Magic SysRq key
The Linux kernel can be compiled with support for a "magic" key combo which will trigger some emergency action. Almost all distribution have this feature turned on. This key is called the Magic SysRq Key.
It is available using a three key combo ALT+PrintScreen+ "another key".
- Press and don't release the ALT key
- Press and don't release the PrintScreen key (also noted SysRq on some keyboards)
- Press the key corresponding to the required function
- b for reBoot (immediate, like pressing the reset button)
- o for powerOff (immediate, like removing the plug !)
- h for Help
- complete list on the Wikipedia article
The Magic SysRq key is available on serial (RS232) terminals, the special combo must be replaced by a break signal then the letter key.
Sending a break:
- Tera term : Control > Send break or ALT+B
- minicom : CTRL+A
- gnome-terminal : Control Signals > Send break or CTRL-B