Virtualization

This page covers the efforts to integrate various virtualization technologies into Fedora. For information on using Fedora as a virtual machine, see Installing a Fedora Virtual Machine.

Introduction
Virtualization allows one to run many guest virtual machines on top of a host operating system such as Fedora. What this means is that using one computer, you can mimic several individual computers and even run different operating systems in each of these virtual machines. There are many different virtualization technologies, including both free and open source software and proprietary offerings. A good article on IBM DeveloperWorks Web site illustrates the four main different virtualization families, namely hardware emulation, hardware-assisted virtualization, para-virtualization (PV) and containers/zones.

Hardware Emulation


Hardware emulation uses a VM to simulate the required hardware. A few implementations:
 * Bochs
 * QEMU

Full Virtualization


Full virtualization uses a hypervisor (a.k.a. VMM, standing for Virtual Machine Monitor) to share the underlying hardware. A few implementations:
 * KVM/QEMU is a full virtualization solution for Linux on x86 hardware containing virtualization extensions (Intel VT or AMD-V). Using KVM, one can run multiple virtual machines running unmodified Linux or Windows images. KVM is part of RedHat Emerging Technologies (ET).
 * Xen is a virtual-machine monitor providing services that allow multiple computer operating systems to execute on the same computer hardware concurrently. Xen has been the solution of choice for RedHat EL distributions since 2005. The kernel-2.6.18 dropped support for Xen, but the necessary modules/modifications have been added to the upstream kernel again, from 2.6.37 for DomU (guests) and from 3.0 for Dom0 (base domain, part of the host). Therefore, Xen Dom0 host support was dropped after Fedora 8, and its re-introduction blocked on the inclusion of Xen Dom0 support in upstream Linux.
 * VirtualBox is a full virtualization solution for x86 and AMD64/Intel64 hardware. Sun Microsystems started that project, which is now fully supported by Oracle. There is a dual licencing scheme, among which GPLv2. VirtualBox is one of the fastest full virtualization solutions.

Para-Virtualization (PV)


Paravirtualization shares the process with the guest operating system. A few implementations:
 * KVM (see above).
 * Xen (see above).
 * xenner is a utility allowing paravirtualized Xen guests to be run using KVM.

Operating System-level virtualization


Operating system-level virtualization partitions a host into insulated guest, which are therefore as kinds of chroot, but with much stronger resource isolation. Hence, we often speak about containers or zones to refer to that family of virtualization. A few implementations:
 * OpenVZ... and the Debian-based ProxMox for the off-the-shelf server
 * LXC (Linux Containers)
 * Linux-VServer, which does not seem to be no longer active (the last news is dated back in 2009)

Fedora Support
At time of writing, Fedora includes full support for KVM/QEMU, Xen and LXC.

A number of third parties (e.g., RPMFusion) provide add-on packages for other virtualization technologies: OpenVZ, Linux-VServer, VirtualBox.

Anticipating this diversification of technology, since the days of Fedora Core 5, all core management applications have been built on top of the libvirt toolkit, which offers a technology independent API for managing virtual systems.

Clouds
As Cloud-based infrastructures rely, by nature, on virtualization technologies, both subjects are therefore heavily inter-related. There is a Cloud SIG (Special Interest Group) dedicated to the subject, worth to follow as well.

History
Fedora Core 5 was the first release to include Xen as a core integrated technology. The new Linux native virtualiation, KVM, was introduced to Fedora 7. For a more detailed account of virtualization progress in Fedora, consult the Virtualization History page.

News
There is semi-regular coverage of Virtualization news in Fedora Weekly News, and more detailed status updates posted to the fedora-virt Mailing List. For ease of reference, there is an archive of virtualization news

Getting started
See getting started with virtualization for an excellent overview to using the virtualization capabilities in Fedora.

A few magazine articles on virtualization have introductory material as well.

Bugs
See How to debug Virtualization problems for some tips on reporting virtualization bugs to bugzilla.

If you wish to help triaging and fixing virtualization bugs, virtualization bugs is a good starting point. On the page Virtualization Preview Repository, you shall find informations if you can be a potential virtualization tester.

Mailing list and IRC
To get in touch with Fedora virtualization users and developers try the virt mailing list or #virt on irc.oftc.net.

Relevant Packages
We have a page containing a catalogue of all the virtualization related packages in Fedora.

oVirt
oVirt is a Fedora based project which provides small host images and a web-based virtual machine management console. See the website to learn more and get involved.

Other virtualization information
You can find more virtualization information at the virtualization category page on this wiki.