[OpenWrt-Devel] watchdog against router crash freezes?

[Alberto Bursi]

On 27/08/2018 18:52, Marcel Partap wrote:
> […]
>> https://openwrt.org/docs/guide-developer/ubus/system has watchdog information
> Well, I was hoping for a watchdog daemon packaged in the repo to easily solve my issue..
> I already set up a timer switch to cut electricity to both cable modem and router at 3AM + 3PM to reset them, but that is just a crude last-resort solution to have me cut off from remote access for 12 hours at most.
>
>> That said, you may be seeing:
>> https://dev.openwrt.org/ticket/12121 where people have reported
>> watchdog resets causing hard lockup on and off for a few years.
> Thanks for the pointer, though I doubt that's my problem, as the issue has started before all of my attempts to activate the watchdog.
>
> Regards,
> #marcel
>
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If your hardware does not have a watchdog but you have a USB port you 
can use a "usb watchdog"
They are cheap devices used by cryptominers on PCs that usually lack a 
hardware watchdog.

They usually come without linux support like all chinese stuff, but it's 
pretty simple to sniff the serial communication and
write a script to send hex values to have it work on Linux/OpenWrt. You 
just need to install serial dongle drivers to communicate with it.
https://www.davidgouveia.net/2018/02/how-to-create-your-own-script-for-a-usb-watchdog/

What he does with python can be done also with a shell script, 
https://unix.stackexchange.com/questions/118247/echo-bytes-to-a-file

You will probably need to wire up the usb watchdog to some switch that 
turns off and on the power to your device though.

-Alberto

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