How to reboot cleanly even when the keyboard/mouse are frozen

There are normally several ways to reboot cleanly using key combinations such as:

• CTRL + ALT+ F2 (get to a terminal, you can then run top/kill/pkill to discover and kill the offending process)
• ALT+ SYSRQ + R then CTRL + ALT+ F2 (as above, but first try to regain control of the keyboard)
• CTRL + ALT + Backspace (kills the graphic session and goes to a console, all graphical applications are terminated too)
• ALT+ SYSRQ + R then ALT + Backspace (as above, but first try to regain control of the keyboard)
• CTRL + ALT + DEL (reboot)
• ALT+ SYSRQ + R then CTRL + ALT + DEL (as above, but first try to regain control of the keyboard)
• ALT+ SYSRQ + R + E + I + S + U + B (forces a clean reboot even when the keyboard is not responding)

The last one is the most effective, but you could try the other commands first.