Adding a dummy monitor

 

sudo apt-get install xserver-xorg-video-dummy

sudo vi /etc/X11/xorg.conf

Section "Device"

    Identifier  "Configured Video Device"

    Driver      "dummy"

EndSection

Section "Monitor"

    Identifier  "Configured Monitor"

    HorizSync 31.5-48.5

    VertRefresh 50-70

EndSection

Section "Screen"

    Identifier  "Default Screen"

    Monitor     "Configured Monitor"

    Device      "Configured Video Device"

    DefaultDepth 24

    SubSection "Display"

    Depth 24

    Modes "1024x800"

    EndSubSection

EndSection