XKB configuration - keyboard mappings

/etc/X11/xorg.conf

Section "InputDevice"
        Identifier      "Generic Keyboard"
        Driver          "kbd"
        Option          "CoreKeyboard"
        Option          "XkbRules"      "xorg"
        Option          "XkbModel"      "pc105"
        Option          "XkbLayout"     "en,de,es"
        Option          "XKbOptions"    "grp:alt_shift_toggle"
EndSection

restart xserver.

After that, alt+shift can change the keyboard layout in the order as english-german-spanish.

Reference

• http://ftp.x.org/pub/X11R6.9.0/doc/html/XKB-Config.html