How to use the command `xvfb-run` (with examples)

The xvfb-run command is used to run a command in a virtual X server environment. It provides a virtual X server, called Xvfb (X virtual framebuffer), that allows you to run graphical applications in a headless or non-graphical environment. This is useful for running tests, automating tasks, or running graphical applications that don’t require a physical display.

Use case 1: Run the specified command in a virtual X server

Code:

xvfb-run command

Motivation: The motivation for using this example is to run a command that requires a graphical environment in a headless or non-graphical environment. For example, you may want to run a GUI-based test suite on a server that doesn’t have a physical display.

Explanation: The xvfb-run command is used to run the specified command in a virtual X server environment. It starts Xvfb, sets the DISPLAY environment variable to the virtual display, and then runs the command. The output of the command will be displayed in the terminal.

Example output:

$ xvfb-run firefox

This will open the Firefox browser in a virtual X server environment and display the browser window in the terminal.

Use case 2: Try to get a free server number, if the default (99) is not available

Code:

xvfb-run --auto-servernum command

Motivation: The motivation for using this example is to automatically assign a free server number to the virtual X server if the default server number (99) is not available. This can prevent conflicts when running multiple instances of xvfb-run simultaneously.

Explanation: The --auto-servernum option tells xvfb-run to automatically assign a free server number if the default server number (99) is not available. This is useful when you want to run multiple instances of xvfb-run simultaneously and avoid conflicts.

Example output:

$ xvfb-run --auto-servernum firefox

This will open the Firefox browser in a virtual X server environment with an automatically assigned server number.

Use case 3: Pass arguments to the Xvfb server

Code:

xvfb-run --server-args "-screen 0 1024x768x24" command

Motivation: The motivation for using this example is to pass custom arguments to the Xvfb server. This allows you to customize the resolution, color depth, or other parameters of the virtual X server.

Explanation: The --server-args option is used to pass custom arguments to the Xvfb server. In this example, the -screen 0 1024x768x24 argument is passed, which sets the resolution of the virtual display to 1024x768 with a color depth of 24 bits per pixel.

Example output:

$ xvfb-run --server-args "-screen 0 1024x768x24" firefox

This will open the Firefox browser in a virtual X server environment with a custom resolution of 1024x768 and a color depth of 24 bits per pixel.

Conclusion:

The xvfb-run command is a useful tool for running commands in a virtual X server environment. It allows you to run graphical applications in a headless or non-graphical environment, making it ideal for running tests, automating tasks, or running graphical applications that don’t require a physical display. The examples provided in this article illustrate different use cases of the xvfb-run command, such as running a command in a virtual X server, automatically assigning a free server number, and passing custom arguments to the Xvfb server.