I am running Ubuntu 10.10 amd64 in a Virtualbox on windows host. whenever i try to take a screenshot by pressing the print screen or by launching the gnome-screenshot option the screenshot appears completely black. any idea how to get a screenshot inside the Virtualbox?
In Ubuntu guest go to System -> Preferences -> Keyboard Shortcuts. On the following window define a new shortcut to take a screenshot (e.g. in this example ShiftAltP):
Thenafter a screenshot will be taken whenever you press your keyboard shortcut. The default setting using Print is not available in the guest (host only).
Taking screenhots will not work with desktop effects activated, i.e. when Compiz is running (see here for reference).
In VirtualBox 4.2.6 with Windows7-host and Ubuntu12.10-guest, I took correct screen shots before installing Guest Addition tools. After this, I get only black screens and desktop background image.
After disabling VirtualBox 3D acceleration in VM configuration, the problem seems to be gone.
Now I can use PrintScreen to take the full screen and Alt + PrintScreen to take a window screen shot through the gnome default capture utility.