Packer example from http://blog.codeship.com/packer-vagrant-tutorial/

gistfile1.txt

{
  "provisioners": [
    {
      "type": "shell",
      "scripts": [
        "scripts/root_setup.sh"
      ],
      "override": {
        "virtualbox": {
          "execute_command": "echo 'vagrant' | sudo -S sh '{{ .Path }}'"
        }
      }
    },
    {
      "type": "shell",
      "scripts": [
        "scripts/setup.sh"
      ]
    }
  ],
  "builders": [
    {
      "type": "virtualbox",
      "boot_command": [
        "<esc><esc><enter><wait>",
        "/install/vmlinuz noapic preseed/url=http://{{ .HTTPIP }}:{{ .HTTPPort }}/preseed.cfg <wait>",
        "debian-installer=en_US auto locale=en_US kbd-chooser/method=us <wait>",
        "hostname={{ .Name }} <wait>",
        "fb=false debconf/frontend=noninteractive <wait>",
        "keyboard-configuration/modelcode=SKIP keyboard-configuration/layout=USA keyboard-configuration/variant=USA console-setup/ask_detect=false <wait>",
        "initrd=/install/initrd.gz -- <enter><wait>"
      ],
      "boot_wait": "4s",
      "guest_os_type": "Ubuntu_64",
      "http_directory": "http",
      "iso_checksum": "4d1a8b720cdd14b76ed9410c63a00d0e",
      "iso_checksum_type": "md5",
      "iso_url": "http://releases.ubuntu.com/13.10/ubuntu-13.10-server-amd64.iso",
      "ssh_username": "vagrant",
      "ssh_password": "vagrant",
      "ssh_port": 22,
      "ssh_wait_timeout": "10000s",
      "shutdown_command": "echo 'shutdown -P now' > shutdown.sh; echo 'vagrant'|sudo -S sh 'shutdown.sh'",
      "guest_additions_path": "VBoxGuestAdditions_{{.Version}}.iso",
      "headless": false,
      "virtualbox_version_file": ".vbox_version",
      "vboxmanage": [
        [
          "modifyvm",
          "{{.Name}}",
          "--memory",
          "2048"
        ],
        [
          "modifyvm",
          "{{.Name}}",
          "--cpus",
          "4"
        ]
      ]
    }
  ],
  "post-processors": ["vagrant"]
}