What is the best way to disable Caps Lock's normal behavior, and make it do something else?
# Caps Lock becomes an additional Ctrl.
setxkbmap -option caps:ctrl_modifier
"xkb configuration is black magic in general and sheer luck in Ubuntu."
keysym BackSpace = Delete
keysym Delete = BackSpace
remove Lock = Caps_Lock
keycode 0x42 = Control_L
add Control = Control_L