Welcome to Xen4CentOS

The Xen4CentOS project came about as a way to help users on CentOS-5/Xen to migrate and upgrade their baseline infrastructure to CentOS-6, while also bringing in the newer Xen-4 toolchain. The project, while hosted at centos.org, is a collaboration between the Xen Project, the Citrix Xen open source teams, the CentOS developers, GoDaddy Cloud Operations team, Rackspace Hosting and members of the CentOS QA Team.

The Xen4CentOS effort delivers the Xen-4.4 based xen stack, a Linux Kernel based on the 3.10 LTS mainline tree, libvirt and qemu with associated tools that target xen support in the distro. All this code is delivered as a self contained repository, with a centos-release-xen rpm included in CentOS-Extras to enable and configure the xen repository.

This code is considered production ready now, with testing having taken place at scale (up to hundreds of hypervisors, some of them running hundreds of VMs, in production grade deployments)

Action needed: Upgrade to libxl

If you are upgrading from an earlier version of Xen4CentOS, be aware that you will need to migrate from the xend toolstack to the libxl toolstack. More information can be found on the MigratingToXl wiki page.

Contents, Policy and process

The RPMs released are based on clean upstream xen project code, with contributions from upstream developers. We have tried to retain compatibility, in build and delivery, with upstream xen so as to not fork the community and to ensure that all support and contribution venues stay open to anyone who would like to join the effort, either within the centos.org ecosystem or with the xenproject mechanisms.

At this point, we are delivering Xen-4.4, with the aim of keeping in sync with upstream releases as close as possible. Security issues are handled and released in sync with public disclosure upstream with zero lag. The Kernel based on the 3.10 LTS kernel, curated and patched by the CentOS team, the Xen team and the Citrix Open Source team, will be maintained for a 2 year lifespan, allowing most people enough 'production' grade outing, with the assurance that best efforts will be made for future kernel updates to be possible via yum, needing no manual intervention.

While the repository is setup in a way that content will make its way to the entire CentOS Mirror network, the repository setup will only hit mirror.centos.org, with users having the ability to manually set it to a local mirror if they so desire. The CentOS mirrorlist infrastructure will not carry the Xen4CentOS repo definitions for now.

Bugs and issues for these rpms should be filed at http://bugs.centos.org/ against CentOS-6 -> Xen4 as the project.

Getting Started

We have a Xen4CentOS specific QuickStart guide at http://wiki.centos.org/HowTos/Xen/Xen4QuickStart that will get you up and running in under 10 minutes, and has instructions on howto build and manage your virtual machines on xen using libvirt or the xen command line tools.

As with any other piece of software, its important to make sure you track security updates and bugfix's as they are released. We will be using the regular channels of announcement for the Xen4CentOS software as well. This includes:

The centos-announce list (http://lists.centos.org/) will get a post every time there is an update pushed to the repos, this includes the xen stack, the required kernel and its deps as well as the xen specific libvirt rpms hosted in the Xen4CentOS repos. Nota bene: Please make sure you run /usr/bin/grub-bootxen.sh after each kernel update. By default grub is configured so that the new kernel will run native, not via the hypervisor

Upstream xen project announces their updates, new releases and security issues at the xen-announce list (http://lists.xen.org/archives/html/xen-announce/) and the security updates are published at http://wiki.xen.org/wiki/Security_Announcements

Known Issues

SELinux support is disabled, and you might need to disable SELinux on the dom0 for some operations; primarily when using qemu-xen and blktap backed storage.

For the time being, we are only supporting Xen4CentOS on CentOS-6/x86_64. Unless there is widespread demand, there are no plans to build it for 32bit support in this version. We hope to revisit this issue once Xen-4.3 is released.

Serial Console must be setup manually if you intend to re-route the dom0 console as well.

While both xenlight and xm are supposed as xen command line tools, and have been extensively tested, libvirt is only completely functional with xm (which needs xend running). We hope to have native xl support in Libvirt in a future release.

There is an error with Xen Ballooning that can be worked around with a pre-balloon setting CentOS bug 6893 report

Getting Help

The Xen4CentOS effort is supported both in the CentOS ecosystem as well as the Xen upstream support venues, the irc channels and lists. Here are a few links to get you started with:

There is a #centos-virt irc channel on irc.freenode.net

We also have a centos-virt list on lists.centos.org

The GettingHelp page in this wiki is another good place to start from

Further Info

Upstream Xen Project http://www.xenproject.org/

CentOS Xen4CentOS Quick Start http://wiki.centos.org/HowTos/Xen/Xen4QuickStart

Contributing and getting involved