Use virt-manager without root password on Debian 9
After installing virt-manager on Debian 9 you’ll notice that every time you try to open it it will ask for your root password.
In order to avoid that you’ll just need to add your user to the libvirt group:
sudo usermod -aG libvirt dferreira
Logout and login again. You can now open virt-manager without your root password.