"NEW" nvidia-headless drivers available
While just upgrading my nvidia driver from 390 to 396 in order to be able to use cuda 9.2 I realized new driver versions that are available from the graphics-drivers/ppa on ubuntu. Those are just what we are looking for in this thread I think 
mpr@x15 >> apt show nvidia-headless-396
Package: nvidia-headless-396
Version: 396.51-0ubuntu0~gpu18.04.1
Priority: optional
Section: libs
Source: nvidia-graphics-drivers-396
Maintainer: Ubuntu Core Developers <ubuntu-devel-discuss@lists.ubuntu.com>
Installed-Size: 20,5 kB
Depends: nvidia-headless-no-dkms-396, nvidia-dkms-396
Download-Size: 8.492 B
APT-Sources: http://ppa.launchpad.net/graphics-drivers/ppa/ubuntu bionic/main amd64 Packages
Description: NVIDIA headless metapackage
This metapackage installs the NVIDIA driver and the libraries that enable
parallel general purpose computation through CUDA and
OpenCL.
.
Install this package if you do not need X11 or Wayland support, which is
provided by the nvidia-driver-396 metapackage.
The last line is what this thread is about, so maybe this is the new simplest form of getting this to work.
Have explicitly NOT tested this myself yet, this just as a heads-up. At least this way you have the option to avoid the xserver driver installation, which was previously only possible via runfiles and the reason people suggested using those in this thread.