Tools/Linux/MagicSysRqKey

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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

Serial ports

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
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