Red Hat ENTERPRISE LINUX 5 - VIRTUAL SERVER... Manuale utente

Red Hat Enterprise Linux 5

Virtualization Guide

The definitive guide for virtualization on Red Hat Enterprise Linux

Christopher Curran

Virtualization Guide

Red Hat Enterprise Linux 5 Virtualization Guide

The definitive guide for virtualization on Red Hat Enterprise Linux

Edition 5

Author Christopher Curran [email protected]

The text of and illustrations in this document are licensed by Red Hat under a Creative Commons

Attribution–Share Alike 3.0 Unported license ("CC-BY-SA"). An explanation of CC-BY-SA is available

at http://creativecommons.org/licenses/by-sa/3.0/. In accordance with CC-BY-SA, if you distribute this

document or an adaptation of it, you must provide the URL for the original version.

Red Hat, as the licensor of this document, waives the right to enforce, and agrees not to assert,

Section 4d of CC-BY-SA to the fullest extent permitted by applicable law.

Red Hat, Red Hat Enterprise Linux, the Shadowman logo, JBoss, MetaMatrix, Fedora, the Infinity

Logo, and RHCE are trademarks of Red Hat, Inc., registered in the United States and other countries.

Linux® is the registered trademark of Linus Torvalds in the United States and other countries.

All other trademarks are the property of their respective owners.

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The Red Hat Enterprise Linux Virtualization Guide contains information on installation, configuring,

administering, and troubleshooting virtualization technologies included with Red Hat Enterprise Linux.

iii

Preface ix

1. About this book .............................................................................................................. ix

2. Document Conventions ................................................................................................... ix

2.1. Typographic Conventions ..................................................................................... ix

2.2. Pull-quote Conventions ........................................................................................ xi

2.3. Notes and Warnings ............................................................................................ xi

3. We need your feedback ................................................................................................. xii

3.1. Technical review requests .................................................................................... xii

4. How should CIO's think about virtualization .................................................................... xiii

I. Requirements and Limitations for Virtualization with Red Hat Enterprise Linux 1

1. System requirements 3

2. Xen restrictions and support 5

3. KVM restrictions and support 9

4. Virtualization limitations 11

4.1. General limitations for virtualization ..................................................................... 11

4.2. KVM limitations .................................................................................................. 11

4.3. Xen limitations .................................................................................................... 12

4.4. Application limitations ......................................................................................... 14

II. Installation 15

5. Installing the virtualization packages 17

5.1. Installing Xen with a new Red Hat Enterprise Linux installation .............................. 17

5.2. Installing Xen packages on an existing Red Hat Enterprise Linux system ................ 21

5.3. Installing KVM with a new Red Hat Enterprise Linux installation ............................. 22

5.4. Installing KVM packages on an existing Red Hat Enterprise Linux system ............... 26

6. Virtualized guest installation overview 29

6.1. Creating guests with virt-install ............................................................................ 29

6.2. Creating guests with virt-manager ....................................................................... 29

6.3. Installing guests with PXE ................................................................................... 42

7. Guest operating system installation procedures 49

7.1. Installing Red Hat Enterprise Linux 5 as a para-virtualized guest ............................ 49

7.2. Installing Red Hat Enterprise Linux as a fully virtualized guest ............................... 91

7.3. Installing Windows XP as a fully virtualized guest ............................................... 100

7.4. Installing Windows Server 2003 as a fully virtualized guest .................................. 118

7.5. Installing Windows Server 2008 as a fully virtualized guest .................................. 121

III. Configuration 133

8. Virtualized storage devices 135

8.1. Creating a virtualized floppy disk controller ......................................................... 135

8.2. Adding storage devices to guests ...................................................................... 136

8.3. Configuring persistent storage in Red Hat Enterprise Linux 5 ............................... 140

8.4. Add a virtualized CD-ROM or DVD device to a guest .......................................... 142

9. Network Configuration 143

9.1. Network address translation (NAT) with libvirt ..................................................... 143

Virtualization Guide

9.2. Bridged networking with libvirt ........................................................................... 144

10. Pre-Red Hat Enterprise Linux 5.4 Xen networking 147

10.1. Configuring multiple guest network bridges to use multiple Ethernet cards ........... 147

10.2. Red Hat Enterprise Linux 5.0 laptop network configuration ................................ 149

11. Xen Para-virtualized Drivers 153

11.1. System requirements ...................................................................................... 154

11.2. Para-virtualization Restrictions and Support ...................................................... 155

11.3. Installing the Para-virtualized Drivers ................................................................ 157

11.3.1. Common installation steps .................................................................... 157

11.3.2. Installation and Configuration of Para-virtualized Drivers on Red Hat

Enterprise Linux 3 ........................................................................................... 158

11.3.3. Installation and Configuration of Para-virtualized Drivers on Red Hat

Enterprise Linux 4 ........................................................................................... 162

11.3.4. Xen Para-virtualized Drivers on Red Hat Enterprise Linux 5 ..................... 165

11.4. Para-virtualized Network Driver Configuration ................................................... 167

11.5. Additional Para-virtualized Hardware Configuration ........................................... 172

11.5.1. Virtualized Network Interfaces ............................................................... 172

11.5.2. Virtual Storage Devices ........................................................................ 173

12. KVM Para-virtualized Drivers 175

12.1. Installing the KVM Windows para-virtualized drivers .......................................... 175

12.2. Installing drivers with a virtualized floppy disk ................................................... 186

12.3. Using KVM para-virtualized drivers for existing devices ..................................... 187

12.4. Using KVM para-virtualized drivers for new devices .......................................... 187

13. PCI passthrough 191

13.1. Adding a PCI device with virsh ........................................................................ 192

13.2. Adding a PCI device with virt-manager ............................................................. 194

13.3. PCI passthrough with virt-install ....................................................................... 199

13.4. PCI passthrough for para-virtualized Xen guests on Red Hat Enterprise Linux

5.3 and older .......................................................................................................... 200

14. SR-IOV 203

14.1. Introduction .................................................................................................... 203

14.2. Using SR-IOV ................................................................................................. 204

14.3. Troubleshooting SR-IOV .................................................................................. 207

15. KVM guest timing management 209

IV. Administration 213

16. Server best practices 215

17. Security for virtualization 217

17.1. Storage security issues ................................................................................... 217

17.2. SELinux and virtualization ............................................................................... 217

17.3. SELinux ......................................................................................................... 218

17.4. Virtualization firewall information ...................................................................... 219

18. Managing guests with xend 221

19. Xen live migration 223

19.1. A live migration example ................................................................................. 224

19.2. Configuring guest live migration ....................................................................... 231

20. KVM live migration 233

20.1. Live migration requirements ............................................................................ 233

20.2. Share storage example: NFS for a simple migration .......................................... 234

20.3. Live KVM migration with virsh ......................................................................... 235

20.4. Migrating with virt-manager ............................................................................. 236

21. Remote management of virtualized guests 247

21.1. Remote management with SSH ....................................................................... 247

21.2. Remote management over TLS and SSL ......................................................... 248

21.3. Transport modes ............................................................................................. 250

V. Virtualization Storage Topics 255

22. Using shared storage with virtual disk images 257

22.1. Using iSCSI for storing virtual disk images ....................................................... 257

22.2. Using NFS for storing virtual disk images ......................................................... 257

22.3. Using GFS2 for storing virtual disk images ....................................................... 257

22.4. Storage Pools ................................................................................................. 257

22.4.1. Configuring storage devices for pools .................................................... 257

22.4.2. Mapping virtualized guests to storage pools ........................................... 257

VI. Virtualization Reference Guide 259

23. Virtualization tools 261

24. Managing guests with virsh 263

25. Managing guests with the Virtual Machine Manager (virt-manager) 273

25.1. The Add Connection window ........................................................................... 273

25.2. The Virtual Machine Manager main window ...................................................... 274

25.3. The guest Overview tab .................................................................................. 275

25.4. Virtual Machine graphical console ................................................................... 276

25.5. Starting virt-manager ....................................................................................... 277

25.6. Restoring a saved machine ............................................................................ 278

25.7. Displaying guest details .................................................................................. 280

25.8. Status monitoring ............................................................................................ 285

25.9. Displaying guest identifiers .............................................................................. 287

25.10. Displaying a guest's status ........................................................................... 288

25.11. Displaying virtual CPUs ................................................................................ 289

25.12. Displaying CPU usage .................................................................................. 290

25.13. Displaying memory usage ............................................................................ 291

25.14. Managing a virtual network ............................................................................ 292

25.15. Creating a virtual network .............................................................................. 293

26. The xm command quick reference 303

27. Configuring the Xen kernel boot parameters 305

28. Configuring ELILO 307

29. libvirt configuration reference 309

30. Xen configuration files 311

Virtualization Guide

VII. Tips and Tricks 319

31. Tips and tricks 321

31.1. Automatically starting guests ........................................................................... 321

31.2. Changing between the KVM and Xen hypervisors ............................................. 321

31.2.1. Xen to KVM ......................................................................................... 321

31.2.2. KVM to Xen ......................................................................................... 323

31.3. Using qemu-img ............................................................................................. 324

31.4. Overcommitting with KVM ............................................................................... 325

31.5. Modifying /etc/grub.conf ................................................................................... 327

31.6. Verifying virtualization extensions ..................................................................... 328

31.7. Accessing data from a guest disk image .......................................................... 329

31.8. Setting KVM processor affinities ...................................................................... 331

31.9. Identifying guest type and implementation ........................................................ 335

31.10. Generating a new unique MAC address ......................................................... 336

31.11. Limit network bandwidth for a Xen guest ........................................................ 337

31.12. Configuring Xen processor affinities ............................................................... 338

31.13. Modifying the Xen hypervisor ......................................................................... 338

31.14. Very Secure ftpd ........................................................................................ 339

31.15. Configuring LUN Persistence ......................................................................... 339

31.16. Disable SMART disk monitoring for guests ..................................................... 341

31.17. Cleaning up old Xen configuration files ........................................................... 341

31.18. Configuring a VNC Server ............................................................................. 341

31.19. Cloning guest configuration files .................................................................... 342

31.20. Duplicating an existing guest and its configuration file ..................................... 342

32. Creating custom libvirt scripts 345

32.1. Using XML configuration files with virsh ........................................................... 345

VIII. Troubleshooting 347

33. Troubleshooting Xen 349

33.1. Debugging and troubleshooting Xen ................................................................ 349

33.2. Log files overview ........................................................................................... 350

33.3. Log file descriptions ........................................................................................ 351

33.4. Important directory locations ............................................................................ 351

33.5. Troubleshooting with the logs .......................................................................... 352

33.6. Troubleshooting with the serial console ............................................................ 352

33.7. Para-virtualized guest console access .............................................................. 353

33.8. Fully virtualized guest console access .............................................................. 353

33.9. Common Xen problems .................................................................................. 353

33.10. Guest creation errors .................................................................................... 354

33.11. Troubleshooting with serial consoles .............................................................. 354

33.11.1. Serial console output for Xen .............................................................. 354

33.11.2. Xen serial console output from para-virtualized guests .......................... 355

33.11.3. Serial console output from fully virtualized guests ................................. 356

33.12. Xen configuration files ................................................................................... 356

33.13. Interpreting Xen error messages .................................................................... 357

33.14. The layout of the log directories ..................................................................... 360

34. Troubleshooting 361

34.1. Identifying available storage and partitions ....................................................... 361

34.2. After rebooting Xen-based guests the console freezes ...................................... 361

vii

34.3. Virtualized Ethernet devices are not found by networking tools ........................... 361

34.4. Loop device errors .......................................................................................... 361

34.5. Failed domain creation caused by a memory shortage ...................................... 362

34.6. Wrong kernel image error ................................................................................ 362

34.7. Wrong kernel image error - non-PAE kernel on a PAE platform .......................... 363

34.8. Fully-virtualized 64 bit guest fails to boot .......................................................... 363

34.9. A missing localhost entry causes virt-manager to fail ......................................... 363

34.10. Microcode error during guest boot ................................................................. 364

34.11. Python depreciation warning messages when starting a virtual machine ............ 364

34.12. Enabling Intel VT and AMD-V virtualization hardware extensions in BIOS .......... 364

34.13. KVM networking performance ........................................................................ 365

35. Troubleshooting the Xen para-virtualized drivers 369

35.1. Red Hat Enterprise Linux 5 Virtualization log file and directories ......................... 369

35.2. Para-virtualized guest fail to load on a Red Hat Enterprise Linux 3 guest

operating system ..................................................................................................... 370

35.3. A warning message is displayed while installing the para-virtualized drivers on

Red Hat Enterprise Linux 3 ..................................................................................... 371

35.4. Manually loading the para-virtualized drivers .................................................... 371

35.5. Verifying the para-virtualized drivers have successfully loaded ........................... 372

35.6. The system has limited throughput with para-virtualized drivers .......................... 372

A. Additional resources 373

A.1. Online resources ...................................................................................................... 373

A.2. Installed documentation ............................................................................................ 373

Glossary 375

B. Revision History 381

C. Colophon 387

viii

Preface

This book is the Red Hat Enterprise Linux Virtualization Guide. The Guide covers all aspects of using

and managing virtualization products included with Red Hat Enterprise Linux.

1. About this book

This book is divided into 7 parts:

• System Requirements

• Installation

• Configuration

• Administration

• Reference

• Tips and Tricks

• Troubleshooting

Key terms and concepts used throughout this book are covered in the glossary, Glossary.

This book covers virtualization topics for Red Hat Enterprise Linux 5. The Kernel-based Virtual

Machine and Xen hypervisors are provided with Red Hat Enterprise Linux 5. Both the KVM and Xen

hypervisors support Full virtualization. The Xen hypervisor also supports Para-virtualization.

2. Document Conventions

This manual uses several conventions to highlight certain words and phrases and draw attention to

specific pieces of information.

In PDF and paper editions, this manual uses typefaces drawn from the Liberation Fonts1 set. The

Liberation Fonts set is also used in HTML editions if the set is installed on your system. If not,

alternative but equivalent typefaces are displayed. Note: Red Hat Enterprise Linux 5 and later includes

the Liberation Fonts set by default.

2.1. Typographic Conventions

Four typographic conventions are used to call attention to specific words and phrases. These

conventions, and the circumstances they apply to, are as follows.

Mono-spaced Bold

Used to highlight system input, including shell commands, file names and paths. Also used to highlight

keycaps and key combinations. For example:

To see the contents of the file my_next_bestselling_novel in your current

working directory, enter the cat my_next_bestselling_novel command at the

shell prompt and press Enter to execute the command.

1 https://fedorahosted.org/liberation-fonts/

Preface

The above includes a file name, a shell command and a keycap, all presented in mono-spaced bold

and all distinguishable thanks to context.

Key combinations can be distinguished from keycaps by the hyphen connecting each part of a key

combination. For example:

Press Enter to execute the command.

Press Ctrl+Alt+F1 to switch to the first virtual terminal. Press Ctrl+Alt+F7 to

return to your X-Windows session.

The first paragraph highlights the particular keycap to press. The second highlights two key

combinations (each a set of three keycaps with each set pressed simultaneously).

If source code is discussed, class names, methods, functions, variable names and returned values

mentioned within a paragraph will be presented as above, in mono-spaced bold. For example:

File-related classes include filesystem for file systems, file for files, and dir for

directories. Each class has its own associated set of permissions.

Proportional Bold

This denotes words or phrases encountered on a system, including application names; dialog box text;

labeled buttons; check-box and radio button labels; menu titles and sub-menu titles. For example:

Choose System → Preferences → Mouse from the main menu bar to launch Mouse

Preferences. In the Buttons tab, click the Left-handed mouse check box and click

Close to switch the primary mouse button from the left to the right (making the mouse

suitable for use in the left hand).

To insert a special character into a gedit file, choose Applications → Accessories

→ Character Map from the main menu bar. Next, choose Search → Find… from the

Character Map menu bar, type the name of the character in the Search field and click

Next. The character you sought will be highlighted in the Character Table. Double-

click this highlighted character to place it in the Text to copy field and then click the

Copy button. Now switch back to your document and choose Edit → Paste from the

gedit menu bar.

The above text includes application names; system-wide menu names and items; application-specific

menu names; and buttons and text found within a GUI interface, all presented in proportional bold and

all distinguishable by context.

Mono-spaced Bold Italic or Proportional Bold Italic

Whether mono-spaced bold or proportional bold, the addition of italics indicates replaceable or

variable text. Italics denotes text you do not input literally or displayed text that changes depending on

circumstance. For example:

To connect to a remote machine using ssh, type ssh username@domain.name at

a shell prompt. If the remote machine is example.com and your username on that

machine is john, type ssh [email protected].

The mount -o remount file-system command remounts the named file

system. For example, to remount the /home file system, the command is mount -o

remount /home.

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