The usual place, /home/username/.config/xfce4/xfconf/xfce-perchannel-xml/xfce4-keyboard-shortcuts.xml, shows nothing for this combo, but pressing it clearly does something. I'm unsure if it reboots X or just logs me out. Where can I find what Ctrl + Alt + Backspace is set up to trigger on my machine?
Since I couldn't find a direct answer, and All I know Ctrl+Alt+Backspace kills X Server. I checked the origin and found useful references ONLY, you may need a +50 year old dinasour for this topic because I'm only a 30y old dinosaur. Hope it helps!
Control-Alt-Delete or "three-finger salute" is a soft reboot function via keyboard was originally designed by David Bradley.
and check,
Before the advent of journaled filesystems a common use of the magic SysRq key was to perform a safe reboot of a Linux computer which has otherwise locked up (abbr. REISUB), which avoided a risk of filesystem corruption. With modern filesystems, this practice is discouraged, offering no upsides over straight re
Boot.
Another past use was to kill a frozen graphical program, as the X Windows System used to have complete control over graphical mode and input devices.
The feature is controlled both by a compile-time option in the kernel configuration, CONFIG_MAGIC_SYSRQ, and a sysctl kernel parameter, kernel.sysrq.
On newer kernels (since 2.6.12[5]), it is possible to have more fine-grained control over how the magic SysRq key can be used.[6] On these machines, the number written to
/proc/sys/kernel/sysrqcan be0,1, or a number greater than 1 which is a bitmask indicating which features to allow. On Ubuntu this is set at boot time to the value defined in/etc/sysctl.d/10-magic-sysrq.conf
While the magic SysRq key was originally implemented as part of the kernel's keyboard handler for debugging, the functionality has been also exposed via the proc filesystem and is commonly used to provide extended management capabilities to headless and remote systems. From user space programs (such as a command line shell), SysRq may be accessed by writing to
/proc/sysrq-trigger(e.g.,echo s > /proc/sysrq-trigger).[1]
Many embedded systems have no attached keyboard, but instead use a serial console for text input/output to the running system. It is possible to invoke a Magic SysRq feature over a serial console by sending a serial break signal, followed by the desired key. The method of sending a break is dependent on the terminal program or hardware used to connect to the serial console. A sysctl option needs to be set to enable this function.[7]
As well look for X display manager and X Windows System
