Open Virtualization File (OVF File): Definition, Different File Formats, Packages, and Features

Open Virtualization File (OVF File): Definition, Different File Formats, Packages, and Features

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An open virtualization format file or OVF file is an industry-standard packaging format for virtualization software solutions. Developed by the Distributed Management Task Force (DMTF), OVF files are used by most modern hypervisors, such as VMware ESXi, Hyper-V, VirtualBox, and others. The file can run directly on these hypervisors and represents virtual machine metadata with a descriptor file, settings, and more.

OVF file is specifically used in virtualization as the files included in this format contain descriptions regarding software running on virtual machines. This is a surface-level definition of the open virtualization format. So, let’s dive deeper into the subject and thoroughly explain the definition, packages, features, and touch on the different file formats.

Open Virtualization Format – What Is It?

An open virtualization format is a file format for packaging and distributing software for virtual machines. In short, an OVF package defines a virtual machine or virtual appliance. The format contains files that tell us everything about a single virtual machine.

The files in an open virtualization format include virtual disk image file formats, virtual hardware specifications, the location of virtual disks, etc. Hypervisors can open an OVF file and create a virtual machine with specific descriptions. Most impressively, OVF allows us to add other relevant items such as virtual machine comments, EULA, virtual machine requirements, and more.

We mentioned that OVF describes a single virtual machine or a virtual appliance. As such, OVF isn’t limited to only a single virtual machine. If we take the virtual appliance route, we can create a suite of virtual machines wrapped into a single appliance.

Since we use OVF to package and distribute virtual appliances, OVF allows access to additional features that make virtual appliances more flexible. Simply put, the OVF file extension enhances the virtualization experience and optimizes the distribution of virtual machines.

Difference Between OVF and OVA

OVA stands for open virtualization application or open virtual appliance and it is a single file archive stored within the open virtualization format OVF package. The file extension stores additional files used by VMs and is labeled as a TAR archive inside the OVF. OVA files come in the ova file extension.

An OVF template contains all relevant information, including OVA. So OVA is part of the OVF. In addition to the OVA file, an OVF template also contains the virtual disk. So, for example, you can export virtual machines in VirtualBox in the OVF extension and include both OVA and VMDK files.

OVF File Components

With the difference between OVF and OVA out of the way, let’s thoroughly see what the are main file components of the OVF file extension.

  • Metadata File

The first and most apparent file component is the metadata file. The metadata file has a .ovf extension, and it is an XML document that describes the virtual machine or virtual appliance. Most notably, the file contains the location of the virtual disks, EULA, and other information essential to a particular virtual machine/appliance.

  • Virtual Disk

Virtual disk images are attached to virtual machines and represent physical disks (hard drives). Naturally, the virtual machine’s contents are included on the virtual disk image.

Virtual disks come in different formats depending on the hypervisor. The most popular virtual disk image format for guest operating systems includes VDI, VMDK, VHD, and raw file formats. One or more virtual disk locations are included in the OVF file.

Every OVF file will contain these two components. However, it’s important to emphasize that an OVF file will contain at least one OVF descriptor file with a .ovf file extension. In addition, OVF files can contain optional resource files such as certificate files.

How to Open OVF Files?

The OVF file format is supposed on all major operating systems. However, you do need a hypervisor to open an OVF file. While we won’t get into how to open OVF files in every hypervisor, we will mention the following hypervisors that support OVF:

  • VirtualBox
  • Red Hat Enterprise Virtualization
  • VMware
  • XenServer
  • IBM Power
  • IBM SmartCloud
  • OpenNode
  • Oracle VM
  • rPath
  • SUSE Studios
  • Microsoft Systems Center Virtual Machine Manager
  • Amazon Elastic Computer Cloud
  • Proxmox VE

Generally speaking, you will need to have one of these hyperviors installed and click on the .ova file extension to open the file. Once you click on the extension, you will need to select the hypervisor (only if you have two hypervisors installed.

OVF Features

Before we finish, here is a rundown of the OVF features:

  • OVF can validate all virtual machines;
  • Can support multiple virtual machine configurations;
  • Comes with full license agreement;
  • Is extensible;
  • Is portable;
  • Not exclusive to any single hypervisor;

Conclusion

That concludes the definition, different file formats, packages, and features of OVF. OVF is the open standard for packaging and distributing virtual machines and virtual appliances. As such, experts consider the OVF file as the standard in building virtual machines, virtual appliances, and cloud images.