ia64/xen-unstable

view docs/src/user.tex @ 10792:49f874c0bd98

Fix docs build after vtpm changes.
Signed-off-by: Keir Fraser <keir@xensource.com>
author kaf24@firebug.cl.cam.ac.uk
date Tue Jul 25 16:03:12 2006 +0100 (2006-07-25)
parents 110c1e853c53
children a438506e241d
line source
1 \documentclass[11pt,twoside,final,openright]{report}
2 \usepackage{a4,graphicx,html,parskip,setspace,times,xspace,url}
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13 \begin{document}
15 % TITLE PAGE
16 \pagestyle{empty}
17 \begin{center}
18 \vspace*{\fill}
19 \includegraphics{figs/xenlogo.eps}
20 \vfill
21 \vfill
22 \vfill
23 \begin{tabular}{l}
24 {\Huge \bf Users' Manual} \\[4mm]
25 {\huge Xen v3.0} \\[80mm]
26 \end{tabular}
27 \end{center}
29 {\bf DISCLAIMER: This documentation is always under active development
30 and as such there may be mistakes and omissions --- watch out for
31 these and please report any you find to the developers' mailing list,
32 xen-devel@lists.xensource.com. The latest version is always available
33 on-line. Contributions of material, suggestions and corrections are
34 welcome.}
36 \vfill
37 \clearpage
40 % COPYRIGHT NOTICE
41 \pagestyle{empty}
43 \vspace*{\fill}
45 Xen is Copyright \copyright 2002-2005, University of Cambridge, UK, XenSource
46 Inc., IBM Corp., Hewlett-Packard Co., Intel Corp., AMD Inc., and others. All
47 rights reserved.
49 Xen is an open-source project. Most portions of Xen are licensed for copying
50 under the terms of the GNU General Public License, version 2. Other portions
51 are licensed under the terms of the GNU Lesser General Public License, the
52 Zope Public License 2.0, or under ``BSD-style'' licenses. Please refer to the
53 COPYING file for details.
55 Xen includes software by Christopher Clark. This software is covered by the
56 following licence:
58 \begin{quote}
59 Copyright (c) 2002, Christopher Clark. All rights reserved.
61 Redistribution and use in source and binary forms, with or without
62 modification, are permitted provided that the following conditions are met:
64 \begin{itemize}
65 \item Redistributions of source code must retain the above copyright notice,
66 this list of conditions and the following disclaimer.
68 \item Redistributions in binary form must reproduce the above copyright
69 notice, this list of conditions and the following disclaimer in the
70 documentation and/or other materials provided with the distribution.
72 \item Neither the name of the original author; nor the names of any
73 contributors may be used to endorse or promote products derived from this
74 software without specific prior written permission.
75 \end{itemize}
77 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
78 AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
79 IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
80 DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE
81 FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
82 DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
83 SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
84 CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
85 OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
86 OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
87 \end{quote}
89 \cleardoublepage
92 % TABLE OF CONTENTS
93 \pagestyle{plain}
94 \pagenumbering{roman}
95 { \parskip 0pt plus 1pt
96 \tableofcontents }
97 \cleardoublepage
100 % PREPARE FOR MAIN TEXT
101 \pagenumbering{arabic}
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111 \setstretch{1.1}
114 %% Chapter Introduction moved to introduction.tex
115 \chapter{Introduction}
118 Xen is an open-source \emph{para-virtualizing} virtual machine monitor
119 (VMM), or ``hypervisor'', for the x86 processor architecture. Xen can
120 securely execute multiple virtual machines on a single physical system
121 with close-to-native performance. Xen facilitates enterprise-grade
122 functionality, including:
124 \begin{itemize}
125 \item Virtual machines with performance close to native hardware.
126 \item Live migration of running virtual machines between physical hosts.
127 \item Up to 32 virtual CPUs per guest virtual machine, with VCPU hotplug.
128 \item x86/32, x86/32 with PAE, and x86/64 platform support.
129 \item Intel Virtualization Technology (VT-x) for unmodified guest operating systems (including Microsoft Windows).
130 \item Excellent hardware support (supports almost all Linux device
131 drivers).
132 \end{itemize}
135 \section{Usage Scenarios}
137 Usage scenarios for Xen include:
139 \begin{description}
140 \item [Server Consolidation.] Move multiple servers onto a single
141 physical host with performance and fault isolation provided at the
142 virtual machine boundaries.
143 \item [Hardware Independence.] Allow legacy applications and operating
144 systems to exploit new hardware.
145 \item [Multiple OS configurations.] Run multiple operating systems
146 simultaneously, for development or testing purposes.
147 \item [Kernel Development.] Test and debug kernel modifications in a
148 sand-boxed virtual machine --- no need for a separate test machine.
149 \item [Cluster Computing.] Management at VM granularity provides more
150 flexibility than separately managing each physical host, but better
151 control and isolation than single-system image solutions,
152 particularly by using live migration for load balancing.
153 \item [Hardware support for custom OSes.] Allow development of new
154 OSes while benefiting from the wide-ranging hardware support of
155 existing OSes such as Linux.
156 \end{description}
159 \section{Operating System Support}
161 Para-virtualization permits very high performance virtualization, even
162 on architectures like x86 that are traditionally very hard to
163 virtualize.
165 This approach requires operating systems to be \emph{ported} to run on
166 Xen. Porting an OS to run on Xen is similar to supporting a new
167 hardware platform, however the process is simplified because the
168 para-virtual machine architecture is very similar to the underlying
169 native hardware. Even though operating system kernels must explicitly
170 support Xen, a key feature is that user space applications and
171 libraries \emph{do not} require modification.
173 With hardware CPU virtualization as provided by Intel VT and AMD
174 SVM technology, the ability to run an unmodified guest OS kernel
175 is available. No porting of the OS is required, although some
176 additional driver support is necessary within Xen itself. Unlike
177 traditional full virtualization hypervisors, which suffer a tremendous
178 performance overhead, the combination of Xen and VT or Xen and
179 Pacifica technology complement one another to offer superb performance
180 for para-virtualized guest operating systems and full support for
181 unmodified guests running natively on the processor. Full support for
182 VT and Pacifica chipsets will appear in early 2006.
184 Paravirtualized Xen support is available for increasingly many
185 operating systems: currently, mature Linux support is available and
186 included in the standard distribution. Other OS ports---including
187 NetBSD, FreeBSD and Solaris x86 v10---are nearing completion.
190 \section{Hardware Support}
192 Xen currently runs on the x86 architecture, requiring a ``P6'' or
193 newer processor (e.g.\ Pentium Pro, Celeron, Pentium~II, Pentium~III,
194 Pentium~IV, Xeon, AMD~Athlon, AMD~Duron). Multiprocessor machines are
195 supported, and there is support for HyperThreading (SMT). In
196 addition, ports to IA64 and Power architectures are in progress.
198 The default 32-bit Xen supports up to 4GB of memory. However Xen 3.0
199 adds support for Intel's Physical Addressing Extensions (PAE), which
200 enable x86/32 machines to address up to 64 GB of physical memory. Xen
201 3.0 also supports x86/64 platforms such as Intel EM64T and AMD Opteron
202 which can currently address up to 1TB of physical memory.
204 Xen offloads most of the hardware support issues to the guest OS
205 running in the \emph{Domain~0} management virtual machine. Xen itself
206 contains only the code required to detect and start secondary
207 processors, set up interrupt routing, and perform PCI bus
208 enumeration. Device drivers run within a privileged guest OS rather
209 than within Xen itself. This approach provides compatibility with the
210 majority of device hardware supported by Linux. The default XenLinux
211 build contains support for most server-class network and disk
212 hardware, but you can add support for other hardware by configuring
213 your XenLinux kernel in the normal way.
216 \section{Structure of a Xen-Based System}
218 A Xen system has multiple layers, the lowest and most privileged of
219 which is Xen itself.
221 Xen may host multiple \emph{guest} operating systems, each of which is
222 executed within a secure virtual machine. In Xen terminology, a
223 \emph{domain}. Domains are scheduled by Xen to make effective use of the
224 available physical CPUs. Each guest OS manages its own applications.
225 This management includes the responsibility of scheduling each
226 application within the time allotted to the VM by Xen.
228 The first domain, \emph{domain~0}, is created automatically when the
229 system boots and has special management privileges. Domain~0 builds
230 other domains and manages their virtual devices. It also performs
231 administrative tasks such as suspending, resuming and migrating other
232 virtual machines.
234 Within domain~0, a process called \emph{xend} runs to manage the system.
235 \Xend\ is responsible for managing virtual machines and providing access
236 to their consoles. Commands are issued to \xend\ over an HTTP interface,
237 via a command-line tool.
240 \section{History}
242 Xen was originally developed by the Systems Research Group at the
243 University of Cambridge Computer Laboratory as part of the XenoServers
244 project, funded by the UK-EPSRC\@.
246 XenoServers aim to provide a ``public infrastructure for global
247 distributed computing''. Xen plays a key part in that, allowing one to
248 efficiently partition a single machine to enable multiple independent
249 clients to run their operating systems and applications in an
250 environment. This environment provides protection, resource isolation
251 and accounting. The project web page contains further information along
252 with pointers to papers and technical reports:
253 \path{http://www.cl.cam.ac.uk/xeno}
255 Xen has grown into a fully-fledged project in its own right, enabling us
256 to investigate interesting research issues regarding the best techniques
257 for virtualizing resources such as the CPU, memory, disk and network.
258 Project contributors now include XenSource, Intel, IBM, HP, AMD, Novell,
259 RedHat.
261 Xen was first described in a paper presented at SOSP in
262 2003\footnote{\tt
263 http://www.cl.cam.ac.uk/netos/papers/2003-xensosp.pdf}, and the first
264 public release (1.0) was made that October. Since then, Xen has
265 significantly matured and is now used in production scenarios on many
266 sites.
268 \section{What's New}
270 Xen 3.0.0 offers:
272 \begin{itemize}
273 \item Support for up to 32-way SMP guest operating systems
274 \item Intel (Physical Addressing Extensions) PAE to support 32-bit
275 servers with more than 4GB physical memory
276 \item x86/64 support (Intel EM64T, AMD Opteron)
277 \item Intel VT-x support to enable the running of unmodified guest
278 operating systems (Windows XP/2003, Legacy Linux)
279 \item Enhanced control tools
280 \item Improved ACPI support
281 \item AGP/DRM graphics
282 \end{itemize}
285 Xen 3.0 features greatly enhanced hardware support, configuration
286 flexibility, usability and a larger complement of supported operating
287 systems. This latest release takes Xen a step closer to being the
288 definitive open source solution for virtualization.
292 \part{Installation}
294 %% Chapter Basic Installation
295 \chapter{Basic Installation}
297 The Xen distribution includes three main components: Xen itself, ports
298 of Linux and NetBSD to run on Xen, and the userspace tools required to
299 manage a Xen-based system. This chapter describes how to install the
300 Xen~3.0 distribution from source. Alternatively, there may be pre-built
301 packages available as part of your operating system distribution.
304 \section{Prerequisites}
305 \label{sec:prerequisites}
307 The following is a full list of prerequisites. Items marked `$\dag$' are
308 required by the \xend\ control tools, and hence required if you want to
309 run more than one virtual machine; items marked `$*$' are only required
310 if you wish to build from source.
311 \begin{itemize}
312 \item A working Linux distribution using the GRUB bootloader and running
313 on a P6-class or newer CPU\@.
314 \item [$\dag$] The \path{iproute2} package.
315 \item [$\dag$] The Linux bridge-utils\footnote{Available from {\tt
316 http://bridge.sourceforge.net}} (e.g., \path{/sbin/brctl})
317 \item [$\dag$] The Linux hotplug system\footnote{Available from {\tt
318 http://linux-hotplug.sourceforge.net/}} (e.g.,
319 \path{/sbin/hotplug} and related scripts). On newer distributions,
320 this is included alongside the Linux udev system\footnote{See {\tt
321 http://www.kernel.org/pub/linux/utils/kernel/hotplug/udev.html/}}.
322 \item [$*$] Build tools (gcc v3.2.x or v3.3.x, binutils, GNU make).
323 \item [$*$] Development installation of zlib (e.g.,\ zlib-dev).
324 \item [$*$] Development installation of Python v2.2 or later (e.g.,\
325 python-dev).
326 \item [$*$] \LaTeX\ and transfig are required to build the
327 documentation.
328 \end{itemize}
330 Once you have satisfied these prerequisites, you can now install either
331 a binary or source distribution of Xen.
333 \section{Installing from Binary Tarball}
335 Pre-built tarballs are available for download from the XenSource downloads
336 page:
337 \begin{quote} {\tt http://www.xensource.com/downloads/}
338 \end{quote}
340 Once you've downloaded the tarball, simply unpack and install:
341 \begin{verbatim}
342 # tar zxvf xen-3.0-install.tgz
343 # cd xen-3.0-install
344 # sh ./install.sh
345 \end{verbatim}
347 Once you've installed the binaries you need to configure your system as
348 described in Section~\ref{s:configure}.
350 \section{Installing from RPMs}
351 Pre-built RPMs are available for download from the XenSource downloads
352 page:
353 \begin{quote} {\tt http://www.xensource.com/downloads/}
354 \end{quote}
356 Once you've downloaded the RPMs, you typically install them via the
357 RPM commands:
359 \verb|# rpm -iv rpmname|
361 See the instructions and the Release Notes for each RPM set referenced at:
362 \begin{quote}
363 {\tt http://www.xensource.com/downloads/}.
364 \end{quote}
366 \section{Installing from Source}
368 This section describes how to obtain, build and install Xen from source.
370 \subsection{Obtaining the Source}
372 The Xen source tree is available as either a compressed source tarball
373 or as a clone of our master Mercurial repository.
375 \begin{description}
376 \item[Obtaining the Source Tarball]\mbox{} \\
377 Stable versions and daily snapshots of the Xen source tree are
378 available from the Xen download page:
379 \begin{quote} {\tt \tt http://www.xensource.com/downloads/}
380 \end{quote}
381 \item[Obtaining the source via Mercurial]\mbox{} \\
382 The source tree may also be obtained via the public Mercurial
383 repository at:
384 \begin{quote}{\tt http://xenbits.xensource.com}
385 \end{quote} See the instructions and the Getting Started Guide
386 referenced at:
387 \begin{quote}
388 {\tt http://www.xensource.com/downloads/}
389 \end{quote}
390 \end{description}
392 % \section{The distribution}
393 %
394 % The Xen source code repository is structured as follows:
395 %
396 % \begin{description}
397 % \item[\path{tools/}] Xen node controller daemon (Xend), command line
398 % tools, control libraries
399 % \item[\path{xen/}] The Xen VMM.
400 % \item[\path{buildconfigs/}] Build configuration files
401 % \item[\path{linux-*-xen-sparse/}] Xen support for Linux.
402 % \item[\path{patches/}] Experimental patches for Linux.
403 % \item[\path{docs/}] Various documentation files for users and
404 % developers.
405 % \item[\path{extras/}] Bonus extras.
406 % \end{description}
408 \subsection{Building from Source}
410 The top-level Xen Makefile includes a target ``world'' that will do the
411 following:
413 \begin{itemize}
414 \item Build Xen.
415 \item Build the control tools, including \xend.
416 \item Download (if necessary) and unpack the Linux 2.6 source code, and
417 patch it for use with Xen.
418 \item Build a Linux kernel to use in domain~0 and a smaller unprivileged
419 kernel, which can be used for unprivileged virtual machines.
420 \end{itemize}
422 After the build has completed you should have a top-level directory
423 called \path{dist/} in which all resulting targets will be placed. Of
424 particular interest are the two XenLinux kernel images, one with a
425 ``-xen0'' extension which contains hardware device drivers and drivers
426 for Xen's virtual devices, and one with a ``-xenU'' extension that
427 just contains the virtual ones. These are found in
428 \path{dist/install/boot/} along with the image for Xen itself and the
429 configuration files used during the build.
431 %The NetBSD port can be built using:
432 %\begin{quote}
433 %\begin{verbatim}
434 %# make netbsd20
435 %\end{verbatim}\end{quote}
436 %NetBSD port is built using a snapshot of the netbsd-2-0 cvs branch.
437 %The snapshot is downloaded as part of the build process if it is not
438 %yet present in the \path{NETBSD\_SRC\_PATH} search path. The build
439 %process also downloads a toolchain which includes all of the tools
440 %necessary to build the NetBSD kernel under Linux.
442 To customize the set of kernels built you need to edit the top-level
443 Makefile. Look for the line:
444 \begin{quote}
445 \begin{verbatim}
446 KERNELS ?= linux-2.6-xen0 linux-2.6-xenU
447 \end{verbatim}
448 \end{quote}
450 You can edit this line to include any set of operating system kernels
451 which have configurations in the top-level \path{buildconfigs/}
452 directory.
454 %% Inspect the Makefile if you want to see what goes on during a
455 %% build. Building Xen and the tools is straightforward, but XenLinux
456 %% is more complicated. The makefile needs a `pristine' Linux kernel
457 %% tree to which it will then add the Xen architecture files. You can
458 %% tell the makefile the location of the appropriate Linux compressed
459 %% tar file by
460 %% setting the LINUX\_SRC environment variable, e.g. \\
461 %% \verb!# LINUX_SRC=/tmp/linux-2.6.11.tar.bz2 make world! \\ or by
462 %% placing the tar file somewhere in the search path of {\tt
463 %% LINUX\_SRC\_PATH} which defaults to `{\tt .:..}'. If the
464 %% makefile can't find a suitable kernel tar file it attempts to
465 %% download it from kernel.org (this won't work if you're behind a
466 %% firewall).
468 %% After untaring the pristine kernel tree, the makefile uses the {\tt
469 %% mkbuildtree} script to add the Xen patches to the kernel.
471 %% \framebox{\parbox{5in}{
472 %% {\bf Distro specific:} \\
473 %% {\it Gentoo} --- if not using udev (most installations,
474 %% currently), you'll need to enable devfs and devfs mount at boot
475 %% time in the xen0 config. }}
477 \subsection{Custom Kernels}
479 % If you have an SMP machine you may wish to give the {\tt '-j4'}
480 % argument to make to get a parallel build.
482 If you wish to build a customized XenLinux kernel (e.g.\ to support
483 additional devices or enable distribution-required features), you can
484 use the standard Linux configuration mechanisms, specifying that the
485 architecture being built for is \path{xen}, e.g:
486 \begin{quote}
487 \begin{verbatim}
488 # cd linux-2.6.12-xen0
489 # make ARCH=xen xconfig
490 # cd ..
491 # make
492 \end{verbatim}
493 \end{quote}
495 You can also copy an existing Linux configuration (\path{.config}) into
496 e.g.\ \path{linux-2.6.12-xen0} and execute:
497 \begin{quote}
498 \begin{verbatim}
499 # make ARCH=xen oldconfig
500 \end{verbatim}
501 \end{quote}
503 You may be prompted with some Xen-specific options. We advise accepting
504 the defaults for these options.
506 Note that the only difference between the two types of Linux kernels
507 that are built is the configuration file used for each. The ``U''
508 suffixed (unprivileged) versions don't contain any of the physical
509 hardware device drivers, leading to a 30\% reduction in size; hence you
510 may prefer these for your non-privileged domains. The ``0'' suffixed
511 privileged versions can be used to boot the system, as well as in driver
512 domains and unprivileged domains.
514 \subsection{Installing Generated Binaries}
516 The files produced by the build process are stored under the
517 \path{dist/install/} directory. To install them in their default
518 locations, do:
519 \begin{quote}
520 \begin{verbatim}
521 # make install
522 \end{verbatim}
523 \end{quote}
525 Alternatively, users with special installation requirements may wish to
526 install them manually by copying the files to their appropriate
527 destinations.
529 %% Files in \path{install/boot/} include:
530 %% \begin{itemize}
531 %% \item \path{install/boot/xen-3.0.gz} Link to the Xen 'kernel'
532 %% \item \path{install/boot/vmlinuz-2.6-xen0} Link to domain 0
533 %% XenLinux kernel
534 %% \item \path{install/boot/vmlinuz-2.6-xenU} Link to unprivileged
535 %% XenLinux kernel
536 %% \end{itemize}
538 The \path{dist/install/boot} directory will also contain the config
539 files used for building the XenLinux kernels, and also versions of Xen
540 and XenLinux kernels that contain debug symbols such as
541 (\path{xen-syms-3.0.0} and \path{vmlinux-syms-2.6.12.6-xen0}) which are
542 essential for interpreting crash dumps. Retain these files as the
543 developers may wish to see them if you post on the mailing list.
546 \section{Configuration}
547 \label{s:configure}
549 Once you have built and installed the Xen distribution, it is simple to
550 prepare the machine for booting and running Xen.
552 \subsection{GRUB Configuration}
554 An entry should be added to \path{grub.conf} (often found under
555 \path{/boot/} or \path{/boot/grub/}) to allow Xen / XenLinux to boot.
556 This file is sometimes called \path{menu.lst}, depending on your
557 distribution. The entry should look something like the following:
559 %% KMSelf Thu Dec 1 19:06:13 PST 2005 262144 is useful for RHEL/RH and
560 %% related Dom0s.
561 {\small
562 \begin{verbatim}
563 title Xen 3.0 / XenLinux 2.6
564 kernel /boot/xen-3.0.gz dom0_mem=262144
565 module /boot/vmlinuz-2.6-xen0 root=/dev/sda4 ro console=tty0
566 \end{verbatim}
567 }
569 The kernel line tells GRUB where to find Xen itself and what boot
570 parameters should be passed to it (in this case, setting the domain~0
571 memory allocation in kilobytes and the settings for the serial port).
572 For more details on the various Xen boot parameters see
573 Section~\ref{s:xboot}.
575 The module line of the configuration describes the location of the
576 XenLinux kernel that Xen should start and the parameters that should be
577 passed to it. These are standard Linux parameters, identifying the root
578 device and specifying it be initially mounted read only and instructing
579 that console output be sent to the screen. Some distributions such as
580 SuSE do not require the \path{ro} parameter.
582 %% \framebox{\parbox{5in}{
583 %% {\bf Distro specific:} \\
584 %% {\it SuSE} --- Omit the {\tt ro} option from the XenLinux
585 %% kernel command line, since the partition won't be remounted rw
586 %% during boot. }}
588 To use an initrd, add another \path{module} line to the configuration,
589 like: {\small
590 \begin{verbatim}
591 module /boot/my_initrd.gz
592 \end{verbatim}
593 }
595 %% KMSelf Thu Dec 1 19:05:30 PST 2005 Other configs as an appendix?
597 When installing a new kernel, it is recommended that you do not delete
598 existing menu options from \path{menu.lst}, as you may wish to boot your
599 old Linux kernel in future, particularly if you have problems.
601 \subsection{Serial Console (optional)}
603 Serial console access allows you to manage, monitor, and interact with
604 your system over a serial console. This can allow access from another
605 nearby system via a null-modem (``LapLink'') cable or remotely via a serial
606 concentrator.
608 You system's BIOS, bootloader (GRUB), Xen, Linux, and login access must
609 each be individually configured for serial console access. It is
610 \emph{not} strictly necessary to have each component fully functional,
611 but it can be quite useful.
613 For general information on serial console configuration under Linux,
614 refer to the ``Remote Serial Console HOWTO'' at The Linux Documentation
615 Project: \url{http://www.tldp.org}
617 \subsubsection{Serial Console BIOS configuration}
619 Enabling system serial console output neither enables nor disables
620 serial capabilities in GRUB, Xen, or Linux, but may make remote
621 management of your system more convenient by displaying POST and other
622 boot messages over serial port and allowing remote BIOS configuration.
624 Refer to your hardware vendor's documentation for capabilities and
625 procedures to enable BIOS serial redirection.
628 \subsubsection{Serial Console GRUB configuration}
630 Enabling GRUB serial console output neither enables nor disables Xen or
631 Linux serial capabilities, but may made remote management of your system
632 more convenient by displaying GRUB prompts, menus, and actions over
633 serial port and allowing remote GRUB management.
635 Adding the following two lines to your GRUB configuration file,
636 typically either \path{/boot/grub/menu.lst} or \path{/boot/grub/grub.conf}
637 depending on your distro, will enable GRUB serial output.
639 \begin{quote}
640 {\small \begin{verbatim}
641 serial --unit=0 --speed=115200 --word=8 --parity=no --stop=1
642 terminal --timeout=10 serial console
643 \end{verbatim}}
644 \end{quote}
646 Note that when both the serial port and the local monitor and keyboard
647 are enabled, the text ``\emph{Press any key to continue}'' will appear
648 at both. Pressing a key on one device will cause GRUB to display to
649 that device. The other device will see no output. If no key is
650 pressed before the timeout period expires, the system will boot to the
651 default GRUB boot entry.
653 Please refer to the GRUB documentation for further information.
656 \subsubsection{Serial Console Xen configuration}
658 Enabling Xen serial console output neither enables nor disables Linux
659 kernel output or logging in to Linux over serial port. It does however
660 allow you to monitor and log the Xen boot process via serial console and
661 can be very useful in debugging.
663 %% kernel /boot/xen-2.0.gz dom0_mem=131072 console=com1,vga com1=115200,8n1
664 %% module /boot/vmlinuz-2.6-xen0 root=/dev/sda4 ro
666 In order to configure Xen serial console output, it is necessary to
667 add a boot option to your GRUB config; e.g.\ replace the previous
668 example kernel line with:
669 \begin{quote} {\small \begin{verbatim}
670 kernel /boot/xen.gz dom0_mem=131072 com1=115200,8n1
671 \end{verbatim}}
672 \end{quote}
674 This configures Xen to output on COM1 at 115,200 baud, 8 data bits, no
675 parity and 1 stop bit. Modify these parameters for your environment.
676 See Section~\ref{s:xboot} for an explanation of all boot parameters.
678 One can also configure XenLinux to share the serial console; to achieve
679 this append ``\path{console=ttyS0}'' to your module line.
682 \subsubsection{Serial Console Linux configuration}
684 Enabling Linux serial console output at boot neither enables nor
685 disables logging in to Linux over serial port. It does however allow
686 you to monitor and log the Linux boot process via serial console and can be
687 very useful in debugging.
689 To enable Linux output at boot time, add the parameter
690 \path{console=ttyS0} (or ttyS1, ttyS2, etc.) to your kernel GRUB line.
691 Under Xen, this might be:
692 \begin{quote}
693 {\footnotesize \begin{verbatim}
694 module /vmlinuz-2.6-xen0 ro root=/dev/VolGroup00/LogVol00 \
695 console=ttyS0, 115200
696 \end{verbatim}}
697 \end{quote}
698 to enable output over ttyS0 at 115200 baud.
702 \subsubsection{Serial Console Login configuration}
704 Logging in to Linux via serial console, under Xen or otherwise, requires
705 specifying a login prompt be started on the serial port. To permit root
706 logins over serial console, the serial port must be added to
707 \path{/etc/securetty}.
709 \newpage
710 To automatically start a login prompt over the serial port,
711 add the line: \begin{quote} {\small {\tt c:2345:respawn:/sbin/mingetty
712 ttyS0}} \end{quote} to \path{/etc/inittab}. Run \path{init q} to force
713 a reload of your inttab and start getty.
715 To enable root logins, add \path{ttyS0} to \path{/etc/securetty} if not
716 already present.
718 Your distribution may use an alternate getty; options include getty,
719 mgetty and agetty. Consult your distribution's documentation
720 for further information.
723 \subsection{TLS Libraries}
725 Users of the XenLinux 2.6 kernel should disable Thread Local Storage
726 (TLS) (e.g.\ by doing a \path{mv /lib/tls /lib/tls.disabled}) before
727 attempting to boot a XenLinux kernel\footnote{If you boot without first
728 disabling TLS, you will get a warning message during the boot process.
729 In this case, simply perform the rename after the machine is up and
730 then run \path{/sbin/ldconfig} to make it take effect.}. You can
731 always reenable TLS by restoring the directory to its original location
732 (i.e.\ \path{mv /lib/tls.disabled /lib/tls}).
734 The reason for this is that the current TLS implementation uses
735 segmentation in a way that is not permissible under Xen. If TLS is not
736 disabled, an emulation mode is used within Xen which reduces performance
737 substantially. To ensure full performance you should install a
738 `Xen-friendly' (nosegneg) version of the library.
741 \section{Booting Xen}
743 It should now be possible to restart the system and use Xen. Reboot and
744 choose the new Xen option when the Grub screen appears.
746 What follows should look much like a conventional Linux boot. The first
747 portion of the output comes from Xen itself, supplying low level
748 information about itself and the underlying hardware. The last portion
749 of the output comes from XenLinux.
751 You may see some error messages during the XenLinux boot. These are not
752 necessarily anything to worry about---they may result from kernel
753 configuration differences between your XenLinux kernel and the one you
754 usually use.
756 When the boot completes, you should be able to log into your system as
757 usual. If you are unable to log in, you should still be able to reboot
758 with your normal Linux kernel by selecting it at the GRUB prompt.
761 % Booting Xen
762 \chapter{Booting a Xen System}
764 Booting the system into Xen will bring you up into the privileged
765 management domain, Domain0. At that point you are ready to create
766 guest domains and ``boot'' them using the \texttt{xm create} command.
768 \section{Booting Domain0}
770 After installation and configuration is complete, reboot the system
771 and and choose the new Xen option when the Grub screen appears.
773 What follows should look much like a conventional Linux boot. The
774 first portion of the output comes from Xen itself, supplying low level
775 information about itself and the underlying hardware. The last
776 portion of the output comes from XenLinux.
778 %% KMSelf Wed Nov 30 18:09:37 PST 2005: We should specify what these are.
780 When the boot completes, you should be able to log into your system as
781 usual. If you are unable to log in, you should still be able to
782 reboot with your normal Linux kernel by selecting it at the GRUB prompt.
784 The first step in creating a new domain is to prepare a root
785 filesystem for it to boot. Typically, this might be stored in a normal
786 partition, an LVM or other volume manager partition, a disk file or on
787 an NFS server. A simple way to do this is simply to boot from your
788 standard OS install CD and install the distribution into another
789 partition on your hard drive.
791 To start the \xend\ control daemon, type
792 \begin{quote}
793 \verb!# xend start!
794 \end{quote}
796 If you wish the daemon to start automatically, see the instructions in
797 Section~\ref{s:xend}. Once the daemon is running, you can use the
798 \path{xm} tool to monitor and maintain the domains running on your
799 system. This chapter provides only a brief tutorial. We provide full
800 details of the \path{xm} tool in the next chapter.
802 % \section{From the web interface}
803 %
804 % Boot the Xen machine and start Xensv (see Chapter~\ref{cha:xensv}
805 % for more details) using the command: \\
806 % \verb_# xensv start_ \\
807 % This will also start Xend (see Chapter~\ref{cha:xend} for more
808 % information).
809 %
810 % The domain management interface will then be available at {\tt
811 % http://your\_machine:8080/}. This provides a user friendly wizard
812 % for starting domains and functions for managing running domains.
813 %
814 % \section{From the command line}
815 \section{Booting Guest Domains}
817 \subsection{Creating a Domain Configuration File}
819 Before you can start an additional domain, you must create a
820 configuration file. We provide two example files which you can use as
821 a starting point:
822 \begin{itemize}
823 \item \path{/etc/xen/xmexample1} is a simple template configuration
824 file for describing a single VM\@.
825 \item \path{/etc/xen/xmexample2} file is a template description that
826 is intended to be reused for multiple virtual machines. Setting the
827 value of the \path{vmid} variable on the \path{xm} command line
828 fills in parts of this template.
829 \end{itemize}
831 There are also a number of other examples which you may find useful.
832 Copy one of these files and edit it as appropriate. Typical values
833 you may wish to edit include:
835 \begin{quote}
836 \begin{description}
837 \item[kernel] Set this to the path of the kernel you compiled for use
838 with Xen (e.g.\ \path{kernel = ``/boot/vmlinuz-2.6-xenU''})
839 \item[memory] Set this to the size of the domain's memory in megabytes
840 (e.g.\ \path{memory = 64})
841 \item[disk] Set the first entry in this list to calculate the offset
842 of the domain's root partition, based on the domain ID\@. Set the
843 second to the location of \path{/usr} if you are sharing it between
844 domains (e.g.\ \path{disk = ['phy:your\_hard\_drive\%d,sda1,w' \%
845 (base\_partition\_number + vmid),
846 'phy:your\_usr\_partition,sda6,r' ]}
847 \item[dhcp] Uncomment the dhcp variable, so that the domain will
848 receive its IP address from a DHCP server (e.g.\ \path{dhcp=``dhcp''})
849 \end{description}
850 \end{quote}
852 You may also want to edit the {\bf vif} variable in order to choose
853 the MAC address of the virtual ethernet interface yourself. For
854 example:
856 \begin{quote}
857 \verb_vif = ['mac=00:16:3E:F6:BB:B3']_
858 \end{quote}
859 If you do not set this variable, \xend\ will automatically generate a
860 random MAC address from the range 00:16:3E:xx:xx:xx, assigned by IEEE to
861 XenSource as an OUI (organizationally unique identifier). XenSource
862 Inc. gives permission for anyone to use addresses randomly allocated
863 from this range for use by their Xen domains.
865 For a list of IEEE OUI assignments, see
866 \url{http://standards.ieee.org/regauth/oui/oui.txt}
869 \subsection{Booting the Guest Domain}
871 The \path{xm} tool provides a variety of commands for managing
872 domains. Use the \path{create} command to start new domains. Assuming
873 you've created a configuration file \path{myvmconf} based around
874 \path{/etc/xen/xmexample2}, to start a domain with virtual machine
875 ID~1 you should type:
877 \begin{quote}
878 \begin{verbatim}
879 # xm create -c myvmconf vmid=1
880 \end{verbatim}
881 \end{quote}
883 The \path{-c} switch causes \path{xm} to turn into the domain's
884 console after creation. The \path{vmid=1} sets the \path{vmid}
885 variable used in the \path{myvmconf} file.
887 You should see the console boot messages from the new domain appearing
888 in the terminal in which you typed the command, culminating in a login
889 prompt.
892 \section{Starting / Stopping Domains Automatically}
894 It is possible to have certain domains start automatically at boot
895 time and to have dom0 wait for all running domains to shutdown before
896 it shuts down the system.
898 To specify a domain is to start at boot-time, place its configuration
899 file (or a link to it) under \path{/etc/xen/auto/}.
901 A Sys-V style init script for Red Hat and LSB-compliant systems is
902 provided and will be automatically copied to \path{/etc/init.d/}
903 during install. You can then enable it in the appropriate way for
904 your distribution.
906 For instance, on Red Hat:
908 \begin{quote}
909 \verb_# chkconfig --add xendomains_
910 \end{quote}
912 By default, this will start the boot-time domains in runlevels 3, 4
913 and 5.
915 You can also use the \path{service} command to run this script
916 manually, e.g:
918 \begin{quote}
919 \verb_# service xendomains start_
921 Starts all the domains with config files under /etc/xen/auto/.
922 \end{quote}
924 \begin{quote}
925 \verb_# service xendomains stop_
927 Shuts down all running Xen domains.
928 \end{quote}
932 \part{Configuration and Management}
934 %% Chapter Domain Management Tools and Daemons
935 \chapter{Domain Management Tools}
937 This chapter summarizes the management software and tools available.
940 \section{\Xend\ }
941 \label{s:xend}
944 The \Xend\ node control daemon performs system management functions
945 related to virtual machines. It forms a central point of control of
946 virtualized resources, and must be running in order to start and manage
947 virtual machines. \Xend\ must be run as root because it needs access to
948 privileged system management functions.
950 An initialization script named \texttt{/etc/init.d/xend} is provided to
951 start \Xend\ at boot time. Use the tool appropriate (i.e. chkconfig) for
952 your Linux distribution to specify the runlevels at which this script
953 should be executed, or manually create symbolic links in the correct
954 runlevel directories.
956 \Xend\ can be started on the command line as well, and supports the
957 following set of parameters:
959 \begin{tabular}{ll}
960 \verb!# xend start! & start \xend, if not already running \\
961 \verb!# xend stop! & stop \xend\ if already running \\
962 \verb!# xend restart! & restart \xend\ if running, otherwise start it \\
963 % \verb!# xend trace_start! & start \xend, with very detailed debug logging \\
964 \verb!# xend status! & indicates \xend\ status by its return code
965 \end{tabular}
967 A SysV init script called {\tt xend} is provided to start \xend\ at
968 boot time. {\tt make install} installs this script in
969 \path{/etc/init.d}. To enable it, you have to make symbolic links in
970 the appropriate runlevel directories or use the {\tt chkconfig} tool,
971 where available. Once \xend\ is running, administration can be done
972 using the \texttt{xm} tool.
974 \subsection{Logging}
976 As \xend\ runs, events will be logged to \path{/var/log/xend.log} and
977 (less frequently) to \path{/var/log/xend-debug.log}. These, along with
978 the standard syslog files, are useful when troubleshooting problems.
980 \subsection{Configuring \Xend\ }
982 \Xend\ is written in Python. At startup, it reads its configuration
983 information from the file \path{/etc/xen/xend-config.sxp}. The Xen
984 installation places an example \texttt{xend-config.sxp} file in the
985 \texttt{/etc/xen} subdirectory which should work for most installations.
987 See the example configuration file \texttt{xend-debug.sxp} and the
988 section 5 man page \texttt{xend-config.sxp} for a full list of
989 parameters and more detailed information. Some of the most important
990 parameters are discussed below.
992 An HTTP interface and a Unix domain socket API are available to
993 communicate with \Xend. This allows remote users to pass commands to the
994 daemon. By default, \Xend does not start an HTTP server. It does start a
995 Unix domain socket management server, as the low level utility
996 \texttt{xm} requires it. For support of cross-machine migration, \Xend\
997 can start a relocation server. This support is not enabled by default
998 for security reasons.
1000 Note: the example \texttt{xend} configuration file modifies the defaults and
1001 starts up \Xend\ as an HTTP server as well as a relocation server.
1003 From the file:
1005 \begin{verbatim}
1006 #(xend-http-server no)
1007 (xend-http-server yes)
1008 #(xend-unix-server yes)
1009 #(xend-relocation-server no)
1010 (xend-relocation-server yes)
1011 \end{verbatim}
1013 Comment or uncomment lines in that file to disable or enable features
1014 that you require.
1016 Connections from remote hosts are disabled by default:
1018 \begin{verbatim}
1019 # Address xend should listen on for HTTP connections, if xend-http-server is
1020 # set.
1021 # Specifying 'localhost' prevents remote connections.
1022 # Specifying the empty string '' (the default) allows all connections.
1023 #(xend-address '')
1024 (xend-address localhost)
1025 \end{verbatim}
1027 It is recommended that if migration support is not needed, the
1028 \texttt{xend-relocation-server} parameter value be changed to
1029 ``\texttt{no}'' or commented out.
1031 \section{Xm}
1032 \label{s:xm}
1034 The xm tool is the primary tool for managing Xen from the console. The
1035 general format of an xm command line is:
1037 \begin{verbatim}
1038 # xm command [switches] [arguments] [variables]
1039 \end{verbatim}
1041 The available \emph{switches} and \emph{arguments} are dependent on the
1042 \emph{command} chosen. The \emph{variables} may be set using
1043 declarations of the form {\tt variable=value} and command line
1044 declarations override any of the values in the configuration file being
1045 used, including the standard variables described above and any custom
1046 variables (for instance, the \path{xmdefconfig} file uses a {\tt vmid}
1047 variable).
1049 For online help for the commands available, type:
1051 \begin{quote}
1052 \begin{verbatim}
1053 # xm help
1054 \end{verbatim}
1055 \end{quote}
1057 This will list the most commonly used commands. The full list can be obtained
1058 using \verb_xm help --long_. You can also type \path{xm help $<$command$>$}
1059 for more information on a given command.
1061 \subsection{Basic Management Commands}
1063 One useful command is \verb_# xm list_ which lists all domains running in rows
1064 of the following format:
1065 \begin{center} {\tt name domid memory vcpus state cputime}
1066 \end{center}
1068 The meaning of each field is as follows:
1069 \begin{quote}
1070 \begin{description}
1071 \item[name] The descriptive name of the virtual machine.
1072 \item[domid] The number of the domain ID this virtual machine is
1073 running in.
1074 \item[memory] Memory size in megabytes.
1075 \item[vcpus] The number of virtual CPUs this domain has.
1076 \item[state] Domain state consists of 5 fields:
1077 \begin{description}
1078 \item[r] running
1079 \item[b] blocked
1080 \item[p] paused
1081 \item[s] shutdown
1082 \item[c] crashed
1083 \end{description}
1084 \item[cputime] How much CPU time (in seconds) the domain has used so
1085 far.
1086 \end{description}
1087 \end{quote}
1089 The \path{xm list} command also supports a long output format when the
1090 \path{-l} switch is used. This outputs the full details of the
1091 running domains in \xend's SXP configuration format.
1094 You can get access to the console of a particular domain using
1095 the \verb_# xm console_ command (e.g.\ \verb_# xm console myVM_).
1097 \subsection{Domain Scheduling Management Commands}
1099 The credit CPU scheduler automatically load balances guest VCPUs
1100 across all available physical CPUs on an SMP host. The user need
1101 not manually pin VCPUs to load balance the system. However, she
1102 can restrict which CPUs a particular VCPU may run on using
1103 the \path{xm vcpu-pin} command.
1105 Each guest domain is assigned a \path{weight} and a \path{cap}.
1107 A domain with a weight of 512 will get twice as much CPU as a
1108 domain with a weight of 256 on a contended host. Legal weights
1109 range from 1 to 65535 and the default is 256.
1111 The cap optionally fixes the maximum amount of CPU a guest will
1112 be able to consume, even if the host system has idle CPU cycles.
1113 The cap is expressed in percentage of one physical CPU: 100 is
1114 1 physical CPU, 50 is half a CPU, 400 is 4 CPUs, etc... The
1115 default, 0, means there is no upper cap.
1117 When you are running with the credit scheduler, you can check and
1118 modify your domains' weights and caps using the \path{xm sched-credit}
1119 command:
1121 \begin{tabular}{ll}
1122 \verb!xm sched-credit -d <domain>! & lists weight and cap \\
1123 \verb!xm sched-credit -d <domain> -w <weight>! & sets the weight \\
1124 \verb!xm sched-credit -d <domain> -c <cap>! & sets the cap
1125 \end{tabular}
1129 %% Chapter Domain Configuration
1130 \chapter{Domain Configuration}
1131 \label{cha:config}
1133 The following contains the syntax of the domain configuration files
1134 and description of how to further specify networking, driver domain
1135 and general scheduling behavior.
1138 \section{Configuration Files}
1139 \label{s:cfiles}
1141 Xen configuration files contain the following standard variables.
1142 Unless otherwise stated, configuration items should be enclosed in
1143 quotes: see the configuration scripts in \path{/etc/xen/}
1144 for concrete examples.
1146 \begin{description}
1147 \item[kernel] Path to the kernel image.
1148 \item[ramdisk] Path to a ramdisk image (optional).
1149 % \item[builder] The name of the domain build function (e.g.
1150 % {\tt'linux'} or {\tt'netbsd'}.
1151 \item[memory] Memory size in megabytes.
1152 \item[vcpus] The number of virtual CPUs.
1153 \item[console] Port to export the domain console on (default 9600 +
1154 domain ID).
1155 \item[vif] Network interface configuration. This may simply contain
1156 an empty string for each desired interface, or may override various
1157 settings, e.g.\
1158 \begin{verbatim}
1159 vif = [ 'mac=00:16:3E:00:00:11, bridge=xen-br0',
1160 'bridge=xen-br1' ]
1161 \end{verbatim}
1162 to assign a MAC address and bridge to the first interface and assign
1163 a different bridge to the second interface, leaving \xend\ to choose
1164 the MAC address. The settings that may be overridden in this way are
1165 type, mac, bridge, ip, script, backend, and vifname.
1166 \item[disk] List of block devices to export to the domain e.g.
1167 \verb_disk = [ 'phy:hda1,sda1,r' ]_
1168 exports physical device \path{/dev/hda1} to the domain as
1169 \path{/dev/sda1} with read-only access. Exporting a disk read-write
1170 which is currently mounted is dangerous -- if you are \emph{certain}
1171 you wish to do this, you can specify \path{w!} as the mode.
1172 \item[dhcp] Set to {\tt `dhcp'} if you want to use DHCP to configure
1173 networking.
1174 \item[netmask] Manually configured IP netmask.
1175 \item[gateway] Manually configured IP gateway.
1176 \item[hostname] Set the hostname for the virtual machine.
1177 \item[root] Specify the root device parameter on the kernel command
1178 line.
1179 \item[nfs\_server] IP address for the NFS server (if any).
1180 \item[nfs\_root] Path of the root filesystem on the NFS server (if
1181 any).
1182 \item[extra] Extra string to append to the kernel command line (if
1183 any)
1184 \end{description}
1186 Additional fields are documented in the example configuration files
1187 (e.g. to configure virtual TPM functionality).
1189 For additional flexibility, it is also possible to include Python
1190 scripting commands in configuration files. An example of this is the
1191 \path{xmexample2} file, which uses Python code to handle the
1192 \path{vmid} variable.
1195 %\part{Advanced Topics}
1198 \section{Network Configuration}
1200 For many users, the default installation should work ``out of the
1201 box''. More complicated network setups, for instance with multiple
1202 Ethernet interfaces and/or existing bridging setups will require some
1203 special configuration.
1205 The purpose of this section is to describe the mechanisms provided by
1206 \xend\ to allow a flexible configuration for Xen's virtual networking.
1208 \subsection{Xen virtual network topology}
1210 Each domain network interface is connected to a virtual network
1211 interface in dom0 by a point to point link (effectively a ``virtual
1212 crossover cable''). These devices are named {\tt
1213 vif$<$domid$>$.$<$vifid$>$} (e.g.\ {\tt vif1.0} for the first
1214 interface in domain~1, {\tt vif3.1} for the second interface in
1215 domain~3).
1217 Traffic on these virtual interfaces is handled in domain~0 using
1218 standard Linux mechanisms for bridging, routing, rate limiting, etc.
1219 Xend calls on two shell scripts to perform initial configuration of
1220 the network and configuration of new virtual interfaces. By default,
1221 these scripts configure a single bridge for all the virtual
1222 interfaces. Arbitrary routing / bridging configurations can be
1223 configured by customizing the scripts, as described in the following
1224 section.
1226 \subsection{Xen networking scripts}
1228 Xen's virtual networking is configured by two shell scripts (by
1229 default \path{network-bridge} and \path{vif-bridge}). These are called
1230 automatically by \xend\ when certain events occur, with arguments to
1231 the scripts providing further contextual information. These scripts
1232 are found by default in \path{/etc/xen/scripts}. The names and
1233 locations of the scripts can be configured in
1234 \path{/etc/xen/xend-config.sxp}.
1236 \begin{description}
1237 \item[network-bridge:] This script is called whenever \xend\ is started or
1238 stopped to respectively initialize or tear down the Xen virtual
1239 network. In the default configuration initialization creates the
1240 bridge `xen-br0' and moves eth0 onto that bridge, modifying the
1241 routing accordingly. When \xend\ exits, it deletes the Xen bridge
1242 and removes eth0, restoring the normal IP and routing configuration.
1244 %% In configurations where the bridge already exists, this script
1245 %% could be replaced with a link to \path{/bin/true} (for instance).
1247 \item[vif-bridge:] This script is called for every domain virtual
1248 interface and can configure firewalling rules and add the vif to the
1249 appropriate bridge. By default, this adds and removes VIFs on the
1250 default Xen bridge.
1251 \end{description}
1253 Other example scripts are available (\path{network-route} and
1254 \path{vif-route}, \path{network-nat} and \path{vif-nat}).
1255 For more complex network setups (e.g.\ where routing is required or
1256 integrate with existing bridges) these scripts may be replaced with
1257 customized variants for your site's preferred configuration.
1259 \section{Driver Domain Configuration}
1260 \label{s:ddconf}
1262 \subsection{PCI}
1263 \label{ss:pcidd}
1265 Individual PCI devices can be assigned to a given domain (a PCI driver domain)
1266 to allow that domain direct access to the PCI hardware.
1268 While PCI Driver Domains can increase the stability and security of a system
1269 by addressing a number of security concerns, there are some security issues
1270 that remain that you can read about in Section~\ref{s:ddsecurity}.
1272 \subsubsection{Compile-Time Setup}
1273 To use this functionality, ensure
1274 that the PCI Backend is compiled in to a privileged domain (e.g. domain 0)
1275 and that the domains which will be assigned PCI devices have the PCI Frontend
1276 compiled in. In XenLinux, the PCI Backend is available under the Xen
1277 configuration section while the PCI Frontend is under the
1278 architecture-specific "Bus Options" section. You may compile both the backend
1279 and the frontend into the same kernel; they will not affect each other.
1281 \subsubsection{PCI Backend Configuration - Binding at Boot}
1282 The PCI devices you wish to assign to unprivileged domains must be "hidden"
1283 from your backend domain (usually domain 0) so that it does not load a driver
1284 for them. Use the \path{pciback.hide} kernel parameter which is specified on
1285 the kernel command-line and is configurable through GRUB (see
1286 Section~\ref{s:configure}). Note that devices are not really hidden from the
1287 backend domain. The PCI Backend appears to the Linux kernel as a regular PCI
1288 device driver. The PCI Backend ensures that no other device driver loads
1289 for the devices by binding itself as the device driver for those devices.
1290 PCI devices are identified by hexadecimal slot/funciton numbers (on Linux,
1291 use \path{lspci} to determine slot/funciton numbers of your devices) and
1292 can be specified with or without the PCI domain: \\
1293 \centerline{ {\tt ({\em bus}:{\em slot}.{\em func})} example {\tt (02:1d.3)}} \\
1294 \centerline{ {\tt ({\em domain}:{\em bus}:{\em slot}.{\em func})} example {\tt (0000:02:1d.3)}} \\
1296 An example kernel command-line which hides two PCI devices might be: \\
1297 \centerline{ {\tt root=/dev/sda4 ro console=tty0 pciback.hide=(02:01.f)(0000:04:1d.0) } } \\
1299 \subsubsection{PCI Backend Configuration - Late Binding}
1300 PCI devices can also be bound to the PCI Backend after boot through the manual
1301 binding/unbinding facilities provided by the Linux kernel in sysfs (allowing
1302 for a Xen user to give PCI devices to driver domains that were not specified
1303 on the kernel command-line). There are several attributes with the PCI
1304 Backend's sysfs directory (\path{/sys/bus/pci/drivers/pciback}) that can be
1305 used to bind/unbind devices:
1307 \begin{description}
1308 \item[slots] lists all of the PCI slots that the PCI Backend will try to seize
1309 (or "hide" from Domain 0). A PCI slot must appear in this list before it can
1310 be bound to the PCI Backend through the \path{bind} attribute.
1311 \item[new\_slot] write the name of a slot here (in 0000:00:00.0 format) to
1312 have the PCI Backend seize the device in this slot.
1313 \item[remove\_slot] write the name of a slot here (same format as
1314 \path{new\_slot}) to have the PCI Backend no longer try to seize devices in
1315 this slot. Note that this does not unbind the driver from a device it has
1316 already seized.
1317 \item[bind] write the name of a slot here (in 0000:00:00.0 format) to have
1318 the Linux kernel attempt to bind the device in that slot to the PCI Backend
1319 driver.
1320 \item[unbind] write the name of a skit here (same format as \path{bind}) to have
1321 the Linux kernel unbind the device from the PCI Backend. DO NOT unbind a
1322 device while it is currently given to a PCI driver domain!
1323 \end{description}
1325 Some examples:
1327 Bind a device to the PCI Backend which is not bound to any other driver.
1328 \begin{verbatim}
1329 # # Add a new slot to the PCI Backend's list
1330 # echo -n 0000:01:04.d > /sys/bus/pci/drivers/pciback/new_slot
1331 # # Now that the backend is watching for the slot, bind to it
1332 # echo -n 0000:01:04.d > /sys/bus/pci/drivers/pciback/bind
1333 \end{verbatim}
1335 Unbind a device from its driver and bind to the PCI Backend.
1336 \begin{verbatim}
1337 # # Unbind a PCI network card from its network driver
1338 # echo -n 0000:05:02.0 > /sys/bus/pci/drivers/3c905/unbind
1339 # # And now bind it to the PCI Backend
1340 # echo -n 0000:05:02.0 > /sys/bus/pci/drivers/pciback/new_slot
1341 # echo -n 0000:05:02.0 > /sys/bus/pci/drivers/pciback/bind
1342 \end{verbatim}
1344 Note that the "-n" option in the example is important as it causes echo to not
1345 output a new-line.
1347 \subsubsection{PCI Frontend Configuration}
1348 To configure a domU to receive a PCI device:
1350 \begin{description}
1351 \item[Command-line:]
1352 Use the {\em pci} command-line flag. For multiple devices, use the option
1353 multiple times. \\
1354 \centerline{ {\tt xm create netcard-dd pci=01:00.0 pci=02:03.0 }} \\
1356 \item[Flat Format configuration file:]
1357 Specify all of your PCI devices in a python list named {\em pci}. \\
1358 \centerline{ {\tt pci=['01:00.0','02:03.0'] }} \\
1360 \item[SXP Format configuration file:]
1361 Use a single PCI device section for all of your devices (specify the numbers
1362 in hexadecimal with the preceding '0x'). Note that {\em domain} here refers
1363 to the PCI domain, not a virtual machine within Xen.
1364 {\small
1365 \begin{verbatim}
1366 (device (pci
1367 (dev (domain 0x0)(bus 0x3)(slot 0x1a)(func 0x1)
1368 (dev (domain 0x0)(bus 0x1)(slot 0x5)(func 0x0)
1370 \end{verbatim}
1372 \end{description}
1374 %% There are two possible types of privileges: IO privileges and
1375 %% administration privileges.
1377 \section{Support for virtual Trusted Platform Module (vTPM)}
1378 \label{ss:vtpm}
1380 Paravirtualized domains can be given access to a virtualized version
1381 of a TPM. This enables applications in these domains to use the services
1382 of the TPM device for example through a TSS stack
1383 \footnote{Trousers TSS stack: http://sourceforge.net/projects/trousers}.
1384 The Xen source repository provides the necessary software components to
1385 enable virtual TPM access. Support is provided through several
1386 different pieces. First, a TPM emulator has been modified to provide TPM's
1387 functionality for the virtual TPM subsystem. Second, a virtual TPM Manager
1388 coordinates the virtual TPMs efforts, manages their creation, and provides
1389 protected key storage using the TPM. Third, a device driver pair providing
1390 a TPM front- and backend is available for XenLinux to deliver TPM commands
1391 from the domain to the virtual TPM manager, which dispatches it to a
1392 software TPM. Since the TPM Manager relies on a HW TPM for protected key
1393 storage, therefore this subsystem requires a Linux-supported hardware TPM.
1394 For development purposes, a TPM emulator is available for use on non-TPM
1395 enabled platforms.
1397 \subsubsection{Compile-Time Setup}
1398 To enable access to the virtual TPM, the virtual TPM backend driver must
1399 be compiled for a privileged domain (e.g. domain 0). Using the XenLinux
1400 configuration, the necessary driver can be selected in the Xen configuration
1401 section. Unless the driver has been compiled into the kernel, its module
1402 must be activated using the following command:
1404 \begin{verbatim}
1405 modprobe tpmbk
1406 \end{verbatim}
1408 Similarly, the TPM frontend driver must be compiled for the kernel trying
1409 to use TPM functionality. Its driver can be selected in the kernel
1410 configuration section Device Driver / Character Devices / TPM Devices.
1411 Along with that the TPM driver for the built-in TPM must be selected.
1412 If the virtual TPM driver has been compiled as module, it
1413 must be activated using the following command:
1415 \begin{verbatim}
1416 modprobe tpm_xenu
1417 \end{verbatim}
1419 Furthermore, it is necessary to build the virtual TPM manager and software
1420 TPM by making changes to entries in Xen build configuration files.
1421 The following entry in the file Config.mk in the Xen root source
1422 directory must be made:
1424 \begin{verbatim}
1425 VTPM_TOOLS ?= y
1426 \end{verbatim}
1428 After a build of the Xen tree and a reboot of the machine, the TPM backend
1429 drive must be loaded. Once loaded, the virtual TPM manager daemon
1430 must be started before TPM-enabled guest domains may be launched.
1431 To enable being the destination of a virtual TPM Migration, the virtual TPM
1432 migration daemon must also be loaded.
1434 \begin{verbatim}
1435 vtpm_managerd
1436 \end{verbatim}
1437 \begin{verbatim}
1438 vtpm_migratord
1439 \end{verbatim}
1441 Once the VTPM manager is running, the VTPM can be accessed by loading the
1442 front end driver in a guest domain.
1444 \subsubsection{Development and Testing TPM Emulator}
1445 For development and testing on non-TPM enabled platforms, a TPM emulator
1446 can be used in replacement of a platform TPM. First, the entry in the file
1447 tools/vtpm/Rules.mk must look as follows:
1449 \begin{verbatim}
1450 BUILD_EMULATOR = y
1451 \end{verbatim}
1453 Second, the entry in the file tool/vtpm\_manager/Rules.mk must be uncommented
1454 as follows:
1456 \begin{verbatim}
1457 # TCS talks to fifo's rather than /dev/tpm. TPM Emulator assumed on fifos
1458 CFLAGS += -DDUMMY_TPM
1459 \end{verbatim}
1461 Before starting the virtual TPM Manager, start the emulator by executing
1462 the following in dom0:
1464 \begin{verbatim}
1465 tpm_emulator clear
1466 \end{verbatim}
1468 \subsubsection{vTPM Frontend Configuration}
1469 To provide TPM functionality to a user domain, a line must be added to
1470 the virtual TPM configuration file using the following format:
1472 \begin{verbatim}
1473 vtpm = ['instance=<instance number>, backend=<domain id>']
1474 \end{verbatim}
1476 The { \it instance number} reflects the preferred virtual TPM instance
1477 to associate with the domain. If the selected instance is
1478 already associated with another domain, the system will automatically
1479 select the next available instance. An instance number greater than
1480 zero must be provided. It is possible to omit the instance
1481 parameter from the configuration file.
1483 The {\it domain id} provides the ID of the domain where the
1484 virtual TPM backend driver and virtual TPM are running in. It should
1485 currently always be set to '0'.
1488 Examples for valid vtpm entries in the configuration file are
1490 \begin{verbatim}
1491 vtpm = ['instance=1, backend=0']
1492 \end{verbatim}
1493 and
1494 \begin{verbatim}
1495 vtpm = ['backend=0'].
1496 \end{verbatim}
1498 \subsubsection{Using the virtual TPM}
1500 Access to TPM functionality is provided by the virtual TPM frontend driver.
1501 Similar to existing hardware TPM drivers, this driver provides basic TPM
1502 status information through the {\it sysfs} filesystem. In a Xen user domain
1503 the sysfs entries can be found in /sys/devices/xen/vtpm-0.
1505 Commands can be sent to the virtual TPM instance using the character
1506 device /dev/tpm0 (major 10, minor 224).
1508 % Chapter Storage and FileSytem Management
1509 \chapter{Storage and File System Management}
1511 Storage can be made available to virtual machines in a number of
1512 different ways. This chapter covers some possible configurations.
1514 The most straightforward method is to export a physical block device (a
1515 hard drive or partition) from dom0 directly to the guest domain as a
1516 virtual block device (VBD).
1518 Storage may also be exported from a filesystem image or a partitioned
1519 filesystem image as a \emph{file-backed VBD}.
1521 Finally, standard network storage protocols such as NBD, iSCSI, NFS,
1522 etc., can be used to provide storage to virtual machines.
1525 \section{Exporting Physical Devices as VBDs}
1526 \label{s:exporting-physical-devices-as-vbds}
1528 One of the simplest configurations is to directly export individual
1529 partitions from domain~0 to other domains. To achieve this use the
1530 \path{phy:} specifier in your domain configuration file. For example a
1531 line like
1532 \begin{quote}
1533 \verb_disk = ['phy:hda3,sda1,w']_
1534 \end{quote}
1535 specifies that the partition \path{/dev/hda3} in domain~0 should be
1536 exported read-write to the new domain as \path{/dev/sda1}; one could
1537 equally well export it as \path{/dev/hda} or \path{/dev/sdb5} should
1538 one wish.
1540 In addition to local disks and partitions, it is possible to export
1541 any device that Linux considers to be ``a disk'' in the same manner.
1542 For example, if you have iSCSI disks or GNBD volumes imported into
1543 domain~0 you can export these to other domains using the \path{phy:}
1544 disk syntax. E.g.:
1545 \begin{quote}
1546 \verb_disk = ['phy:vg/lvm1,sda2,w']_
1547 \end{quote}
1549 \begin{center}
1550 \framebox{\bf Warning: Block device sharing}
1551 \end{center}
1552 \begin{quote}
1553 Block devices should typically only be shared between domains in a
1554 read-only fashion otherwise the Linux kernel's file systems will get
1555 very confused as the file system structure may change underneath
1556 them (having the same ext3 partition mounted \path{rw} twice is a
1557 sure fire way to cause irreparable damage)! \Xend\ will attempt to
1558 prevent you from doing this by checking that the device is not
1559 mounted read-write in domain~0, and hasn't already been exported
1560 read-write to another domain. If you want read-write sharing,
1561 export the directory to other domains via NFS from domain~0 (or use
1562 a cluster file system such as GFS or ocfs2).
1563 \end{quote}
1566 \section{Using File-backed VBDs}
1568 It is also possible to use a file in Domain~0 as the primary storage
1569 for a virtual machine. As well as being convenient, this also has the
1570 advantage that the virtual block device will be \emph{sparse} ---
1571 space will only really be allocated as parts of the file are used. So
1572 if a virtual machine uses only half of its disk space then the file
1573 really takes up half of the size allocated.
1575 For example, to create a 2GB sparse file-backed virtual block device
1576 (actually only consumes 1KB of disk):
1577 \begin{quote}
1578 \verb_# dd if=/dev/zero of=vm1disk bs=1k seek=2048k count=1_
1579 \end{quote}
1581 Make a file system in the disk file:
1582 \begin{quote}
1583 \verb_# mkfs -t ext3 vm1disk_
1584 \end{quote}
1586 (when the tool asks for confirmation, answer `y')
1588 Populate the file system e.g.\ by copying from the current root:
1589 \begin{quote}
1590 \begin{verbatim}
1591 # mount -o loop vm1disk /mnt
1592 # cp -ax /{root,dev,var,etc,usr,bin,sbin,lib} /mnt
1593 # mkdir /mnt/{proc,sys,home,tmp}
1594 \end{verbatim}
1595 \end{quote}
1597 Tailor the file system by editing \path{/etc/fstab},
1598 \path{/etc/hostname}, etc.\ Don't forget to edit the files in the
1599 mounted file system, instead of your domain~0 filesystem, e.g.\ you
1600 would edit \path{/mnt/etc/fstab} instead of \path{/etc/fstab}. For
1601 this example put \path{/dev/sda1} to root in fstab.
1603 Now unmount (this is important!):
1604 \begin{quote}
1605 \verb_# umount /mnt_
1606 \end{quote}
1608 In the configuration file set:
1609 \begin{quote}
1610 \verb_disk = ['file:/full/path/to/vm1disk,sda1,w']_
1611 \end{quote}
1613 As the virtual machine writes to its `disk', the sparse file will be
1614 filled in and consume more space up to the original 2GB.
1616 {\bf Note that file-backed VBDs may not be appropriate for backing
1617 I/O-intensive domains.} File-backed VBDs are known to experience
1618 substantial slowdowns under heavy I/O workloads, due to the I/O
1619 handling by the loopback block device used to support file-backed VBDs
1620 in dom0. Better I/O performance can be achieved by using either
1621 LVM-backed VBDs (Section~\ref{s:using-lvm-backed-vbds}) or physical
1622 devices as VBDs (Section~\ref{s:exporting-physical-devices-as-vbds}).
1624 Linux supports a maximum of eight file-backed VBDs across all domains
1625 by default. This limit can be statically increased by using the
1626 \emph{max\_loop} module parameter if CONFIG\_BLK\_DEV\_LOOP is
1627 compiled as a module in the dom0 kernel, or by using the
1628 \emph{max\_loop=n} boot option if CONFIG\_BLK\_DEV\_LOOP is compiled
1629 directly into the dom0 kernel.
1632 \section{Using LVM-backed VBDs}
1633 \label{s:using-lvm-backed-vbds}
1635 A particularly appealing solution is to use LVM volumes as backing for
1636 domain file-systems since this allows dynamic growing/shrinking of
1637 volumes as well as snapshot and other features.
1639 To initialize a partition to support LVM volumes:
1640 \begin{quote}
1641 \begin{verbatim}
1642 # pvcreate /dev/sda10
1643 \end{verbatim}
1644 \end{quote}
1646 Create a volume group named `vg' on the physical partition:
1647 \begin{quote}
1648 \begin{verbatim}
1649 # vgcreate vg /dev/sda10
1650 \end{verbatim}
1651 \end{quote}
1653 Create a logical volume of size 4GB named `myvmdisk1':
1654 \begin{quote}
1655 \begin{verbatim}
1656 # lvcreate -L4096M -n myvmdisk1 vg
1657 \end{verbatim}
1658 \end{quote}
1660 You should now see that you have a \path{/dev/vg/myvmdisk1} Make a
1661 filesystem, mount it and populate it, e.g.:
1662 \begin{quote}
1663 \begin{verbatim}
1664 # mkfs -t ext3 /dev/vg/myvmdisk1
1665 # mount /dev/vg/myvmdisk1 /mnt
1666 # cp -ax / /mnt
1667 # umount /mnt
1668 \end{verbatim}
1669 \end{quote}
1671 Now configure your VM with the following disk configuration:
1672 \begin{quote}
1673 \begin{verbatim}
1674 disk = [ 'phy:vg/myvmdisk1,sda1,w' ]
1675 \end{verbatim}
1676 \end{quote}
1678 LVM enables you to grow the size of logical volumes, but you'll need
1679 to resize the corresponding file system to make use of the new space.
1680 Some file systems (e.g.\ ext3) now support online resize. See the LVM
1681 manuals for more details.
1683 You can also use LVM for creating copy-on-write (CoW) clones of LVM
1684 volumes (known as writable persistent snapshots in LVM terminology).
1685 This facility is new in Linux 2.6.8, so isn't as stable as one might
1686 hope. In particular, using lots of CoW LVM disks consumes a lot of
1687 dom0 memory, and error conditions such as running out of disk space
1688 are not handled well. Hopefully this will improve in future.
1690 To create two copy-on-write clones of the above file system you would
1691 use the following commands:
1693 \begin{quote}
1694 \begin{verbatim}
1695 # lvcreate -s -L1024M -n myclonedisk1 /dev/vg/myvmdisk1
1696 # lvcreate -s -L1024M -n myclonedisk2 /dev/vg/myvmdisk1
1697 \end{verbatim}
1698 \end{quote}
1700 Each of these can grow to have 1GB of differences from the master
1701 volume. You can grow the amount of space for storing the differences
1702 using the lvextend command, e.g.:
1703 \begin{quote}
1704 \begin{verbatim}
1705 # lvextend +100M /dev/vg/myclonedisk1
1706 \end{verbatim}
1707 \end{quote}
1709 Don't let the `differences volume' ever fill up otherwise LVM gets
1710 rather confused. It may be possible to automate the growing process by
1711 using \path{dmsetup wait} to spot the volume getting full and then
1712 issue an \path{lvextend}.
1714 In principle, it is possible to continue writing to the volume that
1715 has been cloned (the changes will not be visible to the clones), but
1716 we wouldn't recommend this: have the cloned volume as a `pristine'
1717 file system install that isn't mounted directly by any of the virtual
1718 machines.
1721 \section{Using NFS Root}
1723 First, populate a root filesystem in a directory on the server
1724 machine. This can be on a distinct physical machine, or simply run
1725 within a virtual machine on the same node.
1727 Now configure the NFS server to export this filesystem over the
1728 network by adding a line to \path{/etc/exports}, for instance:
1730 \begin{quote}
1731 \begin{small}
1732 \begin{verbatim}
1733 /export/vm1root 1.2.3.4/24 (rw,sync,no_root_squash)
1734 \end{verbatim}
1735 \end{small}
1736 \end{quote}
1738 Finally, configure the domain to use NFS root. In addition to the
1739 normal variables, you should make sure to set the following values in
1740 the domain's configuration file:
1742 \begin{quote}
1743 \begin{small}
1744 \begin{verbatim}
1745 root = '/dev/nfs'
1746 nfs_server = '2.3.4.5' # substitute IP address of server
1747 nfs_root = '/path/to/root' # path to root FS on the server
1748 \end{verbatim}
1749 \end{small}
1750 \end{quote}
1752 The domain will need network access at boot time, so either statically
1753 configure an IP address using the config variables \path{ip},
1754 \path{netmask}, \path{gateway}, \path{hostname}; or enable DHCP
1755 (\path{dhcp='dhcp'}).
1757 Note that the Linux NFS root implementation is known to have stability
1758 problems under high load (this is not a Xen-specific problem), so this
1759 configuration may not be appropriate for critical servers.
1762 \chapter{CPU Management}
1764 %% KMS Something sage about CPU / processor management.
1766 Xen allows a domain's virtual CPU(s) to be associated with one or more
1767 host CPUs. This can be used to allocate real resources among one or
1768 more guests, or to make optimal use of processor resources when
1769 utilizing dual-core, hyperthreading, or other advanced CPU technologies.
1771 Xen enumerates physical CPUs in a `depth first' fashion. For a system
1772 with both hyperthreading and multiple cores, this would be all the
1773 hyperthreads on a given core, then all the cores on a given socket,
1774 and then all sockets. I.e. if you had a two socket, dual core,
1775 hyperthreaded Xeon the CPU order would be:
1778 \begin{center}
1779 \begin{tabular}{l|l|l|l|l|l|l|r}
1780 \multicolumn{4}{c|}{socket0} & \multicolumn{4}{c}{socket1} \\ \hline
1781 \multicolumn{2}{c|}{core0} & \multicolumn{2}{c|}{core1} &
1782 \multicolumn{2}{c|}{core0} & \multicolumn{2}{c}{core1} \\ \hline
1783 ht0 & ht1 & ht0 & ht1 & ht0 & ht1 & ht0 & ht1 \\
1784 \#0 & \#1 & \#2 & \#3 & \#4 & \#5 & \#6 & \#7 \\
1785 \end{tabular}
1786 \end{center}
1789 Having multiple vcpus belonging to the same domain mapped to the same
1790 physical CPU is very likely to lead to poor performance. It's better to
1791 use `vcpus-set' to hot-unplug one of the vcpus and ensure the others are
1792 pinned on different CPUs.
1794 If you are running IO intensive tasks, its typically better to dedicate
1795 either a hyperthread or whole core to running domain 0, and hence pin
1796 other domains so that they can't use CPU 0. If your workload is mostly
1797 compute intensive, you may want to pin vcpus such that all physical CPU
1798 threads are available for guest domains.
1800 \chapter{Migrating Domains}
1802 \section{Domain Save and Restore}
1804 The administrator of a Xen system may suspend a virtual machine's
1805 current state into a disk file in domain~0, allowing it to be resumed at
1806 a later time.
1808 For example you can suspend a domain called ``VM1'' to disk using the
1809 command:
1810 \begin{verbatim}
1811 # xm save VM1 VM1.chk
1812 \end{verbatim}
1814 This will stop the domain named ``VM1'' and save its current state
1815 into a file called \path{VM1.chk}.
1817 To resume execution of this domain, use the \path{xm restore} command:
1818 \begin{verbatim}
1819 # xm restore VM1.chk
1820 \end{verbatim}
1822 This will restore the state of the domain and resume its execution.
1823 The domain will carry on as before and the console may be reconnected
1824 using the \path{xm console} command, as described earlier.
1826 \section{Migration and Live Migration}
1828 Migration is used to transfer a domain between physical hosts. There
1829 are two varieties: regular and live migration. The former moves a
1830 virtual machine from one host to another by pausing it, copying its
1831 memory contents, and then resuming it on the destination. The latter
1832 performs the same logical functionality but without needing to pause
1833 the domain for the duration. In general when performing live migration
1834 the domain continues its usual activities and---from the user's
1835 perspective---the migration should be imperceptible.
1837 To perform a live migration, both hosts must be running Xen / \xend\ and
1838 the destination host must have sufficient resources (e.g.\ memory
1839 capacity) to accommodate the domain after the move. Furthermore we
1840 currently require both source and destination machines to be on the same
1841 L2 subnet.
1843 Currently, there is no support for providing automatic remote access
1844 to filesystems stored on local disk when a domain is migrated.
1845 Administrators should choose an appropriate storage solution (i.e.\
1846 SAN, NAS, etc.) to ensure that domain filesystems are also available
1847 on their destination node. GNBD is a good method for exporting a
1848 volume from one machine to another. iSCSI can do a similar job, but is
1849 more complex to set up.
1851 When a domain migrates, it's MAC and IP address move with it, thus it is
1852 only possible to migrate VMs within the same layer-2 network and IP
1853 subnet. If the destination node is on a different subnet, the
1854 administrator would need to manually configure a suitable etherip or IP
1855 tunnel in the domain~0 of the remote node.
1857 A domain may be migrated using the \path{xm migrate} command. To live
1858 migrate a domain to another machine, we would use the command:
1860 \begin{verbatim}
1861 # xm migrate --live mydomain destination.ournetwork.com
1862 \end{verbatim}
1864 Without the \path{--live} flag, \xend\ simply stops the domain and
1865 copies the memory image over to the new node and restarts it. Since
1866 domains can have large allocations this can be quite time consuming,
1867 even on a Gigabit network. With the \path{--live} flag \xend\ attempts
1868 to keep the domain running while the migration is in progress, resulting
1869 in typical down times of just 60--300ms.
1871 For now it will be necessary to reconnect to the domain's console on the
1872 new machine using the \path{xm console} command. If a migrated domain
1873 has any open network connections then they will be preserved, so SSH
1874 connections do not have this limitation.
1877 %% Chapter Securing Xen
1878 \chapter{Securing Xen}
1880 This chapter describes how to secure a Xen system. It describes a number
1881 of scenarios and provides a corresponding set of best practices. It
1882 begins with a section devoted to understanding the security implications
1883 of a Xen system.
1886 \section{Xen Security Considerations}
1888 When deploying a Xen system, one must be sure to secure the management
1889 domain (Domain-0) as much as possible. If the management domain is
1890 compromised, all other domains are also vulnerable. The following are a
1891 set of best practices for Domain-0:
1893 \begin{enumerate}
1894 \item \textbf{Run the smallest number of necessary services.} The less
1895 things that are present in a management partition, the better.
1896 Remember, a service running as root in the management domain has full
1897 access to all other domains on the system.
1898 \item \textbf{Use a firewall to restrict the traffic to the management
1899 domain.} A firewall with default-reject rules will help prevent
1900 attacks on the management domain.
1901 \item \textbf{Do not allow users to access Domain-0.} The Linux kernel
1902 has been known to have local-user root exploits. If you allow normal
1903 users to access Domain-0 (even as unprivileged users) you run the risk
1904 of a kernel exploit making all of your domains vulnerable.
1905 \end{enumerate}
1907 \section{Driver Domain Security Considerations}
1908 \label{s:ddsecurity}
1910 Driver domains address a range of security problems that exist regarding
1911 the use of device drivers and hardware. On many operating systems in common
1912 use today, device drivers run within the kernel with the same privileges as
1913 the kernel. Few or no mechanisms exist to protect the integrity of the kernel
1914 from a misbehaving (read "buggy") or malicious device driver. Driver
1915 domains exist to aid in isolating a device driver within its own virtual
1916 machine where it cannot affect the stability and integrity of other
1917 domains. If a driver crashes, the driver domain can be restarted rather than
1918 have the entire machine crash (and restart) with it. Drivers written by
1919 unknown or untrusted third-parties can be confined to an isolated space.
1920 Driver domains thus address a number of security and stability issues with
1921 device drivers.
1923 However, due to limitations in current hardware, a number of security
1924 concerns remain that need to be considered when setting up driver domains (it
1925 should be noted that the following list is not intended to be exhaustive).
1927 \begin{enumerate}
1928 \item \textbf{Without an IOMMU, a hardware device can DMA to memory regions
1929 outside of its controlling domain.} Architectures which do not have an
1930 IOMMU (e.g. most x86-based platforms) to restrict DMA usage by hardware
1931 are vulnerable. A hardware device which can perform arbitrary memory reads
1932 and writes can read/write outside of the memory of its controlling domain.
1933 A malicious or misbehaving domain could use a hardware device it controls
1934 to send data overwriting memory in another domain or to read arbitrary
1935 regions of memory in another domain.
1936 \item \textbf{Shared buses are vulnerable to sniffing.} Devices that share
1937 a data bus can sniff (and possible spoof) each others' data. Device A that
1938 is assigned to Domain A could eavesdrop on data being transmitted by
1939 Domain B to Device B and then relay that data back to Domain A.
1940 \item \textbf{Devices which share interrupt lines can either prevent the
1941 reception of that interrupt by the driver domain or can trigger the
1942 interrupt service routine of that guest needlessly.} A devices which shares
1943 a level-triggered interrupt (e.g. PCI devices) with another device can
1944 raise an interrupt and never clear it. This effectively blocks other devices
1945 which share that interrupt line from notifying their controlling driver
1946 domains that they need to be serviced. A device which shares an
1947 any type of interrupt line can trigger its interrupt continually which
1948 forces execution time to be spent (in multiple guests) in the interrupt
1949 service routine (potentially denying time to other processes within that
1950 guest). System architectures which allow each device to have its own
1951 interrupt line (e.g. PCI's Message Signaled Interrupts) are less
1952 vulnerable to this denial-of-service problem.
1953 \item \textbf{Devices may share the use of I/O memory address space.} Xen can
1954 only restrict access to a device's physical I/O resources at a certain
1955 granularity. For interrupt lines and I/O port address space, that
1956 granularity is very fine (per interrupt line and per I/O port). However,
1957 Xen can only restrict access to I/O memory address space on a page size
1958 basis. If more than one device shares use of a page in I/O memory address
1959 space, the domains to which those devices are assigned will be able to
1960 access the I/O memory address space of each other's devices.
1961 \end{enumerate}
1964 \section{Security Scenarios}
1967 \subsection{The Isolated Management Network}
1969 In this scenario, each node has two network cards in the cluster. One
1970 network card is connected to the outside world and one network card is a
1971 physically isolated management network specifically for Xen instances to
1972 use.
1974 As long as all of the management partitions are trusted equally, this is
1975 the most secure scenario. No additional configuration is needed other
1976 than forcing Xend to bind to the management interface for relocation.
1979 \subsection{A Subnet Behind a Firewall}
1981 In this scenario, each node has only one network card but the entire
1982 cluster sits behind a firewall. This firewall should do at least the
1983 following:
1985 \begin{enumerate}
1986 \item Prevent IP spoofing from outside of the subnet.
1987 \item Prevent access to the relocation port of any of the nodes in the
1988 cluster except from within the cluster.
1989 \end{enumerate}
1991 The following iptables rules can be used on each node to prevent
1992 migrations to that node from outside the subnet assuming the main
1993 firewall does not do this for you:
1995 \begin{verbatim}
1996 # this command disables all access to the Xen relocation
1997 # port:
1998 iptables -A INPUT -p tcp --destination-port 8002 -j REJECT
2000 # this command enables Xen relocations only from the specific
2001 # subnet:
2002 iptables -I INPUT -p tcp -{}-source 192.168.1.1/8 \
2003 --destination-port 8002 -j ACCEPT
2004 \end{verbatim}
2006 \subsection{Nodes on an Untrusted Subnet}
2008 Migration on an untrusted subnet is not safe in current versions of Xen.
2009 It may be possible to perform migrations through a secure tunnel via an
2010 VPN or SSH. The only safe option in the absence of a secure tunnel is to
2011 disable migration completely. The easiest way to do this is with
2012 iptables:
2014 \begin{verbatim}
2015 # this command disables all access to the Xen relocation port
2016 iptables -A INPUT -p tcp -{}-destination-port 8002 -j REJECT
2017 \end{verbatim}
2019 \part{Reference}
2021 %% Chapter Build and Boot Options
2022 \chapter{Build and Boot Options}
2024 This chapter describes the build- and boot-time options which may be
2025 used to tailor your Xen system.
2027 \section{Top-level Configuration Options}
2029 Top-level configuration is achieved by editing one of two
2030 files: \path{Config.mk} and \path{Makefile}.
2032 The former allows the overall build target architecture to be
2033 specified. You will typically not need to modify this unless
2034 you are cross-compiling or if you wish to build a PAE-enabled
2035 Xen system. Additional configuration options are documented
2036 in the \path{Config.mk} file.
2038 The top-level \path{Makefile} is chiefly used to customize the set of
2039 kernels built. Look for the line:
2040 \begin{quote}
2041 \begin{verbatim}
2042 KERNELS ?= linux-2.6-xen0 linux-2.6-xenU
2043 \end{verbatim}
2044 \end{quote}
2046 Allowable options here are any kernels which have a corresponding
2047 build configuration file in the \path{buildconfigs/} directory.
2051 \section{Xen Build Options}
2053 Xen provides a number of build-time options which should be set as
2054 environment variables or passed on make's command-line.
2056 \begin{description}
2057 \item[verbose=y] Enable debugging messages when Xen detects an
2058 unexpected condition. Also enables console output from all domains.
2059 \item[debug=y] Enable debug assertions. Implies {\bf verbose=y}.
2060 (Primarily useful for tracing bugs in Xen).
2061 \item[debugger=y] Enable the in-Xen debugger. This can be used to
2062 debug Xen, guest OSes, and applications.
2063 \item[perfc=y] Enable performance counters for significant events
2064 within Xen. The counts can be reset or displayed on Xen's console
2065 via console control keys.
2066 \end{description}
2069 \section{Xen Boot Options}
2070 \label{s:xboot}
2072 These options are used to configure Xen's behaviour at runtime. They
2073 should be appended to Xen's command line, either manually or by
2074 editing \path{grub.conf}.
2076 \begin{description}
2077 \item [ noreboot ] Don't reboot the machine automatically on errors.
2078 This is useful to catch debug output if you aren't catching console
2079 messages via the serial line.
2080 \item [ nosmp ] Disable SMP support. This option is implied by
2081 `ignorebiostables'.
2082 \item [ watchdog ] Enable NMI watchdog which can report certain
2083 failures.
2084 \item [ noirqbalance ] Disable software IRQ balancing and affinity.
2085 This can be used on systems such as Dell 1850/2850 that have
2086 workarounds in hardware for IRQ-routing issues.
2087 \item [ badpage=$<$page number$>$,$<$page number$>$, \ldots ] Specify
2088 a list of pages not to be allocated for use because they contain bad
2089 bytes. For example, if your memory tester says that byte 0x12345678
2090 is bad, you would place `badpage=0x12345' on Xen's command line.
2091 \item [ com1=$<$baud$>$,DPS,$<$io\_base$>$,$<$irq$>$
2092 com2=$<$baud$>$,DPS,$<$io\_base$>$,$<$irq$>$ ] \mbox{}\\
2093 Xen supports up to two 16550-compatible serial ports. For example:
2094 `com1=9600, 8n1, 0x408, 5' maps COM1 to a 9600-baud port, 8 data
2095 bits, no parity, 1 stop bit, I/O port base 0x408, IRQ 5. If some
2096 configuration options are standard (e.g., I/O base and IRQ), then
2097 only a prefix of the full configuration string need be specified. If
2098 the baud rate is pre-configured (e.g., by the bootloader) then you
2099 can specify `auto' in place of a numeric baud rate.
2100 \item [ console=$<$specifier list$>$ ] Specify the destination for Xen
2101 console I/O. This is a comma-separated list of, for example:
2102 \begin{description}
2103 \item[ vga ] Use VGA console (only until domain 0 boots, unless {\bf
2104 vga[keep] } is specified).
2105 \item[ com1 ] Use serial port com1.
2106 \item[ com2H ] Use serial port com2. Transmitted chars will have the
2107 MSB set. Received chars must have MSB set.
2108 \item[ com2L] Use serial port com2. Transmitted chars will have the
2109 MSB cleared. Received chars must have MSB cleared.
2110 \end{description}
2111 The latter two examples allow a single port to be shared by two
2112 subsystems (e.g.\ console and debugger). Sharing is controlled by
2113 MSB of each transmitted/received character. [NB. Default for this
2114 option is `com1,vga']
2115 \item [ sync\_console ] Force synchronous console output. This is
2116 useful if you system fails unexpectedly before it has sent all
2117 available output to the console. In most cases Xen will
2118 automatically enter synchronous mode when an exceptional event
2119 occurs, but this option provides a manual fallback.
2120 \item [ conswitch=$<$switch-char$><$auto-switch-char$>$ ] Specify how
2121 to switch serial-console input between Xen and DOM0. The required
2122 sequence is CTRL-$<$switch-char$>$ pressed three times. Specifying
2123 the backtick character disables switching. The
2124 $<$auto-switch-char$>$ specifies whether Xen should auto-switch
2125 input to DOM0 when it boots --- if it is `x' then auto-switching is
2126 disabled. Any other value, or omitting the character, enables
2127 auto-switching. [NB. Default switch-char is `a'.]
2128 \item [ nmi=xxx ]
2129 Specify what to do with an NMI parity or I/O error. \\
2130 `nmi=fatal': Xen prints a diagnostic and then hangs. \\
2131 `nmi=dom0': Inform DOM0 of the NMI. \\
2132 `nmi=ignore': Ignore the NMI.
2133 \item [ mem=xxx ] Set the physical RAM address limit. Any RAM
2134 appearing beyond this physical address in the memory map will be
2135 ignored. This parameter may be specified with a B, K, M or G suffix,
2136 representing bytes, kilobytes, megabytes and gigabytes respectively.
2137 The default unit, if no suffix is specified, is kilobytes.
2138 \item [ dom0\_mem=xxx ] Set the amount of memory to be allocated to
2139 domain0. In Xen 3.x the parameter may be specified with a B, K, M or
2140 G suffix, representing bytes, kilobytes, megabytes and gigabytes
2141 respectively; if no suffix is specified, the parameter defaults to
2142 kilobytes. In previous versions of Xen, suffixes were not supported
2143 and the value is always interpreted as kilobytes.
2144 \item [ tbuf\_size=xxx ] Set the size of the per-cpu trace buffers, in
2145 pages (default 0).
2146 \item [ sched=xxx ] Select the CPU scheduler Xen should use. The
2147 current possibilities are `sedf' (default), `credit', and `bvt'.
2148 \item [ apic\_verbosity=debug,verbose ] Print more detailed
2149 information about local APIC and IOAPIC configuration.
2150 \item [ lapic ] Force use of local APIC even when left disabled by
2151 uniprocessor BIOS.
2152 \item [ nolapic ] Ignore local APIC in a uniprocessor system, even if
2153 enabled by the BIOS.
2154 \item [ apic=bigsmp,default,es7000,summit ] Specify NUMA platform.
2155 This can usually be probed automatically.
2156 \end{description}
2158 In addition, the following options may be specified on the Xen command
2159 line. Since domain 0 shares responsibility for booting the platform,
2160 Xen will automatically propagate these options to its command line.
2161 These options are taken from Linux's command-line syntax with
2162 unchanged semantics.
2164 \begin{description}
2165 \item [ acpi=off,force,strict,ht,noirq,\ldots ] Modify how Xen (and
2166 domain 0) parses the BIOS ACPI tables.
2167 \item [ acpi\_skip\_timer\_override ] Instruct Xen (and domain~0) to
2168 ignore timer-interrupt override instructions specified by the BIOS
2169 ACPI tables.
2170 \item [ noapic ] Instruct Xen (and domain~0) to ignore any IOAPICs
2171 that are present in the system, and instead continue to use the
2172 legacy PIC.
2173 \end{description}
2176 \section{XenLinux Boot Options}
2178 In addition to the standard Linux kernel boot options, we support:
2179 \begin{description}
2180 \item[ xencons=xxx ] Specify the device node to which the Xen virtual
2181 console driver is attached. The following options are supported:
2182 \begin{center}
2183 \begin{tabular}{l}
2184 `xencons=off': disable virtual console \\
2185 `xencons=tty': attach console to /dev/tty1 (tty0 at boot-time) \\
2186 `xencons=ttyS': attach console to /dev/ttyS0
2187 \end{tabular}
2188 \end{center}
2189 The default is ttyS for dom0 and tty for all other domains.
2190 \end{description}
2193 %% Chapter Further Support
2194 \chapter{Further Support}
2196 If you have questions that are not answered by this manual, the
2197 sources of information listed below may be of interest to you. Note
2198 that bug reports, suggestions and contributions related to the
2199 software (or the documentation) should be sent to the Xen developers'
2200 mailing list (address below).
2203 \section{Other Documentation}
2205 For developers interested in porting operating systems to Xen, the
2206 \emph{Xen Interface Manual} is distributed in the \path{docs/}
2207 directory of the Xen source distribution.
2210 \section{Online References}
2212 The official Xen web site can be found at:
2213 \begin{quote} {\tt http://www.xensource.com}
2214 \end{quote}
2216 This contains links to the latest versions of all online
2217 documentation, including the latest version of the FAQ.
2219 Information regarding Xen is also available at the Xen Wiki at
2220 \begin{quote} {\tt http://wiki.xensource.com/xenwiki/}\end{quote}
2221 The Xen project uses Bugzilla as its bug tracking system. You'll find
2222 the Xen Bugzilla at http://bugzilla.xensource.com/bugzilla/.
2225 \section{Mailing Lists}
2227 There are several mailing lists that are used to discuss Xen related
2228 topics. The most widely relevant are listed below. An official page of
2229 mailing lists and subscription information can be found at \begin{quote}
2230 {\tt http://lists.xensource.com/} \end{quote}
2232 \begin{description}
2233 \item[xen-devel@lists.xensource.com] Used for development
2234 discussions and bug reports. Subscribe at: \\
2235 {\small {\tt http://lists.xensource.com/xen-devel}}
2236 \item[xen-users@lists.xensource.com] Used for installation and usage
2237 discussions and requests for help. Subscribe at: \\
2238 {\small {\tt http://lists.xensource.com/xen-users}}
2239 \item[xen-announce@lists.xensource.com] Used for announcements only.
2240 Subscribe at: \\
2241 {\small {\tt http://lists.xensource.com/xen-announce}}
2242 \item[xen-changelog@lists.xensource.com] Changelog feed
2243 from the unstable and 2.0 trees - developer oriented. Subscribe at: \\
2244 {\small {\tt http://lists.xensource.com/xen-changelog}}
2245 \end{description}
2249 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
2251 \appendix
2253 \chapter{Unmodified (VMX) guest domains in Xen with Intel\textregistered Virtualization Technology (VT)}
2255 Xen supports guest domains running unmodified Guest operating systems using Virtualization Technology (VT) available on recent Intel Processors. More information about the Intel Virtualization Technology implementing Virtual Machine Extensions (VMX) in the processor is available on the Intel website at \\
2256 {\small {\tt http://www.intel.com/technology/computing/vptech}}
2258 \section{Building Xen with VT support}
2260 The following packages need to be installed in order to build Xen with VT support. Some Linux distributions do not provide these packages by default.
2262 \begin{tabular}{lp{11.0cm}}
2263 {\bfseries Package} & {\bfseries Description} \\
2265 dev86 & The dev86 package provides an assembler and linker for real mode 80x86 instructions. You need to have this package installed in order to build the BIOS code which runs in (virtual) real mode.
2267 If the dev86 package is not available on the x86\_64 distribution, you can install the i386 version of it. The dev86 rpm package for various distributions can be found at {\scriptsize {\tt http://www.rpmfind.net/linux/rpm2html/search.php?query=dev86\&submit=Search}} \\
2269 LibVNCServer & The unmodified guest's VGA display, keyboard, and mouse can be virtualized by the vncserver library. You can get the sources of libvncserver from {\small {\tt http://sourceforge.net/projects/libvncserver}}. Build and install the sources on the build system to get the libvncserver library. There is a significant performance degradation in 0.8 version. The current sources in the CVS tree have fixed this degradation. So it is highly recommended to download the latest CVS sources and install them.\\
2271 SDL-devel, SDL & Simple DirectMedia Layer (SDL) is another way of virtualizing the unmodified guest console. It provides an X window for the guest console.
2273 If the SDL and SDL-devel packages are not installed by default on the build system, they can be obtained from {\scriptsize {\tt http://www.rpmfind.net/linux/rpm2html/search.php?query=SDL\&amp;submit=Search}}
2274 , {\scriptsize {\tt http://www.rpmfind.net/linux/rpm2html/search.php?query=SDL-devel\&submit=Search}} \\
2276 \end{tabular}
2278 \section{Configuration file for unmodified VMX guests}
2280 The Xen installation includes a sample configuration file, {\small {\tt /etc/xen/xmexample.vmx}}. There are comments describing all the options. In addition to the common options that are the same as those for paravirtualized guest configurations, VMX guest configurations have the following settings:
2282 \begin{tabular}{lp{11.0cm}}
2284 {\bfseries Parameter} & {\bfseries Description} \\
2286 kernel & The VMX firmware loader, {\small {\tt /usr/lib/xen/boot/vmxloader}}\\
2288 builder & The domain build function. The VMX domain uses the vmx builder.\\
2290 acpi & Enable VMX guest ACPI, default=0 (disabled)\\
2292 apic & Enable VMX guest APIC, default=0 (disabled)\\
2294 pae & Enable VMX guest PAE, default=0 (disabled)\\
2296 vif & Optionally defines MAC address and/or bridge for the network interfaces. Random MACs are assigned if not given. {\small {\tt type=ioemu}} means ioemu is used to virtualize the VMX NIC. If no type is specified, vbd is used, as with paravirtualized guests.\\
2298 disk & Defines the disk devices you want the domain to have access to, and what you want them accessible as. If using a physical device as the VMX guest's disk, each disk entry is of the form
2300 {\small {\tt phy:UNAME,ioemu:DEV,MODE,}}
2302 where UNAME is the device, DEV is the device name the domain will see, and MODE is r for read-only, w for read-write. ioemu means the disk will use ioemu to virtualize the VMX disk. If not adding ioemu, it uses vbd like paravirtualized guests.
2304 If using disk image file, its form should be like
2306 {\small {\tt file:FILEPATH,ioemu:DEV,MODE}}
2308 If using more than one disk, there should be a comma between each disk entry. For example:
2310 {\scriptsize {\tt disk = ['file:/var/images/image1.img,ioemu:hda,w', 'file:/var/images/image2.img,ioemu:hdb,w']}}\\
2312 cdrom & Disk image for CD-ROM. The default is {\small {\tt /dev/cdrom}} for Domain0. Inside the VMX domain, the CD-ROM will available as device {\small {\tt /dev/hdc}}. The entry can also point to an ISO file.\\
2314 boot & Boot from floppy (a), hard disk (c) or CD-ROM (d). For example, to boot from CD-ROM, the entry should be:
2316 boot='d'\\
2318 device\_model & The device emulation tool for VMX guests. This parameter should not be changed.\\
2320 sdl & Enable SDL library for graphics, default = 0 (disabled)\\
2322 vnc & Enable VNC library for graphics, default = 1 (enabled)\\
2324 vncviewer & Enable spawning of the vncviewer (only valid when vnc=1), default = 1 (enabled)
2326 If vnc=1 and vncviewer=0, user can use vncviewer to manually connect VMX from remote. For example:
2328 {\small {\tt vncviewer domain0\_IP\_address:VMX\_domain\_id}} \\
2330 ne2000 & Enable ne2000, default = 0 (disabled; use pcnet)\\
2332 serial & Enable redirection of VMX serial output to pty device\\
2334 \end{tabular}
2336 \begin{tabular}{lp{10cm}}
2338 usb & Enable USB support without defining a specific USB device.
2339 This option defaults to 0 (disabled) unless the option usbdevice is
2340 specified in which case this option then defaults to 1 (enabled).\\
2342 usbdevice & Enable USB support and also enable support for the given
2343 device. Devices that can be specified are {\small {\tt mouse}} (a PS/2 style
2344 mouse), {\small {\tt tablet}} (an absolute pointing device) and
2345 {\small {\tt host:id1:id2}} (a physical USB device on the host machine whose
2346 ids are {\small {\tt id1}} and {\small {\tt id2}}). The advantage
2347 of {\small {\tt tablet}} is that Windows guests will automatically recognize
2348 and support this device so specifying the config line
2350 {\small
2351 \begin{verbatim}
2352 usbdevice='tablet'
2353 \end{verbatim}
2356 will create a mouse that works transparently with Windows guests under VNC.
2357 Linux doesn't recognize the USB tablet yet so Linux guests under VNC will
2358 still need the Summagraphics emulation.
2359 Details about mouse emulation are provided in section \textbf{A.4.3}.\\
2361 localtime & Set the real time clock to local time [default=0, that is, set to UTC].\\
2363 enable-audio & Enable audio support. This is under development.\\
2365 full-screen & Start in full screen. This is under development.\\
2367 nographic & Another way to redirect serial output. If enabled, no 'sdl' or 'vnc' can work. Not recommended.\\
2369 \end{tabular}
2372 \section{Creating virtual disks from scratch}
2373 \subsection{Using physical disks}
2374 If you are using a physical disk or physical disk partition, you need to install a Linux OS on the disk first. Then the boot loader should be installed in the correct place. For example {\small {\tt dev/sda}} for booting from the whole disk, or {\small {\tt /dev/sda1}} for booting from partition 1.
2376 \subsection{Using disk image files}
2377 You need to create a large empty disk image file first; then, you need to install a Linux OS onto it. There are two methods you can choose. One is directly installing it using a VMX guest while booting from the OS installation CD-ROM. The other is copying an installed OS into it. The boot loader will also need to be installed.
2379 \subsubsection*{To create the image file:}
2380 The image size should be big enough to accommodate the entire OS. This example assumes the size is 1G (which is probably too small for most OSes).
2382 {\small {\tt \# dd if=/dev/zero of=hd.img bs=1M count=1 seek=1023}}
2384 \subsubsection*{To directly install Linux OS into an image file using a VMX guest:}
2386 Install Xen and create VMX with the original image file with booting from CD-ROM. Then it is just like a normal Linux OS installation. The VMX configuration file should have these two entries before creating:
2388 {\small {\tt cdrom='/dev/cdrom'
2389 boot='d'}}
2391 If this method does not succeed, you can choose the following method of copying an installed Linux OS into an image file.
2393 \subsubsection*{To copy a installed OS into an image file:}
2394 Directly installing is an easier way to make partitions and install an OS in a disk image file. But if you want to create a specific OS in your disk image, then you will most likely want to use this method.
2396 \begin{enumerate}
2397 \item {\bfseries Install a normal Linux OS on the host machine}\\
2398 You can choose any way to install Linux, such as using yum to install Red Hat Linux or YAST to install Novell SuSE Linux. The rest of this example assumes the Linux OS is installed in {\small {\tt /var/guestos/}}.
2400 \item {\bfseries Make the partition table}\\
2401 The image file will be treated as hard disk, so you should make the partition table in the image file. For example:
2403 {\scriptsize {\tt \# losetup /dev/loop0 hd.img\\
2404 \# fdisk -b 512 -C 4096 -H 16 -S 32 /dev/loop0\\
2405 press 'n' to add new partition\\
2406 press 'p' to choose primary partition\\
2407 press '1' to set partition number\\
2408 press "Enter" keys to choose default value of "First Cylinder" parameter.\\
2409 press "Enter" keys to choose default value of "Last Cylinder" parameter.\\
2410 press 'w' to write partition table and exit\\
2411 \# losetup -d /dev/loop0}}
2413 \item {\bfseries Make the file system and install grub}\\
2414 {\scriptsize {\tt \# ln -s /dev/loop0 /dev/loop\\
2415 \# losetup /dev/loop0 hd.img\\
2416 \# losetup -o 16384 /dev/loop1 hd.img\\
2417 \# mkfs.ext3 /dev/loop1\\
2418 \# mount /dev/loop1 /mnt\\
2419 \# mkdir -p /mnt/boot/grub\\
2420 \# cp /boot/grub/stage* /boot/grub/e2fs\_stage1\_5 /mnt/boot/grub\\
2421 \# umount /mnt\\
2422 \# grub\\
2423 grub> device (hd0) /dev/loop\\
2424 grub> root (hd0,0)\\
2425 grub> setup (hd0)\\
2426 grub> quit\\
2427 \# rm /dev/loop\\
2428 \# losetup -d /dev/loop0\\
2429 \# losetup -d /dev/loop1}}
2431 The {\small {\tt losetup}} option {\small {\tt -o 16384}} skips the partition table in the image file. It is the number of sectors times 512. We need {\small {\tt /dev/loop}} because grub is expecting a disk device \emph{name}, where \emph{name} represents the entire disk and \emph{name1} represents the first partition.
2433 \item {\bfseries Copy the OS files to the image}\\
2434 If you have Xen installed, you can easily use {\small {\tt lomount}} instead of {\small {\tt losetup}} and {\small {\tt mount}} when coping files to some partitions. {\small {\tt lomount}} just needs the partition information.
2436 {\scriptsize {\tt \# lomount -t ext3 -diskimage hd.img -partition 1 /mnt/guest\\
2437 \# cp -ax /var/guestos/\{root,dev,var,etc,usr,bin,sbin,lib\} /mnt/guest\\
2438 \# mkdir /mnt/guest/\{proc,sys,home,tmp\}}}
2440 \item {\bfseries Edit the {\small {\tt /etc/fstab}} of the guest image}\\
2441 The fstab should look like this:
2443 {\scriptsize {\tt \# vim /mnt/guest/etc/fstab\\
2444 /dev/hda1 / ext3 defaults 1 1\\
2445 none /dev/pts devpts gid=5,mode=620 0 0\\
2446 none /dev/shm tmpfs defaults 0 0\\
2447 none /proc proc defaults 0 0\\
2448 none /sys sysfs efaults 0 0}}
2450 \item {\bfseries umount the image file}\\
2451 {\small {\tt \# umount /mnt/guest}}
2452 \end{enumerate}
2454 Now, the guest OS image {\small {\tt hd.img}} is ready. You can also reference {\small {\tt http://free.oszoo.org}} for quickstart images. But make sure to install the boot loader.
2456 \subsection{Install Windows into an Image File using a VMX guest}
2457 In order to install a Windows OS, you should keep {\small {\tt acpi=0}} in your VMX configuration file.
2459 \section{VMX Guests}
2460 \subsection{Editing the Xen VMX config file}
2461 Make a copy of the example VMX configuration file {\small {\tt /etc/xen/xmeaxmple.vmx}} and edit the line that reads
2463 {\small {\tt disk = [ 'file:/var/images/\emph{guest.img},ioemu:hda,w' ]}}
2465 replacing \emph{guest.img} with the name of the guest OS image file you just made.
2467 \subsection{Creating VMX guests}
2468 Simply follow the usual method of creating the guest, using the -f parameter and providing the filename of your VMX configuration file:\\
2470 {\small {\tt \# xend start\\
2471 \# xm create /etc/xen/vmxguest.vmx}}
2473 In the default configuration, VNC is on and SDL is off. Therefore VNC windows will open when VMX guests are created. If you want to use SDL to create VMX guests, set {\small {\tt sdl=1}} in your VMX configuration file. You can also turn off VNC by setting {\small {\tt vnc=0}}.
2475 \subsection{Mouse issues, especially under VNC}
2476 Mouse handling when using VNC is a little problematic.
2477 The problem is that the VNC viewer provides a virtual pointer which is
2478 located at an absolute location in the VNC window and only absolute
2479 coordinates are provided.
2480 The VMX device model converts these absolute mouse coordinates
2481 into the relative motion deltas that are expected by the PS/2
2482 mouse driver running in the guest.
2483 Unfortunately,
2484 it is impossible to keep these generated mouse deltas
2485 accurate enough for the guest cursor to exactly match
2486 the VNC pointer.
2487 This can lead to situations where the guest's cursor
2488 is in the center of the screen and there's no way to
2489 move that cursor to the left
2490 (it can happen that the VNC pointer is at the left
2491 edge of the screen and,
2492 therefore,
2493 there are no longer any left mouse deltas that
2494 can be provided by the device model emulation code.)
2496 To deal with these mouse issues there are 4 different
2497 mouse emulations available from the VMX device model:
2499 \begin{description}
2500 \item[PS/2 mouse over the PS/2 port.]
2501 This is the default mouse
2502 that works perfectly well under SDL.
2503 Under VNC the guest cursor will get
2504 out of sync with the VNC pointer.
2505 When this happens you can re-synchronize
2506 the guest cursor to the VNC pointer by
2507 holding down the
2508 \textbf{left-ctl}
2509 and
2510 \textbf{left-alt}
2511 keys together.
2512 While these keys are down VNC pointer motions
2513 will not be reported to the guest so
2514 that the VNC pointer can be moved
2515 to a place where it is possible
2516 to move the guest cursor again.
2518 \item[Summagraphics mouse over the serial port.]
2519 The device model also provides emulation
2520 for a Summagraphics tablet,
2521 an absolute pointer device.
2522 This emulation is provided over the second
2523 serial port,
2524 \textbf{/dev/ttyS1}
2525 for Linux guests and
2526 \textbf{COM2}
2527 for Windows guests.
2528 Unfortunately,
2529 neither Linux nor Windows provides
2530 default support for the Summagraphics
2531 tablet so the guest will have to be
2532 manually configured for this mouse.
2534 \textbf{Linux configuration.}
2536 First,
2537 configure the GPM service to use the Summagraphics tablet.
2538 This can vary between distributions but,
2539 typically,
2540 all that needs to be done is modify the file
2541 \path{/etc/sysconfig/mouse} to contain the lines:
2543 {\small
2544 \begin{verbatim}
2545 MOUSETYPE="summa"
2546 XMOUSETYPE="SUMMA"
2547 DEVICE=/dev/ttyS1
2548 \end{verbatim}
2551 and then restart the GPM daemon.
2553 Next,
2554 modify the X11 config
2555 \path{/etc/X11/xorg.conf}
2556 to support the Summgraphics tablet by replacing
2557 the input device stanza with the following:
2559 {\small
2560 \begin{verbatim}
2561 Section "InputDevice"
2562 Identifier "Mouse0"
2563 Driver "summa"
2564 Option "Device" "/dev/ttyS1"
2565 Option "InputFashion" "Tablet"
2566 Option "Mode" "Absolute"
2567 Option "Name" "EasyPen"
2568 Option "Compatible" "True"
2569 Option "Protocol" "Auto"
2570 Option "SendCoreEvents" "on"
2571 Option "Vendor" "GENIUS"
2572 EndSection
2573 \end{verbatim}
2576 Restart X and the X cursor should now properly
2577 track the VNC pointer.
2580 \textbf{Windows configuration.}
2582 Get the file
2583 \path{http://www.cad-plan.de/files/download/tw2k.exe}
2584 and execute that file on the guest,
2585 answering the questions as follows:
2587 \begin{enumerate}
2588 \item When the program asks for \textbf{model},
2589 scroll down and selese \textbf{SummaSketch (MM Compatible)}.
2591 \item When the program asks for \textbf{COM Port} specify \textbf{com2}.
2593 \item When the programs asks for a \textbf{Cursor Type} specify
2594 \textbf{4 button cursor/puck}.
2596 \item The guest system will then reboot and,
2597 when it comes back up,
2598 the guest cursor will now properly track
2599 the VNC pointer.
2600 \end{enumerate}
2602 \item[PS/2 mouse over USB port.]
2603 This is just the same PS/2 emulation except it is
2604 provided over a USB port.
2605 This emulation is enabled by the configuration flag:
2606 {\small
2607 \begin{verbatim}
2608 usbdevice='mouse'
2609 \end{verbatim}
2612 \item[USB tablet over USB port.]
2613 The USB tablet is an absolute pointing device
2614 that has the advantage that it is automatically
2615 supported under Windows guests,
2616 although Linux guests still require some
2617 manual configuration.
2618 This mouse emulation is enabled by the
2619 configuration flag:
2620 {\small
2621 \begin{verbatim}
2622 usbdevice='tablet'
2623 \end{verbatim}
2626 \textbf{Linux configuration.}
2628 Unfortunately,
2629 there is no GPM support for the
2630 USB tablet at this point in time.
2631 If you intend to use a GPM pointing
2632 device under VNC you should
2633 configure the guest for Summagraphics
2634 emulation.
2636 Support for X11 is available by following
2637 the instructions at\\
2638 \verb+http://stz-softwaretechnik.com/~ke/touchscreen/evtouch.html+\\
2639 with one minor change.
2640 The
2641 \path{xorg.conf}
2642 given in those instructions
2643 uses the wrong values for the X \& Y minimums and maximums,
2644 use the following config stanza instead:
2646 {\small
2647 \begin{verbatim}
2648 Section "InputDevice"
2649 Identifier "Tablet"
2650 Driver "evtouch"
2651 Option "Device" "/dev/input/event2"
2652 Option "DeviceName" "touchscreen"
2653 Option "MinX" "0"
2654 Option "MinY" "0"
2655 Option "MaxX" "32256"
2656 Option "MaxY" "32256"
2657 Option "ReportingMode" "Raw"
2658 Option "Emulate3Buttons"
2659 Option "Emulate3Timeout" "50"
2660 Option "SendCoreEvents" "On"
2661 EndSection
2662 \end{verbatim}
2665 \textbf{Windows configuration.}
2667 Just enabling the USB tablet in the
2668 guest's configuration file is sufficient,
2669 Windows will automatically recognize and
2670 configure device drivers for this
2671 pointing device.
2673 \end{description}
2675 \subsection{USB Support}
2676 There is support for an emulated USB mouse,
2677 an emulated USB tablet
2678 and physical low speed USB devices
2679 (support for high speed USB 2.0 devices is
2680 still under development).
2682 \begin{description}
2683 \item[USB PS/2 style mouse.]
2684 Details on the USB mouse emulation are
2685 given in sections
2686 \textbf{A.2}
2687 and
2688 \textbf{A.4.3}.
2689 Enabling USB PS/2 style mouse emulation
2690 is just a matter of adding the line
2692 {\small
2693 \begin{verbatim}
2694 usbdevice='mouse'
2695 \end{verbatim}
2698 to the configuration file.
2699 \item[USB tablet.]
2700 Details on the USB tablet emulation are
2701 given in sections
2702 \textbf{A.2}
2703 and
2704 \textbf{A.4.3}.
2705 Enabling USB tablet emulation
2706 is just a matter of adding the line
2708 {\small
2709 \begin{verbatim}
2710 usbdevice='tablet'
2711 \end{verbatim}
2714 to the configuration file.
2715 \item[USB physical devices.]
2716 Access to a physical (low speed) USB device
2717 is enabled by adding a line of the form
2719 {\small
2720 \begin{verbatim}
2721 usbdevice='host:vid:pid'
2722 \end{verbatim}
2725 into the the configuration file.\footnote{
2726 There is an alternate
2727 way of specifying a USB device that
2728 uses the syntax
2729 \textbf{host:bus.addr}
2730 but this syntax suffers from
2731 a major problem that makes
2732 it effectively useless.
2733 The problem is that the
2734 \textbf{addr}
2735 portion of this address
2736 changes every time the USB device
2737 is plugged into the system.
2738 For this reason this addressing
2739 scheme is not recommended and
2740 will not be documented further.
2742 \textbf{vid}
2743 and
2744 \textbf{pid}
2745 are a
2746 product id and
2747 vendor id
2748 that uniquely identify
2749 the USB device.
2750 These ids can be identified
2751 in two ways:
2753 \begin{enumerate}
2754 \item Through the control window.
2755 As described in section
2756 \textbf{A.4.6}
2757 the control window
2758 is activated by pressing
2759 \textbf{ctl-alt-2}
2760 in the guest VGA window.
2761 As long as USB support is
2762 enabled in the guest by including
2763 the config file line
2764 {\small
2765 \begin{verbatim}
2766 usb=1
2767 \end{verbatim}
2769 then executing the command
2770 {\small
2771 \begin{verbatim}
2772 info usbhost
2773 \end{verbatim}
2775 in the control window
2776 will display a list of all
2777 usb devices and their ids.
2778 For example,
2779 this output:
2780 {\small
2781 \begin{verbatim}
2782 Device 1.3, speed 1.5 Mb/s
2783 Class 00: USB device 04b3:310b
2784 \end{verbatim}
2786 was created from a USB mouse with
2787 vendor id
2788 \textbf{04b3}
2789 and product id
2790 \textbf{310b}.
2791 This device could be made available
2792 to the VMX guest by including the
2793 config file entry
2794 {\small
2795 \begin{verbatim}
2796 usbdevice='host:04be:310b'
2797 \end{verbatim}
2800 It is also possible to
2801 enable access to a USB
2802 device dynamically through
2803 the control window.
2804 The control window command
2805 {\small
2806 \begin{verbatim}
2807 usb_add host:vid:pid
2808 \end{verbatim}
2810 will also allow access to a
2811 USB device with vendor id
2812 \textbf{vid}
2813 and product id
2814 \textbf{pid}.
2815 \item Through the
2816 \path{/proc} file system.
2817 The contents of the pseudo file
2818 \path{/proc/bus/usb/devices}
2819 can also be used to identify
2820 vendor and product ids.
2821 Looking at this file,
2822 the line starting with
2823 \textbf{P:}
2824 has a field
2825 \textbf{Vendor}
2826 giving the vendor id and
2827 another field
2828 \textbf{ProdID}
2829 giving the product id.
2830 The contents of
2831 \path{/proc/bus/usb/devices}
2832 for the example mouse is as
2833 follows:
2834 {\small
2835 \begin{verbatim}
2836 T: Bus=01 Lev=01 Prnt=01 Port=01 Cnt=02 Dev#= 3 Spd=1.5 MxCh= 0
2837 D: Ver= 2.00 Cls=00(>ifc ) Sub=00 Prot=00 MxPS= 8 #Cfgs= 1
2838 P: Vendor=04b3 ProdID=310b Rev= 1.60
2839 C:* #Ifs= 1 Cfg#= 1 Atr=a0 MxPwr=100mA
2840 I: If#= 0 Alt= 0 #EPs= 1 Cls=03(HID ) Sub=01 Prot=02 Driver=(none)
2841 E: Ad=81(I) Atr=03(Int.) MxPS= 4 Ivl=10ms
2842 \end{verbatim}
2844 Note that the
2845 \textbf{P:}
2846 line correctly identifies the
2847 vendor id and product id
2848 for this mouse as
2849 \textbf{04b3:310b}.
2850 \end{enumerate}
2851 There is one other issue to
2852 be aware of when accessing a
2853 physical USB device from the guest.
2854 The Dom0 kernel must not have
2855 a device driver loaded for
2856 the device that the guest wishes
2857 to access.
2858 This means that the Dom0
2859 kernel must not have that
2860 device driver compiled into
2861 the kernel or,
2862 if using modules,
2863 that driver module must
2864 not be loaded.
2865 Note that this is the device
2866 specific USB driver that must
2867 not be loaded,
2868 either the
2869 \textbf{UHCI}
2870 or
2871 \textbf{OHCI}
2872 USB controller driver must
2873 still be loaded.
2875 Going back to the USB mouse
2876 as an example,
2877 if \textbf{lsmod}
2878 gives the output:
2880 {\small
2881 \begin{verbatim}
2882 Module Size Used by
2883 usbmouse 4128 0
2884 usbhid 28996 0
2885 uhci_hcd 35409 0
2886 \end{verbatim}
2889 then the USB mouse is being
2890 used by the Dom0 kernel and is
2891 not available to the guest.
2892 Executing the command
2893 \textbf{rmmod usbhid}\footnote{
2894 Turns out the
2895 \textbf{usbhid}
2896 driver is the significant
2897 one for the USB mouse,
2898 the presence or absence of
2899 the module
2900 \textbf{usbmouse}
2901 has no effect on whether or
2902 not the guest can see a USB mouse.}
2903 will remove the USB mouse
2904 driver from the Dom0 kernel
2905 and the mouse will now be
2906 accessible by the VMX guest.
2908 Be aware the the Linux USB
2909 hotplug system will reload
2910 the drivers if a USB device
2911 is removed and plugged back
2912 in.
2913 This means that just unloading
2914 the driver module might not
2915 be sufficient if the USB device
2916 is removed and added back.
2917 A more reliable technique is
2918 to first
2919 \textbf{rmmod}
2920 the driver and then rename the
2921 driver file in the
2922 \path{/lib/modules}
2923 directory,
2924 just to make sure it doesn't get
2925 reloaded.
2926 \end{description}
2928 \subsection{Destroy VMX guests}
2929 VMX guests can be destroyed in the same way as can paravirtualized guests. We recommend that you type the command
2931 {\small {\tt poweroff}}
2933 in the VMX guest's console first to prevent data loss. Then execute the command
2935 {\small {\tt xm destroy \emph{vmx\_guest\_id} }}
2937 at the Domain0 console.
2939 \subsection{VMX window (X or VNC) Hot Key}
2940 If you are running in the X environment after creating a VMX guest, an X window is created. There are several hot keys for control of the VMX guest that can be used in the window.
2942 {\bfseries Ctrl+Alt+2} switches from guest VGA window to the control window. Typing {\small {\tt help }} shows the control commands help. For example, 'q' is the command to destroy the VMX guest.\\
2943 {\bfseries Ctrl+Alt+1} switches back to VMX guest's VGA.\\
2944 {\bfseries Ctrl+Alt+3} switches to serial port output. It captures serial output from the VMX guest. It works only if the VMX guest was configured to use the serial port. \\
2946 \subsection{Save/Restore and Migration}
2947 VMX guests currently cannot be saved and restored, nor migrated. These features are currently under active development.
2949 \chapter{Vnets - Domain Virtual Networking}
2951 Xen optionally supports virtual networking for domains using {\em vnets}.
2952 These emulate private LANs that domains can use. Domains on the same
2953 vnet can be hosted on the same machine or on separate machines, and the
2954 vnets remain connected if domains are migrated. Ethernet traffic
2955 on a vnet is tunneled inside IP packets on the physical network. A vnet is a virtual
2956 network and addressing within it need have no relation to addressing on
2957 the underlying physical network. Separate vnets, or vnets and the physical network,
2958 can be connected using domains with more than one network interface and
2959 enabling IP forwarding or bridging in the usual way.
2961 Vnet support is included in \texttt{xm} and \xend:
2962 \begin{verbatim}
2963 # xm vnet-create <config>
2964 \end{verbatim}
2965 creates a vnet using the configuration in the file \verb|<config>|.
2966 When a vnet is created its configuration is stored by \xend and the vnet persists until it is
2967 deleted using
2968 \begin{verbatim}
2969 # xm vnet-delete <vnetid>
2970 \end{verbatim}
2971 The vnets \xend knows about are listed by
2972 \begin{verbatim}
2973 # xm vnet-list
2974 \end{verbatim}
2975 More vnet management commands are available using the
2976 \texttt{vn} tool included in the vnet distribution.
2978 The format of a vnet configuration file is
2979 \begin{verbatim}
2980 (vnet (id <vnetid>)
2981 (bridge <bridge>)
2982 (vnetif <vnet interface>)
2983 (security <level>))
2984 \end{verbatim}
2985 White space is not significant. The parameters are:
2986 \begin{itemize}
2987 \item \verb|<vnetid>|: vnet id, the 128-bit vnet identifier. This can be given
2988 as 8 4-digit hex numbers separated by colons, or in short form as a single 4-digit hex number.
2989 The short form is the same as the long form with the first 7 fields zero.
2990 Vnet ids must be non-zero and id 1 is reserved.
2992 \item \verb|<bridge>|: the name of a bridge interface to create for the vnet. Domains
2993 are connected to the vnet by connecting their virtual interfaces to the bridge.
2994 Bridge names are limited to 14 characters by the kernel.
2996 \item \verb|<vnetif>|: the name of the virtual interface onto the vnet (optional). The
2997 interface encapsulates and decapsulates vnet traffic for the network and is attached
2998 to the vnet bridge. Interface names are limited to 14 characters by the kernel.
3000 \item \verb|<level>|: security level for the vnet (optional). The level may be one of
3001 \begin{itemize}
3002 \item \verb|none|: no security (default). Vnet traffic is in clear on the network.
3003 \item \verb|auth|: authentication. Vnet traffic is authenticated using IPSEC
3004 ESP with hmac96.
3005 \item \verb|conf|: confidentiality. Vnet traffic is authenticated and encrypted
3006 using IPSEC ESP with hmac96 and AES-128.
3007 \end{itemize}
3008 Authentication and confidentiality are experimental and use hard-wired keys at present.
3009 \end{itemize}
3010 When a vnet is created its configuration is stored by \xend and the vnet persists until it is
3011 deleted using \texttt{xm vnet-delete <vnetid>}. The interfaces and bridges used by vnets
3012 are visible in the output of \texttt{ifconfig} and \texttt{brctl show}.
3014 \section{Example}
3015 If the file \path{vnet97.sxp} contains
3016 \begin{verbatim}
3017 (vnet (id 97) (bridge vnet97) (vnetif vnif97)
3018 (security none))
3019 \end{verbatim}
3020 Then \texttt{xm vnet-create vnet97.sxp} will define a vnet with id 97 and no security.
3021 The bridge for the vnet is called vnet97 and the virtual interface for it is vnif97.
3022 To add an interface on a domain to this vnet set its bridge to vnet97
3023 in its configuration. In Python:
3024 \begin{verbatim}
3025 vif="bridge=vnet97"
3026 \end{verbatim}
3027 In sxp:
3028 \begin{verbatim}
3029 (dev (vif (mac aa:00:00:01:02:03) (bridge vnet97)))
3030 \end{verbatim}
3031 Once the domain is started you should see its interface in the output of \texttt{brctl show}
3032 under the ports for \texttt{vnet97}.
3034 To get best performance it is a good idea to reduce the MTU of a domain's interface
3035 onto a vnet to 1400. For example using \texttt{ifconfig eth0 mtu 1400} or putting
3036 \texttt{MTU=1400} in \texttt{ifcfg-eth0}.
3037 You may also have to change or remove cached config files for eth0 under
3038 \texttt{/etc/sysconfig/networking}. Vnets work anyway, but performance can be reduced
3039 by IP fragmentation caused by the vnet encapsulation exceeding the hardware MTU.
3041 \section{Installing vnet support}
3042 Vnets are implemented using a kernel module, which needs to be loaded before
3043 they can be used. You can either do this manually before starting \xend, using the
3044 command \texttt{vn insmod}, or configure \xend to use the \path{network-vnet}
3045 script in the xend configuration file \texttt{/etc/xend/xend-config.sxp}:
3046 \begin{verbatim}
3047 (network-script network-vnet)
3048 \end{verbatim}
3049 This script insmods the module and calls the \path{network-bridge} script.
3051 The vnet code is not compiled and installed by default.
3052 To compile the code and install on the current system
3053 use \texttt{make install} in the root of the vnet source tree,
3054 \path{tools/vnet}. It is also possible to install to an installation
3055 directory using \texttt{make dist}. See the \path{Makefile} in
3056 the source for details.
3058 The vnet module creates vnet interfaces \texttt{vnif0002},
3059 \texttt{vnif0003} and \texttt{vnif0004} by default. You can test that
3060 vnets are working by configuring IP addresses on these interfaces
3061 and trying to ping them across the network. For example, using machines
3062 hostA and hostB:
3063 \begin{verbatim}
3064 hostA# ifconfig vnif0004 10.0.0.100 up
3065 hostB# ifconfig vnif0004 10.0.0.101 up
3066 hostB# ping 10.0.0.100
3067 \end{verbatim}
3069 The vnet implementation uses IP multicast to discover vnet interfaces, so
3070 all machines hosting vnets must be reachable by multicast. Network switches
3071 are often configured not to forward multicast packets, so this often
3072 means that all machines using a vnet must be on the same LAN segment,
3073 unless you configure vnet forwarding.
3075 You can test multicast coverage by pinging the vnet multicast address:
3076 \begin{verbatim}
3077 # ping -b 224.10.0.1
3078 \end{verbatim}
3079 You should see replies from all machines with the vnet module running.
3080 You can see if vnet packets are being sent or received by dumping traffic
3081 on the vnet UDP port:
3082 \begin{verbatim}
3083 # tcpdump udp port 1798
3084 \end{verbatim}
3086 If multicast is not being forwaded between machines you can configure
3087 multicast forwarding using vn. Suppose we have machines hostA on 10.10.0.100
3088 and hostB on 10.11.0.100 and that multicast is not forwarded between them.
3089 We use vn to configure each machine to forward to the other:
3090 \begin{verbatim}
3091 hostA# vn peer-add hostB
3092 hostB# vn peer-add hostA
3093 \end{verbatim}
3094 Multicast forwarding needs to be used carefully - you must avoid creating forwarding
3095 loops. Typically only one machine on a subnet needs to be configured to forward,
3096 as it will forward multicasts received from other machines on the subnet.
3098 %% Chapter Glossary of Terms moved to glossary.tex
3099 \chapter{Glossary of Terms}
3101 \begin{description}
3103 \item[BVT] The BVT scheduler is used to give proportional fair shares
3104 of the CPU to domains.
3106 \item[Domain] A domain is the execution context that contains a
3107 running {\bf virtual machine}. The relationship between virtual
3108 machines and domains on Xen is similar to that between programs and
3109 processes in an operating system: a virtual machine is a persistent
3110 entity that resides on disk (somewhat like a program). When it is
3111 loaded for execution, it runs in a domain. Each domain has a {\bf
3112 domain ID}.
3114 \item[Domain 0] The first domain to be started on a Xen machine.
3115 Domain 0 is responsible for managing the system.
3117 \item[Domain ID] A unique identifier for a {\bf domain}, analogous to
3118 a process ID in an operating system.
3120 \item[Full virtualization] An approach to virtualization which
3121 requires no modifications to the hosted operating system, providing
3122 the illusion of a complete system of real hardware devices.
3124 \item[Hypervisor] An alternative term for {\bf VMM}, used because it
3125 means `beyond supervisor', since it is responsible for managing
3126 multiple `supervisor' kernels.
3128 \item[Live migration] A technique for moving a running virtual machine
3129 to another physical host, without stopping it or the services
3130 running on it.
3132 \item[Paravirtualization] An approach to virtualization which requires
3133 modifications to the operating system in order to run in a virtual
3134 machine. Xen uses paravirtualization but preserves binary
3135 compatibility for user space applications.
3137 \item[Shadow pagetables] A technique for hiding the layout of machine
3138 memory from a virtual machine's operating system. Used in some {\bf
3139 VMMs} to provide the illusion of contiguous physical memory, in
3140 Xen this is used during {\bf live migration}.
3142 \item[Virtual Block Device] Persistant storage available to a virtual
3143 machine, providing the abstraction of an actual block storage device.
3144 {\bf VBD}s may be actual block devices, filesystem images, or
3145 remote/network storage.
3147 \item[Virtual Machine] The environment in which a hosted operating
3148 system runs, providing the abstraction of a dedicated machine. A
3149 virtual machine may be identical to the underlying hardware (as in
3150 {\bf full virtualization}, or it may differ, as in {\bf
3151 paravirtualization}).
3153 \item[VMM] Virtual Machine Monitor - the software that allows multiple
3154 virtual machines to be multiplexed on a single physical machine.
3156 \item[Xen] Xen is a paravirtualizing virtual machine monitor,
3157 developed primarily by the Systems Research Group at the University
3158 of Cambridge Computer Laboratory.
3160 \item[XenLinux] A name for the port of the Linux kernel that
3161 runs on Xen.
3163 \end{description}
3166 \end{document}
3169 %% Other stuff without a home
3171 %% Instructions Re Python API
3173 %% Other Control Tasks using Python
3174 %% ================================
3176 %% A Python module 'Xc' is installed as part of the tools-install
3177 %% process. This can be imported, and an 'xc object' instantiated, to
3178 %% provide access to privileged command operations:
3180 %% # import Xc
3181 %% # xc = Xc.new()
3182 %% # dir(xc)
3183 %% # help(xc.domain_create)
3185 %% In this way you can see that the class 'xc' contains useful
3186 %% documentation for you to consult.
3188 %% A further package of useful routines (xenctl) is also installed:
3190 %% # import xenctl.utils
3191 %% # help(xenctl.utils)
3193 %% You can use these modules to write your own custom scripts or you
3194 %% can customise the scripts supplied in the Xen distribution.
3198 % Explain about AGP GART
3201 %% If you're not intending to configure the new domain with an IP
3202 %% address on your LAN, then you'll probably want to use NAT. The
3203 %% 'xen_nat_enable' installs a few useful iptables rules into domain0
3204 %% to enable NAT. [NB: We plan to support RSIP in future]
3208 %% Installing the file systems from the CD
3209 %% =======================================
3211 %% If you haven't got an existing Linux installation onto which you
3212 %% can just drop down the Xen and Xenlinux images, then the file
3213 %% systems on the CD provide a quick way of doing an install. However,
3214 %% you would be better off in the long run doing a proper install of
3215 %% your preferred distro and installing Xen onto that, rather than
3216 %% just doing the hack described below:
3218 %% Choose one or two partitions, depending on whether you want a
3219 %% separate /usr or not. Make file systems on it/them e.g.:
3220 %% mkfs -t ext3 /dev/hda3
3221 %% [or mkfs -t ext2 /dev/hda3 && tune2fs -j /dev/hda3 if using an old
3222 %% version of mkfs]
3224 %% Next, mount the file system(s) e.g.:
3225 %% mkdir /mnt/root && mount /dev/hda3 /mnt/root
3226 %% [mkdir /mnt/usr && mount /dev/hda4 /mnt/usr]
3228 %% To install the root file system, simply untar /usr/XenDemoCD/root.tar.gz:
3229 %% cd /mnt/root && tar -zxpf /usr/XenDemoCD/root.tar.gz
3231 %% You'll need to edit /mnt/root/etc/fstab to reflect your file system
3232 %% configuration. Changing the password file (etc/shadow) is probably a
3233 %% good idea too.
3235 %% To install the usr file system, copy the file system from CD on
3236 %% /usr, though leaving out the "XenDemoCD" and "boot" directories:
3237 %% cd /usr && cp -a X11R6 etc java libexec root src bin dict kerberos
3238 %% local sbin tmp doc include lib man share /mnt/usr
3240 %% If you intend to boot off these file systems (i.e. use them for
3241 %% domain 0), then you probably want to copy the /usr/boot
3242 %% directory on the cd over the top of the current symlink to /boot
3243 %% on your root filesystem (after deleting the current symlink)
3244 %% i.e.:
3245 %% cd /mnt/root ; rm boot ; cp -a /usr/boot .