W. David Ashley
Foundations of Libvirt DevelopmentHow to Set Up and Maintain a Virtual Machine Environment with Python
W. David Ashley
Austin, TX, USA
ISBN 978-1-4842-4861-4e-ISBN 978-1-4842-4862-1
https://doi.org/10.1007/978-1-4842-4862-1
© W. David Ashley 2019
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To all the teachers to whom I owe so much, I hope I have made you proud. And to all of my students, I hope I was able to pass some knowledge on to you.

Acknowledgments

I would like to acknowledge the libvirt development team and Red Hat for their contributions to the Linux community. Without their in-depth help and encouragement, this book would not have been possible.

Table of Contents

Chapter 1:​ Introduction 1
What This Book Covers 1
Book Conventions 2
Computer Commands 3
File Names 3
Programming Language Elements and Literals 3
Computer Output and Source Code 4
Notes and Warnings 4
Chapter 2:​ Architecture 7
Object Model 7
Hypervisor Connections 7
Guest Domains 8
Virtual Networks 9
Storage Pools 10
Storage Volumes 11
Host Devices 12
Driver Model 13
Remote Management 16
Basic Usage 17
Data Transports 17
Authentication Schemes 19
Generating TLS Certificates 20
Public Key Infrastructure Setup 21
Summary 22
Chapter 3:​ Connecting to Domains 23
Overview 23
open 24
openReadOnly 25
openAuth 26
close 28
URI Formats 29
Local URIs 29
Remote URIs 31
Capability Information Methods 36
Host Information 42
getHostname 43
getMaxVcpus 43
getInfo 44
getCellsFreeMemo​ry 46
getType 47
getVersion 48
getLibVersion 49
getURI 50
isEncrypted 50
isSecure 51
isAlive 52
compareCPU 53
getFreeMemory 54
getFreePages 55
getMemoryParamet​ers 56
getMemoryStats 57
getSecurityModel​ 58
getSysinfo 58
getCPUMap 59
getCPUStats 60
getCPUModelNames​ 61
Summary 61
Chapter 4:​ Guest Domains 63
Domain Overview 63
Listing Domains 67
Obtaining State Information About a Domain 71
Fetching the ID of a Domain 72
Fetching the UUID of a Domain 73
Fetching the OS Type of a Domain 74
Determining Whether the Domain Has a Current Snapshot 75
Determining Whether the Domain Has Managed Save Images 76
Fetching the Hostname of the Domain 77
Getting the Domain Hardware Information 78
Determining Whether the Domain Is Running 79
Determining Whether the Domain Is Persistent 80
Determining Whether the Domain Is Updated 81
Determining the Max Memory of the Domain 82
Determining the Max VCPUs of the Domain 83
Fetching the Name of the Domain 85
Fetching the State of the Domain 86
Extracting the Time Information from the Domain 87
Extracting the Network Interface Addresses from a Domain 88
Lifecycle Control 90
Provisioning and Starting 91
Stopping 104
Suspending/​Resuming and Saving/​Restoring 105
Migrating 109
Autostarting 114
Domain Configuration 115
Boot Modes 115
Memory/​CPU Resources 116
Monitoring Performance 118
Domain Block Device Performance 119
vCPU Performance 120
Memory Statistics 122
I/​O Statistics 123
Device Configuration 124
Emulator 126
Disks 127
Networking 129
Mice, Keyboard, and Tablets 131
USB Device Passthrough 133
PCI Device Passthrough 133
Block Device Jobs 135
Summary 138
Chapter 5:​ Storage Pools and Volumes 139
Pools Overview 139
NFS Storage Pools 140
iSCSI Storage Pools 140
Other Storage Pools 141
Listing Pools 143
Pool Usage 144
Lifecycle Control 147
Discovering Pool Sources 149
Pool Configuration 150
Volume Overview 151
Listing Volumes 152
Volume Information 153
Creating and Deleting Volumes 154
Cloning Volumes 156
Configuring Volumes 159
Summary 159
Chapter 6:​ Virtual Networks 161
Listing Networks 162
Lifecycle Control 164
Network Configuration 166
Summary 167
Chapter 7:​ Network Interfaces 169
XML Interface Description Format 170
Retrieving Information About Interfaces 172
Enumerating Interfaces 172
Obtaining a virInterface Instance for an Interface 174
Retrieving Detailed Interface Information 175
Retrieving Interface Network Addresses 177
Managing Interface Configuration Files 178
Defining an Interface Configuration 178
Using changeRollback 181
Using changeBegin 181
Using changeCommit 182
Interface Lifecycle Management 183
Activating an Interface 183
Deactivating an Interface 183
Summary 184
Chapter 8:​ Error Handling 185
The libvirtError Class 185
Using virGetLastError 194
Subclassing libvirtError 195
Registering an Error Handler Function 197
Summary 199
Chapter 9:​ Event and Timer Handling 201
Event Handling 201
Timer Handling 205
Summary 206
Chapter 10:​ Using the QEMU Guest Agent 207
Installing the QEMU Guest Agent 208
Using the QEMU Guest Agent 208
virsh and the QEMU Guest Agent 210
QEMU Guest Agent Time Commands 212
QEMU Guest Agent Network Interface Commands 214
Python and the QEMU Guest Agent 216
QEMU Guest Agent Time Commands 219
QEMU Guest Agent Network Interface Commands 223
Summary 225
Chapter 11:​ Debugging/​Logging 227
Logging Facilities 227
Environment Variables 229
Summary 230
Chapter 12:​ A Sample Problem 231
Problem Statement 231
Solution Requirements 232
Using Guest Domains to Solve the Problem 233
Introducing virsh 233
Introducing the Python libvirt Module 234
New Problems Introduced by Using Guest Domains 234
Sample Solution 235
Implementing the Job Information Store 236
Reading the Store 237
Using runJobOnDemand.​py 238
Summary 244
Chapter 13:​ Storing Information About Virtual Machines 245
Deciding What Information Should Be Stored 245
Using Simple Text Files 246
Using a Simple Database 249
Summary 251
Chapter 14:​ Securing Virtual Machines 253
Host Security 253
Guest Domain Security 255
Summary 255
Appendix A:​ Libvirt XML Schemas 257
The Domain Schema 257
Example Paravirtualized XEN Schemas 306
Example Paravirtualized KVM and Qemu Schemas 311
The Networks Schema 313
The Network Schema Details 314
The Connectivity Schema 314
Setting a VLAN Tag (on Supported Network Types Only) 316
Portgroups 317
Static Routes 318
Addressing 318
Example Configurations 320
Storage Pool XML 327
General Metadata 327
Storage Volume XML 330
Storage Volume XML 330
Volume Examples 332
Element and Attribute Overview 334
Host Capabilities 335
Node Device XML Format 336
Snapshot XML Format 339
Snapshot XML Samples 341
The Domain Capabilities XML Format 344
Element and Attribute Overview 344
Network Filters 352
Goals and Background 352
Concepts 353
Element and Attribute Overview 364
Command-Line Tools 388
Writing Your Own Filters 390
Limitations 399
Index 401

About the Author and About the Technical Reviewer

About the Author

W. David Ashley
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is a technical writer for SkillSoft where he specializes in open source, particularly Linux. As a member of the Linux Fedora documentation team, he recently led the libvert project documentation and wrote the Python programs included with it. He has developed in 20 different programming languages during his 35 years as a software developer and IT consultant, including more than 18 years at IBM and 12 years with American Airlines.

 

About the Technical Reviewer

Nishant Krishna
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is an entrepreneur, software architect, innovator, and inventor with 18+ years of experience working on architecture, anticounterfeiting technologies, EdTech, cloud and virtualization, Internet of Things (IoT) technologies, machine learning, security compliance, API development, and network management systems (NMSs). He can be reached at https://in.linkedin.com/in/nishantkrishna and https://twitter.com/nishantkrishna .

 
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