Debian Keyboard Layout

Debian Wiki: Keyboard

$ dpkg-reconfigure keyboard-configuration
$ cat /etc/default/keyboard
$ setxkbmap ch
$ cat /usr/share/doc/keyboard-configuration/README.Debian
After modifying /etc/default/keyboard, you can apply the changes to the Linux
console by running setupcon. If X is configured to use that file too, then the
changes will become visible to X only if

udevadm trigger --subsystem-match=input --action=change

is called, or the system is rebooted.