Simple Vagrantfile that can be used to set up a simple Ubuntu 12.04 LTS box with XFCE GUI.

gistfile1.pp

# Simplest possible Ubuntu 12.04 box with a GUI 
Vagrant.configure("2") do |config|
  
  config.vm.box = "hashicorp/precise32"

  config.vm.provider "virtualbox" do |vb|
      # Don't boot with headless mode
      vb.gui = true
  
      # Set a name that you can remember
      vb.name = "ubuntu_vm_with_xfce_gui_by_queirozfcom"

      # Set 1024M of RAM
      vb.memory = 1024
	  
      # And one processor
      vb.cpus = 1
  end
 
  # This next bit fixes the 'stdin is not a tty' error when shell provisioning Ubuntu boxes
  config.vm.provision :shell,
    #if there a line that only consists of 'mesg n' in /root/.profile, replace it with 'tty -s && mesg n'
    :inline => "(grep -q -E '^mesg n$' /root/.profile && sed -i 's/^mesg n$/tty -s \\&\\& mesg n/g' /root/.profile && echo 'Ignore the previous error about stdin not being a tty. Fixing it now...') || exit 0;"	
	
  # update definitions
  config.vm.provision "shell", inline: "apt-get update"	

  # just the basic desktop environment. if you want the addons, you can install them later
  config.vm.provision "shell", inline: "apt-get install xubuntu-desktop --no-install-recommends --assume-yes"
  
  # otherwise icons don't get loaded
  config.vm.provision "shell", inline: "apt-get install xubuntu-icon-theme --assume-yes"
  
  #activate logon with gui and reboot
  config.vm.provision "shell", inline: "dpkg-reconfigure lightdm"
  config.vm.provision "shell", inline: "reboot"

end