.OVF File Format

Introduction

The Open Virtualization Format (OVF) is the DMTF standard (DSP0243) for describing virtual machines and appliances so they can move between products. An OVF package is a set of files: one XML descriptor with the extension .ovf, an optional manifest (.mf) and certificate (.cert), disk images (VMDK or another format named by URI) and other resources. The package may be stored as that set of files, or as one OVA tar archive. The descriptor validates against the schema DSP8023. This reference follows DSP0243 2.1.1 (read in full) and the DSP8023 2.0.1 and DSP8027 schemas (read).

Structure

The descriptor's root is the Envelope: a list of file References, package-level sections (disks, networks, deployment options), the content (a VirtualSystem or a VirtualSystemCollection) with its own sections and virtual hardware, and optional message bundles. The OVF 2.x namespace is http://schemas.dmtf.org/ovf/envelope/2.

<Envelope xmlns="http://schemas.dmtf.org/ovf/envelope/2" xmlns:ovf="http://schemas.dmtf.org/ovf/envelope/2" …>
  <References><File ovf:id="file1" ovf:href="disk1.vmdk" ovf:size="…"/></References>
  <DiskSection><Info>…</Info><Disk ovf:diskId="vmdisk1" ovf:capacity="…" ovf:fileRef="file1" ovf:format="…"/></DiskSection>
  <NetworkSection>…</NetworkSection>
  <VirtualSystem ovf:id="vm"><Info>…</Info> … <VirtualHardwareSection>…</VirtualHardwareSection></VirtualSystem>
</Envelope>

The viewer reads the XML (tree and text as for any XML file) and adds tables of the files, disks, networks, systems, hardware items and properties, the sections present, and the message bundles; it checks the rules of the specification that say "shall" and that a single file can decide.

The package files

• .ovf: the descriptor (this format).
• .mf: the manifest, with the same base name, a sibling of the .ovf.
• .cert: the certificate with the signed digest of the manifest.
• Disk and resource files named in References. The extensions .mf and .cert may be used for other files of a package, if they are not at the sibling names where they would be read as manifest or certificate.

Not described

Known, not yet covered

• Reference: the names of the CIM ResourceType values 1 to 33 (in DSP1041 and the CIM MOF, not in the sources read: the hardware page gives the four the specification's examples use), the network port profile examples of Annex E, and the OVF environment document (ovf-env.xml, DSP8027), which is a separate file.
• Viewer: the checks cover the shall-rules decided inside one file; encrypted parts (EncryptionSection) are shown as XML, not decrypted; localised strings are listed, not substituted.

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