Dom0

= Xen - [|Dom0] =

Dom0, or domain zero to expand the abbreviation, is the first [|domain] started by the Xen [|hypervisor] on boot. It has special privileges, like being able to cause new domains to start, and being able to access the hardware directly. Unless [|DriverDomain]s are being used, it is responsible for running all of the device drivers for the hardware. For hardware that is made available to other domains, like network interfaces and disks, it will run the [|BackendDriver], which multiplexes and forwards to the hardware requests from the [|FrontendDriver] in each DomU. Modified versions of Linux, NetBSD and Solaris can be used as the dom0. See OS vendor documentation for specific steps. Current official documentation may be found at the following sites:
 * NetBSD -- [|http://www.netbsd.org/ports/xen/howto.html#netbsd-dom0]
 * [|OpenSolaris] -- []
 * Debian --[|http://wiki.debian.org/Xen#Dom0.28host.29]

=[|XenDom0Kernels]=

Linux Distributions which include a Xen Dom0 kernel
If possible we highly recommend choosing one of the following distributions which include a domain 0 kernel out of the box. They provide rpm or deb packages containing a dom0 kernel which can be installed using your favourite package manager. This provides the benefits such as ease of install, good integration with the distribution, support from the distribution, provision of security updates etc.
 * **Distributions** || **Versions** || **Package name** (latest version listed only) ||
 * [|Debian] || [|4.0 (Etch)], [|5.0 (Lenny)], [|6.0 (Squeeze)]//[1]// || Install //[|xen-linux-system-2.6-xen-686]// or //[|xen-linux-system-2.6-xen-amd64]// to install a complete Xen system. For just the kernel install //[|linux-image-2.6-xen-686]// or //[|linux-image-xen-amd64]// ||
 * [|Fedora] || 16[1][2] || See [|here] ||
 * [|OpenSUSE] || 10.x, 11.x || Install //kernel-xen// ||
 * [|Redhat Enterprise Linux (RHEL)] || 5.x || Install //kernel-xen//. Also valid for all the RHEL clones like CentOS or Scientific Linux ||
 * [|SUSE Linux Enterprise Server (SLES)] || 10.x, 11.x || Install //kernel-xen// ||
 * [|Ubuntu] || 11.10[1][2] || See [|here] (note that this page is out-of-date, the Xen 4.1 packages for Ubuntu 11.10 are [|xen-hypervisor-4.1-amd64] & [|xen-hypervisor-4.1-i386]) ||
 * [|Xen Cloud Project (XCP)] || All versions || Xen included in base platform ||
 * [|XenServer] || All versions || Xen included in base platform ||

//[1]// Please note that this kernel requires Xen >= 4.0.

//[2]// Planned or in beta as of October 2011.

Linux Distributions which have a Xen Dom0 kernel provided by a third party
If you are unable to use one of the above distributions then you may be able to use one of the following which have suitable dom0 kernels provided by third party packagers.

Fedora
The last release of [|Fedora]| to include a Xen dom0 kernel was Fedora 16. Now that dom0 kernel support has entered the upstream kernel and Fedora Core 16 supports Xen out of the box.
 * Obsolete information: This is relevant for Fedora Core 15 and lesser**If you are running Fedora Core 15 or earlier you can find third party rpm packages built for you by M A Young (they require Xen >= 4.0):
 * [|http://fedorapeople.org/~myoung/dom0/]
 * Also see [|Fedora 13/14 Xen 4.0 Tutorial]

Red Hat Enterprise Linux and CentOS
The last release of [|RHEL] (and by extension [|CentOS] and other derivatives) to include a Xen dom0 kernel was RHEL 5. We are currently working with the community to provide dom0 kernel packages for RHEL 6.
 * Also see [|Redhat Enterprise Linux 6 Xen 4.0 Tutorial]

Ubuntu
The last release of [|Ubuntu] which includes a Xen dom0 kernel is 11.10 (Oneiric Ocelot). If you are running a older version of Ubuntu we recommend using the Debian Squeeze dom0 deb packages: =Dom0 support in BSDs and other Unix systems=
 * 64 bit version: [|linux-image-xen-amd64]
 * 32 bit version: [|linux-image-xen-686]

This list is currently incomplete. We are in the process of verifying support for other Unixes.
 * **Distributions** || **Versions** || **Package name** (latest version listed only) ||
 * NetBSD || 5.1//[1]// || [] ||

//[1]// See [|NetBSD Xen HowTo] for more information

//[2]// See [|NetBSD Xen User Guide] =Xen dom0 kernels: the detailed version=

Xen hypervisor is not usable without Domain-0 ("dom0"). Privileged dom0 guest is the "host" operating system (or a "service console", if you prefer), it has drivers for hardware, it runs the Xen management toolstack, it is used to manage the whole system, and it provides Xen virtual disks and network access for other guests aka domUs (unprivileged domains). Usually dom0 is running Linux kernel, but Xen dom0 implementations also exist for [|OpenSolaris] and NetBSD. If any of the info on this wiki page is out of date, you have something to add or change, please contact xen-devel mailing list.

How to choose a Xen dom0 kernel?

 * If your Linux distribution includes Xen and dom0 kernel it is recommended to use them. That allows you to easily get the security fixes as a part of the normal package upgrades provided by your distribution.
 * Xen PV domU kernel versions can be different from dom0 kernel versions. There's no need to upgrade domU kernel when you upgrade Xen hypervisor and/or dom0 kernel. Xen hypervisor is backwards compatible, ie. it supports older domU kernels. If your domU distribution includes a Xen domU kernel, it's usually best to use it and not compile your own domU kernel.

What Xen dom0 capable Linux kernel versions are available? Where to get them?
Please see [|XenKernelFeatures] wiki page for more information about available features in different Xen enabled kernels. There are two different types of Xen dom0 capable kernels available today: Xen 4.0 switched to using Linux pv_ops based dom0 kernel as a default. This is the kernel all users should be using and testing, and all the development should be made against the upstream pvops kernel.
 * pvops kernels, featuring new rewritten Xen support based on the upstream (kernel.org) Linux pvops framework. This work has been included in upstream kernel.org kernel since Linux 2.6.37.
 * xenlinux kernels based on the "old" patches originally for Linux 2.6.18. These Xenlinux patches won't be integrated to upstream Linux.

pv_ops Xen dom0 kernel, based on upstream kernel.org linux git tree

 * New default dom0 kernel in Xen >= 4.0, most features have been implemented or forward-ported (compared to the old default linux-2.6.18-xen).
 * pv_ops kernels require Xen >= 4.0.
 * pv_ops dom0 support has been merged into upstream kernel.org Linux 2.6.37 kernel, so dom0 support is included out-of-the-box in Linux 2.6.37 and later versions.
 * Missing features: scsiback and scsifront for pvscsi, usbback and usbfront for pvusb (patches exist).
 * Long-term maintained pv_ops 2.6.32 dom0 kernel is available here, branch name "xen/stable-2.6.32.x": [|git://git.kernel.org/pub/scm/linux/kernel/git/jeremy/xen.git]
 * See this wiki page for more information and for instructions how to get the pv_ops dom0 kernel: []
 * Some help and tips for migrating from linux-2.6.18 to pvops dom0 kernel available from this wiki page: [|2.6.18-to-2.6.31-and-higher]

older Linux 2.6.18 "Xenlinux" based source trees and/or patchsets, and the various forward-ports of them

 * Original "Xenlinux" kernel tree, based on Linux 2.6.18, get it with Mercurial: "hg clone []"
 * This was the default dom0 kernel in all Xen 3.x releases, up to and including Xen 3.4.x.
 * Good choice if Linux 2.6.18 has all the needed drivers for your hardware.
 * These Xenlinux patches were considered too intrusive and had too many changes to core x86 code so they were not accepted into upstream Linux kernel.
 * Xen 4.0 and xen-unstable moved away from this kernel and started using using pv_ops tree as a default dom0 kernel.
 * Citrix [|XenServer] / XCP Linux 2.6.27 and 2.6.32 kernel (based on Novell SLES kernels)
 * XCP (Xen Cloud Platform) uses this Citrix [|XenServer] kernel as is.
 * XCI (Xen Client Initiative) kernel is based on this Citrix [|XenServer] kernel.
 * Available from the mercurial patch queue and in kernel-dom0 directory in source-1.iso from: []
 * XCP v0.1 includes: kernel-2.6.27.29-0.1.1.xs0.1.0.669.1028.src.rpm
 * XCP v0.1.1. includes: kernel-2.6.27.42-0.1.1.xs0.1.1.737.1065.src.rpm
 * XCP v0.5 includes: kernel-2.6.27.42-0.1.1.xs0.5.0.47.111160.src.rpm
 * More information about XCP: []
 * See this email for information about SLES11, [|XenServer], XCP, and XCI kernel relations: []
 * XCP dom0 kernel patch queue announcement (2010/03): []
 * XCP dom0 2.6.27 kernel patch queue mercurial repository: []
 * XCP dom0 2.6.32 kernel patch queue mercurial repository: []
 * XCP 1.0 dom0 Linux 2.6.32 kernel patch queue mercurial repository: []
 * XCP 1.1 dom0 Linux 2.6.32 kernel patch queue mercurial repository: []
 * XCI (Xen Client Initiative) Linux 2.6.27 and 2.6.32 Xen kernel tree
 * Xen dom0 kernel used in XCI development, based on [|XenServer] 2.6.27 kernel.
 * This tree has XCI specific patches and modifications.
 * See this mail for some building related information (June 2009): []
 * XCI project page with more information: []
 * XCI source including build instructions: []
 * Novell SLES and OpenSUSE "Xenified" Xen kernel forward-ported patches
 * These patches are based on the original Xenlinux 2.6.18 patches forward-ported to newer kernels by Novell / OpenSUSE.
 * Andrew Lyon has rebased Novell's OpenSUSE Xen kernel patches against standard kernel.org Linux 2.6.29, 2.6.30, 2.6.31, 2.6.32, 2.6.33, 2.6.34.
 * Announcement for 2.6.31-14 and 2.6.32-1 patches: []
 * Download the patches from here: []
 * OpenSUSE kernel factory: []
 * OpenSUSE 11.2 kernels: []
 * OpenSUSE 11.3 kernels: []
 * OpenSUSE 11.4 kernels: []
 * Git mirror: []
 * Git mirror, master branch: []
 * Novell SLES11 SP1 Linux 2.6.32 Xen kernel, available from: []
 * And also from Novell SLES11 installation media and the usual Novell package updates download channels
 * Redhat Enterprise Linux 5 (RHEL5) kernel-xen
 * Based on Linux 2.6.18 with a LOT of patches, fixes and driver and feature backports from Redhat; it used also on CentOS 5, Scientific Linux 5 and other RHEL5 clones
 * Lots of driver backports included so drivers are pretty much up to date, even the kernel version (2.6.18) seems old
 * Known to be very stable, but doesn't support latest Xen features that can be found from xen.org linux-2.6.18-xen.hg
 * Is known to work with Xen 3.4.x hypervisors ([]), and of course with the official RHEL5 Xen 3.1.2 hypervisor.
 * Available in kernel-2.6.18-*.el5.src.rpm from: []
 * RHEL 5.4 ships with kernel-2.6.18-164.*.el5.src.rpm
 * RHEL 5.5 ships with kernel-2.6.18-194.*.el5.src.rpm
 * If you want to run Xen on RHEL 6, see this tutorial: []

Xen dom0 kernels included in Linux distributions
Please see [|XenKernelFeatures] wiki page for information about features in different Xen enabled kernels! Discussion about different Xen dom0 kernels on xen-devel mailinglist June/2009: * []
 * Redhat Enterprise Linux 5 (RHEL5) and CentOS 5
 * Includes Xen dom0 kernel based on Linux 2.6.18, with a lot of patches and fixes by Redhat.
 * Redhat has also backported a lot of drivers and support for new hardware and features into their version of Linux 2.6.18.
 * Good choice as dom0 because RHEL5 has long lifecycle, and it's actively maintained and bugfixed.
 * Good choice because it's tested and certified to run on many vendors server hardware.
 * Good choice especially if you are trying out Xen virtualization for the first time, and want to use a distribution that has well working and tested Xen included.
 * Fedora
 * Fedora 8 is currently the latest release to include Xen dom0 kernel.
 * Fedora 9 - 14 do not contain Xen dom0 kernels (but they do contain Xen hypervisor and tools and Xen domU enabled kernels).
 * Fedora is planning to add support for Xen dom0 again when pv_ops dom0 is included in the upstream kernel.org Linux kernels.
 * For more information: []
 * M A Young is building unofficial pv_ops xendom0 kernel RPMs for Fedora. Download: [|http://fedorapeople.org/~myoung/dom0/]
 * See fedora-xen and/or fedora-virt mailinglist archives for more information.
 * Debian
 * Debian 4.0 ("Etch") contains 2.6.18 Xen dom0 kernel.
 * Debian 5.0 ("Lenny") contains 2.6.26 Xen dom0 kernel based on early version of OpenSUSE forward-ported patches. Some users have experienced stability problems with this kernel, when used with newer Xen 3.3 and 3.4 hypervisors. Also, some users have reported live migrations being broken with this lenny's kernel.
 * Debian 6.0 ("Squeeze") contains a pv_ops Xen dom0 kernel
 * []
 * Ubuntu
 * Ubuntu 8.04 LTS (Hardy Heron) has Xen dom0 kernel (based on Linux 2.6.24) available in the universe repository (so it's not part of the official release - it's community supported). Unfortunately many users have reported various bugs with this kernel - both as dom0 and as domU.
 * Ubuntu 8.10 (Intrepid) and later ubuntu versions unfortunately don't include Xen dom0 kernels in the repositories. You have to compile/download your own dom0 kernel, or use Debian kernels.
 * Gentoo
 * Gentoo has multiple dom0 kernels available: xen.org-based 2.6.18 (latest is xen-sources-2.6.18-r12) and rebased kernels with OpenSUSE patches (latest is xen-sources-2.6.31-r11).
 * OpenSUSE
 * Novell is forward-porting the original Xenlinux 2.6.18 patches for new kernels in OpenSUSE (and SLES).
 * Currently (as of May 2010) patches and Xen dom0 kernel packages exist up to Linux 2.6.34.
 * OpenSUSE 11.2 ships with Linux 2.6.31 based Xen kernel using the forward-ported Xenlinux patches.
 * OpenSUSE 11.3 will ship with Linux 2.6.34 based Xen kernel using the forward-ported Xenlinux patches.
 * Novell Suse Linux Enterprise (SLES)
 * SLES10 and SLES11 contain Xen dom0 kernels.
 * SLES10 is based on Linux 2.6.16.
 * SLES11 is based on Linux 2.6.27 with forward-ported original Xenlinux 2.6.18 patches.
 * SLES11 SP1 ships with a Linux 2.6.32 dom0 kernel based on the forward-ported Xenlinux patches.
 * Good choice as dom0 because SLES releases have long lifecycle and they are actively maintained and bugfixed.
 * Good choice because it's tested and certified to run on many vendors server hardware.