The keyboard configuration file is located at /etc/default/keyboard (in Debian). The next lines are an example of settings which can be set there:

# Consult the keyboard(5) manual page.

XKBMODEL="thinkpadx220"
# XKBLAYOUT="us"
XKBLAYOUT="us,es,fi"
XKBVARIANT="euro"
# XKBOPTIONS="lv3:ralt_switch,compose:lwin,terminate:ctrl_alt_bksp"
XKBOPTIONS="grp:alt_shift_toggle,lv3:ralt_switch,terminate:ctrl_alt_bksp,ctrl:swapcaps,altwin:left_meta_win"

BACKSPACE="guess"

Alternatively, one can use:

setxkbmap -layout us,es,fi -option grp:ctrl_shift_toggle -option ctrl:swapcaps -option terminate:ctrl_alt_bk    sp-option altwin:left_meta_win