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The magic SysRq key is a key combination understood by the Linux kernel, which allows the user to perform various low-level commands regardless of the system's state. It is often used to recover from freezes, or to reboot a computer without corrupting the filesystem.〔 〕 Its effect is similar to the computer's hardware reset button (or power switch) but with many more options and much more control. This key combination provides access to powerful features for software development and disaster recovery. In this sense, it can be considered a form of escape sequence. Principal among the offered commands are means to forcibly unmount file systems, kill processes, recover keyboard state, and write unwritten data to disk. With respect to these tasks, this feature serves as a tool of last resort. == Commands == The key combination consists of Alt, SysRq and another key, which controls the command issued. The combinations always assume the QWERTY keyboard layout; for example, on a Dvorak Simplified Keyboard, the combination to shut the system down uses the key labelled R instead of O. Furthermore, some keyboards may not provide a separate SysRq key. In this case, a separate "PrintScrn" key should be present. Under graphical environments (such as GNOME or KDE) key combination generally only leads to a screenshot being dumped. To avoid the print screen operation, the magic SysRq combination should include Ctrl becoming . For the same purposes the AltGr key, if present, can be used in place of the Alt key. On some laptops, SysRq is accessible only by pressing . In this case, the combination is a bit trickier: hold , hold , hold , release , press desired letter key or keys. Or, on some newer laptops, press and hold (and also if using X11/XWindows and not a text console) and then press and hold and then press the desired letter keys. (The order of pressing and holding , and doesn't matter, but those keys must be already held down before pressing and holding and then press and release the desired letter key()). The magic SysRq might also be accessible from the serial console (by sending an RS-232 break signal) if the sysctl option is set to allow it.〔 〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Magic SysRq key」の詳細全文を読む スポンサード リンク
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