Using only integrated graphics for display and Nvidia GPU for CUDA on Ubuntu 18.04.2

configure_xorg.md

Steps to follow:

1. Install suitable driver for your Nvidia GPU. Don't worry if nvidia-smi isn't working.
2. Note the output of lspci | egrep 'VGA|3D', mine gives the following:

00:02.0 VGA compatible controller: Intel Corporation Device 3e92
01:00.0 VGA compatible controller: NVIDIA Corporation Device 1f02 (rev a1)

3. Edit your /etc/X11/xorg.conf as follows

Section "ServerLayout"
    Identifier "layout"
    Screen 0 "intel"
#    Screen 1 "nvidia"
EndSection

Section "Device"
    Identifier "intel"
    Driver "intel"
    BusID "PCI:0@0:2:0"
    Option "AccelMethod" "SNA"
EndSection

Section "Screen"
    Identifier "intel"
    Device "intel"
EndSection

Section "Device"
    Identifier "nvidia"
    Driver "nvidia"
    BusID "PCI:1@0:0:0"
    Option "ConstrainCursor" "off"
EndSection

Section "Screen"
    Identifier "nvidia"
    Device "nvidia"
    Option "AllowEmptyInitialConfiguration" "on"
    Option "IgnoreDisplayDevices" "CRT"
EndSection

Replace BusID according to your output of the lspci | egrep 'VGA|3D' command.

4. Do not play with nvidia-settings let it be checked with Nvidia checkbox.

5. Reboot.