Magic SysRq key
As Magic SysRq Key (. Briefly for Magic Sysrequest key, engl "Magic SysRq key" ) is referred to a number of key combinations of the Linux kernel with the SysRq key, with which various functions - for example, a restart of the computer - can perform, which allows the individual functions in succession perform in a meaningful order. This works even if the computer does not respond to other inputs, the kernel has not yet crashed. This type is often used by " death grip " to reboot without causing damage to the file system or to exit a unresponsive X server. A happy used and known in IT circles way to start the computer with hanging system new, it, on a Linux system, the key combination to hold down Alt SysRq and is successively R, E, I, S keys to press U and B ( "Raising Elephants Is So Utterly Boring " or busier backwards). Thus, the file system cache will certainly emptied (ie their contents are written to disk ), all filesystems unmounted safely and thus help to prevent any damage to the file system.
Available combinations
The desired command is issued by pressing simultaneously on the keyboard SysRq Alt. SysRq is on IBM -AT Compatible Keyboards an alternative assignment of the pushbutton.
On keyboards for Germany simultaneously pressing the keys Alt Print key from the table below.
On keyboards for Switzerland and English-speaking countries the SysRq is the German equivalent SysRq key corresponds. The caption is, for example, in Switzerland PrtScr SysRq.
Must, especially on laptops because of vendor-specific keyboard layouts may also have additional keys are pressed, such as on Dell laptops first num, then Fn Alt Print corresponding letter; on eg ThinkPad following sequence can be used: press and hold Alt, press Fn pressure and release, press the corresponding letters, all let go.
The time required for the command button can be read in the following table, uppercase and lowercase letters does not matter. The data refer to the usual in Germany QWERTY keyboard.
- C't compact Linux. Heise, Hannover, 2009.
A large part of this article consists of information that is taken from the official documentation for the Magic SysRq key, which is usually located on Linux systems in the file / usr / src / linux / Documentation / sysrq.txt ( last revised according to the documentation for version 3.4). As a reliable operating instructions precisely this documentation for your kernel version of the system should be used.