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Xen

Xen running NetBSD and three Linux distributions (Fedora Core and two instances of SUSE Linux).
Developer: The Xen Project, XenSource, Inc.
Latest release: 3.0.4 / December 20, 2006
OS: Linux, and other Unix-like, *BSD, OpenSolaris and Microsoft Windows
Use: Virtual machine monitor
License: GPL
Website: http://www.xensource.com/xen

Xen is a free virtual machine monitor for IA-32, x86-64, IA-64 and PowerPC architectures. It is software that runs on a host operating system and allows one to run several guest operating systems on top of the host on the same computer hardware at the same time. Modified versions of Linux and NetBSD can be used as hosts. Several modified Unix-like systems may be employed as guest systems; on certain hardware, since Xen version 3.0, unmodified versions of Windows and other systems can also be used as guests. Image File history File links Xen_logo. ... Image File history File links Download high resolution version (1024x768, 393 KB) Licensing File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... NetBSD is a freely redistributable, open source version of the Unix-like BSD computer operating system. ... Linux (IPA pronunciation: ) is a Unix-like computer operating system family. ... Fedora Core is an RPM-based Linux distribution, developed by the community-supported Fedora Project and sponsored by Red Hat. ... SUSE (pronounced , loosely [SOO-zuh] [1] in English) is a major retail Linux distribution, produced in Germany and owned by Novell, Inc. ... Software development is the translation of a user need or marketing goal into a software product. ... A software release refers to the creation and availability of a new version of a computer software product. ... December 20 is the 354th day of the year (355th in leap years) in the Gregorian calendar. ... For the Manfred Mann album, see 2006 (album). ... An operating system (OS) is a set of computer programs that manage the hardware and software resources of a computer. ... Linux (IPA pronunciation: ) is a Unix-like computer operating system family. ... Filiation of Unix and Unix-like systems Unix (officially trademarked as UNIX®) is a computer operating system originally developed in the 1960s and 1970s by a group of AT&T employees at Bell Labs including Ken Thompson, Dennis Ritchie and Douglas McIlroy. ... Berkeley Software Distribution (BSD, sometimes called Berkeley Unix) is the Unix derivative distributed by the University of California, Berkeley starting in the 1970s. ... OpenSolaris is an open source project created by Sun Microsystems to build a developer community around the Solaris Operating System technology. ... Microsoft Windows is the name of several families of proprietary software operating systems by Microsoft. ... In general terms, a virtual machine in computer science is software that creates an environment between the computer platform and the end user in which the end user can operate software. ... A software license is a legal agreement which may take the form of a proprietary or gratuitous license as well as a memorandum of contract between a producer and a user of computer software. ... The GNU logo The GNU General Public License (GNU GPL or simply GPL) is a widely-used free software license, originally written by Richard Stallman for the GNU project. ... A website (or Web site) is a collection of web pages, images, videos and other digital assets and hosted on a particular domain or subdomain on the World Wide Web. ... This article is about free software as defined by the sociopolitical free software movement; for information on software distributed without charge, see freeware. ... A hypervisor in computing is a scheme which allows multiple operating systems to run, unmodified, on a host computer at the same time. ... It has been suggested that this article or section be merged with X86 assembly language. ... The AMD64 or x86-64 is a 64-bit processor architecture invented by AMD. It is a superset of the x86 architecture, which it natively supports. ... In computing, IA-64 (short for Intel Architecture-64) is a 64-bit processor architecture developed cooperatively by Intel Corporation and Hewlett-Packard (HP), and implemented in the Itanium and Itanium 2 processors. ... PowerPC is a RISC microprocessor architecture created by the 1991 Apple–IBM–Motorola alliance, known as AIM. Originally intended for personal computers, PowerPC CPUs have since become popular embedded and high-performance processors as well. ... Computer hardware is the physical part of a computer, including the digital circuitry, as distinguished from the computer software that executes within the hardware. ... Linux (IPA pronunciation: ) is a Unix-like computer operating system family. ... NetBSD is a freely redistributable, open source version of the Unix-like BSD computer operating system. ... Diagram of the relationships between several Unix-like systems A Unix-like operating system is one that behaves in a manner similar to a Unix system, while not necessarily conforming to or being certified to any version of the Single UNIX Specification. ... Microsoft Windows is the name of several families of proprietary software operating systems by Microsoft. ...


Xen originated as a research project at the University of Cambridge, led by Ian Pratt, senior lecturer at Cambridge and founder of XenSource, Inc. This company now supports the development of the open source project and also sells enterprise versions of the software. The first public release of Xen was made available in 2003. The University of Cambridge (usually abbreviated as Cantab. ... Ian Pratt is a Senior Lecturer at the University of Cambridge Computer Laboratory, and Fellow of Kings College, Cambridge. ... Lecturer is the name given to university teachers in most of the English-speaking world (but not at most universities in the U.S. or Canada) who do not hold a professorship. ... Open source refers to projects that are open to the public and which draw on other projects that are freely available to the general public. ...

Contents

Uses

Virtual machines monitors (also known as hypervisors) are often used by IBM, HP, and others on mainframes and large servers. They are also increasingly being used by Internet hosting service companies to provide virtual dedicated servers. The primary benefits of server virtualization are consolidation, increased utilization, an ability to rapidly provision and start a virtual machine, and increased ability to dynamically respond to faults by re-booting a virtual machine or moving a virtual machine to different hardware. Another benefit is the ability to securely separate virtual operating systems, and the ability to support legacy software as well as new OS instances on the same computer. Xen's support for virtual machine live migration from one host to another allows workload balancing and the avoidance of downtime. A hypervisor in computing is a scheme which allows multiple operating systems to run, unmodified, on a host computer at the same time. ... International Business Machines Corporation (known as IBM or Big Blue; NYSE: IBM) is a multinational computer technology corporation headquartered in Armonk, New York, USA. The company is one of the few information technology companies with a continuous history dating back to the 19th century. ... ... This article or section does not adequately cite its references or sources. ... An Internet hosting service is a service that runs Internet servers, allowing organizations and individuals to serve content on the Internet. ... In computing, Virtual private servers are a means of splitting a single physical server into multiple virtual servers. ...


Xen may also be used on personal computers that run Linux but also have Windows installed. Traditionally, such systems are used in a dual boot setup, but with Xen it is possible to start Windows "in a window" from within Linux, effectively running applications from both systems at the same time. Dual booting or dual-booting is the act of installing multiple operating systems on a computer, and choosing which one when it boots. ...


Virtualization also has benefits when working on operating system development: running the new system as a guest avoids the need to reboot the computer whenever a bug is encountered. Such a "sandboxed" guest system is also useful in computer security research, in order to study the effects of some virus or worm without the possibility of compromising the host system. Finally, hardware appliance vendors may decide to ship their appliance running several guest systems, so as to be able to execute various pieces of software that require different operating systems. A computer virus is a computer program that can copy itself and infect a computer without permission or knowledge of the user. ... This is about the computer worm. ...


Xen can be delivered to market in two ways: as a virtualization platform, such as XenSource, Inc.'s XenEnterprise product, or embedded within the host operating system. An example of the latter configuration is the inclusion of Xen in Novell's SUSE 10 Linux distribution, Red Hat's RHEL 5, Sun Microsystems' Solaris 10, or Debian's Etch release. Novell, Inc. ... Red Hat, Inc. ... Sun Microsystems, Inc. ... Debian is a project based around the development of a free, complete operating system through the collaboration of volunteers from around the world. ...


XenSource is also developing a compatibility layer for Microsoft's Longhorn hypervisor, so that systems that have been modified to run as Xen guests will be able to function on the Longhorn hypervisor.[1] Windows Server Longhorn is the codename for the next server operating system from Microsoft. ...


Technology

Paravirtualization, requiring porting of guest systems

Xen uses a form of virtualization known as paravirtualization, meaning that the guest operating system must be modified to use a special hypercall ABI instead of certain architectural features. Through paravirtualization, Xen can achieve high performance even on its host architecture (x86) which is notoriously uncooperative with traditional virtualization techniques. In computing, virtualization is a broad term that refers to the abstraction of computer resources. ... In computing, paravirtualization is a virtualization technique that presents a software interface to virtual machines that is similar but not identical to that of the underlying hardware. ... In computer software, an application binary interface (ABI) describes the low-level interface between an application program and the operating system, between an application and its libraries, or between component parts of the application. ...


The Xen host kernel code runs in Ring 0, while the Xen domains run in Ring 1. In computer science, hierarchical protection domains, often called protection rings, are a mechanism to protect data and functionality from faults (fault tolerance) and malicious behaviour (computer security). ... In computer science, hierarchical protection domains, often called protection rings, are a mechanism to protect data and functionality from faults (fault tolerance) and malicious behaviour (computer security). ...


Hardware assisted virtualization, allowing for unmodified guests

Intel has contributed modifications to Xen to support their VT-x (formerly Vanderpool) architecture extensions[2]. Similarly AMD has contributed support for their AMD-V extensions. These technologies, while differing quite substantially in their implementation and instruction sets, are managed by a common abstraction layer in Xen and enable unmodified guest operating systems to run within Xen virtual machines, starting with Xen 3.0. Intel Corporation (NASDAQ: INTC, SEHK: 4335), founded in 1968 as Integrated Electronics Corporation, is an American multinational corporation that is best known for designing and manufacturing microprocessors and specialized integrated circuits. ... x86 virtualization is the method by which the x86 processor architecture is virtualized. ... Advanced Micro Devices, Inc. ... x86 virtualization is the method by which the x86 processor architecture is virtualized. ...


In layman's terms, this has been a significant development because it allows proprietary operating systems (such as Microsoft Windows) to be virtualized since the guest system's kernel does not require modification when the host runs on VT-x or AMD-V hardware.


Hardware assisted virtualization offers new instructions to support direct calls by a paravirtualized guest/driver into the hypervisor, typically used for I/O or other so-called hypercalls. It also provides additional execution modes: "root mode" and "non-root mode". Both of these modes have Rings 0-3; the Xen host operates in root mode and has access to the real hardware, while the unmodified guest operates in Rings 0-3 of non-root mode and its "hardware" accesses are under complete control of the hypervisor.


As of Xen 3.0.2, the list of supported unmodified guests is limited to certain versions of Windows (incl. XP) and Linux.


Virtual machine migration

Xen virtual machines can be "live migrated" between physical hosts across a LAN without a noticeable loss of availability. During this procedure, the memory of the virtual machine is iteratively copied to the destination without stopping its execution. A very brief stoppage of around 60–300 ms is required to perform final synchronisation before the virtual machine begins executing at its final destination, providing an illusion of seamless migration. Similar technology is used to suspend running virtual machines to disk and switch to another virtual machine, and resume the first virtual machine at a later date.


Supported operating systems and hardware

An operating system that runs Xen as host is also known as domain number 0 (dom0), while a system that runs as a Xen guest is known as the unprivileged domain (domU).


Unix-like systems as hosts

Xen mainly runs with modified Linux or NetBSD as a host system. Most Linux distributions now include Xen packages. Linux (IPA pronunciation: ) is a Unix-like computer operating system family. ... NetBSD is a freely redistributable, open source version of the Unix-like BSD computer operating system. ...


Xen under Linux currently runs on x86, with Pentium II or newer processors, x86-64 based systems, as well as on IA-64 and PowerPC. Work is under way on a port to the SPARC architecture. Xen supports up to 64-way SMP multi-processing machines. x86 or 80x86 is the generic name of a microprocessor architecture first developed and manufactured by Intel. ... Pentium II – front view The Pentium II is an x86 architecture microprocessor by Intel, introduced on May 7, 1997. ... The AMD64 or x86-64 is a 64-bit processor architecture invented by AMD. It is a superset of the x86 architecture, which it natively supports. ... In computing, IA-64 (short for Intel Architecture-64) is a 64-bit processor architecture developed cooperatively by Intel Corporation and Hewlett-Packard (HP), and implemented in the Itanium and Itanium 2 processors. ... PowerPC is a RISC microprocessor architecture created by the 1991 Apple–IBM–Motorola alliance, known as AIM. Originally intended for personal computers, PowerPC CPUs have since become popular embedded and high-performance processors as well. ... Sun UltraSPARC II Microprocessor Sun UltraSPARC T1 (Niagara 8 Core) SPARC (Scalable Processor ARChitecture) is a pure big-endian RISC microprocessor instruction set architecture originally designed in 1985 by Sun Microsystems. ... Symmetric Multiprocessing, or SMP, is a multiprocessor computer architecture where two or more identical processors are connected to a single shared main memory. ...


XenSource offers a live ISO CD running Debian GNU/Linux as well as other free Linux distributions that enables users to try Xen on their system without installing it to the hard disk.


The first commercial implementation of Xen in this form is Novell's SUSE Linux Enterprise Server 10 release, which is broadly supported. Red Hat Enterprise Linux 5 also offers support for Xen. SUSE Linux Enterprise Server (SLES) is a Linux distribution supplied by Novell, targeted at the business market. ... Red Hat Enterprise Linux (often abbreviated to RHEL) is a Linux distribution produced by Red Hat and targeted toward the commercial market, including mainframes. ...


Fedora Core has included Xen packages since its FC4 release. A quick-start document is available. Fedora Core is an RPM-based Linux distribution, developed by the community-supported Fedora Project and sponsored by Red Hat. ...


openSUSE includes Xen 3.0 support. Graphical VM management is offered by YaST. [1]. Screenshot of SUSE Linux 10. ... YaST from SUSE 9. ...


Ubuntu includes Xen 3.0.3 packages in its 6.10 release (codenamed Edgy Eft). Ubuntu is a desktop Linux distribution, based on Debian GNU/Linux. ... Ubuntu (IPA pronunciation: ) is a Linux distribution offering an operating system predominantly targeted at personal computers. ...


Debian includes Xen 3.0.3 packages in its 4.0 release (codenamed Etch). Packages for Debian 3.1 (Sarge) can be found on http://www.backports.org. Debian is a project based around the development of a free, complete operating system through the collaboration of volunteers from around the world. ... Etching is an intaglio method of printmaking in which the image is incised into the surface of a metal plate using an acid. ... Look up sarge in Wiktionary, the free dictionary. ...


Host support for Xen 2 is included in NetBSD 3.x. Host support for Xen 3.0 is available in current and the 4.0 pre-release branches. [2].


Support for OpenBSD self-hosting is near complete, requiring the correction of a lock-up bug before its release [3]. OpenBSD is a freely available Unix-like computer operating system descended from Berkeley Software Distribution (BSD), a Unix derivative developed at the University of California, Berkeley. ...


Support for using FreeBSD as a Xen host is being worked on.[4] FreeBSD is a Unix-like free operating system descended from AT&T UNIX via the Berkeley Software Distribution (BSD) branch through the 386BSD and 4. ...


A Gentoo package exists for Xen in Portage. [5] The Gentoo Linux operating system (pronounced ) is a Linux distribution named after the Gentoo penguin. ... Portage is an advanced package management system. ...


Unix-like systems as guest

The above mentioned Linux distributions all contain support for running as a Xen guest.


In addition, the following systems have been patched so that they can operate as a Xen guest:

Oz Linux is a Linux distribution (Unix-like operating system) of academic and scientific endeavors. ... Conary is a free software / open source package management system which focuses on installing packages through automated dependency resolution against distributed online repositories. ... MINIX is an open source, Unix-like operating system (OS) based on a microkernel architecture. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... NetBSD is a freely redistributable, open source version of the Unix-like BSD computer operating system. ... OpenBSD is a freely available Unix-like computer operating system descended from Berkeley Software Distribution (BSD), a Unix derivative developed at the University of California, Berkeley. ... FreeBSD is a Unix-like free operating system descended from AT&T UNIX via the Berkeley Software Distribution (BSD) branch through the 386BSD and 4. ... OpenSolaris is an open source project created by Sun Microsystems to build a developer community around the Solaris Operating System technology. ... In the OpenSolaris world, this is a way to upgrade a subset of your systems binaries using cpio archives instead of packages. ... NetWare is a network operating system and the set of network protocols it uses to talk to client machines on the network. ... Novell, Inc. ... The GNU Hurd is a Unix-like kernel that sets the base for the GNU operating system. ...

Windows as guest

It is currently possible to run Microsoft Windows as a guest operating system unmodified, using hardware virtualization provided by Intel's Vanderpool technology or AMD's Pacifica. This is supported beginning with Xen 3.0. Microsoft Windows is the name of several families of proprietary software operating systems by Microsoft. ... Virtualization Technology allows a single machine to run multiple operating systems at once. ... Virtualization Technology is the name of the mutually incompatible virtualization technologies from Intel and AMD, previously known by their respective codenames Vanderpool and Pacifica. They allow a single machine to run multiple operating systems at once without incurring significant emulation costs. ...


During the development of Xen 1.x, Microsoft Research, along with the University of Cambridge Operating System group, developed a port of Windows XP to Xen. This was possible due to Microsoft's Academic Licensing Program. The terms of this license do not allow this port to be published, although the experience is documented in the original Xen SOSP paper.


Xen Management Consoles

A number of third-party tools (known as Xen Management Consoles) have been developed to facilitate the common tasks of administrating a Xen host, such as configuring, starting, monitoring and stopping of Xen guests. Examples include the Python-based Enomalism dashboard (LGPL), Xen Tools, the Perl-based MLN, the web-based HyperVM, and the GUI applications ConVirt (formerly XenMan) and RedHat's Virtual Machine Manager, virt-manager. Python is a high-level programming language first released by Guido van Rossum in 1991. ... Enomalism is a management console for the Xen Hypervisor. ... GNU logo The GNU Lesser General Public License (formerly the GNU Library General Public License) is an FSF approved Free Software license designed as a compromise between the GNU General Public License and simple permissive licenses such as the BSD license and the MIT License. ... Perl is a dynamic programming language created by Larry Wall and first released in 1987. ... HyperVM is a multi-tiered, multi-server, multi-virtualization software allowing a VPS vendor to provision, manage and delegate Xen or OpenVZ VPSs. ... GUI can refer to the following: GUI is short for graphical user interface, a term used to describe a type of interface in computing. ... XenMan is a Xen Hypervisor management tool with a graphical user interface that allows a user to perform the standard set of operations (start, stop, pause, kill, shutdown, reboot, snapshot, etc. ... Alternate meanings: See Red hat Red Hat, Inc. ...


References

  1. ^ Microsoft Press Release, 16 July 2006
  2. ^ Extending Xen with Intel Virtualization Technology, intel.com

Trivia

The name "Xen" appears in Douglas Coupland's 1993 novel "Microserfs" while the characters debate on how to name their company. Douglas Coupland (born December 30, 1961) is a major Canadian fiction writer as well as a playwright and visual artist. ... Microserfs is a novel by Douglas Coupland, published in 1995. ...


See also

Free software Portal

Image File history File links Floss_draft. ... The table below compares basic information about virtual machine packages, including: creator, guest systems supported, license, etc. ... x86 virtualization is the method by which x86-based guest operating systems are run under another host x86 operating system, with little or no modification of the guest OS. The x86 processor architecture did not originally meet the Popek and Goldberg virtualization requirements. ...

External links


  Results from FactBites:
 
A moment of Xen: Virtualize Linux to test your apps (2178 words)
Xen is a virtualization technology available for the Linux™; kernel that lets you enclose and test new upgrades as if running them in the existing environment but without the worries of disturbing the original system.
Xen is a paravirtualizing VMM (Virtual Machine Monitor), meaning that the operating system is modified in select areas to make calls into the hypervisor, whereas the applications that run on that operating system are unmodified.
The source code for Xen is available from the project page (see the Resources section for the link), but if you're already running a Linux distribution, you may be able to get Xen from a package update or installation.
Xen: Information from Answers.com (2220 words)
Xen is also used on client machines, where the use case tends to be related to manageability and security, where the use of embedded VMs in the virtualization stack can deliver additional security and support services to the user, without intervention or awareness on the part of the user's desktop OS.
Xen is also being used by hardware appliance vendors as an ideal way to combine legacy code bases with different pedigrees on a single platform, to offer a unified feature set.
Xen's motivation differs from that of Denali in that it is intended to run a moderate number of full-featured operating systems, rather than a large number of specialised, lightweight ones.
  More results at FactBites »

 
 

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