I use XFCE but this solution should work for any desktop environment on Debian or Ubuntu:
Replace the XKBOPTIONS
definition in /etc/default/keyboard
with
XKBOPTIONS="ctrl:nocaps"
This affects all users on the system.
This won't affect your current session (you have to restart X11),
so you can run this command line to change things until then:
$ setxkbmap -option ctrl:nocaps
To affect only your user, have the above command run as a part of your session: Open your XFCE Settings (run xfce4-settings-manager
) and click on Session and Startup, go to the Application Autostart tab, and Add that command.