Guide: Introduction to Xen

The Xen hypervisor is fast becoming an IT commodity. Get up to speed on the growing Xen-based virtualization products and learn how Xen server virtualization can work in your data center. This guide covers everything from installation to management and Xen-based strategies.

This guide covers server virtualization with Xen-based platforms. Get the basics and detailed step-by-steps from installation to system management with Citrix, Red Hat, Novell, Sun and Oracle's Xen-based products.

If you are planning a virtualization project, you'll find that Xen is an easy to install and easy to manage platform. The 64-bit hypervisor acts more like a hardware abstraction layer than a guest operating system.

Learn more about the options available to a Xen virtualized infrastructure in this guide to Xen.


Introduction to Xen

  Installing Xen
  Xen virtualization platforms
  Xen virtual machines
  Xen configuration and management
  Xen-based virtualization strategies

Installation:

Installing Citrix XenExpress

This tutorial offers an introduction to Citrix's free virtualization platform, XenExpress. You'll learn how to download and install XenExpress, and best of all, how to get started with XenExpress for free.

Citrix XenSource is a Xen hypervisor-based paravirtualization product; that is, XenSource is architected as a thin software layer that manages access to underlying hardware resources. A thin hypervisor layer enables Xen-based virtualization to attain near-native performance levels. The XenServer product comes in three versions: Enterprise, Standard and Express. Despite the fact that the company offers three different versions, they are identical in terms of actual code.

XenExpress installs in two parts: the server, which hosts guest virtual machines, and the management console, which controls the server and is used to install and manage guests. This tip will guide you along the process and show you how to get connected to XenCenter, the XenSource management console.

Xen virtualization platforms:

Choosing Xen platforms, preparing SUSE for virtualization

Learn which Xen platform you should use and how to prepare SUSE for virtualization in this tip.

When installing a server as the hosting hardware for several virtual machines, the server itself must be powerful enough to support all the virtual machines you wish to run on it. Since SUSE Linux Enterprise Server is a general purpose server platform, you risk installing software that you typically wouldn't want to install when using SUSE for virtualization. It is important not run any other services than the virtualization services in the first instance of SUSE Linux Enterprise Server that you're installing. This tip shows how to make the right choices when installing virtualization software.

Xen virtual machines:

Creating Xen virtual machines

Learn how to create virtual machines with the Virtual Machine Manager utility with Xen.

The procedure for setting up Xen virtual machines is different for some Linux distributions, but Red Hat and SUSE make virtualization easy with the graphical Virtual Machine Manager utility. Virtual Machine Manager works for both paravirtualized and fully virtualized environments.

Follow this step-by-step tutorial to create a virtual machine using the Virtual Machine Manager utility. The procedure will demonstrate an installation of a paravirtualized SUSE Linux Enterprise Server 10 SP1 on top of a SUSE Linux Enterprise 10 SP1 virtualization host. After creating a virtual machine, it can be monitored with this utility as well.

Managing Xen block devices

Before installing a Xen virtual machine, the kind of block devices to work with must be determined. There are three possibilities: installing directly on a dedicated partition, using an important disk image file or creating your own disk image file with dd. This tip provides an overview of the most important options.

For maximum performance, a physical disk device is the best way to go. They can be installed on a partition or on a logical volume, which can be resized and allows for snapshot backups.When installing a virtual machine on SUSE or Red Hat, Xen disk image files are used by default. The last disk type for use in a virtual machine is the network disk type. The network disk type can be either a network block device or an iSCSI device. This disk image type is not portable, so precautionary measures should be taken on the storage-area network to protect this type of disk image file.

Using Xen with Red Hat Enterprise Linux 5

Install a Red Hat Enterprise Linux 5 guest operating system on Xen by following Bernard Golden's step-by-step guide, which warns about complications wrought by Intel and AMD chips.

First, it is necessary to create virtual machines with Red Hat Enterprise Linux 5. Red Hat provides both a command line interface (CLI) and a graphical interface to its Xen virtualization capability,Virtual Machine Manager, which is by far the easier way to go.

Xen's approach to virtualization enables high performance by modifying guest virtual machines so that they can cooperate with the underlying hypervisor. This modification takes the form of changing portions of the virtual machine's operating system kernel so that calls are made to the hypervisor rather than to the physical hardware. However, a new generation of chips available from AMD and Intel provide some hardware enhancements that allow unmodified guest OSes to interact with the Xen hypervisor.

Xen configuration and management:

Network-bridge and ifconfig

Learn how to use network-bridge and ifconfig commands with Xen on SUSE Linux Enterprise to control the network bridge and see all available interfaces on your network.

Configuring Xen virtual networks can be quite confusing. The domain 0 operating system shows a lot of network interfaces and it isn't always clear which one is doing what. In this article you'll learn the differences and learn how to do proper analysis and troubleshooting on the virtual network boards. Read about configuration of virtual network interfaces such as Xenbr0, peth0, Eth0 and vif in this tip.

Xen virtual machines: Management options

After you set up a Xen virtual machine, you need to know how to manage it. This tip goes over the management options offered by the xm utility, a powerful command line tool.

The xm utility is a command line tool that allows you to do virtually everything you ever need to do with a virtual machine. Graphical utilities are available as well, but they are not half as powerful as the xm command line tool.

For example, executing an xm list output shows you a summary of the most important information for operating the virtual machine. To activate virtual machines, xm create is used, then xm new command is needed to add the machine to the managed environment. Once this has been done, use xm start to start the domain. This tip covers the functions of xm that are essential for performing basic Xen virtual machine management.

Xen-based virtualization strategies:

Xen-based virtualization minimizes hypervisor relevance

Lower-priced rebel virtualization platforms built on the Xen hypervisor have the power to take on VMware Infrastructure (VI). This article considers two of them: Citrix Systems Inc.'s XenServer and Sun Microsystems' Sun xVM. Both Citrix and Sun have challenged VMware's dominance by subtly offering Xen as part of complete, vertical and, most important, inexpensive packages. I'll reveal some of their strategies to usurp the throne from the would-be virtualization monarch and make a prediction on the ultimate legacy of the Xen hypervisor.

This was first published in June 2008

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