What does echo C proc SysRq trigger do?

What does echo C proc SysRq trigger do?

SysRq or “System Request” also known as Magic Keys, which allows us to send some specific instructions directly to the Linux kernel. This can be invoked by using a specific keyboard sequence(according to the system hardware) or by echoing letter commands to /proc/sysrq-trigger.

Where is the SysRq key?

The SysRq key is located near the Scroll Lock key on your keyboard – the Sys Rq key is generally the same as your Print Screen key. The “magic” SysRq combination is Alt+SysRq. If you see a “1”, all functions of the magic SysRq key are enabled.

How do I use SysRq?

To use Magic SysRq keys, you’ll need to use a three-key combination of Alt + SysRq + a single letter that performs the desired operation. Your first venture into the world of Magic SysRq keys should be to open up a terminal (if you’re using a windowing system) and then press Alt+SysRq+h.

What is SysRq key on laptop?

The SysRq key (sometimes Sys Req) is an abbreviation for System Request. These days, keyboards generally combine the SysRq key with the Print Screen (or Prt Scr) key. To actually invoke the System Request key, you’d need to press Alt+SysRq. This key was meant for invoking low-level operating system functions.

How do I enable SysRq on my laptop?

Most laptops require pressing Fn to get the SysRq key….The following sequence works on all the laptops I’ve seen:

1. Press and hold Alt .
2. Press Fn , press the SysRq key, and release both.
3. Briefly the letter or punctuation key, e.g. S to sync.
4. Release Alt .

How to use / proc / sysrq-trigger in Linux?

This can be invoked by using a specific keyboard sequence (according to the system hardware) or by echoing letter commands to /proc/sysrq-trigger. We need to make sure that sysrq functionality is enabled in order to use this feature. Lets have a look how to use these magical keys. To enable sysrq, we need to echo 1 to /proc/sys/kernel/sysrq file.

Where do I find the sysrq trigger key?

Invocation of any operation via /proc/sysrq-trigger is always allowed (by a user with admin privileges). You press the key combo ALT-SysRq- . Some keyboards may not have a key labeled ‘SysRq’.

How to enable or disable SysRq in Linux?

To enable sysrq, we need to echo 1 to /proc/sys/kernel/sysrq file. Following are the options we can echo to this file. 1. Available options 2. Power off the machine immediately.

What is the default value for SysRq in Linux?

When running a kernel with SysRq compiled in, /proc/sys/kernel/sysrq controls the functions allowed to be invoked via the SysRq key. The default value in this file is set by the CONFIG_MAGIC_SYSRQ_DEFAULT_ENABLE config symbol, which itself defaults to 1. Here is the list of possible values in /proc/sys/kernel/sysrq: 0 – disable sysrq completely.