Here is How to install xvfb in Ubuntu 18.04. Just copy and paste the commands below into your Ubuntu terminal to get this package.
What is xvfb?
Xvfb provides an X server that can run on machines with no display hardware and no physical input devices. It emulates a dumb framebuffer using virtual memory. The primary use of this server was intended to be server testing, but other novel uses for it have been found, including testing clients against unusual depths and screen configurations, doing batch processing with Xvfb as a background rendering engine, load testing, as an aid to porting the X server to a new platform, and providing an unobtrusive way to run applications that don’t really need an X server but insist on having one anyway.
How to install xvfb in Ubuntu?
Update your system first then install the xvfb package in your Ubuntu os. Open your Ubuntu terminal and just copy and paste these commands:
sudo apt update sudo apt install gnuplot-x11
If you want to do it forcefully then use these commands
sudo apt update -y sudo apt install gnuplot-x11 -y