Ask Ubuntu is a question and answer site for Ubuntu users and developers. It's 100% free.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I have just upgraded from 12.04 to 12.10 (was actually a fresh install with the home partition kept and '/' wiped).

I am attempting to make my laptop monitor (Hp dv6) and my Samsung BX2450 monitor work together successfully without the nvidia package (12.04 and down needed these just to detect the extra model).

I am met with the following inconsistencies and don't really know how to go about finding the problem and fixing these:

  • When I plug the monitor in when already logged in, it works perfectly with the settings configured in System Settings -> Displays

  • When I plug the monitor in for the first time at the log in screen (from a fresh boot - i.e. without the monitor having been inserted at any time in the boot process), it once again works perfectly

  • When I boot with the monitor plugged in (or have it plugged in before the initial log in screen)
    1. the login screen is entered with my laptop display normal and my monitor has just a mirrored (without any resizing) display of my laptop screen (only takes up like 80% of the monitor screen). This is in contrast to my monitor settings which are to not mirror
    2. When I login, both monitors go black, then the main display (my laptop) does the log in (displays the unity launcher with that 'white-ish flash'. After this point erratic things happen. Both screens completely freeze (my extra monitor stays black), my laptop screen goes like the picture in this question, etc
    3. The system is completely frozen and I have to hard reboot (sometimes after a few minutes a black screen has come up with a random page full of HEX numbers)

Can anyone offer me any suggestions as to how to get this working (I would really rather not install nvidia settings as I prefer Unity successfully recognising my system as two screens)?

I am not sure if there could be remnants of my old nVidia settings on my home partition somewhere or if I need to configure something?


share|improve this question
up vote 1 down vote accepted

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


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.

See this answer for more information, but not that it's using the proprietary driver and that's not what you want. It should still work though.

share|improve this answer
Great answer. Solves the problem. Seems it was definitely lightDM causing the problems. – B T Nov 16 '12 at 6:20

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.