If VirtualBox opens fine, but when you try to start a virtual machine (VM) you get the following error:
Failed to start the virtual machine Windows XP.
VirtualBox can’t operate in VMX root mode. Please disable the KVM kernel extension, recompile your kernel and reboot (VERR_VMX_IN_VMX_ROOT_MODE).
… it means another virtualisation package – kvm – is interfering with VirtualBox. kvm isn’t installed on Ubuntu by default, so you probably installed qemu, the popular open-source emulator.
A quick fix is to stop kvm via the terminal:
sudo /etc/init.d/kvm stop
To stop this happening completely, mark the following packages for complete removal in Synaptic if they’re installed: kvm, qemu, qemu-kvm & qemu-launcher. Or you can do it via the terminal, and ignore errors regarding packages that weren’t installed (so can’t be uninstalled):
sudo apt-get remove kvm qemu qemu-kvm qemu-launcher
You should now be able to start your VM, without having to close and restart VirtualBox.
Did this information make your day? Did it rescue you from hours of headache? Then please consider making a donation via PayPal, to buy me a donut, beer, or some fish’n’chips for my time and effort! Many thanks!