Xephyr

Xephyr is a nested X server that runs as an X application.

Installation

xorg-server-xephyr is available from official repositories. Install it with pacman.

Execution

If you wish to run a nested X window, you'll need to specify a new display.

$ Xephyr -br -ac -noreset -screen 800x600 :1

This will launch a new Xephyr window with a DISPLAY of ":1". In order to launch an application in that window, you would need to specify that display.

$ DISPLAY=:1 xterm

Launching Window Managers

If you want to launch a specific WM, spectrwm for example, you would type:

$ DISPLAY=:1 spectrwm

You can also launch Xephyr with your xinitrc using startx:

$ startx -- /usr/bin/Xephyr :1

Grabbing and Ungrabbing User Input

Pressing Ctrl + Shift should lock/unlock your mouse pointer and your keystrokes inside Xephyr window exclusively if possible.