Create a Vagrant Box from an existing Virtualbox image

my_box.json

{
  "builders": [
    {
      "type": "virtualbox-ovf",
      "source_path": "my_box.ova",
      "ssh_username": "vagrant",
      "ssh_password": "vagrant",
      "shutdown_command": "echo 'vagrant' | sudo -S /sbin/shutdown -h now"
    }
  ],
  "post-processors": [
    {
      "type": "vagrant",
      "output": "my_box.box"
    }
  ]
}