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Running Xen: A Hands-on Guide to the Art of Virtualization
“This accessible and immediately useful book expertly provides the Xen community with everything it needs to know to download, build, deploy and manage Xen implementations.”
—Ian Pratt, Xen Project Leader VP Advanced Technology, Citrix Systems
The Real–World, 100% Practical Guide
to Xen Virtualization in Production Environments
Using free, open source Xen virtualization software, you can save money, gain new flexibility, improve utilization, and simplify everything from disaster recovery to software testing. Running Xen brings together all the knowledge you need to create and manage high–performance Xen virtual machines in any environment. Drawing on the unparalleled experience of a world–class Xen team, it covers everything from installation to administration—sharing field-tested insights, best practices, and case studies you can find nowhere else.
The authors begin with a primer on virtualization: its concepts, uses, and advantages. Next, they tour Xen’s capabilities, explore the Xen LiveCD, introduce the Xen hypervisor, and walk you through configuring your own hard–disk–based Xen installation. After you’re running, they guide you through each leading method for creating “guests” and migrating existing systems to run as Xen guests. Then they offer comprehensive coverage of managing and securing Xen guests, devices, networks, and distributed resources. Whether you’re an administrator, data center manager, developer, system integrator, or ISP, Running Xen will help you achieve your goals with Xen–reliably, efficiently, with outstanding performance, and at a surprisingly low cost.
•Understanding the Xen hypervisor: what it does, and how it works
•Using pre-built system images, including compressed file systems
•Managing domains with the xm console
•Populating and storing guest images
•Planning, designing, and configuring networks in Xen
•Utilizing Xen security: special purpose VMs, virtual network segments, remote access, firewalls, network monitors, sHype access control, Xen Security Modules (XSM), and more
•Managing guest resources: memory, CPU, and I/O
•Employing Xen in the enterprise: tools, products, and techniques
CONTENTS:
Foreword xxi
Preface xxiii
Chapter 1: Xen–Background and Virtualization Basics 1
Common Uses and Benefits of Virtualization 2
Types of Virtualization 5
Emulation 6
Full Virtualization 7
Paravirtualization 8
Operating System Level Virtualization 9
Other Types of Virtualization 11
Overview of Virtualization Types 12
Virtualization Heritage 13
The IBM Mainframe 14
Virtualization on Commodity Hardware 15
Virtualization Extensions for x86 15
Xen Origins and Time Line 15
Other Virtualization Systems for Commodity Hardware 18
Emulation 18
Full Virtualization 19
Paravirtualization 21
Operating System Virtualization 23
Popular Virtualization Products 24
Summary 25
References and Further Reading 26
Chapter 2: A Quick Tour with the Xen LiveCD 27
Running the LiveCD 28
Step 1: Downloading the LiveCD Image and Creating the CD 29
Step 2: Choosing a Domain0 Image from the GRUB Menu 30
Step 3: Logging In and the Desktop 31
Step 4: Creating Guests 33
Step 5: Deleting a Guest 38
Step 6: Interacting with Your Guests 38
Step 7: Testing Your Networking 41
Too Many Guests 44
Summary 44
References and Further Reading 45
Chapter 3: The Xen Hypervisor 47
Xen Hypervisor 48
A Privileged Position 50
Protection Rings 50
Domain0 51
Xen Boot Options 54
Choosing an OS for Domain0 59
xend 60
Controlling xend 60
xend Logs 62
xend Configuration 63
XenStore 67
Summary 73
References and Further Reading 73
Chapter 4: Hardware Requirements and Installation of Xen Domain0 75
Xen Domain0 Processor Requirements 76
Intel VT 77
AMD-V 77
HVM 78
Hardware Device Support and Recommendations 78
Disks and Controllers 78
Networking Devices 80
Graphics Devices 80
Power Management 81
Help for Unsupported Hardware 81
Memory Requirements 81
Choosing and Obtaining a Version of Xen 83
Open Source Distributions 83
Commercially Supported Options 84
Methods of Installing Domain0 Hosts 86
Common Prerequisite: The Grand Unified Boot Loader (GRUB) 87
Linux Distributions 87
OpenSUSE 88
CentOS 91
Ubuntu 98
Xen from Binary Packages 101
Gentoo 105
XenExpress 112
Non-Linux Domain0 Installations 114
Building from Source 116
Summary 118
References and Further Reading 118
Chapter 5: Using Prebuilt Guest Images 121
Introduction to DomU Guests 122
Guest Images 122
Operating System Kernels 123
Configuration Files 123
Working with Prebuilt Guest Images 128
Types of Guest Images 128
Downloading Prebuilt Guest Images 130
Mounting and Booting Prebuilt Images 131
Downloading Compressed File Guest Images 146
Converting Images from Other Virtualization Platforms 161
Summary 162
References and Further Reading 163
Chapter 6: Managing Unprivileged Domains 165
Introduction to the xm Utility 166
Prerequisites for Running the xm Utility 166
Generic Format of an xm Command 167
The xm list Subcommand 169
Basic List Information 169
Listing Information about a Specific Guest 171
long Option 172
Label Option 173
The xm create Subcommand 174
Prerequisites for xm create 174
Simple Examples of xm create 175
Guest Configuration Files 178
Python Format 178
Common Configuration Options 179
S-Expression (SXP) Format 180
Path to Configuration Files 181
Diagnosing Problems with Guest Creation 182
Dry Run 182
Console Output 183
Sample Problems 184
Automatically Starting DomUs 191
Shutting Down Guest Domains 193
xm shutdown 193
xm reboot 196
xm destroy 198
Pausing Domains 199
xm pause 200
xm unpause 200
Interacting with a Guest Nongraphically 201
xm console 202
SSH 204
Interacting with a Guest Graphically 204
X Forwarding with SSH 205
Configuration of SSH Server and Client 205
VNC 207
Virtual Frame Buffer and Integrated VNC/SDL Libraries 210
Freenx 212
Remote Desktop 213
Summary 215
References and Further Reading 216
Chapter 7: Populating Guest Images 217
Hardware Virtual Machine (HVM) Guest Population 218
Populating a Guest Image from a Disc or Disc Image (Windows XP Example) 218
Automated Population with virt-install 225
Paravirtualized (PV) Guest Population 228
OpenSUSE: YaST Virtual Machine Management 229
CentOS/Fedora: virt-manager 233
Debian/Ubuntu: debootstrap 242
Gentoo: quickpkg and domi Scripts 246
Xen Express 256
Guest Image Customization 266
Customizing Hostnames 266
Customizing Users 267
Customizing Packages and Services 268
Customizing the File System Table (/etc/fstab) 268
Converting Existing Installations 270
Summary 274
References and Further Reading 274
Chapter 8: Storing Guest Images 277
Logical Volumes 278
Basic LVM Usage 279
Resizing Images 282
Image Snapshots Using Copy on Write 286
Network Image Storage Options 287
iSCSI 288
ATA over Ethernet (AoE) 293
NFS 297
Comparing Network Storage Options 300
Guest Image Files 301
Preparing Compressed tar Image Files 301
Preparing Disk Image Files 302
Preparing Guest Partition Image Files 312
Mounting Disks and Partition Images 314
Summary 316
References and Further Reading 316
Chapter 9: Device Virtualization and Management 319
Device Virtualization 320
Paravirtualization of Devices 320
Full Virtualization of Devices 321
No Virtualization 321
Backends and Frontends 322
Backend Information in XenStore 323
Frontend Information in XenStore 325
Granting Control of a PCI Device 326
Identifying a PCI Device 326
Hiding a PCI Device from Domain0 at Boot 327
Manually Unbinding/Binding a PCI Device at Runtime 328
Granting a PCI Device to Another Domain 329
Exclusive Device Access Versus Trusted Driver Domains 331
Exclusive Device Access 331
Trusted Driver Domains 332
Problems Using Trusted Driver Domains 333
Device Emulation with QEMU-DM 334
Future Directions 335
More Devices 336
Smart Devices 336
Summary 336
References and Further Reading 337
Chapter 10: Network Configuration 339
Network Virtualization Overview 340
Designing a Virtual Network Topology 341
Bridging, Routing, and Network Address Translation 343
Frontend and Backend Network Drivers and Naming 347
Overview of Network Configuration in Xen 349
High-Level Steps 349
Xend Configuration File 350
Guest Domain’s Configuration File 352
Details of Bridging Mode 354
Bridging Configuration Example 355
Testing Results 361
Details of Routing Mode 364
Routing Configuration Example 365
Testing Results 371
Details of NAT Mode 373
NAT Configuration Example 373
Testing Results 379
Configuring Purely Virtual Network Segments 382
Configuring dummy0 383
Testing dummy0 385
Configuring Dummy Bridge 385
Testing Dummy Bridge 388
Assigning MAC Addresses to Virtual Network Interfaces 389
MAC Addresses 389
Specifying or Generating a MAC Address for a Guest Domain 390
Assigning IP Addresses 391
Using an External DHCP Server to Obtain an IP for a Guest Domain 392
Manually Assigning an IP to a Guest Domain 392
Using an Internal DHCP Server to Obtain an IP for a Guest Domain 393
Handling Multiple Network Interfaces in a Domain 394
Handling Multiple Network Interfaces in a driver domain 394
Handling Multiple Network Interfaces in a Guest Domain 396
vnet—Domain Virtual Network 399
Installing vnet 400
Running vnet 401
Summary 403
References and Further Reading 403
Chapter 11: Securing a Xen System 405
Structuring Your System for Security 406
Special Purpose Virtual Machines 406
Creating Virtual Network Segments 407
Securing the Privileged Domain 407
Removing Software and Services 407
Limiting Remote Access 408
Limiting the Local Users 412
Move Device Drivers into DriverDomains 412
Firewall and Network Monitors 413
Running a Firewall with iptables 413
Snort 419
Obtaining Snort 419
Snort and Network Intrusion Detection Mode 420
Mandatory Access Control with sHype and Xen Security Modules 422
sHype 423
Xen Security Modules (XSM) 432
DomU Security 433
Running VMs Only When Needed 434
Backing Up Virtual Machine Images 434
Summary 435
References and Further Reading 436
Chapter 12: Managing Guest Resources 437
Accessing Information about Guests and the Hypervisor 438
xm info 438
xm dmesg 443
xm log 444
xm top 446
xm uptime 449
Allocating Guest Memory 449
Shadow Page Tables 451
Balloon Driver 451
Improving Stability with Swap Space 454
Managing the Allocation of Guest Memory 454
Managing Guest Virtual CPUs 458
Comparing Virtual, Logical, and Physical Processors 458
HVM VCPU Management 459
VCPU Subcommands 460
When to Manually Administer VCPUs 462
Tuning the Hypervisor Scheduler 463
Weight and Cap 463
Protection from Misbehaving Guests 464
Using the Credit Scheduler Command 465
Choosing a Guest IO Scheduler 466
Noop Scheduler 466
Deadline Scheduler 466
Anticipatory Scheduler (as) 467
Complete Fair Queuing Scheduler (cfq) 467
Using IO Schedulers 467
Summary 469
References and Further Reading 469
Chapter 13: Guest Save, Restore, and Live Migration 471
Representing the State of a Virtual Machine 472
Basic Guest Domain Save and Restore 473
xm save 474
xm restore 476
Possible Save and Restore Errors 478
Types of Guest Relocation 479
Cold Static Relocation 480
Warm Static (Regular) Migration 481
Live Migration 482
Preparing for xm migrate 484
Configuring xend 485
Proximity of Sources and Destinations on the Network 488
Network-Accessible Storage 489
Guest Domain Configuration 489
Version and Physical Resource Requirements 491
Experience with xm migrate 491
xm migrate 491
Using xm migrate for Warm Static Migration 492
Using xm migrate for Live Migration 494
Possible Migration Errors 497
Summary 498
References and Further Reading 498
Chapter 14: An Overview of Xen Enterprise Management Tools 499
Programmatic Interfaces to the Xen Hypervisor 500
Libvirt 500
Xen–CIM 501
Xen API 501
Legacy Interfaces to Xend 502
Citrix XenServer Enterprise, Standard and XenExpress Editions 502
Virtual Iron 504
IBM Virtualization Manager 506
Enomalism 507
virt-manager 509
XenMan 513
Managing Multiple Systems 518
Summary 518
References and Further Reading 519
Appendix A: Resources 521
Xen Community 522
XenWiki 523
Xen Mailing Lists and Bug Reporting 524
Xen Summits 525
Xen Source Code 526
Academic Papers and Conferences 528
Distribution-Specific Resources 530
Appendix B: The xm Command 531
Appendix C: Xend Configuration Parameter 537
Appendix D: Guest Configuration Parameter 541
Appendix E: Xen Performance Evaluation 545
Xen Performance Measurements 546
Repeatability of the Xen Team’s Results 546
Xen and Virtual Web Hosting 548
Comparing XenoLinux to Native Linux on Older PC Hardware 550
Xen on x86 Versus IBM zServer 551
Performance Isolation in Xen 553
Performance of Xen Virtual Network and Real Network 556
Summary 558
Index 559
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