I am running automated tests on an app while recording the desktop for future analysis.

I am working from a standard Ubuntu Linux setup.

I would like to be able to switch to another user while these tests are running to continue working on other tasks.

When I switch to another user using a different virtual console logging in and starting a second x11 session using startx the screen recording of the X11 server running on Ctrl+Alt+F7 records nothing but a black screen.

I have discovered that this is because the X11 screen buffer stops rendering on none active run levels .

What configuration setting for X11 keeps will keep it rendering when switched away from that virtual console?

Patching and building X11 is not preferable but acceptable .

1 Answer 1


Don't run your tests on an X server that displays to your hardware. Run them in an X server that “displays” to a virtual framebuffer that's just a chunk of memory, such as Xvfb. Xvfb is commonly used for testing GUI applications such as web browsers.

This won't work if your application needs to work closely with hardware features, e.g. because it needs 3D acceleration. But if this was the case your application wouldn't work when the X server isn't rendering anyway.

  • it is in fact using HW acceleration to render Jun 5, 2015 at 0:15
  • @JamesAndino So what happens when you switch to another tty and X stops rendering? Jun 5, 2015 at 0:18
  • the screen recording of the application just stops and goes blank , i have a little program that compares those recordings between test runs and looks for visual discrepancies . Jun 5, 2015 at 0:19
  • @JamesAndino But not the application? How do you know that the problem is with the screen recording and not with the application? Jun 5, 2015 at 0:19
  • the data output from the application is correct , points progress level etc . also silly but you can still hear the audio output . I found a short blurb about how x11 does not render when switched to another tty , but no further info after a fair amount of searching . Jun 5, 2015 at 0:20

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