template.json
{
  "builders": [
  {
    "type": "virtualbox-iso",
    "guest_os_type": "Linux_64",
    "iso_url": "http://debirf.cmrg.net/autobuilds/amd64/stable/rescue/debirf-rescue_stable_3.2.0-4-amd64.iso",
    "iso_checksum": "2b314975a9180576aad44492d8c6aab7eadbc696a28d36c13a2048a2ad4ed6b9",
    "iso_checksum_type": "sha256",
    "ssh_username": "root",
    "ssh_password": "",
    "shutdown_command": "echo 'packer' | sudo -S shutdown -P now",
    "boot_wait": "5m",
    "disk_size": "4000",
    "headless": "false"
    }
  ],

  "provisioners": [
    {
      "type": "shell",
        "script": "debirf-setup.sh"
    }
  ]
}