X Window

Xvfb Common Use Cases

Use Case	Traditional X Server	Xvfb (Virtual Framebuffer)
Desktop Interactive	Requires physical display	Runs in memory buffer
Screen Recording	Depends on graphics rendering	Renders to memory buffer
CI/CD Automation	May be impacted by user activity	Provides isolated environment

Install packages

# Useful utils
sudo apt install x11-apps
sudo apt install x11-utils

# Install imagemagick for screenshot
sudo apt install imagemagick

# Install for screen record
sudo apt install ffmpeg

Commands

Start Virtual X Server

Xvfb :99 -screen 0 1280x1024x24 -nolisten tcp -auth /tmp/xvfb-run.1/Xauthority
export XAUTHORITY=/tmp/xvfb-run.1/Xauthority
export DISPLAY=:99

Open X terminal and type hello then return and copy all screen

xterm -class HostWindow
xdotool search --class "HostWindow" windowsize --sync %@ 800 600 windowfocus %@ type --window %@ "hello" key --window %@ Return
xdotool search --class "HostWindow" key --window %@ "ctrl+a" "ctrl+c"

type hello then return and copy all screen on active window

xdotool type "hello"
xdotool key Return
xdotool key "ctrl+a" "ctrl+c"

Other useful commands

xprop | grep WM_CLASS

xwininfo -tree -root

xeyes # Shows eyes following cursor
xclock # Displays clock

xdpyinfo -display $DISPLAY

xdotool search --class "HostWindow" getwindowname
xdotool search --class "HostWindow" getwindowgeometry

# Capture to screenshot.png
import -window root -display $DISPLAY screenshot.png # $DISPLAY env have higher priority than -display

# Install FFmpeg and record
ffmpeg -f x11grab -s 1280x1024 -i :99 -vcodec libx264 out.mp4