory: 864.0K
     CGroup: /system.slice/watchdog.service
             └─3385 /usr/sbin/watchdog -s -v -c /etc/watchdog.conf

Mar 26 10:15:38 Khadas watchdog[3385]: still alive after 120 interval(s)
Mar 26 10:15:39 Khadas watchdog[3385]: still alive after 121 interval(s)
Mar 26 10:15:40 Khadas watchdog[3385]: still alive after 122 interval(s)
Mar 26 10:15:41 Khadas watchdog[3385]: still alive after 123 interval(s)
Mar 26 10:15:42 Khadas watchdog[3385]: still alive after 124 interval(s)
Mar 26 10:15:43 Khadas watchdog[3385]: still alive after 125 interval(s)
Mar 26 10:15:44 Khadas watchdog[3385]: still alive after 126 interval(s)
Mar 26 10:15:45 Khadas watchdog[3385]: still alive after 127 interval(s)
Mar 26 10:15:46 Khadas watchdog[3385]: still alive after 128 interval(s)
Mar 26 10:15:47 Khadas watchdog[3385]: still alive after 129 interval(s)
lines 1-21/21 (END) 
```
===== Test Internal Watchdog =====

==== Set Watchdog Timeout ====

The default timeout is ''15'' seconds, you can edit the file ''/etc/watchdog.conf'' to change the value ''watchdog-timeout''.

Restart the watchdog service to take effect.

```shell
sudo systemctl restart watchdog
```

==== Run and Test ====

Trigger a Kernel crash.

```shell
echo 0 | sudo tee /sys/module/kernel/parameters/panic
echo c | sudo tee /proc/sysrq-trigger 
```

Kill the Watchdog daemon.

You can also kill the watchdog daemon to prevent an automatic restart after a Kernel crash.

```shell
$ sudo pkill -9 watchdog
$ sudo pkill -9 wd_keepalive
$
$
$ G12B:BL:6e7c85:2a3b91;FEAT:E0F83180:402000;POC:F;RCY:0;EMMC:0;READ:0;0.
bl2_stage_init 0x01
bl2_stage_init 0x81
hw id: 0x0000 - pwm id 0x01
bl2_stage_init 0xc1
bl2_stage_init 0x02

L0:00000000
L1:20000703
L2:00008067
L3:14000000
B2:00402000
B1:e0f83180

TE: 207260

BL2 Built : 15:22:05, Aug 28 2019. g12b g1bf2b53 - user@domain
...
```

If watchdog was setup successfully, the system will automatically reboot after the Kernel crash, in accordance with the timeout you have set above.

===== Disable Internal Watchdog =====

Disable the Watchdog daemon.

```shell
sudo systemctl disable watchdog
sudo reboot
```

Disable Watchdog driver [Optional].

You can also disable the watchdog driver. Edit ''/boot/env.txt'' and remove ''watchdog'' in the ''overlays'' node, then save and reboot the system.