If you press Ctrl-Alt-Del (or whatever key was assigned the keysym Boot by
loadkeys) then either the machine reboots immediately (without sync), or
init is sent a SIGINT. The former behaviour is the default. The default
can be changed by root, using the system call reboot(), see ctrlaltdel(8).
Some init's change the default. What happens when init gets SIGINT depends
on the version of init used - often it will be determined by the pf entry in
/etc/inittab (which means that you can run an arbitrary program
in this case).
In the current kernel Ctrl-AltGr-Del is no longer by default assigned to Boot.
Name Default binding
-------------------------------
Show_Memory Shift-Scrollock
Show_Registers AltGr-ScrollLock
Show_State Ctrl-ScrollLock
Console_n Alt-Fn and Ctrl-Alt-Fn (1 <= n <= 12)
Console_{n+12} AltGr-Fn (1 <= n <= 12)
Incr_Console Alt-RightArrow
Decr_Console Alt-LeftArrow
Last_Console Alt[Gr]-PrintScreen
Scroll_Backward Shift-PageUp
Scroll_Forward Shift-PageDown
Caps_On (CapsLock is a toggle; this key sets)
Compose Ctrl-.
Ctrl-Alt-Fn Switch to VT n Ctrl-Alt-KP+ Next mode Ctrl-Alt-KP- Previous mode Ctrl-Alt-Backspace Kill XOn some motherboards, Ctrl-Alt-KP- and Ctrl-Alt-KP+ will be equivalent to pressing the Turbo button. That is, both will produce the scancodes 1d 38 4a ca b8 9d and 1d 38 4e ce b8 9d, and both will switch between Turbo (>= 25MHz) and non-Turbo (8 or 12 MHz). (Often these key combinations only function this way when enabled by jumpers on the motherboard.)
Perry F Nguyen (pfnguyen@netcom22.netcom.com) writes:
AMI BIOS has a feature that locks up the keyboard and flashes the LED's
if the Ctrl-Alt-Backspace combination is pressed while a BIOS password
is enabled, until the CMOS/BIOS password is typed in.
On some SiS based motherboards the combination Ctrl-Alt-Backspace will cause a power off, or puts the machine in power save mode. (Reported for SiS 630 and for SiS645DX.)
Ctrl-Alt-Fn Switch to VT n (from version 0.50; earlier Alt-Fn) Ctrl-Alt-PgDn Kill dosemu (when in RAW keyboard mode) (and many other combinations - see the dosemu documentation)
One symbol may be constructed using several keystrokes.