To enable or disable the touchpad:
Press
Type gconf-editor to bring up the
Click
Check/uncheck
Click
If the touchpad is your only pointing device and you accidentally disabled it, you can enable it again using just the keyboard:
Press
Type
Press
There is currently no simple way of having your touchpad automatically disabled when a mouse is plugged in.
gconftool --set /desktop/gnome/peripherals/mouse/touchpad_enabled -t bool True
gconftool --set /desktop/gnome/peripherals/mouse/touchpad_enabled -t bool False
ENV{ID_CLASS}="mouse", ACTION=="add", RUN+="synclient touchpadoff=1"
ENV{ID_CLASS}="mouse", ACTION=="remove", RUN+="synclient touchpadoff=0"