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ContentsContents
Virtualization Guide
  1. Preface
  2. I Introduction
    1. 1 Virtualization technology
    2. 2 Virtualization scenarios
    3. 3 Introduction to Xen virtualization
    4. 4 Introduction to KVM virtualization
    5. 5 Virtualization tools
    6. 6 Installation of virtualization components
    7. 7 Virtualization limits and support
  3. II Managing virtual machines with libvirt
    1. 8 Starting and stopping libvirtd
    2. 9 Preparing the VM Host Server
    3. 10 Guest installation
    4. 11 Basic VM Guest management
    5. 12 Connecting and authorizing
    6. 13 Advanced storage topics
    7. 14 Configuring virtual machines with Virtual Machine Manager
    8. 15 Configuring virtual machines with virsh
    9. 16 Managing virtual machines with Vagrant
    10. 17 Xen to KVM migration guide
  4. III Hypervisor-independent features
    1. 18 Disk cache modes
    2. 19 VM Guest clock settings
    3. 20 libguestfs
    4. 21 QEMU guest agent
    5. 22 Software TPM emulator
  5. IV Managing virtual machines with Xen
    1. 23 Setting up a virtual machine host
    2. 24 Virtual networking
    3. 25 Managing a virtualization environment
    4. 26 Block devices in Xen
    5. 27 Virtualization: configuration options and settings
    6. 28 Administrative tasks
    7. 29 XenStore: configuration database shared between domains
    8. 30 Xen as a high-availability virtualization host
    9. 31 Xen: converting a paravirtual (PV) guest into a fully virtual (FV/HVM) guest
  6. V Managing virtual machines with QEMU
    1. 32 QEMU overview
    2. 33 Setting up a KVM VM Host Server
    3. 34 Guest installation
    4. 35 Running virtual machines with qemu-system-ARCH
    5. 36 Virtual machine administration using QEMU monitor
  7. Glossary
  8. A Virtual machine drivers
  9. B Configuring GPU Pass-Through for NVIDIA cards
  10. C XM, XL toolstacks, and the libvirt framework
  11. D GNU licenses
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Applies to SUSE Linux Enterprise Server 15 SP3

3 Introduction to Xen virtualization

This chapter introduces and explains the components and technologies you need to understand to set up and manage a Xen-based virtualization environment.

3.1 Basic components

The basic components of a Xen-based virtualization environment are the Xen hypervisor, the Dom0, any number of other VM Guests, and the tools, commands, and configuration files that let you manage virtualization. Collectively, the physical computer running all these components is called a VM Host Server because together these components form a platform for hosting virtual machines.

The Xen hypervisor

The Xen hypervisor, sometimes simply called a virtual machine monitor, is an open source software program that coordinates the low-level interaction between virtual machines and physical hardware.

The Dom0

The virtual machine host environment, also called Dom0 or controlling domain, is composed of several components, such as:

  • SUSE Linux Enterprise Server provides a graphical and a command line environment to manage the virtual machine host components and its virtual machines.

    Note
    Note

    The term Dom0 refers to a special domain that provides the management environment. This may be run either in graphical or in command line mode.

  • The xl tool stack based on the xenlight library (libxl). Use it to manage Xen guest domains.

  • QEMU—an open source software that emulates a full computer system, including a processor and various peripherals. It provides the ability to host operating systems in both full virtualization or paravirtualization mode.

Xen-based virtual machines

A Xen-based virtual machine, also called a VM Guest or DomU, consists of the following components:

  • At least one virtual disk that contains a bootable operating system. The virtual disk can be based on a file, partition, volume, or other type of block device.

  • A configuration file for each guest domain. It is a text file following the syntax described in the manual page man 5 xl.conf.

  • Several network devices, connected to the virtual network provided by the controlling domain.

Management tools, commands, and configuration files

There is a combination of GUI tools, commands, and configuration files to help you manage and customize your virtualization environment.

3.2 Xen virtualization architecture

The following graphic depicts a virtual machine host with four virtual machines. The Xen hypervisor is shown as running directly on the physical hardware platform. Note that the controlling domain is also a virtual machine, although it has several additional management tasks compared to all the other virtual machines.

Xen virtualization architecture
Figure 3.1: Xen virtualization architecture

On the left, the virtual machine host’s Dom0 is shown running the SUSE Linux Enterprise Server operating system. The two virtual machines shown in the middle are running paravirtualized operating systems. The virtual machine on the right shows a fully virtual machine running an unmodified operating system, such as the latest version of Microsoft Windows/Server.

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