I’m used to my Mac where the direction of scrolling was changed to a more ‘natural’ way starting with OSX Lion. It’s the same way scrolling works on mobile devices. When working on Ubuntu, I want to have the same behaviour because I’m used to it.
To do so you need to edit (or create) the .Xmodmap file in your homedir.
This is the default:
cat ~/.Xmodmap pointer = 1 2 3 4 5
I changed it to:
vim ~/.Xmodmap pointer = 1 2 3 5 4
This essentially makes the last two (scroll wheel) buttons work the other way around, and that is exactly the behaviour I want.
To enable this setting you have to either logout (and back in) of your X environment, or run this oneliner (Thanks James!):
xmodmap -e "pointer = 1 2 3 5 4"
By editing both the Xmodmap file and running the above oneliner, the new setting works immediately and also keeps working when you (for example) reboot your machine.
Remi Bergsma's blog 