Fix some issues with starting vagrant

Sometimes after some upgrades of your ubuntu, when you want to start machine with vagrant up, you receive some errors like:

Vagrant exited after cleanup due to external interrupt.

Open Vagrantfile with your editor and after Vagrant.require_version '>= 1.6.0 line add:

Vagrant.configure('2') do |config|

  config.vm.provider :virtualbox do |vb|
    vb.gui = false
  end

end

and set vb.gui to true to boot vagrant with prompt of virtualbox window. There, fix what you should to (in most cases you should confirm some changes in ubuntu boot system).

Ubuntu login data are:

user: vagrant
pass: vagrant

After that, close virtualbox window and set back vb.gui to false

Now you could see if vagrant starts in your console.