I've seen this answer, and it doesn't work. (I've tried the following shortcuts: alt+ctrl+del|Esc|F2|Backspace,I've tried alt+ctrl+R,E,I,S,U,B under normal conditions and the system didn't respond so I doubt it will when the system freezes )
The freeze is apparently caused by Firefox 58.0.1 even though I didn't installed any extension
I'm using Ubuntu 16.04 looking for any shortcut to regain control of the system instead of rebooting every time this occurs (several times a day).
I appreciate your help
As @Byte Commander have pointed out the shortcut is rather alt+SysRq+R,E,I,S,U,B and it causes a hard reboot, then I'd like instead to have control over the system to issue a
kill command to the process causing the freeze.