Solved - Second Monitor on my Ubuntu 12.10

Is there a lot of complaints about using second monitor with Ubuntu 12.10

When i setup Ubuntu, all monitors was detected and works perfectly.  After some restarts , things was not working anymore.

I try several commands but this one works

from this topic

The problem is, in my opinion, the lightDM is not great with multi-monitors. There is a good fix though.

install disper

sudo apt-get install disper

then edit /etc/lightdm/lightdm.conf to have a

display-setup-script=disper -s line

example:

[SeatDefaults] user-session=ubuntu greeter-session=unity-greeter display-setup-script=disper -s

This will use only the primary monitor for the greeter and unity will take over once your actually logged in.