Lock screen frozen

[xircon]

Hold the power button in till it reboots (then read up on, and enable REISUB).

[Tip] Enable Magic SysRq Key (REISUB)

The Linux kernel authors have provided a very nice feature of issuing low-level commands to the kernel directly, regardless of the state the system is in. This is called the “Magic SysRq Key”, because these commands are issued by pressing the SysRq key on the keyboard (if you can’t find it, typically, it shares the same physical key as the Print Screen key, but on some laptops it can be elsewhere). A common use is to reboot when the computer freezes and becomes unresponsive due to some software…