Gnome Boxes on Ubuntu 18.04
I've recently tried to install Gnome Boxes on my computers. Mainly because I wanted to test how it performance against Virtualbox. Virtualbox is currently still owned by Oracle and they don't have a great track record with free software. Therefore it's a good idea to have an eye on alternatives to the products they provide.
While the main installation went fine I wasn't able to get a VM up and running. When I launched Boxes from the command line, it showed me this error message:
Failed to start windows-10: Unable to start domain: unsupported configuration: CPU mode 'custom' for x86_64 kvm domain on x86_64 host is not supported by hypervisor
After a bit of searching around I've found this bug report: https://bugs.launchpad.net/ubuntu/+source/gnome-boxes/+bug/1762205
The last post from Stephen Matin contained the solution. You basically have to do the following:
Install Gnome Boxes and the
sudo apt install gnome-boxes qemu-kvm libvirt-bin
Add your user to the group
sudo usermod -a -G kvm $USER
Allow users in the kvm group to start KVM virtual machines.
sudo sed -i -e 's/\#group\ =\ "root"/group=kvm/g' /etc/libvirt/qemu.conf
Now you can restart your computer and Gnome Boxes should work as expected.