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The keyboard settings are stored in /etc/default/keyboard
Keyboard layout (keymap), see debian-reference.
"dpkg-reconfigure --priority=low xserver-xorg" suggested by the above linked page does not work in Squeeze. You may try to add something like "setxkbmap us,ru -option grp:ctrl_shift_toggle" into ~/.xsessionrc instead.
Change Keyboard Layout
A keyboard layout can be changed on command line:
dpkg-reconfigure keyboard-configuration
Use the tool mentioned above if you want to change your keyboard map e.g from qwerty to qwertz.