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<?xml version='1.0' encoding='UTF-8'?>
<!DOCTYPE topic PUBLIC "-//OASIS//DTD DITA Topic//EN" "topic.dtd">
<topic xml:lang="en-us" id="ovf-about">
<title>About the OVF Format</title>
<body>
<p>OVF is a cross-platform standard supported by many virtualization products which enables the creation of
ready-made virtual machines that can then be imported into a hypervisor such as <ph
conkeyref="vbox-conkeyref-phrases/product-name"/>. <ph conkeyref="vbox-conkeyref-phrases/product-name"/> makes
OVF import and export easy to do, using <ph conkeyref="vbox-conkeyref-phrases/vbox-mgr"/> or the command-line
interface. </p>
<p>Using OVF enables packaging of <i>virtual appliances</i>. These are disk images, together with configuration
settings that can be distributed easily. This way one can offer complete ready-to-use software packages, including
OSes with applications, that need no configuration or installation except for importing into <ph
conkeyref="vbox-conkeyref-phrases/product-name"/>. </p>
<note>
<p>The OVF standard is complex, and support in <ph conkeyref="vbox-conkeyref-phrases/product-name"/> is an ongoing
process. In particular, no guarantee is made that <ph conkeyref="vbox-conkeyref-phrases/product-name"/> supports
all appliances created by other virtualization software. For a list of known limitations, see <xref
href="KnownIssues.dita">Known Limitations</xref>. </p>
</note>
<p>Appliances in OVF format can appear in the following variants: </p>
<ul>
<li>
<p>They can come in several files, as one or several disk images, typically in the widely-used VMDK format. See
<xref href="vdidetails.dita"/>. They also include a textual description file in an XML dialect with an
<filepath>.ovf</filepath> extension. These files must then reside in the same directory for <ph
conkeyref="vbox-conkeyref-phrases/product-name"/> to be able to import them. </p>
</li>
<li>
<p>Alternatively, the above files can be packed together into a single archive file, typically with an
<filepath>.ova</filepath> extension. Such archive files use a variant of the TAR archive format and can
therefore be unpacked outside of <ph conkeyref="vbox-conkeyref-phrases/product-name"/> with any utility that
can unpack standard TAR files. </p>
</li>
</ul>
<note>
<p>OVF cannot describe snapshots that were taken for a virtual machine. As a result, when you export a virtual
machine that has snapshots, only the current state of the machine will be exported. The disk images in the
export will have a <i>flattened</i> state identical to the current state of the virtual machine. </p>
</note>
</body>
</topic>
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