Sysrq what is it for

What was the single key that was added? The SysRq key! The original intent of the SysRq key has been long abandoned. However, some OSs still use it for their own purposes. Linux, for example, has been listening for the old interrupt since the mid-nineties.

The Linux kernel is capable of listening for and processing several commands that rely on the SysRq key. That means at least kernel 2. Let it suffice to say that if you have any reasonably modern Linux kernel, you should be okay. If disabled, enable SysRq using one of several methods.

To enable SysRq temporarily it falls back to being disabled at the next reboot you can use the sysctl command: sysctl -w kernel. This prints the SysRq help screen in your terminal.

To begin testing more dangerous keystrokes, you could fire up a virtual machine and test SysRq keys that way. The last few examples of Magic SysRq were spectacularly destructive. The above examples probably led you to wonder why you would even use Magic SysRq commands at all.

To answer that quandary, you should take a look at the SysRq documentation. Within the documentation, you will see quite a number of different key combinations. New to Red Hat?

Here are the common uses of Markdown. Learn more Close. It seems others find it useful as System Attention Key which is useful when you want to exit a program that will not let you switch consoles. For example, X or a svgalib program. Note that this just triggers a crash if there is no dump mechanism available. The loglevels 0 - 9 are useful when your console is being flooded with kernel messages you do not want to see.

Selecting 0 will prevent all but the most urgent kernel messages from reaching your console. When this happens, try tapping shift, alt and control on both sides of the keyboard, and hitting an invalid sysrq sequence again. Oh, and by the way, you exit showkey by not typing anything for ten seconds.

This is in case the slot has been overwritten since you registered it. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Learn more. What does the SysRq key do? Ask Question. Asked 12 years, 4 months ago. Active 1 year, 10 months ago. Viewed 17k times. Improve this question. Tamara Wijsman 56k 27 27 gold badges silver badges bronze badges. There is a Wikipedia page for the System Request key. Any chance of choosing a correct answer?

Thanks — Dominic Zukiewicz. Post-bounty note: The bounty was given to a 5-year old answer that was relatively underappreciated until recently.