Aby utworzyć skrót lub zdarzenie do klawiszy funkcyjnych, potrzebujemy najpierw ustalić tzw. keycode

Jak sprawdzić wartość keycode do poszczególnych klawiszy?

Sposób I.

xev -event keyboard

admin@PU551:~$ xev -event keyboard
Outer window is 0x3800001, inner window is 0x3800002

KeymapNotify event, serial 24, synthetic NO, window 0x0,
    keys:  4294967199 0   0   0   16  0   0   0   0   0   0   0   0   0   0   0
           0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0

KeyRelease event, serial 25, synthetic NO, window 0x3800001,
    root 0xd4, subw 0x0, time 34144487, (268,-279), root:(269,129),
    state 0x10, keycode 36 (keysym 0xff0d, Return), same_screen YES,
"   XLookupString gives 1 bytes: (0d) "
    XFilterEvent returns: False

KeymapNotify event, serial 26, synthetic NO, window 0x0,
    keys:  4294967252 0   0   0   0   0   0   0   0   0   0   0   0   0   0   4
           0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0

KeyRelease event, serial 28, synthetic NO, window 0x3800001,
    root 0xd4, subw 0x0, time 34148415, (268,-279), root:(269,129),
    state 0x10, keycode 122 (keysym 0x1008ff11, XF86AudioLowerVolume), same_screen YES,
    XLookupString gives 0 bytes:
    XFilterEvent returns: False
^C

Sposób II.

Najlepiej bezpośrednio w trybie tekstowym (ctrl+alt+f1)

showkey -k

-h –help display this help text
-a –ascii display the decimal/octal/hex values of the keys
-s –scancodes display only the raw scan-codes
-k –keycodes display only the interpreted keycodes (default)

Sposób III.

admin@PU551:~$ xbindkeys -k
Press combination of keys or/and click under the window.
You can use one of the two lines after "NoCommand"
in $HOME/.xbindkeysrc to bind a key.
"NoCommand"
    m:0x10 + c:122
    Mod2 + XF86AudioLowerVolume

źródła:
http://www.fascinatingcaptain.com/howto/remap-keyboard-keys-for-ubuntu/

Sposób IV.

admin@PU551:~$ xmodmap -pke | grep Brig
keycode 232 = XF86MonBrightnessDown NoSymbol XF86MonBrightnessDown
keycode 233 = XF86MonBrightnessUp NoSymbol XF86MonBrightnessUp
keycode 237 = XF86KbdBrightnessDown NoSymbol XF86KbdBrightnessDown

źródła:
https://wiki.archlinux.org/index.php/Xbindkeys
http://forums.fedoraforum.org/showthread.php?t=296958
http://www.pclinuxos.com/forum/index.php?topic=127998.0