kvm configuration - problem adding user to libvirtd

Hi,

I'm following this tutorial to install e configure kvm on my ubuntu 17.10:
https://help.ubuntu.com/community/KVM/Installation

But when I try to add my user to the group libvirtd I get error as this group doesn't exist.

Maybe the tutorial is obsolete and that group has been renamed?

In my system there are these groups related to kvm/qemu/libvirt:
kvm
libvirt
libvirt-qemu

To which group should I add my user?

Thanks

LK