Reboot on ssh command locks up device, how to solve?

[Bo Berglund]

I have an HP Prodesk computer where I have installed Linuxmint 20.03 (based on
Ubuntu).
It sits on a remote location and I usually only access it via SSH (PuTTY or VNC
from Windows).

Unlike a couple of other devices, both HP laptops running Ubuntu 20.04.4 LTS,
when I issue the command:
sudo reboot
on this device it seems *not* to cleanly do a reboot (the ssh session is not
exited but just locks up).

Instead the computer gets into an inaccessible state which lasts forever.
When I first discovered this I could do nothing for a month until I could travel
to the remote location. And there I had to power cycle the computer.

But then I installed a ShellyPlug device in the power feed to the computer as a
last resort thing to power cycle it remotely.

Today I had to reboot since the system had been up for 51 days and after a sudo
apt full-upgrade I needed the reboot.

And again it hung!

So this time I could use the ShellyPlug device to power cycle the system,
whereupon it did a full start.

But now I want to get to the bottom of this!
It seems like issuing the command "sudo reboot" just partly works, I lose SSH
connection immediately but the reboot seems not to be performed anyway.

Is there some command that will *really* FORCE a reboot to happen?

I have seen the "reboot -f" command to force the reboot, but I have not yet used
it.
If it does work mabe I could add it as an alias, but how do I create aliases for
sudo?

And how can I find out what was actually happening when it didn't reboot?


-- 
Bo Berglund
Developer in Sweden