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Due to some reason, my machine is not responding and remains in frozen state.

  • I am unable to ping it
  • I am unable to use keyboard/mouse
  • No script runs as per scheduled in cron
  • Only way to use the system is to hard-boot it

Is there any way, maybe sysctl, to reboot the system on its own as soon as system is (or about to) entering into freeze mode.

I prefer to find the root cause and resolve it but unable to get reason. Hence knocking back door.

EDIT_1:

Is there any case where H/W watchdog fails to reboot the system ?

SHW
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  • @StephenKitt No. Daemon is missing in system. – SHW Feb 06 '20 at 16:55
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    I am not sure about it. How do I check it ? – SHW Feb 06 '20 at 16:57
  • If you have a manual (for your system or your motherboard), it should mention it if there is one. If your system has a setup (BIOS or UEFI), there would normally be an option there to control the watchdog, if there is one; but in some cases the hardware has a watchdog without any mention in the setup. What kind of system is it? – Stephen Kitt Feb 06 '20 at 17:00
  • I just verified on hardware and found nothing related to watchdog. Underlying board is Lenovo Thinkpad – SHW Feb 06 '20 at 17:23
  • It’s possible your Thinkpad has an AMT watchdog, but I’m not sure that can be configured to reboot the system. Regarding the general approach, see [this Q&A](https://unix.stackexchange.com/q/64057/86440). – Stephen Kitt Feb 06 '20 at 17:38
  • `dmesg | grep -i watchdog` gives following output [ 0.013281] NMI watchdog: Enabled. Permanently consumes one hw-PMU counter. [ 7.437287] sp5100_tco: SP5100/SB800 TCO WatchDog Timer Driver v0.05 [ 1745.077590] iTCO_wdt: Intel TCO WatchDog Timer Driver v1.11 – SHW Feb 06 '20 at 17:47
  • You might be able to use the magic SysRq key to reboot (if your kernel supports it). Hold `[ALT]` and `[SysRq]`, then type `reisub`. – Panki Feb 07 '20 at 08:17
  • I am unable to use keyboard as it is not responding. – SHW Feb 07 '20 at 15:38

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