This is how I managed to provision my vagrant development environment using libvirt instead of Virtualbox, so it now loads faster.

Using_Libvirt_With_Vagrant.sh

sudo apt-get -y install libvirt-dev qemu-kvm libvirt-bin ubuntu-vm-builder bridge-utils
vagrant plugin install vagrant-libvirt
vagrant plugin install vagrant-share
sudo addgroup libvirtd
sudo usermod -a -G libvirtd $user
sudo apt install nfs-kernel-server
sudo reboot
vagrant up --provider=libvirt

Vagrantfile

# This is just an example, use the libvirt provider with your own Vagrantfile

# -*- mode: ruby -*-                                                                                                                                                                                         
# vi: set ft=ruby :                                                                                                                                                                                          
                                                                                                                                                                                                             
VAGRANTFILE_API_VERSION = "2"                                                                                                                                                                                
                                                                                                                                                                                                             
Vagrant.configure(VAGRANTFILE_API_VERSION) do |config|                                                                                                                                                       
                                                                                                                                                                                                             
  # linux version                                                                                                                                                                                            
  config.vm.box = "debian/jessie64"
  
  config.vm.provider :libvirt do |libvirt|
    libvirt.memory = 4096
    libvirt.cpus = 2
  end
end