»VirtualBox Builder (from an existing VM)

Type: virtualbox-vm

The VirtualBox Packer builder is able to create VirtualBox virtual machines snapshots and (optionally) export them in the OVF format, starting from an existing virtual machine.

The builder builds a virtual machine snapshot by using an existing virtual machine, booting it, provisioning software within the OS, then shutting it down. The result of the VirtualBox builder is a new snapshot persisting all changes from the applied provisioners.

»Basic Example

Here is a basic example. which serves to show the basic configuration:

  "type": "virtualbox-vm",
  "communicator": "winrm",
  "headless": "{{user `headless`}}",
  "winrm_username": "vagrant",
  "winrm_password": "vagrant",
  "winrm_timeout": "2h",
  "shutdown_command": "shutdown /s /t 10 /f /d p:4:1 /c \"Packer Shutdown\"",
  "guest_additions_mode": "disable",
  "output_directory": "./builds-vm",
  "vm_name": "target-vm",
  "attach_snapshot": "Snapshot",
  "target_snapshot": "Target-Snapshot",
  "force_delete_snapshot": "true",
  "keep_registered": "false",
  "skip_export": "false"

It is important to add a shutdown_command. By default Packer halts the virtual machine and the file system may not be sync'd. Thus, changes made in a provisioner might not be saved.

»Configuration Reference

There are many configuration options available for the VirtualBox builder. They are organized below into two categories: required and optional. Within each category, the available options are alphabetized and described.

In addition to the options listed here, a communicator can be configured for this builder.


  • vm_name (string) - This is the name of the virtual machine to which the builder shall attach.


  • attach_snapshot (string) - Default to null/empty. The name of an existing snapshot to which the builder shall attach the VM before starting it. If no snapshot is specified the builder will simply start the VM from it's current state i.e. snapshot.

  • boot_command (array of strings) - This is an array of commands to type when the virtual machine is first booted. The goal of these commands should be to type just enough to initialize the operating system installer. Special keys can be typed as well, and are covered in the section below on the boot command. If this is not specified, it is assumed the installer will start itself.

  • boot_wait (string) - The time to wait after booting the initial virtual machine before typing the boot_command. The value of this should be a duration. Examples are 5s and 1m30s which will cause Packer to wait five seconds and one minute 30 seconds, respectively. If this isn't specified, the default is 10s or 10 seconds.

  • export_opts (array of strings) - Additional options to pass to the VBoxManage export. This can be useful for passing product information to include in the resulting appliance file. Packer JSON configuration file example:

      "type": "virtualbox-vm",
      "export_opts": [
        "{{user `vm_description`}}",
        "{{user `vm_version`}}"
      "format": "ova"

    A VirtualBox VM description may contain arbitrary strings; the GUI interprets HTML formatting. However, the JSON format does not allow arbitrary newlines within a value. Add a multi-line description by preparing the string in the shell before the packer call like this (shell > continuation character snipped for easier copy & paste):

    packer build \
        -var "vm_description=${vm_description}" \
        -var "vm_version=${vm_version}"         \
  • floppy_dirs (array of strings) - A list of directories to place onto the floppy disk recursively. This is similar to the floppy_files option except that the directory structure is preserved. This is useful for when your floppy disk includes drivers or if you just want to organize it's contents as a hierarchy. Wildcard characters (*, ?, and []) are allowed.

  • floppy_files (array of strings) - A list of files to place onto a floppy disk that is attached when the VM is booted. This is most useful for unattended Windows installs, which look for an Autounattend.xml file on removable media. By default, no floppy will be attached. All files listed in this setting get placed into the root directory of the floppy and the floppy is attached as the first floppy device. Currently, no support exists for creating sub-directories on the floppy. Wildcard characters (*, ?, and []) are allowed. Directory names are also allowed, which will add all the files found in the directory to the floppy.

  • force_delete_snapshot (boolean) - Defaults to false. If set to true, overwrite an existing target_snapshot. Otherwise the builder will yield an error if the specified target snapshot already exists.

  • format (string) - Either ovf or ova, this specifies the output format of the exported virtual machine. This defaults to ovf.

  • guest_additions_interface (string) - The interface type to use to mount guest additions when guest_additions_mode is set to attach. Will default to the value set in iso_interface, if iso_interface is set. Will default to "ide", if iso_interface is not set. Options are "ide" and "sata".

  • guest_additions_mode (string) - The method by which guest additions are made available to the guest for installation. Valid options are upload, attach, or disable. If the mode is attach the guest additions ISO will be attached as a CD device to the virtual machine. If the mode is upload the guest additions ISO will be uploaded to the path specified by guest_additions_path. The default value is upload. If disable is used, guest additions won't be downloaded, either.

  • guest_additions_path (string) - The path on the guest virtual machine where the VirtualBox guest additions ISO will be uploaded. By default this is VBoxGuestAdditions.iso which should upload into the login directory of the user. This is a configuration template where the Version variable is replaced with the VirtualBox version.

  • guest_additions_sha256 (string) - The SHA256 checksum of the guest additions ISO that will be uploaded to the guest VM. By default the checksums will be downloaded from the VirtualBox website, so this only needs to be set if you want to be explicit about the checksum.

  • guest_additions_url (string) - The URL to the guest additions ISO to upload. This can also be a file URL if the ISO is at a local path. By default, the VirtualBox builder will attempt to find the guest additions ISO on the local file system. If it is not available locally, the builder will download the proper guest additions ISO from the internet.

  • guest_os_type (string) - The guest OS type being installed. By default this is other, but you can get dramatic performance improvements by setting this to the proper value. To view all available values for this run VBoxManage list ostypes. Setting the correct value hints to VirtualBox how to optimize the virtual hardware to work best with that operating system.

  • headless (boolean) - Packer defaults to building VirtualBox virtual machines by launching a GUI that shows the console of the machine being built. When this value is set to true, the machine will start without a console.

  • http_directory (string) - Path to a directory to serve using an HTTP server. The files in this directory will be available over HTTP that will be requestable from the virtual machine. This is useful for hosting kickstart files and so on. By default this is an empty string, which means no HTTP server will be started. The address and port of the HTTP server will be available as variables in boot_command. This is covered in more detail below.

  • http_port_min and http_port_max (number) - These are the minimum and maximum port to use for the HTTP server started to serve the http_directory. Because Packer often runs in parallel, Packer will choose a randomly available port in this range to run the HTTP server. If you want to force the HTTP server to be on one port, make this minimum and maximum port the same. By default the values are 8000 and 9000, respectively.

  • keep_registered (boolean) - Set this to true if you would like to keep the VM attached to the snapshot specified by attach_snapshot. Otherwise the builder will reset the VM to the snapshot to which the VM was attached before the builder started. Defaults to false.

  • output_directory (string) - This is the path to the directory where the resulting virtual machine will be created. This may be relative or absolute. If relative, the path is relative to the working directory when packer is executed. This directory must not exist or be empty prior to running the builder. By default this is output-BUILDNAME where "BUILDNAME" is the name of the build.

  • skip_export (boolean) - Defaults to false. When enabled, Packer will not export the VM. Useful if the builder should be applied again on the created target snapshot.

  • host_port_min (int) - The minimum port to use for the Communicator port on the host machine which is forwarded to the SSH or WinRM port on the guest machine. By default this is 2222.
  • host_port_max (int) - The maximum port to use for the Communicator port on the host machine which is forwarded to the SSH or WinRM port on the guest machine. Because Packer often runs in parallel, Packer will choose a randomly available port in this range to use as the host port. By default this is 4444.
  • skip_nat_mapping (bool) - Defaults to false. When enabled, Packer does not setup forwarded port mapping for communicator (SSH or WinRM) requests and uses ssh_port or winrm_port on the host to communicate to the virtual machine.
  • target_snapshot (string) - Default to null/empty. The name of the snapshot which shall be created after all provisioners has been run by the builder. If no target snapshot is specified and keep_registered is set to false the builder will revert to the snapshot to which the VM was attached before the builder has been executed, which will revert all changes applied by the provisioners. This is handy if only an export shall be created and no further snapshot is required.

  • vboxmanage (array of array of strings) - Custom VBoxManage commands to execute in order to further customize the virtual machine being created. The value of this is an array of commands to execute. The commands are executed in the order defined in the template. For each command, the command is defined itself as an array of strings, where each string represents a single argument on the command-line to VBoxManage (but excluding VBoxManage itself). Each arg is treated as a configuration template, where the Name variable is replaced with the VM name. More details on how to use VBoxManage are below.

  • vboxmanage_post (array of array of strings) - Identical to vboxmanage, except that it is run after the virtual machine is shutdown, and before the virtual machine is exported.

  • virtualbox_version_file (string) - The path within the virtual machine to upload a file that contains the VirtualBox version that was used to create the machine. This information can be useful for provisioning. By default this is .vbox_version, which will generally be uploaded into the home directory. Set to an empty string to skip uploading this file, which can be useful when using the none communicator.

  • vrdp_bind_address (string / IP address) - The IP address that should be binded to for VRDP. By default packer will use for this. If you wish to bind to all interfaces use

  • vrdp_port_min and vrdp_port_max (number) - The minimum and maximum port to use for VRDP access to the virtual machine. Packer uses a randomly chosen port in this range that appears available. By default this is 5900 to 6000. The minimum and maximum ports are inclusive.

»Shutdown configuration


  • shutdown_command (string) - The command to use to gracefully shut down the machine once all the provisioning is done. By default this is an empty string, which tells Packer to just forcefully shut down the machine unless a shutdown command takes place inside script so this may safely be omitted. If one or more scripts require a reboot it is suggested to leave this blank since reboots may fail and specify the final shutdown command in your last script.
  • shutdown_timeout (duration string | ex: "1h5m2s") - The amount of time to wait after executing the shutdown_command for the virtual machine to actually shut down. If it doesn't shut down in this time, it is an error. By default, the timeout is 5m or five minutes.
  • post_shutdown_delay (duration string | ex: "1h5m2s") - The amount of time to wait after shutting down the virtual machine. If you get the error Error removing floppy controller, you might need to set this to 5m or so. By default, the delay is 0s or disabled.
  • disable_shutdown (bool) - Packer normally halts the virtual machine after all provisioners have run when no shutdown_command is defined. If this is set to true, Packer will not halt the virtual machine but will assume that you will send the stop signal yourself through the preseed.cfg or your final provisioner. Packer will wait for a default of 5 minutes until the virtual machine is shutdown. The timeout can be changed using shutdown_timeout option.
  • acpi_shutdown (bool) - If it's set to true, it will shutdown the VM via power button. It could be a good option when keeping the machine state is necessary after shutting it down.

»Boot Command

The boot_command configuration is very important: it specifies the keys to type when the virtual machine is first booted in order to start the OS installer. This command is typed after boot_wait, which gives the virtual machine some time to actually load the ISO.

As documented above, the boot_command is an array of strings. The strings are all typed in sequence. It is an array only to improve readability within the template.

The boot command is sent to the VM through the VBoxManage utility in as few invocations as possible. We send each character in groups of 25, with a default delay of 100ms between groups. The delay alleviates issues with latency and CPU contention. If you notice missing keys, you can tune this delay by specifying "boot_keygroup_interval" in your Packer template, for example:

  "builders": [
      "type": "virtualbox",
      "boot_keygroup_interval": "500ms"

There are a set of special keys available. If these are in your boot command, they will be replaced by the proper key:

  • <bs> - Backspace

  • <del> - Delete

  • <enter> <return> - Simulates an actual "enter" or "return" keypress.

  • <esc> - Simulates pressing the escape key.

  • <tab> - Simulates pressing the tab key.

  • <f1> - <f12> - Simulates pressing a function key.

  • <up> <down> <left> <right> - Simulates pressing an arrow key.

  • <spacebar> - Simulates pressing the spacebar.

  • <insert> - Simulates pressing the insert key.

  • <home> <end> - Simulates pressing the home and end keys.

  • <pageUp> <pageDown> - Simulates pressing the page up and page down keys.

  • <menu> - Simulates pressing the Menu key.

  • <leftAlt> <rightAlt> - Simulates pressing the alt key.

  • <leftCtrl> <rightCtrl> - Simulates pressing the ctrl key.

  • <leftShift> <rightShift> - Simulates pressing the shift key.

  • <leftSuper> <rightSuper> - Simulates pressing the ⌘ or Windows key.

  • <wait> <wait5> <wait10> - Adds a 1, 5 or 10 second pause before sending any additional keys. This is useful if you have to generally wait for the UI to update before typing more.

  • <waitXX> - Add an arbitrary pause before sending any additional keys. The format of XX is a sequence of positive decimal numbers, each with optional fraction and a unit suffix, such as 300ms, 1.5h or 2h45m. Valid time units are ns, us (or µs), ms, s, m, h. For example <wait10m> or <wait1m20s>

»On/Off variants

Any printable keyboard character, and of these "special" expressions, with the exception of the <wait> types, can also be toggled on or off. For example, to simulate ctrl+c, use <leftCtrlOn>c<leftCtrlOff>. Be sure to release them, otherwise they will be held down until the machine reboots.

To hold the c key down, you would use <cOn>. Likewise, <cOff> to release.

»Templates inside boot command

In addition to the special keys, each command to type is treated as a template engine. The available variables are:

  • HTTPIP and HTTPPort - The IP and port, respectively of an HTTP server that is started serving the directory specified by the http_directory configuration parameter. If http_directory isn't specified, these will be blank!
  • Name - The name of the VM.

For more examples of various boot commands, see the sample projects from our community templates page.

»SSH key pair automation

The VirtualBox builders can inject the current SSH key pair's public key into the template using the following variable:

  • SSHPublicKey (VirtualBox builders only) - This is the SSH public key as a line in OpenSSH authorized_keys format.

When a private key is provided using ssh_private_key_file, the key's corresponding public key can be accessed using the above variables.

If ssh_password and ssh_private_key_file are not specified, Packer will automatically generate en ephemeral key pair. The key pair's public key can be accessed using the template variables.

For example, the public key can be provided in the boot command as a URL encoded string by appending | urlquery to the variable:

  "type": "virtualbox-iso",
  "boot_command": [
    "<up><wait><tab> text ks=http://{{ .HTTPIP }}:{{ .HTTPPort }}/ks.cfg PACKER_USER={{ user `username` }} PACKER_AUTHORIZED_KEY={{ .SSHPublicKey | urlquery }}<enter>"

A kickstart could then leverage those fields from the kernel command line by decoding the URL-encoded public key:


# Newly created users need the file/folder framework for SSH key authentication.
umask 0077
mkdir /etc/skel/.ssh
touch /etc/skel/.ssh/authorized_keys

# Loop over the command line. Set interesting variables.
for x in $(cat /proc/cmdline)
  case $x in
      # URL decode $encoded into $PACKER_AUTHORIZED_KEY
      encoded=$(echo "${x#*=}" | tr '+' ' ')
      printf -v PACKER_AUTHORIZED_KEY '%b' "${encoded//%/\\x}"

# Create/configure packer user, if any.
if [ -n "$PACKER_USER" ]
  useradd $PACKER_USER
  echo "%$PACKER_USER ALL=(ALL) NOPASSWD: ALL" >> /etc/sudoers.d/$PACKER_USER
  [ -n "$PACKER_AUTHORIZED_KEY" ] && echo $PACKER_AUTHORIZED_KEY >> $(eval echo ~"$PACKER_USER")/.ssh/authorized_keys


Example boot command. This is actually a working boot command used to start an Ubuntu 12.04 installer:

  "/install/vmlinuz noapic ",
  "preseed/url=http://{{ .HTTPIP }}:{{ .HTTPPort }}/preseed.cfg ",
  "debian-installer=en_US auto locale=en_US kbd-chooser/method=us ",
  "hostname={{ .Name }} ",
  "fb=false debconf/frontend=noninteractive ",
  "keyboard-configuration/modelcode=SKIP keyboard-configuration/layout=USA ",
  "keyboard-configuration/variant=USA console-setup/ask_detect=false ",
  "initrd=/install/initrd.gz -- <enter>"

Please note that for the Virtuabox builder, the IP address of the HTTP server Packer launches for you to access files like the preseed file in the example above ({{ .HTTPIP }}) is hardcoded to If you change the network of your VM you must guarantee that you can still access this HTTP server.

For more examples of various boot commands, see the sample projects from our community templates page.

»Guest Additions

Packer will automatically download the proper guest additions for the version of VirtualBox that is running and upload those guest additions into the virtual machine so that provisioners can easily install them.

Packer downloads the guest additions from the official VirtualBox website, and verifies the file with the official checksums released by VirtualBox.

After the virtual machine is up and the operating system is installed, Packer uploads the guest additions into the virtual machine. The path where they are uploaded is controllable by guest_additions_path, and defaults to "VBoxGuestAdditions.iso". Without an absolute path, it is uploaded to the home directory of the SSH user.

»VBoxManage Commands

In order to perform extra customization of the virtual machine, a template can define extra calls to VBoxManage to perform. VBoxManage is the command-line interface to VirtualBox where you can completely control VirtualBox. It can be used to do things such as set RAM, CPUs, etc.

Extra VBoxManage commands are defined in the template in the vboxmanage section. An example is shown below that sets the VRAM within the virtual machine:

  "vboxmanage": [["modifyvm", "{{.Name}}", "--vram", "64"]]

The value of vboxmanage is an array of commands to execute. These commands are executed in the order defined. So in the above example, the memory will be set followed by the CPUs.

Each command itself is an array of strings, where each string is an argument to VBoxManage. Each argument is treated as a configuration template. The only available variable is Name which is replaced with the unique name of the VM, which is required for many VBoxManage calls.