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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
  3. II Managing virtual machines with libvirt
    1. 7 libvirt daemons
    2. 8 Preparing the VM Host Server
    3. 9 Guest installation
    4. 10 Basic VM Guest management
    5. 11 Connecting and authorizing
    6. 12 Advanced storage topics
    7. 13 Configuring virtual machines with Virtual Machine Manager
    8. 14 Configuring virtual machines with virsh
    9. 15 Xen to KVM migration guide
  4. III Hypervisor-independent features
    1. 16 Disk cache modes
    2. 17 VM Guest clock settings
    3. 18 libguestfs
    4. 19 QEMU guest agent
    5. 20 Software TPM emulator
    6. 21 Creating crash dumps of a VM Guest
  5. IV Managing virtual machines with Xen
    1. 22 Setting up a virtual machine host
    2. 23 Virtual networking
    3. 24 Managing a virtualization environment
    4. 25 Block devices in Xen
    5. 26 Virtualization: configuration options and settings
    6. 27 Administrative tasks
    7. 28 XenStore: configuration database shared between domains
    8. 29 Xen as a high-availability virtualization host
    9. 30 Xen: converting a paravirtual (PV) guest into a fully virtual (FV/HVM) guest
  6. V Managing virtual machines with QEMU
    1. 31 QEMU overview
    2. 32 Setting up a KVM VM Host Server
    3. 33 Guest installation
    4. 34 Running virtual machines with qemu-system-ARCH
    5. 35 Virtual machine administration using QEMU monitor
  7. VI Troubleshooting
    1. 36 Integrated help and package documentation
    2. 37 Gathering system information and logs
  8. Glossary
  9. A Configuring GPU Pass-Through for NVIDIA cards
  10. B GNU licenses
Applies to openSUSE Leap 15.5

3 Introduction to Xen virtualization Edit source

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 Edit source

The basic components of a Xen-based virtualization environment are the following:

  • Xen hypervisor

  • Dom0

  • any number of other VM Guests

  • tools, commands and configuration files to 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:

  • openSUSE Leap provides a graphical and a command line environment to manage the virtual machine host components and its virtual machines.


    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 multiple 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 Edit source

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 openSUSE Leap 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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