- `communicator` (string) - Communicator - `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_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_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](/docs/templates/engine) 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 of 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.