Example of vboxmanage command in Packer template

template.json

{
  "builders": [
    {
      "type": "virtualbox-ovf",
      "source_path": "ubuntu-16.04-server-cloudimg-amd64.ova",
      "vboxmanage": [
        ["storageattach", "{{.Name}}", "--storagectl", "IDE", "--port", "0", "--device", "0", "--type", "dvddrive", "--medium", "files/cloud.iso"],
        ["modifyvm", "{{.Name}}", "--nic1", "nat" ],
        ["modifyvm", "{{.Name}}", "--uart1", "0x3F8", "4"],
        ["modifyvm", "{{.Name}}", "--uartmode1", "file", "console.log"]
      ]
    }
  ]
}