[396.54] [GTX1050Ti] [Ubuntu 18.04] All monitors of second GPU are disconnected

I’m setting up a workstation with 2 GPU (Nvidia GTX1050 Ti) and 6 displays (samsung md230x6) on Ubuntu 18.04.

It’s all working fine except that the desktop shows only on the displays of the first GPU; the other three are black: I cannot move any window upon but the mouse cursor actually shows as a black cross with white outline.

Funny fact is that I can actually change the color of the black screens via nvidia-settigs GUI Color Correction.

The same rig works fine on Win10.

I tried to physically disconnect three monitors and modified xorg.conf following https://wiki.archlinux.org/index.php/multihead without any change.

$ xrandr
 Screen 0: minimum 8 x 8, current 5760 x 1080, maximum 32767 x 32767
 DVI-D-0 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 510mm x 287mm
    1920x1080     60.00*+  50.00  
    ...
 HDMI-0 disconnected (normal left inverted right x axis y axis)
 DP-0 connected 1920x1080+1920+0 (normal left inverted right x axis y axis) 510mm x 278mm
    1920x1080     60.00*+  59.94    50.00  
    ...
 DP-1 disconnected (normal left inverted right x axis y axis)
 HDMI-1 disconnected (normal left inverted right x axis y axis)
 HDMI-2 connected 1920x1080+3840+0 (normal left inverted right x axis y axis) 510mm x 287mm
    1920x1080     60.00*+  50.00  
    ...
$ nvidia-smi
+-----------------------------------------------------------------------------+
| NVIDIA-SMI 396.54                 Driver Version: 396.54                    |
|-------------------------------+----------------------+----------------------+
| GPU  Name        Persistence-M| Bus-Id        Disp.A | Volatile Uncorr. ECC |
| Fan  Temp  Perf  Pwr:Usage/Cap|         Memory-Usage | GPU-Util  Compute M. |
|===============================+======================+======================|
|   0  GeForce GTX 105...  Off  | 00000000:01:00.0  On |                  N/A |
|  0%   46C    P8    N/A / 120W |    624MiB /  4037MiB |      1%      Default |
+-------------------------------+----------------------+----------------------+
|   1  GeForce GTX 105...  Off  | 00000000:02:00.0  On |                  N/A |
| 45%   29C    P0    N/A /  75W |     64MiB /  4040MiB |      0%      Default |
+-------------------------------+----------------------+----------------------+

+-----------------------------------------------------------------------------+
| Processes:                                                       GPU Memory |
|  GPU       PID   Type   Process name                             Usage      |
|=============================================================================|
|    0       953      G   /usr/lib/xorg/Xorg                            34MiB |
|    0      1003      G   /usr/bin/gnome-shell                          48MiB |
|    0      1250      G   /usr/lib/xorg/Xorg                           286MiB |
|    0      1393      G   /usr/bin/gnome-shell                         147MiB |
|    0      2355      G   ...-token=C398224CE3FA660C9FF3A88B97994567   105MiB |
|    1       953      G   /usr/lib/xorg/Xorg                            30MiB |
|    1      1250      G   /usr/lib/xorg/Xorg                            31MiB |
+-----------------------------------------------------------------------------+
$ uname -a
Linux myhostname 4.15.0-33-generic #36-Ubuntu SMP Wed Aug 15 16:00:05 UTC 2018 x86_64 x86_64 x86_64 GNU/
$ lspci | grep VGA
01:00.0 VGA compatible controller: NVIDIA Corporation GP107 [GeForce GTX 1050 Ti] (rev a1)
02:00.0 VGA compatible controller: NVIDIA Corporation GP107 [GeForce GTX 1050 Ti] (rev a1)

/usr/share/X11/xorg.conf.d/10-nvidia.conf:

Section "OutputClass"
    Identifier "nvidia"
    MatchDriver "nvidia-drm"
    Driver "nvidia"
    Option "AllowEmptyInitialConfiguration"
    ModulePath "/usr/lib/x86_64-linux-gnu/nvidia/xorg"
EndSection

/etc/X11/xorg.conf: https://gist.github.com/pliski/73a68ba3cd2b489a008e4c822db0c717

/var/log/Xorg.log: https://gist.github.com/pliski/b3ede6b301c16199e8ebd84f876fb8f2

See also:

_ https://askubuntu.com/questions/843561/3rd-monitor-showing-x-cursor
_ https://askubuntu.com/questions/1071480/ubuntu-18-04-display-disconnected

nvidia-bug-report.log.gz (143 KB)

That doesn’t work when using the proprietary driver.
You now have two screens, your desktop running on the first screen. You can start applications on the second screen by specifying the DISPLAY variable, e.g.
DISPLAY=:1.1 xterm &
or maybe even start a second desktop
DISPLAY=:1.1 gnome-shell &
but you can’t move windows between those.
(syntax for DISPLAY=hostname:#xserver.#screen)

Ok. It’s more clear now, thanx.

So if I want the desktop to extend to 6 monitors with two cards in xorg.conf I have to define 1 Screen served by 2 Devices with 3 Monitors each.

Is that possible with the proprietary driver?

Only with Quadro cards, not with Geforce types.

A probably less favorable possibility for you is to rip out one card, enable the on-board intel gpu, connect three monitors to that and use PRIME.

Ok, thanks I will try also this, for now I’m trying with the standard driver.

One option I left out is Xinerama, but that’s outdated and has limitations.