How to Use Xephyr (with examples)
Xephyr is a nested X server that runs as an X application. It provides a way to emulate another X server within your current X session, offering users the capability to create and test different graphical environments without affecting their permanent X server. It’s a valuable tool for developers and testers looking to experiment with graphical settings or applications in a controlled environment. More information on its functionality can be found here .
Use Case 1: Create a Black Window with Display ID “:2”
Code:
Xephyr -br -ac -noreset -screen 800x600 :2
Motivation:
Creating a separate X window or session is essential for isolating a particular graphical environment. You might want to test how a program behaves in a different screen resolution, color depth, or other graphical settings without changing your current X server settings and potentially disrupting your workflow. Additionally, such isolation helps when developing X applications, as it allows for repeatable testing without risk to the primary display.
Explanation:
Xephyr: This initiates the nested X server application.-br: This option specifies that the background of the window should be black. It’s useful for reducing distractions or unnecessary background details, especially when focusing on the application being tested.-ac: Allow clients to connect from any host. This casually disables access control checks, permitting easier setup for testing environments where strict host checking is unnecessary.-noreset: Prevents the X server from resetting when the last client disconnects. This is useful in development testing to keep the Xephyr window open for rapid iterations.-screen 800x600: Sets the resolution of the created X window to 800x600 pixels, which is a standard resolution for various testing scenarios.:2: This assigns the display ID “:2” to the window, allowing applications to connect to this specific instance of the X server.
Example Output:
Running the command opens a new black window on your display, identified by the display ID “:2”. This window stands ready to host X applications independently from your primary X session.
Use Case 2: Start an X Application on the New Screen
Code:
DISPLAY=:2 command_name
Motivation:
Once you have created a new X environment using Xephyr, the next logical step is to launch applications within that environment to test how they behave. By directing commands to use the specified display ID, you ensure they run in the new graphical session. This is particularly useful when testing software compatibility with different graphical configurations or conducting parallel experiments on the same machine.
Explanation:
DISPLAY=:2: This environment variable command specifies that the application should run on the X server that is identified by display ID “:2”. Using this variable redirects output from the default display to the Xephyr session.command_name: Replace this with the actual command you want to run. It can be any X application or graphical program you wish to test within the newly created environment.
Example Output:
If command_name is replaced with an application like xterm, an X term window opens within the Xephyr session on display “:2”. You can execute commands here without interfering with the primary X session, observing how the application functions in isolation.
Conclusion:
Xephyr is a powerful tool for users seeking to test and develop X applications or environments within isolated sessions. By creating a nested X server, it allows for safe experimentation and customization without altering the primary graphical environment. The flexibility of specifying screen resolution, access control, and maintaining session persistence facilitates diverse application testing scenarios.
