Xen FAQ General: Difference between revisions

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== What is Xen? ==
== What is the Xen Project Hypervisor? ==
Xen is a virtual machine monitor (VMM) for x86-compatible computers. Xen can securely execute multiple virtual machines, each running its own OS, on a single physical system with close-to-native performance.
The Xen Project Hypervisor is a virtual machine monitor (VMM) for x86-compatible computers. The hypervisor can securely execute multiple virtual machines, each running its own OS, on a single physical system with close-to-native performance. You can find an overview at [[Xen Project Software Overview]].


== I'd like to read some kind of overview about Xen Project software ==
== How is Xen licensed? ==
See the [[Xen Project Software Overview]] wiki page and [[:Category:Overview]]. Also check the following PDF documents (which are somewhat out-of-date):
Xen is Open Source, and is released under terms of the [http://www.gnu.org/licenses/gpl-2.0.html GNU General Public License v2]. Some Xen projects may contain licensing exceptions or a small number of files which are licensed under a GPL compatible license. If so, the source repository contains a '''COPYING''' file providing more information (see [http://lxr.xensource.com/lxr/source/COPYING here] for the COPYING file for the hypervisor).


* http://www.xen.org/files/Marketing/WhatisXen.pdf
Xen projects do not come with an End User License as the GPL suffices. There is however a trademark policy that restricts the use of the Xen brand to ensure that all Xen branded hypervisors are compatible and will run the same guest VMs. You can find the [http:/www.xen.org/files/XenTMPolicy2008June.pdf trademark policy here].
* http://www.xen.org/files/Marketing/WhyXen.pdf
* http://www.xen.org/files/Marketing/NewtoXenGuide.pdf
* http://www.xen.org/files/Marketing/HowDoesXenWork.pdf


== How is the Xen Project software licensed? ==
Operating systems or other applications written to use Xen's hypercall interface are not derived works of Xen, hence may be licensed differently.
Xen Project software is Open Source, and is released under terms of the [http://www.gnu.org/licenses/gpl-2.0.html GNU General Public License v2]. Some Xen Project elements may contain licensing exceptions or a small number of files which are licensed under a GPL compatible license. If so, the source repository contains a '''COPYING''' file providing more information (see [http://lxr.xensource.com/lxr/source/COPYING here] for the COPYING file for the hypervisor).


Xen Project software does not come with an End User License as the GPL suffices. There is however a trademark policy that restricts the use of the '''Xen Project''' brand to ensure that all Xen Project branded hypervisors are compatible and will run the same guest VMs. You can find the [http://xenproject.org/trademark-policy.html trademark policy here].
== Which OSes run on Xen? ==
To achieve such high performance, Xen requires that OSes are ported to run on it.


There is a separate trademark for '''Xen''' alone. That trademark is owned by Citrix, which controls the use of that mark.
See [[XenDom0Kernels|Xen Dom 0 Kernels]] and [[XenDomUSupport|Xen Dom U support]]


Operating systems or other applications written to use Xen Project's hypercall interface are not derived works of Xen Project, hence may be licensed differently.
== Does Xen support Microsoft Windows? ==
The paravirtualized approach we use to get such high performance has not been usable directly for Windows to date. However Xen 3.0 added [[IntelVT|Intel VT-x]] support to enable the running of unmodified guest operating systems, including Windows XP & 2003 Server, using hardware virtualization technology. Xen 3.0.2 and later support AMD Pacifica technology as well. Check to see if your CPU is among the list of [[HVM Compatible Processors]], and if your motherboard is among the list of [[HVM Compatible Motherboards]].


== Where can I read about the history of the Xen Project? ==
''(Note: This does not necessarily mean, that just about _any_ OS runs in HVM Mode! Reports vary about getting *BSD to work in HVM mode, on the Mailing List there's only 1 success for OpenBSD (http://www.openbsd-france.org/ml/archives/msg02494.html), no success message for the others, but some problem reports)''
Please see the [http://www.xenproject.org/about/history.html history article on the main XenProject.org website].


== Does Xen run on laptops? ==
== Where do I find information on Compatibility? ==
You can find answers to questions such as the following, at [[Xen Project FAQ Compatibility]]:
Xen will typically run on laptops.
* Which OSes run on the hypervisor?
* Does Xen Project support Microsoft Windows?
* Does Xen Project run on laptops?
* Which architectures does Xen Project support?
* Does Xen Project support 32bit and 64bit?


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== Which architectures does Xen support? ==
Xen currently runs on the x86, x86_64, IA64 (Itanium) and ARM architectures. On x86 Xen requires a "P6" or newer processor (that's any Intel or AMD x86 CPU purchased in the last seven years). Multiprocessor and multicore machines are supported, including support for Hyper-Threading (SMT). Support for x86/64 is available since Xen 3.0. We hope to add other architectures such as PPC.

== 32bit and 64bit ==
The 32bit and 64bit questions are many and more complex than you might think. Things can be 32bit, 32bit PAE or 64bit. There is the hardware, the xen hypervisor, the dom0 kernel and userland and the domU kernel and userland.
{| border="1" cellpadding="2" cellspacing="0"
|
| '''32bit PAE Hypervisor'''
|-
| '''32bit PAE PV DomU'''
| Yes
|-
| '''64bit PV DomU'''
| No
|-
| '''32bit HVM DomU'''
| Yes
|-
| '''64bit HVM DomU'''
| No
|}


== Where do I find more General FAQs? ==
See [[Xen_Common_Problems#General|the common problems document]]


[[Category:Xen]]
[[Category:Xen]]

Latest revision as of 02:37, 26 March 2015


What is the Xen Project Hypervisor?

The Xen Project Hypervisor is a virtual machine monitor (VMM) for x86-compatible computers. The hypervisor can securely execute multiple virtual machines, each running its own OS, on a single physical system with close-to-native performance. You can find an overview at Xen Project Software Overview.

I'd like to read some kind of overview about Xen Project software

See the Xen Project Software Overview wiki page and Category:Overview. Also check the following PDF documents (which are somewhat out-of-date):

How is the Xen Project software licensed?

Xen Project software is Open Source, and is released under terms of the GNU General Public License v2. Some Xen Project elements may contain licensing exceptions or a small number of files which are licensed under a GPL compatible license. If so, the source repository contains a COPYING file providing more information (see here for the COPYING file for the hypervisor).

Xen Project software does not come with an End User License as the GPL suffices. There is however a trademark policy that restricts the use of the Xen Project brand to ensure that all Xen Project branded hypervisors are compatible and will run the same guest VMs. You can find the trademark policy here.

There is a separate trademark for Xen alone. That trademark is owned by Citrix, which controls the use of that mark.

Operating systems or other applications written to use Xen Project's hypercall interface are not derived works of Xen Project, hence may be licensed differently.

Where can I read about the history of the Xen Project?

Please see the history article on the main XenProject.org website.

Where do I find information on Compatibility?

You can find answers to questions such as the following, at Xen Project FAQ Compatibility:

  • Which OSes run on the hypervisor?
  • Does Xen Project support Microsoft Windows?
  • Does Xen Project run on laptops?
  • Which architectures does Xen Project support?
  • Does Xen Project support 32bit and 64bit?


Where do I find more General FAQs?

See the common problems document