Some folks prefer the Left Control key just to the left of the A key on their keyboards. If this is you, read on.

Linux

If you are the only user of your machine, you can edit /etc/default/keyboard and add or change the XKBOPTIONS line so it reads as:

    XKBOPTIONS="ctrl:swapcaps"

[I don't think this affects X sessions, so there is more to do.]

XFCE4

If you share your machine with others, change the keyboard mapping in your own account. Under the Xfce4 desktop environment (Xubuntu), open the Session and Startup settings in your Settings menu or System Settings application (xfce4-settings-manager).

Select the Application Autostart tab and click and the application configuration dialog opens:

Fill in the fields:

• Name: Swap CapsLock/LCtrl
• Description: swap CapsLock and LeftCtrl
• Command: /usr/bin/setxkbmap -option "ctrl:swapcaps"

This creates a file in $HOME/.config/autostart called Swap CapsLock-Ctrl.desktop that contains:

    [Desktop Entry]
    Encoding=UTF-8
    Version=0.9.4
    Type=Application
    Name=Swap CapsLock/Ctrl
    Comment=swap CapsLock and Left-Ctrl
    Exec=/usr/bin/setxkbmap -option "ctrl:swapcaps"
    OnlyShowIn=XFCE;
    StartupNotify=false
    Terminal=false
    Hidden=false

Variations

If ctrl:swapcaps does not tweak your keyboard as you like, read the manual page for keyboard(5):

    man keyboard

In its FILES sections it suggests looking at /usr/share/X11/xkb/rules/xorg.lst for a complete list of options. Here are some of them: