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I am trying to get a 2+1 trihead setup with two phyically connected displays and an old mac running Debian (which could if need be become anything else) as a vnc display. I am running 18.04 and my desktop environment is GNOME.

The problem is that I can not for the life of me set up a fake xrandr screen. I do not have a VIRTUAL1 output and the classical trick of repurposing an unconnected output fails:

gegaine@puppisrausku:~$ cvt 1920 1200
# 1920x1200 59.88 Hz (CVT 2.30MA) hsync: 74.56 kHz; pclk: 193.25 MHz
Modeline "1920x1200_60.00"  193.25  1920 2056 2256 2592  1200 1203 1209 1245 -hsync +vsync
gegaine@puppisrausku:~$ xrandr
Screen 0: minimum 8 x 8, current 3280 x 1080, maximum 16384 x 16384
DVI-I-0 connected primary 1360x768+0+0 (normal left inverted right x axis y axis) 406mm x 229mm
   1360x768      60.02*+
   1024x768      75.03    60.00  
   800x600       75.00    60.32  
   640x480       75.00    59.94  
DVI-I-1 disconnected (normal left inverted right x axis y axis)
HDMI-0 connected 1920x1080+1360+0 (normal left inverted right x axis y axis) 598mm x 336mm
   1920x1080     60.00*+  59.94    50.00  
   1680x1050     59.95  
   1600x900      60.00  
   1440x900      59.89  
   1280x1024     60.02  
   1280x800      59.81  
   1280x720      60.00    59.94    50.00  
   1024x768      60.00  
   800x600       60.32    56.25  
   720x576       50.00  
   720x480       59.94  
   640x480       59.94  
DP-0 disconnected (normal left inverted right x axis y axis)
DVI-D-0 disconnected (normal left inverted right x axis y axis)
DP-1 disconnected (normal left inverted right x axis y axis)
  3840x1080_60.00 (0x2fa) 346.000MHz -HSync +VSync
        h: width  3840 start 4088 end 4496 total 5152 skew    0 clock  67.16KHz
        v: height 1080 start 1083 end 1093 total 1120           clock  59.96Hz
gegaine@puppisrausku:~$ xrandr --newmode "1920x1200_60.00"  193.25  1920 2056 2256 2592  1200 1203 1209 1245 -hsync +vsync
gegaine@puppisrausku:~$ xrandr --addmode DVI-I-1 1920x1200_60.00
X Error of failed request:  BadMatch (invalid parameter attributes)
  Major opcode of failed request:  140 (RANDR)
  Minor opcode of failed request:  18 (RRAddOutputMode)
  Serial number of failed request:  41
  Current serial number in output stream:  42
gegaine@puppisrausku:~$

I am running the nvidia closed source driver and my graphics card introduces itself as follows:

gegaine@puppisrausku:~$ lspci |grep VGA
01:00.0 VGA compatible controller: NVIDIA Corporation GK106 [GeForce GTX 660] (rev a1)

I have attempted multiple variants of directly modifying xorg conf files to introduce a dummy device. No measurable effect was produced by any. I would be willing to give it a shot if someone enlightened wished to help me. I tried these:

https://devtalk.nvidia.com/default/topic/585014/how-to-configure-x-server-to-work-headless-as-well-with-any-monitor-connected-/

Add Fake Display when No Monitor is Plugged In

Temporarily giving up I did also attempt to just grow the display size and use unmapped buffer real estate to run x11vnc. This - being to the best of my understanding undefined behaviour - was too glitchy to use. If another driver or any hack forces all of the buffer to be consistent, I am willing to go for it aswell.

I have also attempted everything I could find in the graphical nvidia xorg server configuration tool, again to no avail.

Mörkö
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  • What exactly have you tried in the linked questions you posted here? In the second link you posted, https://askubuntu.com/a/713768/231142 I was able to get a fake display working there. I also left a comment below that answer because someone was having an issue. – Terrance Oct 16 '18 at 17:27
  • I tried to follow both the accepted answer and the very lowest one seeing as the middlemost doesn't seem applicable. That is: I created the files as they were and rebooted. Given that my setup contains an intel processor with an integrated GPU, I didn't think that the driver thing was crucial. No visible change in xrandr occured. – Mörkö Oct 16 '18 at 17:30
  • OK, I can set the larger screen to extend with --fb. If I can disable panning I think it might work – Mörkö Oct 16 '18 at 17:35
  • Thank you @Terrance, that is definitely closer. I can extend one of my screens with fb as shown (xrandr --fb 5200x1080), but I can't figure the panning thing out. – Mörkö Oct 16 '18 at 18:02
  • I've only used it for fitting to my present screen at the time. I wish I was more help on that one. – Terrance Oct 16 '18 at 18:07

0 Answers0