Дуже коротко

cat /etc/X11/xorg.conf.d/30-keyboard.conf 
Section "InputClass"
        Identifier "system-keyboard"
        MatchIsKeyboard "on"
        Option "XkbLayout" "us,ru,ua"
        Option "XkbModel" "pc105"
        Option "XkbOptions" "grp:caps_toggle"
EndSection