If your running Ubuntu with the Gnome desktop is simple to swap Caps Lock and Control keys. Do this:
Click System > Preferences > Keyboard > Layouts > Layout Options > Ctrl key position
Here you can select:
Swap Ctrl and CapsLock
Make CapsLock an additional Ctrl
I selected the latter as I never use Caps Lock. I find it a pain, when I sometimes hit it and find I type text in UPPERCASE.
So I went with an additional Ctrl key.
. . .