I recently installed Ubuntu 16.04 on my 5 year old Lenovo and immediately my touchpad didn't work. I looked around and found a solution (can't find the link) which told me to do this:
sudo apt-get install aptitude sudo aptitude update sudo aptitude install xserver-xorg-input-synaptics
aptitude told me that a bunch of other
xserver-xorg items would be removed to deal with the dependencies (apologies but I did not write down which ones though there were about 10 of them all related to
xserver-xorg), and after installing and rebooting, my touchpad, keyboard and touchscreen all worked. I rebooted again the other day and now only my touchpad works.
I've looked online for other solutions, but none of the ones I've looked at have been helpful. I was thinking it might just be a case of reinstalling all the
xserver-xorg packages that I uninstalled, but I'm not sure how to go about this since there are so many of them. Also any deeper insight into why my touchpad wouldn't work would be appreciated - it used to do the same thing to me on Windows until I installed the Synaptics drivers.
EDIT: The mouse and keyboard which I plugged in to my laptop were also not recognised.
EDIT #2: I ran
sudo apt-get install xserver-xorg-input-all and now I'm right back where I started - touchpad not working, everything else fine.