What do I do if Ubuntu 16.04 freezes, but I can move only the mouse? [duplicate]

I sometimes experience whole Ubuntu freezes (from 14.04 to 16.04, I upgrade by a clean installation), just mouse can move (that's why this question is different from others). I think this is caused by one of the cores stop working when 100% load by unresponsive Desktop Environment. There isn't any magic key combination like Ctrl+Alt+Del or Ctrl+Shift+Esc known from Windows. The only thing I could do is hold power button for 5-10 seconds and hard shut down. Is there any other recommended solution?

Could I e.g. with some keyword combination reset CPU or kill all additional services or reset Unity or force soft reboot or I don't know what else could help?

Solution 1:

Well there is a magic key combination (to reboot):

While holding Alt and the SysReq (Print Screen) keys, type REISUB

For more details visit this answer : https://askubuntu.com/a/36717/497359

Solution 2:

Switch to the console: CTRL + ALT + F1

After login, you can see which processes are running using this command:

ps -ef

If you see a process which has high CPU usage, you can kill it.

sudo kill <pid>

Of course, you can simply restart the PC too:

sudo reboot