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I'd like to do OpenGL rendering from an application that talks to an X11 server. The application reads the value of the DISPLAY variable.

I have access to a CentOS 7 box that has a nice graphics card capable of doing 3D rendering, but I don't have a monitor plugged into it.

When I run xstart, to start the X11 server, I get the following error:

Fatal server error:
(EE) no screens found(EE)

How do I start an X11 server for rendering on a graphics card, without a physical display?

This box sits in a server room, so I can't plug a physical display into it.

Also, xvfb or software renderers are perhaps not useful for this task, because it does not handle instructions needed for rendering. I would need to use the graphics adapter.

Here are the graphics adapters available to me:

# lspci | egrep 'VGA|3D'
04:00.0 VGA compatible controller: NVIDIA Corporation GP104 [GeForce GTX 1080] (rev a1)
0a:00.0 VGA compatible controller: Matrox Electronics Systems Ltd. G200eR2 (rev 01)

Here is my xorg.conf file:

# more /etc/X11/xorg.conf
# nvidia-xconfig: X configuration file generated by nvidia-xconfig
# nvidia-xconfig:  version 375.20  (buildmeister@swio-display-x86-rhel47-06)  Tue Nov 15 17:49:44 PST 2016

Section "ServerLayout"
    Identifier     "Layout0"
    Screen      0  "Screen0"
    InputDevice    "Keyboard0" "CoreKeyboard"
    InputDevice    "Mouse0" "CorePointer"
EndSection

Section "Files"
    FontPath        "/usr/share/fonts/default/Type1"
EndSection

Section "InputDevice"
    # generated from default
    Identifier     "Mouse0"
    Driver         "mouse"
    Option         "Protocol" "auto"
    Option         "Device" "/dev/input/mice"
    Option         "Emulate3Buttons" "no"
    Option         "ZAxisMapping" "4 5"
EndSection

Section "InputDevice"
    # generated from default
    Identifier     "Keyboard0"
    Driver         "kbd"
EndSection

Section "Monitor"
    Identifier     "Monitor0"
    VendorName     "Unknown"
    ModelName      "Unknown"
    HorizSync       28.0 - 33.0
    VertRefresh     43.0 - 72.0
    Option         "DPMS"
EndSection

Section "Device"
    Identifier     "Device0"
    Driver         "nvidia"
    VendorName     "NVIDIA Corporation"
EndSection

Section "Screen"
    Identifier     "Screen0"
    Device         "Device0"
    Monitor        "Monitor0"
    DefaultDepth    24
    SubSection     "Display"
        Depth       24
    EndSubSection
EndSection

I can post transcripts of any other useful logs. Thanks for any advice!

1

I've run into this problem before. Unfortunately, the best answer I've been able to come up with is a hardware solution: trick the graphics card into thinking a monitor is installed by plugging a VGA terminator into the VGA output. You can make one at home or buy one; googling for "VGA terminator" returns plenty of results for both.

Another option may be to run a VNC server on the headless system, but I'm not sure whether the graphics card can render to a VNC output.

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