I have Fedora 20, with zshell and Mate desktop. I have just come across this article about using SysRq  keys, but they don't give the results shown there. I am using Alt with the key marked Home with Print Scr above it as the SysRq key combination. I have also tried holding the yellow FN key as well, but this made no difference.Since the  Reboot Even If System Utterly Broken sequence looks very useful, I would please like to know what I am doing wrong.
Why doesn't this sequence of keys, using SyRq, work
linux;keyboard shortcuts;reboot;crash
Normally when you press a button, the keyboard generates a single keycode. The OS receives keycodes, applies some key mapping, and tries to handle key combinations independently of the underlying hardware.The SysRq mechanism is a little bit different:The keyboard catches the combination and sends a special keycode to the OS as if the single button was pressed. The Linux kerenel catches the special keycode and handles it internally without forwarding the input to higher-level applications like the X server.That implies the two consequences:The key combination really depends on the keyboard. The keyboard must catch the key all pressings on its own and only the keyboard knows where the actual SysRq key is located and which combination triggers sending the special keycode. So:The SysRq is not necessarily located on the same button as Home or Print Screen, try to search it, usually it is marked explicitly as SysRq.Try different combinations: Ctrl+Alt+SysRq+b  or  Ctrl+Alt+Fn+SysRq+b, etc (warning, the system will reboot on success). On keyboards that have the Fn key you usually have to press it to reach the actual SysRq key, so likely your combination will involve the Fn key.You actually can know when you get the combination right. Run xev from a terminal, focus the xev's window and hit some buttons on the keyboard, you should see events appeared in the terminal. When you get a right combination, you should NOT get an event because it is caught by the kernel and not delivered to the X server.Also refer to the documentation: https://www.kernel.org/doc/Documentation/sysrq.txt