Xinerama breaks Ubuntu 16.04?

my setup

  • i have a brand new machine with 2 geforce 1080 ti cards
  • i have 4 monitors arranged in a square 2x2 pattern
  • each of the cards is connected to 2 monitors via hdmi cables
  • i have a fresh install of Ubuntu 16.04

i boot up the machine and all 4 monitors are recognized and i can arrange them into my 2x2 through the built in “displays” gui within Ubuntu

i then go through these instructions for the CUDA installation
https://docs.nvidia.com/cuda/cuda-installation-guide-linux/index.html

after rebooting, 2 of the displays are dark, but it appears that CUDA installed perfectly fine. the 2 dark displays are no longer visible through the native “displays” area, but if i start NVIDIA X server, i can see the 2 disabled displays, enable them, save the configuration file and then reboot

now upon restarting, the two displays are black, but i can run a mouse through them and it changes into a white outline X

so i go back to X server, enable Xinerama, arrange the monitors, save the file and reboot.

i get to the login screen with 4 monitors active and displaying a background, but immediately after logging in, and box pops up saying there has been a problem, and the screens go black, display a message that starts out, “lvmetad is not active yet, using direct activation during sysinit” and then it kicks me back to the login screen, again with 4 monitors active.

i’m stuck as to where to go from here.

thanks