reconfiguring mouse buttons

to remap the buttons

 xinput set-button-map $id  1 2 3 4 5 6 7 8 9 2 11 12 13

where $id can be found by 

xinput list

To enable the 3 mouse button

in /etc/X11/xorg.conf

Section "InputClass" 

        Identifier  "yes 3 button emulation"

        MatchIsPointer "on"

        MatchDevicePath "/dev/input/event*"

        Driver "evdev"

        Option  "Emulate3Buttons" "true"

EndSection

(and not in "InputDevice" )

On 12.04,

edit
/usr/share/X11/xorg.conf.d/10-evdev.conf

by assing the Option to this section


Section "InputClass"
        Identifier "evdev touchpad catchall"
        MatchIsTouchpad "on"
        MatchDevicePath "/dev/input/event*"
        Driver "evdev"
        Option "Emulate3Buttons" "True"
EndSection