# What's Key\_Sysreq?

**URL:** <https://community.keyboard.io/t/whats-key-sysreq/2813>\
**Category:** Kaleidoscope Internals\
**Tags:** question\
**Created:** [April 26, 2019, 7:19pm UTC](https://community.keyboard.io/t/whats-key-sysreq/2813 "2019-04-26T19:19:15Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![flussence](https://yyz1.discourse-cdn.com/flex031/user_avatar/community.keyboard.io/flussence/32/19_2.png) [@flussence](https://community.keyboard.io/u/flussence)\
**Post date:** [April 26, 2019, 7:19pm UTC](https://community.keyboard.io/t/whats-key-sysreq/2813/1 "2019-04-26T19:19:15Z")

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I mapped Fn+Prog to Key\_Sysreq, for the rare occasion I need to do a three finger salute in Linux. It wasn’t working for me, and I was stumped for a while until I compared the output with other keyboards and realised I had the wrong keycode entirely! Linux actually wants the “print screen” scancode, and it’s already present on the default layout (Fn+Z).

But I’m curious to know now, where did this other thing I unearthed come from? `showkey` gives me keycode 240 for it and `xev` recognises it only as an unnamed keycode 248.

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**Author:** ![andrewg](https://yyz1.discourse-cdn.com/flex031/user_avatar/community.keyboard.io/andrewg/32/43_2.png) [@andrewg](https://community.keyboard.io/u/andrewg)\
**Post date:** [April 29, 2019, 2:30pm UTC](https://community.keyboard.io/t/whats-key-sysreq/2813/2 "2019-04-29T14:30:57Z")

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Back in the long lost days of the IBM PC, pressing alt+printScreen activated a _hardware_ option that sent a completely separate keycode to the computer, bypassing all software features. It was intended as a non-maskable interrupt but has fallen into disuse.

The Linux “Magic SysRq” key is an emulation of this behaviour, but because it is implemented in software it doesn’t use the hardware Key\_Sysreq.

> **[System request](https://en.wikipedia.org/wiki/System_request)**
>
> System request (often abbreviated SysRq or Sys Req) is a key on personal computer keyboards that has no standard use. Introduced by IBM with the PC/AT, it was intended to be available as a special key to directly invoke low-level operating system functions with no possibility of conflicting with any existing software. A special BIOS routine – software interrupt 0x15, subfunction 0x85 – was added to signal the OS when SysRq was pushed or released. Unlike most keys, when it is pressed nothing The s...