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Neither is my OS virtualized inside VirtualBox nor do I have any VirtualBox packages installed (at least no packages matching "virtual" or "vbox").
Still, on every boot up (in the end of the phase displaying the gnome foot and the 3 blinking dots) the following message pops up in the upper right corner:
VBoxClient: the VirtualBox kernel service is not running. Exiting
I believe this causes boot delays.