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  • Open Virtualization Format White Paper

    Version 1.0.0

    Status: Informational Publication Date: 2/6/2009


  • Open Virtualization Format White Paper DSP2017

    Copyright 2009 Distributed Management Task Force, Inc. (DMTF). All rights reserved.

    DMTF is a not-for-profit association of industry members dedicated to promoting enterprise and systems management and interoperability. Members and non-members may reproduce DMTF specifications and documents provided that correct attribution is given. As DMTF specifications may be revised from time to time, the particular version and release date should always be noted.

    Implementation of certain elements of this standard or proposed standard may be subject to third party patent rights, including provisional patent rights (herein "patent rights"). DMTF makes no representations to users of the standard as to the existence of such rights, and is not responsible to recognize, disclose, or identify any or all such third party patent right, owners or claimants, nor for any incomplete or inaccurate identification or disclosure of such rights, owners or claimants. DMTF shall have no liability to any party, in any manner or circumstance, under any legal theory whatsoever, for failure to recognize, disclose, or identify any such third party patent rights, or for such partys reliance on the standard or incorporation thereof in its product, protocols or testing procedures. DMTF shall have no liability to any party implementing such standard, whether such implementation is foreseeable or not, nor to any patent owner or claimant, and shall have no liability or responsibility for costs or losses incurred if a standard is withdrawn or modified after publication, and shall be indemnified and held harmless by any party implementing the standard from any and all claims of infringement by a patent owner for such implementations.

    For information about patents held by third-parties which have notified the DMTF that, in their opinion, such patent may relate to or impact implementations of DMTF standards, visit

  • Open Virtualization Format White Paper OVF version 1.0.0e

    Version 1.0.0 Publication Date: 2/6/2009

    DSP2017 Status: Informational


    This white paper describes the Open Virtualization Format (OVF). OVF is a hypervisor-neutral, efficient, extensible, and open specification for the packaging and distribution of virtual appliances composed of one or more virtual computer systems. The target audience of this white paper is anyone who wants to understand OVF and its reason for development. Some familiarity with virtualization and the general concepts of the CIM model is assumed.

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    Table of Contents

    1 Introduction 5 1.1 Overview 5 1.2 Virtual Appliances 6 1.3 Design Goals 6 1.4 Virtual Appliance Life-Cycle 8

    2 Portable Virtualization Format 9 2.1 OVF Package 9 2.2 OVF Environment 9 2.3 Sample OVF Descriptor 10

    3 Using the Open Virtualization Format 11 3.1 Creation 11 3.2 Deployment 12

    4 Features 13 4.1 Virtual Hardware Description 13 4.2 Deployment Options 14 4.3 Deployment Customization 15 4.4 Internationalization 15 4.5 Extensibility 16 4.6 Conformance 16

    5 Portability 17 6 Future Versions of the OVF Specification 18 7 Conclusion 18 A Multi-tiered Petstore Example 20

    Architecture and Packaging 20 Properties 20 Disk Layout 21 Complete OVF Descriptor 22 Complete OVF Environments 27

    B LAMP Stack Example 29 Deployment-time Customization 29 Simple LAMP OVF Descriptor 30 Two-tier LAMP OVF Descriptor 33

    C Extensibility Example 38 Custom Schema 38 Descriptor with custom extensions 39

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    1 Introduction 1.1 Overview The rapid adoption of virtual infrastructure has highlighted the need for a standard, portable meta-data model for the distribution of virtual machines to and between virtualization platforms. Packaging an application together with the operating system on which it is certified, into a virtual machine that can be easily transferred from an ISV, through test and development and into production as a pre-configured, pre-packaged unit with no external dependencies, is extremely attractive. Such pre-deployed, ready to run applications packaged as virtual machines (VMs) are called virtual appliances. In order to make this concept practical on a large scale it is important that the industry adopts a vendor-neutral standard for the packaging of such VMs and the meta-data that are required to automatically and securely install, configure, and run the virtual appliance on any virtualization platform.

    Virtual appliances are changing the software distribution paradigm because they allow application builders to optimize the software stack for their application and deliver a turnkey software service to the end user. For solution providers, building a virtual appliance is simpler and more cost effective than building a hardware appliance, since the application is pre-packaged with the operating system that it uses, reducing application/OS compatibility testing and certification, and allowing the software to be pre-installed in the OS environment it will run in by the ISV. For end users, virtual appliances offer an opportunity to dramatically simplify the software management lifecycle through the adoption of a standardized, automated, and efficient set of processes that replace OS and application specific management tasks today.

    Whereas current virtual appliances contain a single VM only, modern enterprise applications model service oriented architectures (SOA) with multiple tiers, where each tier contains one or more machines. A single VM model is thus not sufficient to distribute a multi-tier service. In addition, complex applications require install-time customization of networks and other customer specific properties. Furthermore, a virtual appliance is packaged in a run-time format with hard disk images and configuration data suitable for a particular hypervisor. Run-time formats are optimized for execution and not for distribution. For efficient software distribution, a number of additional features become critical, including portability, platform independence, verification, signing, versioning, and licensing terms.

    The Open Virtualization Format (OVF) specification is a hypervisor-neutral, efficient, extensible, and open specification for the packaging and distribution of virtual appliances composed of one or more VMs. It aims to facilitate the automated, secure management not only of virtual machines but the appliance as a functional unit. For the OVF format to succeed it must be developed and endorsed by ISVs, virtual appliance vendors, operating system vendors, as well as virtual platform vendors, and must be developed within a standards-based framework.

    This document gives a detailed description of the motivation and goals behind the design of OVF, and should be read as an accompaniment to the OVF specification of the same revision number.

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    1.2 Virtual Appliances A virtual appliance is a pre-configured software stack comprising one or more virtual machines. Each virtual machine is an independently installable run-time entity comprising an operating system, applications and other application-specific data, as well as a specification of the virtual hardware that is required by the virtual machine. Many infrastructure applications and even end-user applications that are accessible over a network, such as a DNS server, a bug tracking database, or a complete CRM solution composed of a web, application and database tier, can be delivered as virtual appliances. Delivering complex software systems and services as a pre-configured software stack can dramatically increase robustness and simplify installation. Virtual appliances need not be developed and delivered by 3rd party ISVs the concept is equally useful and often used within an enterprise in which a virtual machine template for a particular service is assembled, tested, and certified by an IT organization and then packaged for repeated, cookie cutter deployment throughout the enterprise. Commonly, a software service is implemented as a multi-tier application running in multiple virtual machines and communicating across the network. Services are often composed of other services, which themselves might be multi-tier applications or composed of other services. This is known as service-oriented architecture or SOA. Indeed the SOA-type model naturally fits into a virtual appliance-based infrastructure, since virtual appliances are typified by the use of network facing, XML based management and service interfaces that allow composition of appliances to deliver a complete application.

    For example, consider a typical web application that consists of three tiers. A web tier that implements the presentation logic, and application server tier that implements the business logic, and a back-end database tier. A straightforward implementation would divide this into 3 virtual machines, one for each tier. In this way, the application can scale from the fraction of a single physical host to 3 physical hosts. Another approach is to treat each tier as a service in itself. Hence, each tier is a multi-VM service that provides a clustered solution. This can provide far greater scalability than just up to 3 physical hosts. Taking the web-front example, a common scenario is to have many web servers, fewer applications servers, and one or two database servers. Implemented as virtual machines, each tier can scale across as many or as few physical machines as required, and each tier can support multiple instances of service VMs.

    1.3 Design Goals The Open Virtualization Format (OVF) describes an open, secure, portable, efficient and extensible format for the packaging and distribution of (collections of) virtual machines. The key properties of the format are:

    Optimized for distribution Supports content verification and integrity checking based on industry standard public key infrastructure, and provides a basic scheme for management of software licensing.

    Optimized for a simple, automated user experience Supports validation of the entire package and each virtual machine or meta-data component of the OVF during the installation phases of the VM lifecycle management process. It also packages with the appliance relevant user-readable descriptive information that can be use by a virtualization platform to streamline the installation experience.

    Supports both single VM and multi-VM configurations Supports both standard single VM packages, and packages containing complex, multi-tier services consisting of multiple interdependent VMs.

    Portable VM packaging OVF is virtualization platform neutral, while also enabling platform-specific enhancements to be captured. It supports the full range of virtual hard disk formats used for VMs today, and is extensible to deal with future formats that may arise. Virtual machine properties are captured concisely and accurately.

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    Vendor and platform independent The OVF does not rely on the use of a specific host platform, virtualization platform, or guest operating system (within the appliance).

    Extensible OVF is immediately useful and extensible. It is designed to be extended as the industry moves forward with the virtual appliance technology. It also supports and permits the encoding of custom meta-data to support specific vertical markets.

    Localizable Supports user visible descriptions in multiple locales, and supports localization of the interactive processes during installation of an appliance. This allows a single packaged appliance to serve multiple market opportunities.

    Open standard The OVF has arisen from the collaboration of key vendors in the industry, and will be developed as a future standard for portable virtual machines.

    From the user's point of view, an OVF is a packaging format for software appliances. Once installed, an OVF adds to the users infrastructure a self-contained, self-consistent, software solution for achieving a particular goal. For example, an OVF might contain a fully-functional and tested web-server / database / OS combination, such as a LAMP stack (Linux + Apache + MySQL + PHP), or it may contain a virus checker, including its update software, spyware detector, etc. From a technical point of view, an OVF is a transport mechanism for virtual machine templates. One OVF may contain a single VM, or many VMs (it is left to the software appliance developer to decide which arrangement best suits their application). OVFs must be installed before they can be run; a particular virtualization platform may run the VM from the OVF, but this is not required. If this is done, the OVF itself can no longer be viewed as a golden image version of the appliance, since run-time state for the virtual machine(s) will pervade the OVF. Moreover the digital signature that allows the platform to check the integrity of the OVF will be invalid. As a transport mechanism, OVF differs from VMware's VMDK Virtual Disk Format and Microsoft's VHD Virtual Hard Disk format or the open source QCOW format. These are run-time VM image formats, operating at the scope of a single VM disk, and though they are frequently used as transport formats today, they are not designed to solve the VM portability problem; they don't help you if you have a VM with multiple disks, or multiple VMs, or need customization of the VM at install time, or if your VM is intended to run on multiple virtualization platforms (even if the virtualization platforms claim support of the particular virtual hard disk format used). Included within the OVF remit is the concept of the certification and integrity of a packaged software virtual appliance, allowing the platform to determine the provenance of the appliance, and to allow the end-user to make the appropriate trust decisions. The OVF specification has been constructed so that the appliance is responsible for its own configuration and modification. In particular, this means that the virtualization platform does not need to be able to read from the appliance's file systems. This decoupling of platform from appliance means that OVFs may be implemented using any operating system, and installed on any virtualization platform that supports the OVF format. A specific mechanism is provided for appliances to detect the platform on which they are installed, and react to it. This allows platforms to extend this specification in unique ways without breaking compatibility of appliances across the industry. The OVF format has several specific features that are designed for complex, multi-tier services and their associated distribution, installation, configuration and execution workflow:

    It directly supports the configuration of multi-tier applications and the composition of virtual machines to deliver composed services.

    It permits the specification of both VM and application-level configuration.

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    It offers robust mechanisms for validation of the contents of the OVF, and full support for unattended installation to ease the burden of deployment for users, and thereby enhance the users experience.

    It uses commercially accepted procedures for integrity checking of the contents of the OVF, through the use of signatures and trusted third parties. This serves to reassure the consumer of an appliance that it has not been modified since signed by the creator of the appliance. This is seen as critical to the success of the virtual appliance market, and to the viability of independent creation and online download of appliances.

    It permits commercial interests of the appliance vendor and user to be respected, by providing a basic method for presentation and acknowledgement of licensing terms associated with the appliance.

    1.4 Virtual Appliance Life-Cycle The software life cycle for virtual appliances is shown below:

    Package, Distribute Deploy Manage Retire Develop

    OVF version 1 scope

    A service, consisting of one or more VMs and the relevant configuration and deployment meta data, is packaged into the OVF format at the end of the development phase. The components used here can be third-party components. For example, a clustered database component might be acquired from a third-party ISV. The deployment phase is the installation of an OVF package. The management and retirement phase is specific to the virtualization product used, and to the contents of the OVF itself. Management includes, for example, ongoing maintenance and upgrade of the appliance, which is likely to be highly dependent on the contents of the VMs in the OVF. In the retirement phase, the software is decommissioned and any resources it consumes are released. In this version of the OVF specification we deal specifically with the packaging, distribution and deployment phases. Later versions of the specification may address management and retirement in detail.

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    2 Portable Virtualization Format The Open Virtualization Format defines a format for distributing software to be deployed in virtual machines, and an environment for which they execute. This is respectively known as the OVF package and the OVF environment.

    2.1 OVF Package The OVF package consists of an OVF descriptor and a set of additional content, typically virtual disks. Content can accompany the package directly or be referred externally via HTTP. The specification also enables an entire OVF package to be distributed as a single file.

    The OVF descriptor is an XML document that describes meta-data about the software installed on the virtual disks. The OVF specification 1.0 specification defines the common sections used for deploying software efficiently, such as virtual hardware, disks, networks, resource requirements, and customization parameters. The descriptor is designed to be extensible so further information can be added later.

    The specification allows any virtual disk format to be used, as long as the disk format specification is public and without restrictions. This supports the full range of virtual hard disk formats used for hypervisors today, and it is extensible to allow for future formats.

    The virtual disk format will commonly be some simple basic disk block format agnostic to the guest OS installed. By way of example, VMware VMDK formats deal with 512 byte disk sectors stored in 64KB blocks, in a number of flat, sparse, and compressed variants. At deployment time, the virtualization platform creates virtual disks in a basic disk block format it prefers. The runtime virtual disk format may be identical to the distribution format, but will often be different; it may for instance not be efficient to run out of a compressed virtual disk format. Finally, the guest OS installed on the virtual disk has its own disk file format, such as NTFS, EXT3, or ZFS, but this is not relevant to describe or understand at the OVF level.

    See section 2.3and appendix A and B for examples of OVF descriptors.

    2.2 OVF Environment A virtual appliance often needs to be customized to function properly in the particular environment where it is deployed. The OVF environment provides a standard and extensible way for the virtualization platform to communicate deployment configuration to the guest software.

    The OVF environment is an XML document containing deployment time customization information for the guest software. Examples of information that could be provided in the XML document include:

    Operating system level configuration, such as host names, IP address, subnets, gateways, etc.

    Application-level configuration such as DNS name of active directory server, databases and other external services.

    The set of properties that are to be configured during deployment are specified in the OVF descriptor using the ProductSection meta-data, and is typically entered by the user using a Wizard style interface during deployment.

    For instance, the OVF environment allows guest software to automate the network settings between multi-tiered services, and the web server may automatically configure itself with the IP address of the database server without any manual user interaction.

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    Defining a standard OVF environment does pose some challenges, since no standard cross-vendor para-virtualized device exists for communicating between the guest software running in a virtual machine and the underlying virtualization platform. The approach taken by the OVF specification is to split the OVF environment definitions into two parts: i) A standard protocol that specifies what information is available and what format it is available in, and ii) a transport, that specifies how the information is obtained.

    The specification requires all implementations to support an ISO transport, which will make the OVF environment (XML document) available to the guest software on a dynamically generated ISO image.

    See appendix A and B for examples of OVF environment documents.

    2.3 Sample OVF Descriptor The following listing shows a complete OVF descriptor for a typical single virtual machine appliance: 258 264 265 266 267 268 269 270 271 Describes the set of virtual disks 272 274 275 276 277 List of logical networks used in the package 278 279 The network that the service will be available on 280 281 282 283 Describes a virtual machine 284 Virtual Appliance One 285 286 Describes product information for the appliance 287 The Great Appliance 288 Some Great Corporation 289 13.00 290 13.00-b5 291 292 293 294 Email address of administrator 295 296 297 The IP address of this appliance 298 299 300 301 A random annotation on this service. It can be ignored 302 Contact customer support if you have any problems 303 304 305 License information for the appliance 306 Insert your favorite license here 307 308 309 256MB, 1 CPU, 1 disk, 1 nic 310 311

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    Number of virtual CPUs 312 1 virtual CPU 313 1 314 3 315 1 316 317 318 byte * 2^20 319 Memory Size 320 256 MB of memory 321 2 322 4 323 256 324 325 326 true 327 VM Network 328 Ethernet adapter on "VM Network" 329 4000 330 10 331 332 333 Harddisk 1 334 ovf:/disk/vmdisk1 335 22001 336 17 337 338 339 340 Guest Operating System 341 Windows 2000 Advanced Server 342 343 344 345

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    Most of the descriptor is boilerplate. It starts out by describing the set of files in addition to the descriptor itself. In this case there is a single file (vmdisk1.vmdk). It then describes the set of virtual disks and the set of networks used by the appliance. Each file, disk, and network resource is given a unique identifier. These are all in separate namespaces, but the best practice is to use distinct names.

    The content of the example OVF is a single virtual machine. The content contains 5 sections:

    ProductSection, which provides product information such as name and vendor of the appliance and a set of properties that can be used to customize the appliance. These properties will be configured at installation time of the appliance, typically by prompting the user. This is discussed in more detail below.

    AnnotationSection, which is a free form annotation.

    EulaSection, the licensing terms for the appliance. This is typically shown during install.

    HardwareSection, which describes the virtual hardware. This is a required section that describes the kind of virtual hardware and set of devices that the virtual machine requires. In this particular case, a fairly typical set of hardware (500 MB of guest memory, 1 CPU, 1 NIC, and one virtual disk) is specified. The network and disk identifiers from the outer sections are referenced here.

    OperatingSystemSection, which describes the guest operating system.

    3 Using the Open Virtualization Format 3.1 Creation The creation of an OVF involves the i) packaging of a set of VMs onto a set of virtual disks, ii) appropriately encoding those virtual disks, iii) attaching an OVF descriptor with a specification of the

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    virtual hardware, licensing, and other customization metadata, and iv) optionally digitally signing the package. The process of installing or importing an OVF occurs when a virtualization platform consumes the OVF and creates a set of virtual machines from its contents.

    Creating an OVF can be made as simple as exporting an existing virtual machine from a virtualization platform into an OVF package, and adding to it the relevant meta-data needed to correctly install and execute it. This will transform the virtual machine from its current runtime state on a particular hypervisor into an OVF package. During this process, the virtual machine's disks may be compressed to make it more convenient to distribute.

    For commercial-grade virtual appliances, a standard build environment may be used to produce an OVF package. For example, the OVF descriptor can be managed using a source control system, and the OVF package can be built using a reproducible scripting environment (such as make files) or, through the use of appliance building toolkits that are available from multiple vendors.

    When an OVF is created, it must be accompanied with appliance-specific post-installation configuration metadata. This includes metadata for optional localization of the interface language(s) of the appliance, review/signoff and/or enforcement of the EULA, and resource configuration. It can also involve the addition of special drivers, agents and other tools to the guest to enhance (for example) I/O, timekeeping, memory management, monitoring and orderly shutdown.

    3.2 Deployment Deployment transforms the virtual machines in an OVF package into the runtime format understood by the target virtualization platform, with the appropriate resource assignments and supported by the correct virtual hardware. During deployment, the platform validates the OVF integrity, making sure that the OVF package has not been modified in transit, and checks that it is compatible with the local virtual hardware. It also assigns resources to, and configures the virtual machines for the particular environment on the target virtualization platform. This includes assigning and configuring the (physical and virtual) networks to which the virtual machines must be connected; assigning storage resources for the VMs, including virtual hard disks as well as any transient data sets, connections to clustered or networked storage and the like; configuring CPU and memory resources, and customizing application level properties. OVF does not support the conversion of guest software between processor architectures or hardware platforms. Deployment instantiates one or more virtual machines with a hardware profile that is compatible with the requirements captured in the OVF descriptor, and a set of virtual disks with the content specified in the OVF package.

    The deployment experience of an OVF package depends on the virtualization platform on which it is deployed. It could be command-line based, scripted, or a graphical deployment wizard. The typical OVF deployment tool will show or prompt for the following information:

    Show information about the OVF package (from the ProductSection), and ask the user to accept the licensing agreement, or deal with an unattended installation.

    Validate that the virtual hardware is compatible with the specification in the OVF.

    Ask the user for the storage location of the virtual machines and what physical networks the logical networks in the OVF package should be connected to.

    Ask the user to enter the specific values for the properties configured in the ProductSection.

    After this configuration, it is expected that the virtual machines can be successfully started to obtain (using standard procedures such as DHCP) an identity that is valid on the local network. Properties are used to prompt for specific IP network configuration and other values that are particular to the deployment environment. Once the appliance is booted for the first time, additional configuration of software inside the appliance can be done through a management interface provided by the appliance itself, such as a web interface.

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    4 Features 4.1 Virtual Hardware Description The hardware description shown in section 2.3is very general. In particular, it simply specifies that a virtual disk and a network adaptor is needed. It does not specify what the specific hardware should be. For example, a SCSI or IDE disk, or an E1000 or Vlance network card should be appropriate. More specifically, it can reasonably be assumed that if the specification is generic, then the appliance will undertake discovery of the devices present, and load relevant drivers. In this case, it must be assumed that the appliance creator has developed the appliance with a broad set of drivers, and has tested the appliance on relevant virtual hardware to ensure that it works.

    If an OVF package is installed on a platform that does not offer the same hardware devices and/or categories of devices that are required by the guest OS that is included in the appliance, non-trivial and non-obvious installation failures can occur. The risk is not that the appliance will run incorrectly more that it will fail to install and boot, and that the user will not be able to debug the problem. With this comes the risk of increased volume in customer support calls, and general customer dissatisfaction. A more constrained and detailed virtual hardware specification can reduce the chance of incorrect execution (since the specific devices required are listed) but this will limit the number of systems upon which the appliance will correctly install.

    It should be borne in mind that simplicity, robustness, and predictability of installation are key reasons that ISVs are moving to the virtual appliance model, and therefore appliance developers should create appliances for which the hardware specification is more rather than less generic, unless the appliance has very specific hardware needs. At the outset, the portability of the appliance is based on the guest OS used in the virtual machines.

    Ideally, the appliance vendor will create a virtual machine that has device drivers for the virtual hardware of all of the vendors desired target virtualization platforms. However, many virtualization platform vendors today do not distribute drivers independently to virtual appliance vendors/creators. Instead, to further simplify the management of the virtual hardware / appliance interface, the OVF model supports an explicit installation mode, in which each virtual machine is booted once right after installation, to permit localization/customization for the specific virtualization platform. This allows the virtual machine to detect the virtualization platform and install the correct set of device drivers, including any platform specific drivers that are made available to the guest when it first re-boots (via for example, floppy or CD drives attached to the guest on first boot). In addition, for sysprepped Windows VMs, which need only re-installation and customization with naming etc, the re-boot technique allows naming and tailoring of the image to be achieved in an automated fashion.

    Example where multiple virtual hardware profiles are specified in the same descriptor: 450 500Mb, 1 CPU, 1 disk, 1 nic virtual machine 451 452 ... 453 454 455 ... 456 457 ... 458 459 460 500Mb, 1 CPU, 1 disk, 1 nic virtual machine 461 462 ... 463 464 465 ... 466 467 ... 468 469

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    This allows the vendor to tailor the hardware description to support different virtualization platforms and features. A specific virtualization platform may choose between any of the specific virtual hardware sections that it can support, with the assumption that the OVF installer will choose the latest or most capable feature set that is available on the local platform.

    Example where specific device types are specified: 475 SCSI Controller 0 476 1000 477 LsiLogic BusLogic 478 6 479 480 481 Harddisk 1 482 ovf:/disk/vmdisk1 483 22001 484 1000 485 17 486 487

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    In the above examples, the ResourceSubType is used to specify the exact devices that are supported by the guest OS in the appliance.

    4.2 Deployment Options The author of an OVF package will have the ability to include meta-data about the intended resource requirements for a virtual appliance. This is formatted as a human-readable list of configurations, for instance:

    1. Software evaluation setup

    2. 10-100 person workgroup setup

    3. 100-1000 person workgroup setup

    4. Large enterprise workgroup setup

    The deployer of the package will be prompted to select a configuration during deployment. In addition to exact values, ranges can also be specified. For example, the memory size can be specified as being 600MB, and that the recommended range is between 500MB to 1000MB. Typically, a user will not be prompted to specify a value for a range when deploying an OVF package. The list of configurations described above is expected to be used to get to a good initial resource configuration. A range specification becomes useful when the installation later needs to be changed based on different resource needs.

    Example list of configurations: 507 508 Minimal 509 Minimal setup 510 511 512 Normal 513 Standard setup 514 515 ... more configurations ... 516 517



    Resource requirement example: 520 Defines reservations for CPU and memory 521 522

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    ... normal configuration ... 523 524 525 ... overwrites for minimal configuration ... 526 527 528

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    VirtualHardwareSection example: 531 ... 532 533 hertz * 10^6 534 1 CPU and 500 MHz reservation 535 1 536 500 537 4 538 1 539 540 ... 541 542 1 CPU and 800 MHz reservation 543 0 544 600 545 3 546 547 548

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    4.3 Deployment Customization The OVF descriptor can contain a description of the software product installed in the guest, including how it can be customized through the OVF environment.

    554 Describes product information for the service 555 MyService Web Portal 556 Some Random Organization 557 4.5 558 4.5-b4523 559 560 561 562 Email address of administrator 563 564 565 IP address of the application 566 567 568

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    Property elements specify application-level customization parameters and are particularly relevant to appliances that need to be customized during deployment with specific settings such as network identity, the IP addresses of DNS servers, gateways, and others.

    Appendix 0 contains a detailed example of customization of a complex multi-tiered application.

    4.4 Internationalization

    The OVF specification support localizable messages using the optional ovf:msgid attribute: 577 ... 578 Operating System 579 ... 580 581

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    In the example above the localized strings are stored inside the OVF descriptor, but localized strings may also be stored outside the OVF descriptor using external string bundles. For example: 593 594 ... 595 596 597 ... 598 599 ... 600 601 602 603


    605 606 607 608 609 610 611 612 613 614 615 616 617 618

    4.5 Extensibility A design goal of the OVF specification is to ensure backwards- and forwards compatibility. For forwards compatibility, this means that an OVF descriptor using features of a later specification (or custom extensions) can be understood by an OVF consumer that is written to either i) an earlier version of the specification, or ii) has no knowledge of the particular extensions. OVF consumer should be able to reliably, predictably, and in a user-friendly manner, decide whether to reject or accept an OVF package that contains extensions. OVF supports an open-content model that allows additional sections to be added, as well as allowing existing sections to be extended with new content. On extensions, a Boolean ovf:required attribute specifies whether the information in the element is required for correct behavior or optional. Example of adding new section: 619 Specifies information on how a virtual machine was created 620 ... 621 ... 622 ... 623 ... 624 625

    626 627 628

    Example of extending existing section: 629 Specifies an annotation for this virtual machine 630 This is an example of how a future element (Author) can still be parsed by older 631 clients 632 633 John Smith 634 635

    636 637 638 639

    640 641

    See appendix C for detailed examples on OVF documents extensions.

    4.6 Conformance The OVF specification defines three conformance levels for OVF descriptors, with 1 being the highest level of conformance:

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    645 646

    647 648 649

    650 651


    653 654 655 656 657 658 659

    660 661 662 663

    664 665 666 667 668 669

    670 671 672 673

    674 675 676

    677 678 679 680


    682 683 684 685 686

    OVF descriptor only contains meta-data defined in the OVF specification, i.e. no custom extensions are present. Conformance Level: 1.

    OVF descriptor contains meta-data with custom extensions, but all such extensions are optional. Conformance Level: 2.

    OVF descriptor contains meta-data with custom extensions, and at least one such extension is required. Conformance Level: 3.

    The use of conformance level 3 limits portability and should be avoided if at all possible.

    5 Portability OVF is an enabling technology for enhancing portability of virtual appliances and their associated virtual machines. An OVF package contains a recipe for creating virtual machines that can be interpreted concisely by a virtualization platform. The packaged meta-data enables a robust and user-friendly experience when installing a virtual appliance. In particular, the meta-data can be used by the management infrastructure to confidently decide whether a particular VM described in an OVF can be installed or whether it should be rejected, and potentially to guide appropriate conversions and localizations to make it runnable in the specific execution context in which it is to be installed.

    There are many factors that are beyond the control of the OVF format specification and even a fully compliant implementation of it, that determine the portability of a packaged virtual machine. That is, the act of packaging a virtual machine into an OVF package does not guarantee universal portability or install-ability across all hypervisors. Below are some of the factors that could limit portability:

    The VMs in the OVF could contain virtual disks in a format that is not understood by the hypervisor attempting the installation. While it is reasonable to expect that most hypervisors will be able to import and/or export VMs in any of the major virtual hard disk formats, newer formats may arise that are supported by the OVF and not a particular hypervisor. It may be useful in future versions of this specification, to stipulate a required set of virtual hard disk formats that must be supported by an OVF compliant hypervisor.

    The installed guest software may not support the virtual hardware presented by the hypervisor. By way of example, the Xen hypervisor does not by default offer a virtualized floppy disk device to guests. One could conceive of a guest VM that would require interaction with a floppy disk controller and which therefore would not be able to execute the VM correctly.

    The installed guest software does not support the CPU architecture. For example, the guest software might execute CPU operations specific to certain processor models or require specific floating point support, or contain opcodes specific to a particular vendors CPU.

    The virtualization platform might not understand a feature requested in the OVF descriptor. For example, composed services may not be supported. Since the OVF standard will evolve independently of virtualization products, at any point an OVF might be unsupportable on a virtualization platform that pre-dates that OVF specification.

    The portability of an OVF can be categorized into the following 3 levels:

    Level 1. Only runs on a particular virtualization product and/or CPU architecture and/or virtual hardware selection. This would typically be due to the OVF containing suspended virtual machines or snapshots of powered on virtual machines, including the current run-time state of the CPU and real or emulated devices. Such state ties the OVF to a very specific virtualization and hardware platform.

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    697 698 699 700 701 702

    703 704 705 706 707 708 709 710 711 712 713 714 715 716



    719 720 721

    722 723 724 725

    726 727 728 729



    732 733

    Level 2. Runs on a specific family of virtual hardware. This would typically be due to lack of driver support by the installed guest software.

    Level 3. Runs on multiple families of virtual hardware. For example, the appliance could be runnable on Xen, Sun, Microsoft, and VMware hypervisors. For level 3 compatibility, the guest software has been developed to support the devices of multiple hypervisors. A clean install and boot of a guest OS, during which the guest OS performs hardware device discovery and installs any specialized drivers required to interact with the virtual platform, is an example of Level 3 portability of an OVF. The sysprep level of portability for Microsoft Windows operating systems is another example. Such OS instances can be re-installed, re-named and re-personalized on multiple hardware platforms, including virtual hardware.

    For use within an organization, Level 1 or Level 2 compatibility may be good enough, since the OVF package is distributed within a controlled environment where specific purchasing decisions of hardware or virtualization platforms can ensure consistency of the underlying feature set for the OVF. A simple export of a virtual machine will typically create an OVF with Level 1 or Level 2 compatibility (tied to a specific set of virtual hardware), however it is easy to extend the metaphor to support the export of Level 3 compatibility, for example through the use of utilities such as sysprep for Windows.

    For commercial appliances independently created and distributed by ISVs, Level 3 compatibility is highly desirable. Indeed, Level 3 compatibility ensures that the appliance is readily available for the broadest possible customer base both for evaluation and production. Toolkits will generally be used to create certified known good Level 3 packages of the appliance for broad distribution and installation on multiple virtual platforms, or Level 2 compatibility packages if the appliance is to be consumed within the context of a narrower set of virtual hardware, such as within a particular development group in an enterprise. The OVF virtual hardware description is designed to support Level 1 through Level 3 portability. For Level 3 portability it is possible to include only very general descriptions of hardware requirements, or to specify multiple alternative virtual hardware descriptions. The appliance provider is in full control of how flexible or restrictive the virtual hardware specification is made. A narrow specification can be used to constrain an appliance to run on only known-good virtual hardware, while limiting its portability somewhat. A broad specification makes the appliance useful across as wide a set of virtual hardware as possible. This ensures that customers have the best possible user experience, which is one of the main requirements for the success of the virtual appliance concept.

    6 Future Versions of the OVF Specification The scope of OVF specification version 1.0 is the packaging and deployment phases of the virtual appliance software life cycle. OVF 1.0 provides the core framework that allows workflow and system-level meta-data to be encoded, stored, and transported.

    In the OVF package, information can be stored that describes how the appliance is to interact with external processes and systems. Examples of such functionality are appliance upgrade, cataloging, and integrity and/or security checking, dependency checking, and enhanced license management. Future versions of the specification may look at standardizing such metadata.

    An OVF package can contain multi-tiered applications, including complex nested configurations, but OVF currently does not support composition of existing OVF packages. Composing existing packages can be attractive when software in an existing signed OVF package is to be embedded in a new context. Future versions of the specification may look at supporting this.

    7 Conclusion The OVF specification offers a portable virtual appliance format that is intended for broad adoption across the IT industry. The OVF specification is intended to be immediately useful, to solve an immediate

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    business need, and to facilitate the rapid adoption of a common, backwards compatible, yet rich virtual machine format. OVF is complementary to existing IT management standards and frameworks, and will be further developed within a standards organization. OVF promotes customer confidence through the collaborative development of common standards for portability and interchange of virtual machines between different vendors virtualization platforms, and promotes best-of-breed competition through its openness and extensibility.

    The OVF specification is intended to evolve in an appropriate standards organization. The explicit copyright notice attached to this document is intended to avoid arbitrary piece-wise extensions to the format outside the context of a standards organization, while permitting free distribution and implementation of the specification.

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    A Multi-tiered Petstore Example This example will demonstrate several advanced OVF concepts:

    Multi-VM packages - use of the VirtualMachineCollection entity subtype Composite service organization - use of nested VirtualMachineCollection entity subtype Propagation of user defined deployment configuration. Deployment time customization of the service using the OVF Environment. The use of virtual disk chains to minimize downloads. Nesting of ProductSections for providing information about the installed software in an individual

    virtual machine The example service is called PetStore and consists of a front-end web-server and a database. The database server is itself a complex multi-tiered server consisting of two VMs for fault-tolerance.

    Architecture and Packaging The Petstore OVF package consists of 3 virtual systems (WebTier, DB1, and DB2) and 2 virtual system collections (Petstore and DBTier). The diagram below shows the structure of the OVF package as well as the properties and startup order of the virtual machines:


    DB Tier vm1=${dbIp}

    vm2=${db2Ip} log=${logLevel}

    Web Tier

    DB1 ip=${vm1}

    ip2=${vm2} primaryAtBoot=yes

    DB2 ip=${vm2}

    ip2=${vm1} primaryAtBoot=no VirtualSystem


    Properties: adminEmail, appIp, dbIp, db2Ip, logLevel

    1 2


    1 Startup Order

    The complete OVF descriptor is listed at the end of this document. The use of properties and disk layout of the OVF is discussed in more details in the following.

    Properties The Petstore service has 5 user-configurable properties. These are the key control parameters for the service that needs to be configured in order for it to start up correctly in the deployed environment. The properties are passed up to the guest software in the form of an OVF environment document. The guest software is written to read the OVF environment on startup, extract the values of the properties, and apply them to the software configuration. Thus, the OVF descriptor reflects the properties that are handled by the guest software. For this particular service, there are two different software configurations, one for the Web tier and one for the Database tier. The properties supported in each software configuration are:

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    Web Guest Software:

    Property Description appIp IP address of the WebServer. dbIp IP address of the database server to connect to. adminEmail Email address for support logLevel Logging level

    780 781 782 783 784 785 786

    All properties defined on the immediate parent VirtualSystemCollection container is available to a child VirtualSystem or VirtualSystemCollection. Thus, the OVF descriptor does not need to contain an explicit ProductSection each VM, as demonstrated for WebVM. Database Guest Software:

    Property Description Ip IP address of the virtual machine primaryAtBoot Whether the instance should act as the primary or secondary when booting ip2 IP address of the twin database VM that acts as the hot-spare or primary log Here the logging level is called log

    787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810

    811 812 813 814 815 816

    The clustered database is organized as a virtual system collection itself with a specific set of properties for configuration: vm1, vm2, and log. This organization separates the database implementation from the rest of the software in the OVF package and allows virtual appliances (guest software + virtual machine configurations) to be easily composed and thereby promotes reuse. The database software is an off-the-shelf software package and the vendor has chosen the "com.mydb.db" as the unique name for all the properties. This can be seen in the OVF descriptor with the inclusion of the ovf:class attribute on the ProductSection. The ${} property syntax is used to propagate values from the outer level into the inner nodes in the OVF Descriptor's entity hierarchy. This mechanism allows linking up different components without having to pre-negotiate naming conventions or changing guest software. Only properties defined on the immediate parent VirtualSystemCollection container are available to a child entity. Thus, properties defined on Petstore will not be available to a DB1. This ensures that the interface for a VirtualSystemCollection is encapsulated and well described in its parent VirtualSystemCollection, which makes the software composable and easy to reuse. The OVF descriptor uses fixed non-user assignable properties to ensure that the two database virtual machines boots up into different roles even though they are, initially, booting of the exact same software image. The property named com.mydb.db.primaryAtBoot is specified with a fixed, non-user configurable value but is different value for the two images. The software inspects this at boot time and customizes its operation accordingly.

    Disk Layout The Petstore OVF package uses the ability to share disks and encode a delta disk hierarchy to minimize the size and thereby the download time for the package. In this particular case, we only have two different images (Database and Web), and if we further assume they are build on top of the same base OS distribution, we can encode this in the OVF descriptor as.

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    829 830


    DB VM 1

    DB VM 2 Base



    Thus, while the package contains 3 distinct virtual machines, the total download size will be significantly smaller. In fact, only one full VM and then two relative small deltas need to be downloaded. The physical layout of the virtual disks on the deployment system is independent of the disk structure in the OVF package. The OVF package describes the size of the virtual disk and the content (i.e., bits that needs to be on the disk). It also specifies that each virtual machine must get independent disks. Thus, a virtualization platform could install the above package as a 3 VMs with 3 independent flat disks, or it could chose to replicate the above organization, or something third, as long as each virtual machine sees a disk with the content described on initial boot and that changes written by one virtual machine does not affect the others.

    Complete OVF Descriptor 831 847 848 Describes the set of virtual disks 849 852 855 858 859 860 861 List of logical networks used in the package 862 863 The network that the service 864 will be available on 865 866 867 868 869 List of deployment options available in the package 870 871 Minimal 872

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    Deploy service with minimal 873 resource use 874 875 876 Standard 877 Deploy service with standard 878 resource use 879 880 881 882 883 The packaging of the PetStoreService multi-tier application 884 PetStore Service 885 886 887 Describes product information for the service 888 PetStore Web Portal 889 Some Random Organization 890 4.5 891 4.5-b4523 892 893 894 Email properties 895 896 Admin email 897 Email address of 898 service administrator 899 900 Network properties 901 903 IP 904 IP address of the 905 service 906 907 908 IP for DB 909 Primary IP address of 910 the database 911 912 914 IP for DB2 915 A secondary IP 916 address for the database 917 918 Logging properties 919 921 Loglevel 922 Logging level for 923 the service 924 925 926 927 928 A annotation on this service 929 Contact customer support for 930 any urgent issues 931 932 933 Defines minimum reservations for CPU and memory 934 935 byte * 2^20 936 512 MB reservation 937 0 938 512 939 4 940 941 942 byte * 2^20 943 384 MB reservation 944 0 945 384 946

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    4 947 948 949 MHz 950 1000 MHz reservation 951 1 952 500 953 3 954 955 956 MHz 957 500 MHz reservation 958 1 959 500 960 3 961 962 963 MHz 964 1500 MHz reservation 965 1 966 1500 967 3 968 969 970 971 Specifies how the composite service is powered-on and off 972 975 978 979 980 The virtual machine containing the WebServer application 981 982 Describes the product information 983 Apache Webserver 984 Apache Software Foundation 985 6.5 986 6.5-b2432 987 988 989 Guest Operating System 990 Linux 2.4.x 991 992 993 256 MB, 1 CPU, 1 disk, 1 nic virtual machine 994 995 Virtual Hardware Family 996 0 997 vmx-04 998 999 1000 Number of virtual CPUs 1001 1 virtual CPU 1002 1 1003 3 1004 1 1005 1006 1007 byte * 2^20 1008 Memory Size 1009 256 MB of memory 1010 2 1011 4 1012 256 1013 1014 1015 true 1016 VM Network 1017 Ethernet adapter on "VM Network" 1018 3 1019 PCNet32 1020

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    10 1021 1022 1023 1 1024 SCSI Controller 0 - LSI Logic 1025 1000 1026 LsiLogic 1027 6 1028 1029 1030 0 1031 Harddisk 1 1032 ovf:/disk/web 1033 22001 1034 1000 1035 17 1036 1037 1038 1039 1040 1041 Describes a clustered database instance 1042 1043 Product Information 1044 Somebody Clustered SQL Server 1045 TBD 1046 2.5 1047 2.5-b1234 1048 1049 1050 1051 1052 1053 Specifies how the composite service is powered-on and off 1054 1057 1060 1061 1062 1063 Describes a virtual machine with the database image installed 1064 Database Instance I 1065 1066 Specifies the OVF properties available in the OVF environment 1067 1068 1069 1070 1071 1072 256 MB, 1 CPU, 1 disk, 1 nic virtual machine 1073 1074 Virtual Hardware Family 1075 0 1076 vmx-04 1077 1078 1079 Number of virtual CPUs 1080 1 virtual CPU 1081 1 1082 3 1083 1 1084 1085 1086 byte * 2^20 1087 Memory Size 1088 256 MB of memory 1089 2 1090 4 1091 256 1092 1093 1094

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    true 1095 VM Network 1096 Ethernet adapter on "VM Network" 1097 3 1098 PCNet32 1099 10 1100 1101 1102 1 1103 SCSI Controller 0 - LSI Logic 1104 1000 1105 LsiLogic 1106 6 1107 1108 1109 0 1110 Harddisk 1 1111 ovf:/disk/db 1112 22001 1113 1000 1114 17 1115 1116 1117 1118 Guest Operating System 1119 Linux 2.4.x 1120 1121 1122 1123 1124 Describes a virtual machine with the database image installed 1125 Database Instance II 1126 1127 Specifies the OVF properties available in the OVF environment 1128 1129 1130 1131 1132 1133 256 MB, 1 CPU, 1 disk, 1 nic virtual machine 1134 1135 Virtual Hardware Family 1136 0 1137 vmx-04 1138 1139 1140 Number of virtual CPUs 1141 1 virtual CPU 1142 1 1143 3 1144 1 1145 1146 1147 byte * 2^20 1148 Memory Size 1149 256 MB of memory 1150 2 1151 4 1152 256 1153 1154 1155 true 1156 VM Network 1157 Ethernet adapter on "VM Network" 1158 3 1159 PCNet32 1160 10 1161 1162 1163 1 1164 SCSI Controller 0 - LSI Logic 1165 1000 1166 LsiLogic 1167 6 1168

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    1169 1170 0 1171 Harddisk 1 1172 ovf:/disk/db 1173 22001 1174 1000 1175 17 1176 1177 1178 1179 Guest Operating System 1180 Linux 2.4.x 1181 1182 1183 1184 1185 1186 1187 1188 1189 Netvrket servicen skal vre tilgngelig p 1190 Kontakt kundeservice i tilflde af 1191 kritiske problemer 1192 Email adresse for administrator 1193 IP adresse for service 1194 Primr IP adresse for database 1195 Sekundr IP adresse for database 1196 Logningsniveau for service 1197 Minimal 1198 Installer service med minimal brug af 1199 resourcer 1200 Normal 1201 Installer service med normal brug af 1202 resourcer 1203 1204 1205


    1207 1208 1209 1210 1211 1212 1213

    Complete OVF Environments The following lists the OVF environments seen by the WebTier and DB1 virtual machines (DB2 is is virtually identical to the one for DB1 and is omitted). OVF environment for the WebTier virtual machine: 1214 1219 1220 1221 1222 ESX Server 1223 3.0.1 1224 VMware, Inc. 1225 en_US 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237

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    1251 1252 1253

    OVF environment for the DB1 virtual machine: 1254 1259 1260 1261 1262 ESX Server 1263 3.0.1 1264 VMware, Inc. 1265 en_US 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289


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    1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302

    1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314

    B LAMP Stack Example In this example we provide two concrete examples on how an OVF descriptor for a LAMP virtual appliance could look like. We show both a single-VM LAMP virtual appliance and a multi-VM LAMP virtual appliance. LAMP is an abbreviation for a service built using the Linux operating system, Apache web server, MySQL database, and the PHP web development software packages. This examples show how the ProductSection can be used to specify both operating system and application-level deployment parameters. For example, these parameters can be used to optimize the performance of a service when deployed into a particular environment. The descriptors are complete, but otherwise kept minimal, so there are, for example, no EULA sections.

    Deployment-time Customization A part of the deployment phase of an OVF package is to provide customization parameters. The customization parameters are specified in the OVF descriptor and are provided to the guest software using the OVF environment. This deployment time customization is in addition to the virtual machine level parameters, which includes virtual switch connectivity and physical storage location. For a LAMP-based virtual appliance, the deployment time customization includes IP address and port number of the service, network information such as gateway and subnet, and also parameters so the performance can be optimized for a given deployment. The properties that will be exposed to the deployer will vary from vendor to vendor and service to service. In our example descriptors, we use the following set of parameters for the 4 different LAMP components:

    Product Property Description hostname ip subnet gateway dns

    Network identity of the application, including IP address.



    netCoreWmemMax Parameters to optimize the transfer rate of the IP stack

    httpPort httpsPort

    Port numbers for web server

    startThreads minSpareThreads maxSpareThreads



    Parameters to optimize the performance of the web server

    queryCacheSize maxConnections



    Parameters to optimize the performance of database

    sessionTimeout concurrentSessions



    Parameters to customize the behavior of the PHP engine, including how sessions timeout and number of sessions.

    1315 1316 1317 1318 1319 1320 1321

    The parameters in italic are required configuration from the user. Otherwise, they have reasonable defaults, so the user does not necessarily need to provide a value. The customization parameters for each software product are encapsulated in separate product sections. For example, for the Apache web server the following section is used: 1322 Product customization for the installed Apache Web Server 1323 Apache Distribution Y 1324

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    2.6.6 1325 1327 Port number for HTTP requests 1328 1329 1331 Port number for HTTPS requests 1332 1333 1335 Number of threads created on startup. 1336 1337 1339 Minimum number of idle threads to handle request spikes. 1340 1341 1343 Maximum number of idle threads 1344 1345 1347 Limit the number of simultaneous requests that will be served. 1348 1349 1350 1351

    1352 1353

    The ovf:class="org.apache.httpd" attribute specifies the prefix for the properties. Hence, the Apache database is expected to look for the following properties in the OVF environment: 1379 1380 1381 1382 1383 1384 List of the virtual disks used in the package 1385 1388 1389 1390 1391

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    Logical networks used in the package 1392 1393 The network that the LAMP Service will be available 1394 on 1395 1396 1397 1398 Single-VM Virtual appliance with LAMP stack 1399 LAMP Virtual Appliance 1400 1401 1402 Product information for the service 1403 Lamp Service 1404 1.0 1405 1.0.0 1406 1407 1408 1409 Product customization for the installed Linux system 1410 Linux Distribution X 1411 2.6.3 1412 1413 Specifies the hostname for the appliance 1414 1415 1416 Specifies the IP address for the appliance 1417 1418 1419 Specifies the subnet to use on the deployed network 1420 1421 1422 1423 Specifies the gateway on the deployed network 1424 1425 1426 1427 A comma separated list of DNS servers on the deployed 1428 network 1429 1430 1432 Specify TCP read max buffer size in mega bytes. Default is 1433 16. 1434 1435 1437 Specify TCP write max buffer size in mega bytes. Default is 1438 16. 1439 1440 1441 1442 1443 Product customization for the installed Apache Web Server 1444 Apache Distribution Y 1445 2.6.6 1446 1448 Port number for HTTP requests 1449 1450 1452 Port number for HTTPS requests 1453 1454 1456 Number of threads created on startup. 1457 1458 1460 Minimum number of idle threads to handle request spikes. 1461 1462 1463 1465

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    Maximum number of idle threads 1466 1467 1469 Limit the number of simultaneous requests that will be 1470 served. 1471 1472 1473 1474 1475 Product customization for the installed MySql Database Server 1476 MySQL Distribution Z 1477 5.0 1478 1480 Buffer to cache repeated queries for faster access (in 1481 MB) 1482 1483 1485 The number of concurrent connections that can be 1486 served 1487 1488 1490 Number of seconds to wait before timing out a connection 1491 1492 1493 1494 1495 1496 Product customization for the installed PHP component 1497 PHP Distribution U 1498 5.0 1499 1501 How many minutes a session has to be idle before it is 1502 timed out 1503 1504 1506 The number of concurrent sessions that can be served 1507 1508 1509 1511 How much memory in megabytes a script can consume before 1512 being killed 1513 1514 1515 1516 Guest Operating System 1517 Linux 2.6.x 1518 1519 1520 Virtual Hardware Requirements: 256MB, 1 CPU, 1 disk, 1 NIC 1521 1522 Virtual Hardware Family 1523 0 1524 vmx-04 1525 1526 1527 Number of virtual CPUs 1528 1 virtual CPU 1529 1 1530 3 1531 1 1532 1533 1534 byte * 2^20 1535 Memory Size 1536 256 MB of memory 1537 2 1538 4 1539

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    256 1540 1541 1542 true 1543 VM Network 1544 Ethernet adapter on "VM Network" 1545 3 1546 10 1547 1548 1549 SCSI Controller 0 - LSI Logic 1550 4 1551 LsiLogic 1552 6 1553 1554 1555 Harddisk 1 1556 ovf:/disk/lamp 1557 5 1558 4 1559 17 1560 1561 1562 1563 1564



    1567 1568

    1569 1570 1571


    1573 1574

    1575 1576 1577 1578

    1579 1580 1581


    Two-tier LAMP OVF Descriptor In a two tier LAMP stack, the application tier (Linux, Apache, PHP) and the database tier (Linux, MySQL) server) are run as separate virtual machines for greater scalability.

    The OVF format makes it largely transparent to the user how a service is implemented. In particular, the deployment experience when installing a single-VM or a two-tier LAMP appliance is very similar. The only visible difference is that the user will need to supply two IP addresses and two DNS host names.

    As compared to the single-VM descriptor, the following changes are made:

    Alll the user-configurable parameters must be put in the VirtualSystemCollection entity. The ProductSections for Apache, MySQL, and PHP are unchanged from the single VM case.

    The Linux software in the two virtual machines needs to be configured slightly different (IP and hostname) while sharing most parameters. A new ProductSection is added to the VirtualSystemCollection to prompt the user, and the ${property} expression is used to assign the values in each VirtualSystem entity.

    Disk chains are used to keep the download size comparable to that of a single VM appliance. Since the Linux installation is stored on a shared base disk, effectively only one copy of Linux needs to be downloaded.

    The complete OVF descriptor is shown below: 1583

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    This example is encoded as a delta-disk hierarchy. 1598 --> 1599 1600 List of the virtual disks used in the package 1601 1604 1608 1612 1613 1614 1615 Logical networks used in the package 1616 1617 The network that the LAMP Service will be available 1618 on 1619 1620 1621 1622 Virtual appliance with a 2-tier distributed LAMP stack 1623 LAMP Service 1624 1625 1626 Product information for the service 1627 My Lamp Service 1628 1.0 1629 1.0.0 1630 1631 1632 Product customization for Operating System Level 1633 Linux Distribution X 1634 2.6.3 1635 1636 Specifies the hostname for database virtual 1637 machine 1638 1639 1640 Specifies the hostname for application server virtual 1641 machine 1642 1643 1644 Specifies the IP address for the database virtual 1645 machine 1646 1647 1648 Specifies the IP address for application server 1649 VM 1650 1651 1652 Specifies the subnet to use on the deployed network 1653 1654 1655 1656 Specifies the gateway on the deployed network 1657 1658 1659 1660 A comma separated list of DNS servers on the deployed 1661 network 1662 1663 1665 Specify TCP read max buffer size in mega bytes. Default is 1666 16. 1667 1668 1670 Specify TCP write max buffer size in mega bytes. Default is 1671

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    16. 1672 1673 1674 1675 1676 Product customization for the installed Apache Web Server 1677 Apache Distribution Y 1678 2.6.6 1679 1681 Port number for HTTP requests 1682 1683 1685 Port number for HTTPS requests 1686 1687 1689 Number of threads created on startup. 1690 1691 1693 Minimum number of idle threads to handle request spikes. 1694 1695 1696 1698 Maximum number of idle threads 1699 1700 1702 Limits the number of simultaneous requests that will be 1703 served. 1704 1705 1706 1707 1708 Product customization for the installed MySql Database Server 1709 MySQL Distribution Z 1710 5.0 1711 1713 Buffer to cache repeated queries for faster access (in 1714 MB) 1715 1716 1718 The number of concurrent connections that can be 1719 served 1720 1721 1723 Number of seconds to wait before timing out a connection 1724 1725 1726 1727 1728 1729 Product customization for the installed PHP component 1730 PHP Distribution U 1731 5.0 1732 1734 How many minutes a session has to be idle before it is 1735 timed out 1736 1737 1739 The number of concurrent sessions that can be served 1740 1741 1742 1744 How much memory in megabytes a script can consume before 1745

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    being killed 1746 1747 1748 1749 Startup order of the virtual machines 1750 1753 1756 1757 1758 The configuration of the AppServer virtual machine 1759 Application Server 1760 1761 1762 Product customization for the installed Linux system 1763 Linux Distribution X 1764 2.6.3 1765 1766 1767 1768 1769 1770 1772 1774 1775 1776 Guest Operating System 1777 Linux 2.6.x 1778 1779 1780 Virtual Hardware Requirements: 256 MB, 1 CPU, 1 disk, 1 NIC 1781 1782 Virtual Hardware Family 1783 0 1784 vmx-04 1785 1786 1787 Number of virtual CPUs 1788 1 virtual CPU 1789 1 1790 3 1791 1 1792 1793 1794 byte * 2^20 1795 Memory Size 1796 256 MB of memory 1797 2 1798 4 1799 256 1800 1801 1802 true 1803 VM Network 1804 Ethernet adapter on "VM Network" 1805 3 1806 PCNet32 1807 10 1808 1809 1810 SCSI Controller 0 - LSI Logic 1811 4 1812 LsiLogic 1813 6 1814 1815 1816 Harddisk 1 1817 ovf:/disk/lamp-app 1818 5 1819

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    4 1820 17 1821 1822 1823 1824 1825 The configuration of the database virtual machine 1826 Database Server 1827 1828 1829 Product customization for the installed Linux system 1830 Linux Distribution X 1831 2.6.3 1832 1834 1835 1836 1837 1838 1840 1842 1843 1844 Guest Operating System 1845 Linux 2.6.x 1846 1847 1848 Virtual Hardware Requirements: 256 MB, 1 CPU, 1 disk, 1 nic 1849 1850 Virtual Hardware Family 1851 0 1852 vmx-04 1853 1854 1855 Number of virtual CPUs 1856 1 virtual CPU 1857 1 1858 3 1859 1 1860 1861 1862 byte * 2^20 1863 Memory Size 1864 256 MB of memory 1865 2 1866 4 1867 256 1868 1869 1870 true 1871 VM Network 1872 Ethernet adapter on "VM Network" 1873 3 1874 10 1875 1876 1877 SCSI Controller 0 - LSI Logic 1878 4 1879 LsiLogic 1880 6 1881 1882 1883 Harddisk 1 1884 ovf:/disk/lamp-db 1885 5 1886 4 1887 17 1888 1889 1890 1891 1892 1893

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    1895 1896 1897

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    C Extensibility Example The OVF specification allows custom meta-data to be added to OVF descriptors in several ways:

    New section elements may be defined as part of the Section substitution group, and used wherever the OVF schemas allow sections to be present.

    The OVF schemas use an open content model, where all existing types may be extended at the end with additional elements. Extension points are declared in the OVF schemas with xs:any declarations with namespace="##other".

    The OVF schemas allow additional attributes on existing types.

    Custom meta-data is not allowed to use OVF XML namespaces. On custom elements, a boolean ovf:required attribute specifies whether the information in the element is required for correct behavior or optional. The open content model in the OVF schemas only allows extending existing types at the end. Using XML Schema 1.0 it is not easy to allow for a more flexible open content model, due to the Unique Particle Attribution rule and the necessity of adding xs:any declarations everywhere in the schema. The XML Schema 1.1 draft standard contains a much more flexible open content mechanism, using xs:openContent mode="interleave" declarations. Future versions of the OVF specification may look at supporting this.

    Custom Schema A custom XML schema defining two extension types is listed below. The first declaration defines a custom member of the OVF Section substitution group, while the second declaration defines a simple custom type. 1921 1929 1930 1931 1933 1934 1935 1936 1937 1938 1939 1940 1941 1942 1943 1944 1945 1946 1947 1948

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    Descriptor with custom extensions A complete OVF descriptor using the custom schema above is listed below. The descriptor validates against the OVF schema and the custom schema, but apart from extension examples the descriptor is kept minimal and is as such not useful.

    The descriptor contains all three extension types: a custom OVF Section element, a custom element at an extension point, and a custom attribute. 1967 1974 1975 1976 1977 1978 1979 1980 Description of custom extension 1981 somevalue 1982 1983 1984 1985 1986 Logical networks used in the package 1987 1988 1989 1991 1992 somevalue 1993 1994 1995 1996 1997 1998 Dummy VirtualSystem 1999 2000 2001


    2003 2004

    The OVF environment XML schemas contain extension mechanisms matching those of the OVF envelope XML schemas, so OVF environment documents are similarly extensible.

    1 Introduction1.1 Overview1.2 Virtual Appliances1.3 Design Goals1.4 Virtual Appliance Life-Cycle

    2 Portable Virtualization Format2.1 OVF Package2.2 OVF Environment2.3 Sample OVF Descriptor

    3 Using the Open Virtualization Format3.1 Creation3.2 Deployment

    4 Features4.1 Virtual Hardware Description4.2 Deployment Options4.3 Deployment Customization4.4 Internationalization4.5 Extensibility4.6 Conformance

    5 Portability6 Future Versions of the OVF Specification7 ConclusionA Multi-tiered Petstore ExampleArchitecture and PackagingProperties Disk LayoutComplete OVF DescriptorComplete OVF EnvironmentsB LAMP Stack ExampleDeployment-time CustomizationSimple LAMP OVF DescriptorTwo-tier LAMP OVF Descriptor

    C Extensibility ExampleCustom SchemaDescriptor with custom extensions