Current Vagrant file that I use for 16.04 VMs on Virtual Box

Vagrantfile

VM_BOX  = 'ubuntu/xenial64'
Vagrant.configure(2) do |config|
  config.vm.box = VM_BOX
  config.vm.network "private_network", type: "dhcp"
  config.vm.provider "virtualbox" do |vb|
    vb.memory = 1024
  end
  config.vm.provision 'shell', inline: <<-SHELL
    echo 'ubuntu:ubuntu' | sudo chpasswd
  SHELL
end