gpu-manager overwrites xorg.conf

Solution 1:

OK, as per this blogpost, adding nogpumanager to GRUB_CMDLINE_LINUX_DEFAULT in /etc/default/grub solves the issue. Thus, the line in /etc/default/grub should look like:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash nogpumanager"

After you edit the file, don't forget to run:

sudo update-grub

Solution 2:

Look here for all possible solution https://vxlabs.com/2015/02/05/solving-the-ubuntu-14-04-nvidia-346-nvidia-prime-black-screen-issue/#comments

one good solution is

 By doing sudo chattr +i /etc/X11/xorg.conf you can prevent any process from changing the file. 

But then I am not sure aticonfig --initial will work