ia64/xen-unstable

view docs/src/user.tex @ 18402:266758b689e0

docs: Update user manual for 3.3.

From: Stephen Spector <stephen.spector@citrix.com>
Signed-off-by: Keir Fraser <keir.fraser@citrix.com>
author Keir Fraser <keir.fraser@citrix.com>
date Thu Aug 28 09:49:52 2008 +0100 (2008-08-28)
parents 445681d122c0
children 5f3bb7f1a4cb
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 v3.3} \\[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 2002-2008, Citrix Systems, Inc., University of Cambridge, UK, XenSource Inc., IBM Corp., Hewlett-Packard Co., Intel Corp., AMD Inc., and others. All rights reserved.
47 Xen is an open-source project. Most portions of Xen are licensed for copying
48 under the terms of the GNU General Public License, version 2. Other portions
49 are licensed under the terms of the GNU Lesser General Public License, the
50 Zope Public License 2.0, or under ``BSD-style'' licenses. Please refer to the
51 COPYING file for details.
53 Xen includes software by Christopher Clark. This software is covered by the
54 following licence:
56 \begin{quote}
57 Copyright (c) 2002, Christopher Clark. All rights reserved.
59 Redistribution and use in source and binary forms, with or without
60 modification, are permitted provided that the following conditions are met:
62 \begin{itemize}
63 \item Redistributions of source code must retain the above copyright notice,
64 this list of conditions and the following disclaimer.
66 \item Redistributions in binary form must reproduce the above copyright
67 notice, this list of conditions and the following disclaimer in the
68 documentation and/or other materials provided with the distribution.
70 \item Neither the name of the original author; nor the names of any
71 contributors may be used to endorse or promote products derived from this
72 software without specific prior written permission.
73 \end{itemize}
75 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
76 AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
77 IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
78 DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE
79 FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
80 DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
81 SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
82 CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
83 OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
84 OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
85 \end{quote}
87 \cleardoublepage
90 % TABLE OF CONTENTS
91 \pagestyle{plain}
92 \pagenumbering{roman}
93 { \parskip 0pt plus 1pt
94 \tableofcontents }
95 \cleardoublepage
98 % PREPARE FOR MAIN TEXT
99 \pagenumbering{arabic}
100 \raggedbottom
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109 \setstretch{1.1}
112 %% Chapter Introduction moved to introduction.tex
113 \chapter{Introduction}
116 Xen is an open-source \emph{para-virtualizing} virtual machine monitor
117 (VMM), or ``hypervisor'', for a variety of processor architectures including x86. Xen can securely execute multiple virtual machines on a single physical system with near native performance. Xen facilitates enterprise-grade functionality, including:
119 \begin{itemize}
120 \item Virtual machines with performance close to native hardware.
121 \item Live migration of running virtual machines between physical hosts.
122 \item Up to 32\footnote{IA64 supports up to 64 virtual CPUs per guest virtual machine} virtual CPUs per guest virtual machine, with VCPU hotplug.
123 \item x86/32 with PAE, x86/64, and IA64 platform support.
124 \item Intel and AMD Virtualization Technology for unmodified guest operating systems (including Microsoft Windows).
125 \item Excellent hardware support (supports almost all Linux device
126 drivers).
127 \end{itemize}
130 \section{Usage Scenarios}
132 Usage scenarios for Xen include:
134 \begin{description}
135 \item [Server Consolidation.] Move multiple servers onto a single
136 physical host with performance and fault isolation provided at the
137 virtual machine boundaries.
138 \item [Hardware Independence.] Allow legacy applications and operating
139 systems to exploit new hardware.
140 \item [Multiple OS configurations.] Run multiple operating systems
141 simultaneously, for development or testing purposes.
142 \item [Kernel Development.] Test and debug kernel modifications in a
143 sand-boxed virtual machine --- no need for a separate test machine.
144 \item [Cluster Computing.] Management at VM granularity provides more
145 flexibility than separately managing each physical host, but better
146 control and isolation than single-system image solutions,
147 particularly by using live migration for load balancing.
148 \item [Hardware support for custom OSes.] Allow development of new
149 OSes while benefiting from the wide-ranging hardware support of
150 existing OSes such as Linux.
151 \end{description}
154 \section{Operating System Support}
156 Para-virtualization permits very high performance virtualization, even
157 on architectures like x86 that are traditionally very hard to
158 virtualize.
160 This approach requires operating systems to be \emph{ported} to run on
161 Xen. Porting an OS to run on Xen is similar to supporting a new
162 hardware platform, however the process is simplified because the
163 para-virtual machine architecture is very similar to the underlying
164 native hardware. Even though operating system kernels must explicitly
165 support Xen, a key feature is that user space applications and
166 libraries \emph{do not} require modification.
168 With hardware CPU virtualization as provided by Intel VT and AMD
169 SVM technology, the ability to run an unmodified guest OS kernel
170 is available. No porting of the OS is required, although some
171 additional driver support is necessary within Xen itself. Unlike
172 traditional full virtualization hypervisors, which suffer a tremendous
173 performance overhead, the combination of Xen and VT or Xen and
174 Pacifica technology complement one another to offer superb performance
175 for para-virtualized guest operating systems and full support for
176 unmodified guests running natively on the processor.
178 Paravirtualized Xen support is available for increasingly many
179 operating systems: currently, mature Linux support is available and
180 included in the standard distribution. Other OS ports, including
181 NetBSD, FreeBSD and Solaris are also complete.
184 \section{Hardware Support}
186 Xen currently runs on the IA64 and x86 architectures. Multiprocessor
187 machines are supported, and there is support for HyperThreading (SMT).
189 The default 32-bit Xen requires processor support for Physical
190 Addressing Extensions (PAE), which enables the hypervisor to address
191 up to 16GB of physical memory. Xen also supports x86/64 platforms
192 such as Intel EM64T and AMD Opteron which can currently address up to
193 1TB of physical memory.
195 Xen offloads most of the hardware support issues to the guest OS
196 running in the \emph{Domain~0} management virtual machine. Xen itself
197 contains only the code required to detect and start secondary
198 processors, set up interrupt routing, and perform PCI bus
199 enumeration. Device drivers run within a privileged guest OS rather
200 than within Xen itself. This approach provides compatibility with the
201 majority of device hardware supported by Linux. The default XenLinux
202 build contains support for most server-class network and disk
203 hardware, but you can add support for other hardware by configuring
204 your XenLinux kernel in the normal way.
207 \section{Structure of a Xen-Based System}
209 A Xen system has multiple layers, the lowest and most privileged of
210 which is Xen itself.
212 Xen may host multiple \emph{guest} operating systems, each of which is
213 executed within a secure virtual machine. In Xen terminology, a
214 \emph{domain}. Domains are scheduled by Xen to make effective use of the
215 available physical CPUs. Each guest OS manages its own applications.
216 This management includes the responsibility of scheduling each
217 application within the time allotted to the VM by Xen.
219 The first domain, \emph{domain~0}, is created automatically when the
220 system boots and has special management privileges. Domain~0 builds
221 other domains and manages their virtual devices. It also performs
222 administrative tasks such as suspending, resuming and migrating other
223 virtual machines.
225 Within domain~0, a process called \emph{xend} runs to manage the system.
226 \Xend\ is responsible for managing virtual machines and providing access
227 to their consoles. Commands are issued to \xend\ over an HTTP interface,
228 via a command-line tool.
231 \section{History}
233 Xen was originally developed by the Systems Research Group at the
234 University of Cambridge Computer Laboratory as part of the XenoServers
235 project, funded by the UK-EPSRC\@.
237 XenoServers aim to provide a ``public infrastructure for global
238 distributed computing''. Xen plays a key part in that, allowing one to
239 efficiently partition a single machine to enable multiple independent
240 clients to run their operating systems and applications in an
241 environment. This environment provides protection, resource isolation
242 and accounting. The project web page contains further information along
243 with pointers to papers and technical reports:
244 \path{http://www.cl.cam.ac.uk/xeno}
246 Xen has grown into a fully-fledged project in its own right, enabling us
247 to investigate interesting research issues regarding the best techniques
248 for virtualizing resources such as the CPU, memory, disk and network.
249 Project contributors now include Citrix, Intel, IBM, HP, AMD, Novell,
250 RedHat, Sun, Fujitsu, and Samsung.
252 Xen was first described in a paper presented at SOSP in
253 2003\footnote{\tt
254 http://www.cl.cam.ac.uk/netos/papers/2003-xensosp.pdf}, and the first
255 public release (1.0) was made that October. Since then, Xen has
256 significantly matured and is now used in production scenarios on many
257 sites.
259 \section{What's New}
261 Xen 3.3.0 offers:
263 \begin{itemize}
264 \item IO Emulation (stub domains) for HVM IO performance and scailability
265 \item Replacement of Intel VT vmxassist by new 16b emulation code
266 \item Improved VT-d device pass-through e.g. for graphics devices
267 \item Enhanced C and P state power management
268 \item Exploitation of multi-queue support on modern NICs
269 \item Removal of domain lock for improved PV guest scalability
270 \item 2MB page support for HVM and PV guests
271 \item CPU Portability
272 \end{itemize}
274 Xen 3.3 delivers the capabilities needed by enterprise customers and gives computing industry leaders a solid, secure platform to build upon for their virtualization solutions. This latest release establishes Xen as the definitive open source solution for virtualization.
278 \part{Installation}
280 %% Chapter Basic Installation
281 \chapter{Basic Installation}
283 The Xen distribution includes three main components: Xen itself, ports
284 of Linux and NetBSD to run on Xen, and the userspace tools required to
285 manage a Xen-based system. This chapter describes how to install the
286 Xen~3.3 distribution from source. Alternatively, there may be pre-built
287 packages available as part of your operating system distribution.
290 \section{Prerequisites}
291 \label{sec:prerequisites}
293 The following is a full list of prerequisites. Items marked `$\dag$' are
294 required by the \xend\ control tools, and hence required if you want to
295 run more than one virtual machine; items marked `$*$' are only required
296 if you wish to build from source.
297 \begin{itemize}
298 \item A working Linux distribution using the GRUB bootloader and running
299 on a P6-class or newer CPU\@.
300 \item [$\dag$] The \path{iproute2} package.
301 \item [$\dag$] The Linux bridge-utils\footnote{Available from {\tt
302 http://bridge.sourceforge.net}} (e.g., \path{/sbin/brctl})
303 \item [$\dag$] The Linux hotplug system\footnote{Available from {\tt
304 http://linux-hotplug.sourceforge.net/}} (e.g.,
305 \path{/sbin/hotplug} and related scripts). On newer distributions,
306 this is included alongside the Linux udev system\footnote{See {\tt
307 http://www.kernel.org/pub/linux/utils/kernel/hotplug/udev.html/}}.
308 \item [$*$] Build tools (gcc v3.2.x or v3.3.x, binutils, GNU make).
309 \item [$*$] Development installation of zlib (e.g.,\ zlib-dev).
310 \item [$*$] Development installation of Python v2.2 or later (e.g.,\
311 python-dev).
312 \item [$*$] \LaTeX\ and transfig are required to build the
313 documentation.
314 \end{itemize}
316 Once you have satisfied these prerequisites, you can now install either
317 a binary or source distribution of Xen.
319 \section{Installing from Binary Tarball}
321 Pre-built tarballs are available for download from the XenSource downloads
322 page:
323 \begin{quote} {\tt http://www.xensource.com/downloads/}
324 \end{quote}
326 Once you've downloaded the tarball, simply unpack and install:
327 \begin{verbatim}
328 # tar zxvf xen-3.0-install.tgz
329 # cd xen-3.0-install
330 # sh ./install.sh
331 \end{verbatim}
333 Once you've installed the binaries you need to configure your system as
334 described in Section~\ref{s:configure}.
336 \section{Installing from RPMs}
337 Pre-built RPMs are available for download from the XenSource downloads
338 page:
339 \begin{quote} {\tt http://www.xensource.com/downloads/}
340 \end{quote}
342 Once you've downloaded the RPMs, you typically install them via the
343 RPM commands:
345 \verb|# rpm -iv rpmname|
347 See the instructions and the Release Notes for each RPM set referenced at:
348 \begin{quote}
349 {\tt http://www.xensource.com/downloads/}.
350 \end{quote}
352 \section{Installing from Source}
354 This section describes how to obtain, build and install Xen from source.
356 \subsection{Obtaining the Source}
358 The Xen source tree is available as either a compressed source tarball
359 or as a clone of our master Mercurial repository.
361 \begin{description}
362 \item[Obtaining the Source Tarball]\mbox{} \\
363 Stable versions and daily snapshots of the Xen source tree are
364 available from the Xen download page:
365 \begin{quote} {\tt \tt http://www.xensource.com/downloads/}
366 \end{quote}
367 \item[Obtaining the source via Mercurial]\mbox{} \\
368 The source tree may also be obtained via the public Mercurial
369 repository at:
370 \begin{quote}{\tt http://xenbits.xensource.com}
371 \end{quote} See the instructions and the Getting Started Guide
372 referenced at:
373 \begin{quote}
374 {\tt http://www.xensource.com/downloads/}
375 \end{quote}
376 \end{description}
378 % \section{The distribution}
379 %
380 % The Xen source code repository is structured as follows:
381 %
382 % \begin{description}
383 % \item[\path{tools/}] Xen node controller daemon (Xend), command line
384 % tools, control libraries
385 % \item[\path{xen/}] The Xen VMM.
386 % \item[\path{buildconfigs/}] Build configuration files
387 % \item[\path{linux-*-xen-sparse/}] Xen support for Linux.
388 % \item[\path{patches/}] Experimental patches for Linux.
389 % \item[\path{docs/}] Various documentation files for users and
390 % developers.
391 % \item[\path{extras/}] Bonus extras.
392 % \end{description}
394 \subsection{Building from Source}
396 The top-level Xen Makefile includes a target ``world'' that will do the
397 following:
399 \begin{itemize}
400 \item Build Xen.
401 \item Build the control tools, including \xend.
402 \item Download (if necessary) and unpack the Linux 2.6 source code, and
403 patch it for use with Xen.
404 \item Build a Linux kernel to use in domain~0 and a smaller unprivileged
405 kernel, which can be used for unprivileged virtual machines.
406 \end{itemize}
408 After the build has completed you should have a top-level directory
409 called \path{dist/} in which all resulting targets will be placed. Of
410 particular interest are the two XenLinux kernel images, one with a
411 ``-xen0'' extension which contains hardware device drivers and drivers
412 for Xen's virtual devices, and one with a ``-xenU'' extension that
413 just contains the virtual ones. These are found in
414 \path{dist/install/boot/} along with the image for Xen itself and the
415 configuration files used during the build.
417 %The NetBSD port can be built using:
418 %\begin{quote}
419 %\begin{verbatim}
420 %# make netbsd20
421 %\end{verbatim}\end{quote}
422 %NetBSD port is built using a snapshot of the netbsd-2-0 cvs branch.
423 %The snapshot is downloaded as part of the build process if it is not
424 %yet present in the \path{NETBSD\_SRC\_PATH} search path. The build
425 %process also downloads a toolchain which includes all of the tools
426 %necessary to build the NetBSD kernel under Linux.
428 To customize the set of kernels built you need to edit the top-level
429 Makefile. Look for the line:
430 \begin{quote}
431 \begin{verbatim}
432 KERNELS ?= linux-2.6-xen0 linux-2.6-xenU
433 \end{verbatim}
434 \end{quote}
436 You can edit this line to include any set of operating system kernels
437 which have configurations in the top-level \path{buildconfigs/}
438 directory.
440 %% Inspect the Makefile if you want to see what goes on during a
441 %% build. Building Xen and the tools is straightforward, but XenLinux
442 %% is more complicated. The makefile needs a `pristine' Linux kernel
443 %% tree to which it will then add the Xen architecture files. You can
444 %% tell the makefile the location of the appropriate Linux compressed
445 %% tar file by
446 %% setting the LINUX\_SRC environment variable, e.g. \\
447 %% \verb!# LINUX_SRC=/tmp/linux-2.6.11.tar.bz2 make world! \\ or by
448 %% placing the tar file somewhere in the search path of {\tt
449 %% LINUX\_SRC\_PATH} which defaults to `{\tt .:..}'. If the
450 %% makefile can't find a suitable kernel tar file it attempts to
451 %% download it from kernel.org (this won't work if you're behind a
452 %% firewall).
454 %% After untaring the pristine kernel tree, the makefile uses the {\tt
455 %% mkbuildtree} script to add the Xen patches to the kernel.
457 %% \framebox{\parbox{5in}{
458 %% {\bf Distro specific:} \\
459 %% {\it Gentoo} --- if not using udev (most installations,
460 %% currently), you'll need to enable devfs and devfs mount at boot
461 %% time in the xen0 config. }}
463 \subsection{Custom Kernels}
465 % If you have an SMP machine you may wish to give the {\tt '-j4'}
466 % argument to make to get a parallel build.
468 If you wish to build a customized XenLinux kernel (e.g.\ to support
469 additional devices or enable distribution-required features), you can
470 use the standard Linux configuration mechanisms, specifying that the
471 architecture being built for is \path{xen}, e.g:
472 \begin{quote}
473 \begin{verbatim}
474 # cd linux-2.6.12-xen0
475 # make ARCH=xen xconfig
476 # cd ..
477 # make
478 \end{verbatim}
479 \end{quote}
481 You can also copy an existing Linux configuration (\path{.config}) into
482 e.g.\ \path{linux-2.6.12-xen0} and execute:
483 \begin{quote}
484 \begin{verbatim}
485 # make ARCH=xen oldconfig
486 \end{verbatim}
487 \end{quote}
489 You may be prompted with some Xen-specific options. We advise accepting
490 the defaults for these options.
492 Note that the only difference between the two types of Linux kernels
493 that are built is the configuration file used for each. The ``U''
494 suffixed (unprivileged) versions don't contain any of the physical
495 hardware device drivers, leading to a 30\% reduction in size; hence you
496 may prefer these for your non-privileged domains. The ``0'' suffixed
497 privileged versions can be used to boot the system, as well as in driver
498 domains and unprivileged domains.
500 \subsection{Installing Generated Binaries}
502 The files produced by the build process are stored under the
503 \path{dist/install/} directory. To install them in their default
504 locations, do:
505 \begin{quote}
506 \begin{verbatim}
507 # make install
508 \end{verbatim}
509 \end{quote}
511 Alternatively, users with special installation requirements may wish to
512 install them manually by copying the files to their appropriate
513 destinations.
515 %% Files in \path{install/boot/} include:
516 %% \begin{itemize}
517 %% \item \path{install/boot/xen-3.0.gz} Link to the Xen 'kernel'
518 %% \item \path{install/boot/vmlinuz-2.6-xen0} Link to domain 0
519 %% XenLinux kernel
520 %% \item \path{install/boot/vmlinuz-2.6-xenU} Link to unprivileged
521 %% XenLinux kernel
522 %% \end{itemize}
524 The \path{dist/install/boot} directory will also contain the config
525 files used for building the XenLinux kernels, and also versions of Xen
526 and XenLinux kernels that contain debug symbols such as
527 (\path{xen-syms-3.0.0} and \path{vmlinux-syms-2.6.12.6-xen0}) which are
528 essential for interpreting crash dumps. Retain these files as the
529 developers may wish to see them if you post on the mailing list.
532 \section{Configuration}
533 \label{s:configure}
535 Once you have built and installed the Xen distribution, it is simple to
536 prepare the machine for booting and running Xen.
538 \subsection{GRUB Configuration}
540 An entry should be added to \path{grub.conf} (often found under
541 \path{/boot/} or \path{/boot/grub/}) to allow Xen / XenLinux to boot.
542 This file is sometimes called \path{menu.lst}, depending on your
543 distribution. The entry should look something like the following:
545 %% KMSelf Thu Dec 1 19:06:13 PST 2005 262144 is useful for RHEL/RH and
546 %% related Dom0s.
547 {\small
548 \begin{verbatim}
549 title Xen 3.0 / XenLinux 2.6
550 kernel /boot/xen-3.0.gz dom0_mem=262144
551 module /boot/vmlinuz-2.6-xen0 root=/dev/sda4 ro console=tty0
552 \end{verbatim}
553 }
555 The kernel line tells GRUB where to find Xen itself and what boot
556 parameters should be passed to it (in this case, setting the domain~0
557 memory allocation in kilobytes and the settings for the serial port).
558 For more details on the various Xen boot parameters see
559 Section~\ref{s:xboot}.
561 The module line of the configuration describes the location of the
562 XenLinux kernel that Xen should start and the parameters that should be
563 passed to it. These are standard Linux parameters, identifying the root
564 device and specifying it be initially mounted read only and instructing
565 that console output be sent to the screen. Some distributions such as
566 SuSE do not require the \path{ro} parameter.
568 %% \framebox{\parbox{5in}{
569 %% {\bf Distro specific:} \\
570 %% {\it SuSE} --- Omit the {\tt ro} option from the XenLinux
571 %% kernel command line, since the partition won't be remounted rw
572 %% during boot. }}
574 To use an initrd, add another \path{module} line to the configuration,
575 like: {\small
576 \begin{verbatim}
577 module /boot/my_initrd.gz
578 \end{verbatim}
579 }
581 %% KMSelf Thu Dec 1 19:05:30 PST 2005 Other configs as an appendix?
583 When installing a new kernel, it is recommended that you do not delete
584 existing menu options from \path{menu.lst}, as you may wish to boot your
585 old Linux kernel in future, particularly if you have problems.
587 \subsection{Serial Console (optional)}
589 Serial console access allows you to manage, monitor, and interact with
590 your system over a serial console. This can allow access from another
591 nearby system via a null-modem (``LapLink'') cable or remotely via a serial
592 concentrator.
594 You system's BIOS, bootloader (GRUB), Xen, Linux, and login access must
595 each be individually configured for serial console access. It is
596 \emph{not} strictly necessary to have each component fully functional,
597 but it can be quite useful.
599 For general information on serial console configuration under Linux,
600 refer to the ``Remote Serial Console HOWTO'' at The Linux Documentation
601 Project: \url{http://www.tldp.org}
603 \subsubsection{Serial Console BIOS configuration}
605 Enabling system serial console output neither enables nor disables
606 serial capabilities in GRUB, Xen, or Linux, but may make remote
607 management of your system more convenient by displaying POST and other
608 boot messages over serial port and allowing remote BIOS configuration.
610 Refer to your hardware vendor's documentation for capabilities and
611 procedures to enable BIOS serial redirection.
614 \subsubsection{Serial Console GRUB configuration}
616 Enabling GRUB serial console output neither enables nor disables Xen or
617 Linux serial capabilities, but may made remote management of your system
618 more convenient by displaying GRUB prompts, menus, and actions over
619 serial port and allowing remote GRUB management.
621 Adding the following two lines to your GRUB configuration file,
622 typically either \path{/boot/grub/menu.lst} or \path{/boot/grub/grub.conf}
623 depending on your distro, will enable GRUB serial output.
625 \begin{quote}
626 {\small \begin{verbatim}
627 serial --unit=0 --speed=115200 --word=8 --parity=no --stop=1
628 terminal --timeout=10 serial console
629 \end{verbatim}}
630 \end{quote}
632 Note that when both the serial port and the local monitor and keyboard
633 are enabled, the text ``\emph{Press any key to continue}'' will appear
634 at both. Pressing a key on one device will cause GRUB to display to
635 that device. The other device will see no output. If no key is
636 pressed before the timeout period expires, the system will boot to the
637 default GRUB boot entry.
639 Please refer to the GRUB documentation for further information.
642 \subsubsection{Serial Console Xen configuration}
644 Enabling Xen serial console output neither enables nor disables Linux
645 kernel output or logging in to Linux over serial port. It does however
646 allow you to monitor and log the Xen boot process via serial console and
647 can be very useful in debugging.
649 %% kernel /boot/xen-2.0.gz dom0_mem=131072 console=com1,vga com1=115200,8n1
650 %% module /boot/vmlinuz-2.6-xen0 root=/dev/sda4 ro
652 In order to configure Xen serial console output, it is necessary to
653 add a boot option to your GRUB config; e.g.\ replace the previous
654 example kernel line with:
655 \begin{quote} {\small \begin{verbatim}
656 kernel /boot/xen.gz dom0_mem=131072 com1=115200,8n1 console=com1,vga
657 \end{verbatim}}
658 \end{quote}
660 This configures Xen to output on COM1 at 115,200 baud, 8 data bits, no
661 parity and 1 stop bit. Modify these parameters for your environment.
662 See Section~\ref{s:xboot} for an explanation of all boot parameters.
664 One can also configure XenLinux to share the serial console; to achieve
665 this append ``\path{console=ttyS0}'' to your module line.
668 \subsubsection{Serial Console Linux configuration}
670 Enabling Linux serial console output at boot neither enables nor
671 disables logging in to Linux over serial port. It does however allow
672 you to monitor and log the Linux boot process via serial console and can be
673 very useful in debugging.
675 To enable Linux output at boot time, add the parameter
676 \path{console=ttyS0} (or ttyS1, ttyS2, etc.) to your kernel GRUB line.
677 Under Xen, this might be:
678 \begin{quote}
679 {\footnotesize \begin{verbatim}
680 module /vmlinuz-2.6-xen0 ro root=/dev/VolGroup00/LogVol00 \
681 console=ttyS0, 115200
682 \end{verbatim}}
683 \end{quote}
684 to enable output over ttyS0 at 115200 baud.
688 \subsubsection{Serial Console Login configuration}
690 Logging in to Linux via serial console, under Xen or otherwise, requires
691 specifying a login prompt be started on the serial port. To permit root
692 logins over serial console, the serial port must be added to
693 \path{/etc/securetty}.
695 \newpage
696 To automatically start a login prompt over the serial port,
697 add the line: \begin{quote} {\small {\tt c:2345:respawn:/sbin/mingetty
698 ttyS0}} \end{quote} to \path{/etc/inittab}. Run \path{init q} to force
699 a reload of your inttab and start getty.
701 To enable root logins, add \path{ttyS0} to \path{/etc/securetty} if not
702 already present.
704 Your distribution may use an alternate getty; options include getty,
705 mgetty and agetty. Consult your distribution's documentation
706 for further information.
709 \subsection{TLS Libraries}
711 Users of the XenLinux 2.6 kernel should disable Thread Local Storage
712 (TLS) (e.g.\ by doing a \path{mv /lib/tls /lib/tls.disabled}) before
713 attempting to boot a XenLinux kernel\footnote{If you boot without first
714 disabling TLS, you will get a warning message during the boot process.
715 In this case, simply perform the rename after the machine is up and
716 then run \path{/sbin/ldconfig} to make it take effect.}. You can
717 always reenable TLS by restoring the directory to its original location
718 (i.e.\ \path{mv /lib/tls.disabled /lib/tls}).
720 The reason for this is that the current TLS implementation uses
721 segmentation in a way that is not permissible under Xen. If TLS is not
722 disabled, an emulation mode is used within Xen which reduces performance
723 substantially. To ensure full performance you should install a
724 `Xen-friendly' (nosegneg) version of the library.
727 \section{Booting Xen}
729 It should now be possible to restart the system and use Xen. Reboot and
730 choose the new Xen option when the Grub screen appears.
732 What follows should look much like a conventional Linux boot. The first
733 portion of the output comes from Xen itself, supplying low level
734 information about itself and the underlying hardware. The last portion
735 of the output comes from XenLinux.
737 You may see some error messages during the XenLinux boot. These are not
738 necessarily anything to worry about---they may result from kernel
739 configuration differences between your XenLinux kernel and the one you
740 usually use.
742 When the boot completes, you should be able to log into your system as
743 usual. If you are unable to log in, you should still be able to reboot
744 with your normal Linux kernel by selecting it at the GRUB prompt.
747 % Booting Xen
748 \chapter{Booting a Xen System}
750 Booting the system into Xen will bring you up into the privileged
751 management domain, Domain0. At that point you are ready to create
752 guest domains and ``boot'' them using the \texttt{xm create} command.
754 \section{Booting Domain0}
756 After installation and configuration is complete, reboot the system
757 and and choose the new Xen option when the Grub screen appears.
759 What follows should look much like a conventional Linux boot. The
760 first portion of the output comes from Xen itself, supplying low level
761 information about itself and the underlying hardware. The last
762 portion of the output comes from XenLinux.
764 %% KMSelf Wed Nov 30 18:09:37 PST 2005: We should specify what these are.
766 When the boot completes, you should be able to log into your system as
767 usual. If you are unable to log in, you should still be able to
768 reboot with your normal Linux kernel by selecting it at the GRUB prompt.
770 The first step in creating a new domain is to prepare a root
771 filesystem for it to boot. Typically, this might be stored in a normal
772 partition, an LVM or other volume manager partition, a disk file or on
773 an NFS server. A simple way to do this is simply to boot from your
774 standard OS install CD and install the distribution into another
775 partition on your hard drive.
777 To start the \xend\ control daemon, type
778 \begin{quote}
779 \verb!# xend start!
780 \end{quote}
782 If you wish the daemon to start automatically, see the instructions in
783 Section~\ref{s:xend}. Once the daemon is running, you can use the
784 \path{xm} tool to monitor and maintain the domains running on your
785 system. This chapter provides only a brief tutorial. We provide full
786 details of the \path{xm} tool in the next chapter.
788 % \section{From the web interface}
789 %
790 % Boot the Xen machine and start Xensv (see Chapter~\ref{cha:xensv}
791 % for more details) using the command: \\
792 % \verb_# xensv start_ \\
793 % This will also start Xend (see Chapter~\ref{cha:xend} for more
794 % information).
795 %
796 % The domain management interface will then be available at {\tt
797 % http://your\_machine:8080/}. This provides a user friendly wizard
798 % for starting domains and functions for managing running domains.
799 %
800 % \section{From the command line}
801 \section{Booting Guest Domains}
803 \subsection{Creating a Domain Configuration File}
805 Before you can start an additional domain, you must create a
806 configuration file. We provide two example files which you can use as
807 a starting point:
808 \begin{itemize}
809 \item \path{/etc/xen/xmexample1} is a simple template configuration
810 file for describing a single VM\@.
811 \item \path{/etc/xen/xmexample2} file is a template description that
812 is intended to be reused for multiple virtual machines. Setting the
813 value of the \path{vmid} variable on the \path{xm} command line
814 fills in parts of this template.
815 \end{itemize}
817 There are also a number of other examples which you may find useful.
818 Copy one of these files and edit it as appropriate. Typical values
819 you may wish to edit include:
821 \begin{quote}
822 \begin{description}
823 \item[kernel] Set this to the path of the kernel you compiled for use
824 with Xen (e.g.\ \path{kernel = ``/boot/vmlinuz-2.6-xenU''})
825 \item[memory] Set this to the size of the domain's memory in megabytes
826 (e.g.\ \path{memory = 64})
827 \item[disk] Set the first entry in this list to calculate the offset
828 of the domain's root partition, based on the domain ID\@. Set the
829 second to the location of \path{/usr} if you are sharing it between
830 domains (e.g.\ \path{disk = ['phy:your\_hard\_drive\%d,sda1,w' \%
831 (base\_partition\_number + vmid),
832 'phy:your\_usr\_partition,sda6,r' ]}
833 \item[dhcp] Uncomment the dhcp variable, so that the domain will
834 receive its IP address from a DHCP server (e.g.\ \path{dhcp=``dhcp''})
835 \end{description}
836 \end{quote}
838 You may also want to edit the {\bf vif} variable in order to choose
839 the MAC address of the virtual ethernet interface yourself. For
840 example:
842 \begin{quote}
843 \verb_vif = ['mac=00:16:3E:F6:BB:B3']_
844 \end{quote}
845 If you do not set this variable, \xend\ will automatically generate a
846 random MAC address from the range 00:16:3E:xx:xx:xx, assigned by IEEE to
847 XenSource as an OUI (organizationally unique identifier). XenSource
848 Inc. gives permission for anyone to use addresses randomly allocated
849 from this range for use by their Xen domains.
851 For a list of IEEE OUI assignments, see
852 \url{http://standards.ieee.org/regauth/oui/oui.txt}
855 \subsection{Booting the Guest Domain}
857 The \path{xm} tool provides a variety of commands for managing
858 domains. Use the \path{create} command to start new domains. Assuming
859 you've created a configuration file \path{myvmconf} based around
860 \path{/etc/xen/xmexample2}, to start a domain with virtual machine
861 ID~1 you should type:
863 \begin{quote}
864 \begin{verbatim}
865 # xm create -c myvmconf vmid=1
866 \end{verbatim}
867 \end{quote}
869 The \path{-c} switch causes \path{xm} to turn into the domain's
870 console after creation. The \path{vmid=1} sets the \path{vmid}
871 variable used in the \path{myvmconf} file.
873 You should see the console boot messages from the new domain appearing
874 in the terminal in which you typed the command, culminating in a login
875 prompt.
878 \section{Starting / Stopping Domains Automatically}
880 It is possible to have certain domains start automatically at boot
881 time and to have dom0 wait for all running domains to shutdown before
882 it shuts down the system.
884 To specify a domain is to start at boot-time, place its configuration
885 file (or a link to it) under \path{/etc/xen/auto/}.
887 A Sys-V style init script for Red Hat and LSB-compliant systems is
888 provided and will be automatically copied to \path{/etc/init.d/}
889 during install. You can then enable it in the appropriate way for
890 your distribution.
892 For instance, on Red Hat:
894 \begin{quote}
895 \verb_# chkconfig --add xendomains_
896 \end{quote}
898 By default, this will start the boot-time domains in runlevels 3, 4
899 and 5.
901 You can also use the \path{service} command to run this script
902 manually, e.g:
904 \begin{quote}
905 \verb_# service xendomains start_
907 Starts all the domains with config files under /etc/xen/auto/.
908 \end{quote}
910 \begin{quote}
911 \verb_# service xendomains stop_
913 Shuts down all running Xen domains.
914 \end{quote}
918 \part{Configuration and Management}
920 %% Chapter Domain Management Tools and Daemons
921 \chapter{Domain Management Tools}
923 This chapter summarizes the management software and tools available.
926 \section{\Xend\ }
927 \label{s:xend}
930 The \Xend\ node control daemon performs system management functions
931 related to virtual machines. It forms a central point of control of
932 virtualized resources, and must be running in order to start and manage
933 virtual machines. \Xend\ must be run as root because it needs access to
934 privileged system management functions.
936 An initialization script named \texttt{/etc/init.d/xend} is provided to
937 start \Xend\ at boot time. Use the tool appropriate (i.e. chkconfig) for
938 your Linux distribution to specify the runlevels at which this script
939 should be executed, or manually create symbolic links in the correct
940 runlevel directories.
942 \Xend\ can be started on the command line as well, and supports the
943 following set of parameters:
945 \begin{tabular}{ll}
946 \verb!# xend start! & start \xend, if not already running \\
947 \verb!# xend stop! & stop \xend\ if already running \\
948 \verb!# xend restart! & restart \xend\ if running, otherwise start it \\
949 % \verb!# xend trace_start! & start \xend, with very detailed debug logging \\
950 \verb!# xend status! & indicates \xend\ status by its return code
951 \end{tabular}
953 A SysV init script called {\tt xend} is provided to start \xend\ at
954 boot time. {\tt make install} installs this script in
955 \path{/etc/init.d}. To enable it, you have to make symbolic links in
956 the appropriate runlevel directories or use the {\tt chkconfig} tool,
957 where available. Once \xend\ is running, administration can be done
958 using the \texttt{xm} tool.
960 \subsection{Logging}
962 As \xend\ runs, events will be logged to \path{/var/log/xen/xend.log} and
963 (less frequently) to \path{/var/log/xen/xend-debug.log}. These, along with
964 the standard syslog files, are useful when troubleshooting problems.
966 \subsection{Configuring \Xend\ }
968 \Xend\ is written in Python. At startup, it reads its configuration
969 information from the file \path{/etc/xen/xend-config.sxp}. The Xen
970 installation places an example \texttt{xend-config.sxp} file in the
971 \texttt{/etc/xen} subdirectory which should work for most installations.
973 See the example configuration file \texttt{xend-debug.sxp} and the
974 section 5 man page \texttt{xend-config.sxp} for a full list of
975 parameters and more detailed information. Some of the most important
976 parameters are discussed below.
978 An HTTP interface and a Unix domain socket API are available to
979 communicate with \Xend. This allows remote users to pass commands to the
980 daemon. By default, \Xend does not start an HTTP server. It does start a
981 Unix domain socket management server, as the low level utility
982 \texttt{xm} requires it. For support of cross-machine migration, \Xend\
983 can start a relocation server. This support is not enabled by default
984 for security reasons.
986 Note: the example \texttt{xend} configuration file modifies the defaults and
987 starts up \Xend\ as an HTTP server as well as a relocation server.
989 From the file:
991 \begin{verbatim}
992 #(xend-http-server no)
993 (xend-http-server yes)
994 #(xend-unix-server yes)
995 #(xend-relocation-server no)
996 (xend-relocation-server yes)
997 \end{verbatim}
999 Comment or uncomment lines in that file to disable or enable features
1000 that you require.
1002 Connections from remote hosts are disabled by default:
1004 \begin{verbatim}
1005 # Address xend should listen on for HTTP connections, if xend-http-server is
1006 # set.
1007 # Specifying 'localhost' prevents remote connections.
1008 # Specifying the empty string '' (the default) allows all connections.
1009 #(xend-address '')
1010 (xend-address localhost)
1011 \end{verbatim}
1013 It is recommended that if migration support is not needed, the
1014 \texttt{xend-relocation-server} parameter value be changed to
1015 ``\texttt{no}'' or commented out.
1017 \section{Xm}
1018 \label{s:xm}
1020 The xm tool is the primary tool for managing Xen from the console. The
1021 general format of an xm command line is:
1023 \begin{verbatim}
1024 # xm command [switches] [arguments] [variables]
1025 \end{verbatim}
1027 The available \emph{switches} and \emph{arguments} are dependent on the
1028 \emph{command} chosen. The \emph{variables} may be set using
1029 declarations of the form {\tt variable=value} and command line
1030 declarations override any of the values in the configuration file being
1031 used, including the standard variables described above and any custom
1032 variables (for instance, the \path{xmdefconfig} file uses a {\tt vmid}
1033 variable).
1035 For online help for the commands available, type:
1037 \begin{quote}
1038 \begin{verbatim}
1039 # xm help
1040 \end{verbatim}
1041 \end{quote}
1043 This will list the most commonly used commands. The full list can be obtained
1044 using \verb_xm help --long_. You can also type \path{xm help $<$command$>$}
1045 for more information on a given command.
1047 \subsection{Basic Management Commands}
1049 One useful command is \verb_# xm list_ which lists all domains running in rows
1050 of the following format:
1051 \begin{center} {\tt name domid memory vcpus state cputime}
1052 \end{center}
1054 The meaning of each field is as follows:
1055 \begin{quote}
1056 \begin{description}
1057 \item[name] The descriptive name of the virtual machine.
1058 \item[domid] The number of the domain ID this virtual machine is
1059 running in.
1060 \item[memory] Memory size in megabytes.
1061 \item[vcpus] The number of virtual CPUs this domain has.
1062 \item[state] Domain state consists of 5 fields:
1063 \begin{description}
1064 \item[r] running
1065 \item[b] blocked
1066 \item[p] paused
1067 \item[s] shutdown
1068 \item[c] crashed
1069 \end{description}
1070 \item[cputime] How much CPU time (in seconds) the domain has used so
1071 far.
1072 \end{description}
1073 \end{quote}
1075 The \path{xm list} command also supports a long output format when the
1076 \path{-l} switch is used. This outputs the full details of the
1077 running domains in \xend's SXP configuration format.
1079 If you want to know how long your domains have been running for, then
1080 you can use the \verb_# xm uptime_ command.
1083 You can get access to the console of a particular domain using
1084 the \verb_# xm console_ command (e.g.\ \verb_# xm console myVM_).
1086 \subsection{Domain Scheduling Management Commands}
1088 The credit CPU scheduler automatically load balances guest VCPUs
1089 across all available physical CPUs on an SMP host. The user need
1090 not manually pin VCPUs to load balance the system. However, she
1091 can restrict which CPUs a particular VCPU may run on using
1092 the \path{xm vcpu-pin} command.
1094 Each guest domain is assigned a \path{weight} and a \path{cap}.
1096 A domain with a weight of 512 will get twice as much CPU as a
1097 domain with a weight of 256 on a contended host. Legal weights
1098 range from 1 to 65535 and the default is 256.
1100 The cap optionally fixes the maximum amount of CPU a guest will
1101 be able to consume, even if the host system has idle CPU cycles.
1102 The cap is expressed in percentage of one physical CPU: 100 is
1103 1 physical CPU, 50 is half a CPU, 400 is 4 CPUs, etc... The
1104 default, 0, means there is no upper cap.
1106 When you are running with the credit scheduler, you can check and
1107 modify your domains' weights and caps using the \path{xm sched-credit}
1108 command:
1110 \begin{tabular}{ll}
1111 \verb!xm sched-credit -d <domain>! & lists weight and cap \\
1112 \verb!xm sched-credit -d <domain> -w <weight>! & sets the weight \\
1113 \verb!xm sched-credit -d <domain> -c <cap>! & sets the cap
1114 \end{tabular}
1118 %% Chapter Domain Configuration
1119 \chapter{Domain Configuration}
1120 \label{cha:config}
1122 The following contains the syntax of the domain configuration files
1123 and description of how to further specify networking, driver domain
1124 and general scheduling behavior.
1127 \section{Configuration Files}
1128 \label{s:cfiles}
1130 Xen configuration files contain the following standard variables.
1131 Unless otherwise stated, configuration items should be enclosed in
1132 quotes: see the configuration scripts in \path{/etc/xen/}
1133 for concrete examples.
1135 \begin{description}
1136 \item[kernel] Path to the kernel image.
1137 \item[ramdisk] Path to a ramdisk image (optional).
1138 % \item[builder] The name of the domain build function (e.g.
1139 % {\tt'linux'} or {\tt'netbsd'}.
1140 \item[memory] Memory size in megabytes.
1141 \item[vcpus] The number of virtual CPUs.
1142 \item[console] Port to export the domain console on (default 9600 +
1143 domain ID).
1144 \item[vif] Network interface configuration. This may simply contain
1145 an empty string for each desired interface, or may override various
1146 settings, e.g.\
1147 \begin{verbatim}
1148 vif = [ 'mac=00:16:3E:00:00:11, bridge=xen-br0',
1149 'bridge=xen-br1' ]
1150 \end{verbatim}
1151 to assign a MAC address and bridge to the first interface and assign
1152 a different bridge to the second interface, leaving \xend\ to choose
1153 the MAC address. The settings that may be overridden in this way are
1154 type, mac, bridge, ip, script, backend, and vifname.
1155 \item[disk] List of block devices to export to the domain e.g.
1156 \verb_disk = [ 'phy:hda1,sda1,r' ]_
1157 exports physical device \path{/dev/hda1} to the domain as
1158 \path{/dev/sda1} with read-only access. Exporting a disk read-write
1159 which is currently mounted is dangerous -- if you are \emph{certain}
1160 you wish to do this, you can specify \path{w!} as the mode.
1161 \item[dhcp] Set to {\tt `dhcp'} if you want to use DHCP to configure
1162 networking.
1163 \item[netmask] Manually configured IP netmask.
1164 \item[gateway] Manually configured IP gateway.
1165 \item[hostname] Set the hostname for the virtual machine.
1166 \item[root] Specify the root device parameter on the kernel command
1167 line.
1168 \item[nfs\_server] IP address for the NFS server (if any).
1169 \item[nfs\_root] Path of the root filesystem on the NFS server (if
1170 any).
1171 \item[extra] Extra string to append to the kernel command line (if
1172 any)
1173 \end{description}
1175 Additional fields are documented in the example configuration files
1176 (e.g. to configure virtual TPM functionality).
1178 For additional flexibility, it is also possible to include Python
1179 scripting commands in configuration files. An example of this is the
1180 \path{xmexample2} file, which uses Python code to handle the
1181 \path{vmid} variable.
1184 %\part{Advanced Topics}
1187 \section{Network Configuration}
1189 For many users, the default installation should work ``out of the
1190 box''. More complicated network setups, for instance with multiple
1191 Ethernet interfaces and/or existing bridging setups will require some
1192 special configuration.
1194 The purpose of this section is to describe the mechanisms provided by
1195 \xend\ to allow a flexible configuration for Xen's virtual networking.
1197 \subsection{Xen virtual network topology}
1199 Each domain network interface is connected to a virtual network
1200 interface in dom0 by a point to point link (effectively a ``virtual
1201 crossover cable''). These devices are named {\tt
1202 vif$<$domid$>$.$<$vifid$>$} (e.g.\ {\tt vif1.0} for the first
1203 interface in domain~1, {\tt vif3.1} for the second interface in
1204 domain~3).
1206 Traffic on these virtual interfaces is handled in domain~0 using
1207 standard Linux mechanisms for bridging, routing, rate limiting, etc.
1208 Xend calls on two shell scripts to perform initial configuration of
1209 the network and configuration of new virtual interfaces. By default,
1210 these scripts configure a single bridge for all the virtual
1211 interfaces. Arbitrary routing / bridging configurations can be
1212 configured by customizing the scripts, as described in the following
1213 section.
1215 \subsection{Xen networking scripts}
1217 Xen's virtual networking is configured by two shell scripts (by
1218 default \path{network-bridge} and \path{vif-bridge}). These are called
1219 automatically by \xend\ when certain events occur, with arguments to
1220 the scripts providing further contextual information. These scripts
1221 are found by default in \path{/etc/xen/scripts}. The names and
1222 locations of the scripts can be configured in
1223 \path{/etc/xen/xend-config.sxp}.
1225 \begin{description}
1226 \item[network-bridge:] This script is called whenever \xend\ is started or
1227 stopped to respectively initialize or tear down the Xen virtual
1228 network. In the default configuration initialization creates the
1229 bridge `xen-br0' and moves eth0 onto that bridge, modifying the
1230 routing accordingly. When \xend\ exits, it deletes the Xen bridge
1231 and removes eth0, restoring the normal IP and routing configuration.
1233 %% In configurations where the bridge already exists, this script
1234 %% could be replaced with a link to \path{/bin/true} (for instance).
1236 \item[vif-bridge:] This script is called for every domain virtual
1237 interface and can configure firewalling rules and add the vif to the
1238 appropriate bridge. By default, this adds and removes VIFs on the
1239 default Xen bridge.
1240 \end{description}
1242 Other example scripts are available (\path{network-route} and
1243 \path{vif-route}, \path{network-nat} and \path{vif-nat}).
1244 For more complex network setups (e.g.\ where routing is required or
1245 integrate with existing bridges) these scripts may be replaced with
1246 customized variants for your site's preferred configuration.
1248 \section{Driver Domain Configuration}
1249 \label{s:ddconf}
1251 \subsection{PCI}
1252 \label{ss:pcidd}
1254 Individual PCI devices can be assigned to a given domain (a PCI driver domain)
1255 to allow that domain direct access to the PCI hardware.
1257 While PCI Driver Domains can increase the stability and security of a system
1258 by addressing a number of security concerns, there are some security issues
1259 that remain that you can read about in Section~\ref{s:ddsecurity}.
1261 \subsubsection{Compile-Time Setup}
1262 To use this functionality, ensure
1263 that the PCI Backend is compiled in to a privileged domain (e.g. domain 0)
1264 and that the domains which will be assigned PCI devices have the PCI Frontend
1265 compiled in. In XenLinux, the PCI Backend is available under the Xen
1266 configuration section while the PCI Frontend is under the
1267 architecture-specific "Bus Options" section. You may compile both the backend
1268 and the frontend into the same kernel; they will not affect each other.
1270 \subsubsection{PCI Backend Configuration - Binding at Boot}
1271 The PCI devices you wish to assign to unprivileged domains must be "hidden"
1272 from your backend domain (usually domain 0) so that it does not load a driver
1273 for them. Use the \path{pciback.hide} kernel parameter which is specified on
1274 the kernel command-line and is configurable through GRUB (see
1275 Section~\ref{s:configure}). Note that devices are not really hidden from the
1276 backend domain. The PCI Backend appears to the Linux kernel as a regular PCI
1277 device driver. The PCI Backend ensures that no other device driver loads
1278 for the devices by binding itself as the device driver for those devices.
1279 PCI devices are identified by hexadecimal slot/function numbers (on Linux,
1280 use \path{lspci} to determine slot/function numbers of your devices) and
1281 can be specified with or without the PCI domain: \\
1282 \centerline{ {\tt ({\em bus}:{\em slot}.{\em func})} example {\tt (02:1d.3)}} \\
1283 \centerline{ {\tt ({\em domain}:{\em bus}:{\em slot}.{\em func})} example {\tt (0000:02:1d.3)}} \\
1285 An example kernel command-line which hides two PCI devices might be: \\
1286 \centerline{ {\tt root=/dev/sda4 ro console=tty0 pciback.hide=(02:01.f)(0000:04:1d.0) } } \\
1288 \subsubsection{PCI Backend Configuration - Late Binding}
1289 PCI devices can also be bound to the PCI Backend after boot through the manual
1290 binding/unbinding facilities provided by the Linux kernel in sysfs (allowing
1291 for a Xen user to give PCI devices to driver domains that were not specified
1292 on the kernel command-line). There are several attributes with the PCI
1293 Backend's sysfs directory (\path{/sys/bus/pci/drivers/pciback}) that can be
1294 used to bind/unbind devices:
1296 \begin{description}
1297 \item[slots] lists all of the PCI slots that the PCI Backend will try to seize
1298 (or "hide" from Domain 0). A PCI slot must appear in this list before it can
1299 be bound to the PCI Backend through the \path{bind} attribute.
1300 \item[new\_slot] write the name of a slot here (in 0000:00:00.0 format) to
1301 have the PCI Backend seize the device in this slot.
1302 \item[remove\_slot] write the name of a slot here (same format as
1303 \path{new\_slot}) to have the PCI Backend no longer try to seize devices in
1304 this slot. Note that this does not unbind the driver from a device it has
1305 already seized.
1306 \item[bind] write the name of a slot here (in 0000:00:00.0 format) to have
1307 the Linux kernel attempt to bind the device in that slot to the PCI Backend
1308 driver.
1309 \item[unbind] write the name of a skit here (same format as \path{bind}) to have
1310 the Linux kernel unbind the device from the PCI Backend. DO NOT unbind a
1311 device while it is currently given to a PCI driver domain!
1312 \end{description}
1314 Some examples:
1316 Bind a device to the PCI Backend which is not bound to any other driver.
1317 \begin{verbatim}
1318 # # Add a new slot to the PCI Backend's list
1319 # echo -n 0000:01:04.d > /sys/bus/pci/drivers/pciback/new_slot
1320 # # Now that the backend is watching for the slot, bind to it
1321 # echo -n 0000:01:04.d > /sys/bus/pci/drivers/pciback/bind
1322 \end{verbatim}
1324 Unbind a device from its driver and bind to the PCI Backend.
1325 \begin{verbatim}
1326 # # Unbind a PCI network card from its network driver
1327 # echo -n 0000:05:02.0 > /sys/bus/pci/drivers/3c905/unbind
1328 # # And now bind it to the PCI Backend
1329 # echo -n 0000:05:02.0 > /sys/bus/pci/drivers/pciback/new_slot
1330 # echo -n 0000:05:02.0 > /sys/bus/pci/drivers/pciback/bind
1331 \end{verbatim}
1333 Note that the "-n" option in the example is important as it causes echo to not
1334 output a new-line.
1336 \subsubsection{PCI Backend Configuration - User-space Quirks}
1337 Quirky devices (such as the Broadcom Tigon 3) may need write access to their
1338 configuration space registers. Xen can be instructed to allow specified PCI
1339 devices write access to specific configuration space registers. The policy may
1340 be found in:
1342 \centerline{ \path{/etc/xen/xend-pci-quirks.sxp} }
1344 The policy file is heavily commented and is intended to provide enough
1345 documentation for developers to extend it.
1347 \subsubsection{PCI Backend Configuration - Permissive Flag}
1348 If the user-space quirks approach doesn't meet your needs you may want to enable
1349 the permissive flag for that device. To do so, first get the PCI domain, bus,
1350 slot, and function information from dom0 via \path{lspci}. Then augment the
1351 user-space policy for permissive devices. The permissive policy can be found
1352 in:
1354 \centerline{ \path{/etc/xen/xend-pci-permissive.sxp} }
1356 Currently, the only way to reset the permissive flag is to unbind the device
1357 from the PCI Backend driver.
1359 \subsubsection{PCI Backend - Checking Status}
1360 There two important sysfs nodes that provide a mechanism to view specifics on
1361 quirks and permissive devices:
1362 \begin{description}
1363 \item \path{/sys/bus/drivers/pciback/permissive} \\
1364 Use \path{cat} on this file to view a list of permissive slots.
1365 \item \path{/sys/bus/drivers/pciback/quirks} \\
1366 Use \path{cat} on this file view a hierarchical view of devices bound to the
1367 PCI backend, their PCI vendor/device ID, and any quirks that are associated with
1368 that particular slot.
1369 \end{description}
1371 You may notice that every device bound to the PCI backend has 17 quirks standard
1372 "quirks" regardless of \path{xend-pci-quirks.sxp}. These default entries are
1373 necessary to support interactions between the PCI bus manager and the device bound
1374 to it. Even non-quirky devices should have these standard entries.
1376 In this case, preference was given to accuracy over aesthetics by choosing to
1377 show the standard quirks in the quirks list rather than hide them from the
1378 inquiring user
1380 \subsubsection{PCI Frontend Configuration}
1381 To configure a domU to receive a PCI device:
1383 \begin{description}
1384 \item[Command-line:]
1385 Use the {\em pci} command-line flag. For multiple devices, use the option
1386 multiple times. \\
1387 \centerline{ {\tt xm create netcard-dd pci=01:00.0 pci=02:03.0 }} \\
1389 \item[Flat Format configuration file:]
1390 Specify all of your PCI devices in a python list named {\em pci}. \\
1391 \centerline{ {\tt pci=['01:00.0','02:03.0'] }} \\
1393 \item[SXP Format configuration file:]
1394 Use a single PCI device section for all of your devices (specify the numbers
1395 in hexadecimal with the preceding '0x'). Note that {\em domain} here refers
1396 to the PCI domain, not a virtual machine within Xen.
1397 {\small
1398 \begin{verbatim}
1399 (device (pci
1400 (dev (domain 0x0)(bus 0x3)(slot 0x1a)(func 0x1)
1401 (dev (domain 0x0)(bus 0x1)(slot 0x5)(func 0x0)
1403 \end{verbatim}
1405 \end{description}
1407 %% There are two possible types of privileges: IO privileges and
1408 %% administration privileges.
1410 \section{Support for virtual Trusted Platform Module (vTPM)}
1411 \label{ss:vtpm}
1413 Paravirtualized domains can be given access to a virtualized version
1414 of a TPM. This enables applications in these domains to use the services
1415 of the TPM device for example through a TSS stack
1416 \footnote{Trousers TSS stack: http://sourceforge.net/projects/trousers}.
1417 The Xen source repository provides the necessary software components to
1418 enable virtual TPM access. Support is provided through several
1419 different pieces. First, a TPM emulator has been modified to provide TPM's
1420 functionality for the virtual TPM subsystem. Second, a virtual TPM Manager
1421 coordinates the virtual TPMs efforts, manages their creation, and provides
1422 protected key storage using the TPM. Third, a device driver pair providing
1423 a TPM front- and backend is available for XenLinux to deliver TPM commands
1424 from the domain to the virtual TPM manager, which dispatches it to a
1425 software TPM. Since the TPM Manager relies on a HW TPM for protected key
1426 storage, therefore this subsystem requires a Linux-supported hardware TPM.
1427 For development purposes, a TPM emulator is available for use on non-TPM
1428 enabled platforms.
1430 \subsubsection{Compile-Time Setup}
1431 To enable access to the virtual TPM, the virtual TPM backend driver must
1432 be compiled for a privileged domain (e.g. domain 0). Using the XenLinux
1433 configuration, the necessary driver can be selected in the Xen configuration
1434 section. Unless the driver has been compiled into the kernel, its module
1435 must be activated using the following command:
1437 \begin{verbatim}
1438 modprobe tpmbk
1439 \end{verbatim}
1441 Similarly, the TPM frontend driver must be compiled for the kernel trying
1442 to use TPM functionality. Its driver can be selected in the kernel
1443 configuration section Device Driver / Character Devices / TPM Devices.
1444 Along with that the TPM driver for the built-in TPM must be selected.
1445 If the virtual TPM driver has been compiled as module, it
1446 must be activated using the following command:
1448 \begin{verbatim}
1449 modprobe tpm_xenu
1450 \end{verbatim}
1452 Furthermore, it is necessary to build the virtual TPM manager and software
1453 TPM by making changes to entries in Xen build configuration files.
1454 The following entry in the file Config.mk in the Xen root source
1455 directory must be made:
1457 \begin{verbatim}
1458 VTPM_TOOLS ?= y
1459 \end{verbatim}
1461 After a build of the Xen tree and a reboot of the machine, the TPM backend
1462 drive must be loaded. Once loaded, the virtual TPM manager daemon
1463 must be started before TPM-enabled guest domains may be launched.
1464 To enable being the destination of a virtual TPM Migration, the virtual TPM
1465 migration daemon must also be loaded.
1467 \begin{verbatim}
1468 vtpm_managerd
1469 \end{verbatim}
1470 \begin{verbatim}
1471 vtpm_migratord
1472 \end{verbatim}
1474 Once the VTPM manager is running, the VTPM can be accessed by loading the
1475 front end driver in a guest domain.
1477 \subsubsection{Development and Testing TPM Emulator}
1478 For development and testing on non-TPM enabled platforms, a TPM emulator
1479 can be used in replacement of a platform TPM. First, the entry in the file
1480 tools/vtpm/Rules.mk must look as follows:
1482 \begin{verbatim}
1483 BUILD_EMULATOR = y
1484 \end{verbatim}
1486 Second, the entry in the file tool/vtpm\_manager/Rules.mk must be uncommented
1487 as follows:
1489 \begin{verbatim}
1490 # TCS talks to fifo's rather than /dev/tpm. TPM Emulator assumed on fifos
1491 CFLAGS += -DDUMMY_TPM
1492 \end{verbatim}
1494 Before starting the virtual TPM Manager, start the emulator by executing
1495 the following in dom0:
1497 \begin{verbatim}
1498 tpm_emulator clear
1499 \end{verbatim}
1501 \subsubsection{vTPM Frontend Configuration}
1502 To provide TPM functionality to a user domain, a line must be added to
1503 the virtual TPM configuration file using the following format:
1505 \begin{verbatim}
1506 vtpm = ['instance=<instance number>, backend=<domain id>']
1507 \end{verbatim}
1509 The { \it instance number} reflects the preferred virtual TPM instance
1510 to associate with the domain. If the selected instance is
1511 already associated with another domain, the system will automatically
1512 select the next available instance. An instance number greater than
1513 zero must be provided. It is possible to omit the instance
1514 parameter from the configuration file.
1516 The {\it domain id} provides the ID of the domain where the
1517 virtual TPM backend driver and virtual TPM are running in. It should
1518 currently always be set to '0'.
1521 Examples for valid vtpm entries in the configuration file are
1523 \begin{verbatim}
1524 vtpm = ['instance=1, backend=0']
1525 \end{verbatim}
1526 and
1527 \begin{verbatim}
1528 vtpm = ['backend=0'].
1529 \end{verbatim}
1531 \subsubsection{Using the virtual TPM}
1533 Access to TPM functionality is provided by the virtual TPM frontend driver.
1534 Similar to existing hardware TPM drivers, this driver provides basic TPM
1535 status information through the {\it sysfs} filesystem. In a Xen user domain
1536 the sysfs entries can be found in /sys/devices/xen/vtpm-0.
1538 Commands can be sent to the virtual TPM instance using the character
1539 device /dev/tpm0 (major 10, minor 224).
1541 % Chapter Storage and FileSytem Management
1542 \chapter{Storage and File System Management}
1544 Storage can be made available to virtual machines in a number of
1545 different ways. This chapter covers some possible configurations.
1547 The most straightforward method is to export a physical block device (a
1548 hard drive or partition) from dom0 directly to the guest domain as a
1549 virtual block device (VBD).
1551 Storage may also be exported from a filesystem image or a partitioned
1552 filesystem image as a \emph{file-backed VBD}.
1554 Finally, standard network storage protocols such as NBD, iSCSI, NFS,
1555 etc., can be used to provide storage to virtual machines.
1558 \section{Exporting Physical Devices as VBDs}
1559 \label{s:exporting-physical-devices-as-vbds}
1561 One of the simplest configurations is to directly export individual
1562 partitions from domain~0 to other domains. To achieve this use the
1563 \path{phy:} specifier in your domain configuration file. For example a
1564 line like
1565 \begin{quote}
1566 \verb_disk = ['phy:hda3,sda1,w']_
1567 \end{quote}
1568 specifies that the partition \path{/dev/hda3} in domain~0 should be
1569 exported read-write to the new domain as \path{/dev/sda1}; one could
1570 equally well export it as \path{/dev/hda} or \path{/dev/sdb5} should
1571 one wish.
1573 In addition to local disks and partitions, it is possible to export
1574 any device that Linux considers to be ``a disk'' in the same manner.
1575 For example, if you have iSCSI disks or GNBD volumes imported into
1576 domain~0 you can export these to other domains using the \path{phy:}
1577 disk syntax. E.g.:
1578 \begin{quote}
1579 \verb_disk = ['phy:vg/lvm1,sda2,w']_
1580 \end{quote}
1582 \begin{center}
1583 \framebox{\bf Warning: Block device sharing}
1584 \end{center}
1585 \begin{quote}
1586 Block devices should typically only be shared between domains in a
1587 read-only fashion otherwise the Linux kernel's file systems will get
1588 very confused as the file system structure may change underneath
1589 them (having the same ext3 partition mounted \path{rw} twice is a
1590 sure fire way to cause irreparable damage)! \Xend\ will attempt to
1591 prevent you from doing this by checking that the device is not
1592 mounted read-write in domain~0, and hasn't already been exported
1593 read-write to another domain. If you want read-write sharing,
1594 export the directory to other domains via NFS from domain~0 (or use
1595 a cluster file system such as GFS or ocfs2).
1596 \end{quote}
1599 \section{Using File-backed VBDs}
1601 It is also possible to use a file in Domain~0 as the primary storage
1602 for a virtual machine. As well as being convenient, this also has the
1603 advantage that the virtual block device will be \emph{sparse} ---
1604 space will only really be allocated as parts of the file are used. So
1605 if a virtual machine uses only half of its disk space then the file
1606 really takes up half of the size allocated.
1608 For example, to create a 2GB sparse file-backed virtual block device
1609 (actually only consumes no disk space at all):
1610 \begin{quote}
1611 \verb_# dd if=/dev/zero of=vm1disk bs=1k seek=2048k count=0_
1612 \end{quote}
1614 Make a file system in the disk file:
1615 \begin{quote}
1616 \verb_# mkfs -t ext3 vm1disk_
1617 \end{quote}
1619 (when the tool asks for confirmation, answer `y')
1621 Populate the file system e.g.\ by copying from the current root:
1622 \begin{quote}
1623 \begin{verbatim}
1624 # mount -o loop vm1disk /mnt
1625 # cp -ax /{root,dev,var,etc,usr,bin,sbin,lib} /mnt
1626 # mkdir /mnt/{proc,sys,home,tmp}
1627 \end{verbatim}
1628 \end{quote}
1630 Tailor the file system by editing \path{/etc/fstab},
1631 \path{/etc/hostname}, etc.\ Don't forget to edit the files in the
1632 mounted file system, instead of your domain~0 filesystem, e.g.\ you
1633 would edit \path{/mnt/etc/fstab} instead of \path{/etc/fstab}. For
1634 this example put \path{/dev/sda1} to root in fstab.
1636 Now unmount (this is important!):
1637 \begin{quote}
1638 \verb_# umount /mnt_
1639 \end{quote}
1641 In the configuration file set:
1642 \begin{quote}
1643 \verb_disk = ['tap:aio:/full/path/to/vm1disk,sda1,w']_
1644 \end{quote}
1646 As the virtual machine writes to its `disk', the sparse file will be
1647 filled in and consume more space up to the original 2GB.
1649 {\em{Note:}} Users that have worked with file-backed VBDs on Xen in previous
1650 versions will be interested to know that this support is now provided through
1651 the blktap driver instead of the loopback driver. This change results in
1652 file-based block devices that are higher-performance, more scalable, and which
1653 provide better safety properties for VBD data. All that is required to update
1654 your existing file-backed VM configurations is to change VBD configuration
1655 lines from:
1656 \begin{quote}
1657 \verb_disk = ['file:/full/path/to/vm1disk,sda1,w']_
1658 \end{quote}
1659 to:
1660 \begin{quote}
1661 \verb_disk = ['tap:aio:/full/path/to/vm1disk,sda1,w']_
1662 \end{quote}
1665 \subsection{Loopback-mounted file-backed VBDs (deprecated)}
1667 {\em{{\bf{Note:}} Loopback mounted VBDs have now been replaced with
1668 blktap-based support for raw image files, as described above. This
1669 section remains to detail a configuration that was used by older Xen
1670 versions.}}
1672 Raw image file-backed VBDs may also be attached to VMs using the
1673 Linux loopback driver. The only required change to the raw file
1674 instructions above are to specify the configuration entry as:
1675 \begin{quote}
1676 \verb_disk = ['file:/full/path/to/vm1disk,sda1,w']_
1677 \end{quote}
1679 {\bf Note that loopback file-backed VBDs may not be appropriate for backing
1680 I/O-intensive domains.} This approach is known to experience
1681 substantial slowdowns under heavy I/O workloads, due to the I/O
1682 handling by the loopback block device used to support file-backed VBDs
1683 in dom0. Loopback support remains for old Xen installations, and users
1684 are strongly encouraged to use the blktap-based file support (using
1685 ``{\tt{tap:aio}}'' as described above).
1687 Additionally, Linux supports a maximum of eight loopback file-backed
1688 VBDs across all domains by default. This limit can be statically
1689 increased by using the \emph{max\_loop} module parameter if
1690 CONFIG\_BLK\_DEV\_LOOP is compiled as a module in the dom0 kernel, or
1691 by using the \emph{max\_loop=n} boot option if CONFIG\_BLK\_DEV\_LOOP
1692 is compiled directly into the dom0 kernel. Again, users are encouraged
1693 to use the blktap-based file support described above which scales to much
1694 larger number of active VBDs.
1697 \section{Using LVM-backed VBDs}
1698 \label{s:using-lvm-backed-vbds}
1700 A particularly appealing solution is to use LVM volumes as backing for
1701 domain file-systems since this allows dynamic growing/shrinking of
1702 volumes as well as snapshot and other features.
1704 To initialize a partition to support LVM volumes:
1705 \begin{quote}
1706 \begin{verbatim}
1707 # pvcreate /dev/sda10
1708 \end{verbatim}
1709 \end{quote}
1711 Create a volume group named `vg' on the physical partition:
1712 \begin{quote}
1713 \begin{verbatim}
1714 # vgcreate vg /dev/sda10
1715 \end{verbatim}
1716 \end{quote}
1718 Create a logical volume of size 4GB named `myvmdisk1':
1719 \begin{quote}
1720 \begin{verbatim}
1721 # lvcreate -L4096M -n myvmdisk1 vg
1722 \end{verbatim}
1723 \end{quote}
1725 You should now see that you have a \path{/dev/vg/myvmdisk1} Make a
1726 filesystem, mount it and populate it, e.g.:
1727 \begin{quote}
1728 \begin{verbatim}
1729 # mkfs -t ext3 /dev/vg/myvmdisk1
1730 # mount /dev/vg/myvmdisk1 /mnt
1731 # cp -ax / /mnt
1732 # umount /mnt
1733 \end{verbatim}
1734 \end{quote}
1736 Now configure your VM with the following disk configuration:
1737 \begin{quote}
1738 \begin{verbatim}
1739 disk = [ 'phy:vg/myvmdisk1,sda1,w' ]
1740 \end{verbatim}
1741 \end{quote}
1743 LVM enables you to grow the size of logical volumes, but you'll need
1744 to resize the corresponding file system to make use of the new space.
1745 Some file systems (e.g.\ ext3) now support online resize. See the LVM
1746 manuals for more details.
1748 You can also use LVM for creating copy-on-write (CoW) clones of LVM
1749 volumes (known as writable persistent snapshots in LVM terminology).
1750 This facility is new in Linux 2.6.8, so isn't as stable as one might
1751 hope. In particular, using lots of CoW LVM disks consumes a lot of
1752 dom0 memory, and error conditions such as running out of disk space
1753 are not handled well. Hopefully this will improve in future.
1755 To create two copy-on-write clones of the above file system you would
1756 use the following commands:
1758 \begin{quote}
1759 \begin{verbatim}
1760 # lvcreate -s -L1024M -n myclonedisk1 /dev/vg/myvmdisk1
1761 # lvcreate -s -L1024M -n myclonedisk2 /dev/vg/myvmdisk1
1762 \end{verbatim}
1763 \end{quote}
1765 Each of these can grow to have 1GB of differences from the master
1766 volume. You can grow the amount of space for storing the differences
1767 using the lvextend command, e.g.:
1768 \begin{quote}
1769 \begin{verbatim}
1770 # lvextend +100M /dev/vg/myclonedisk1
1771 \end{verbatim}
1772 \end{quote}
1774 Don't let the `differences volume' ever fill up otherwise LVM gets
1775 rather confused. It may be possible to automate the growing process by
1776 using \path{dmsetup wait} to spot the volume getting full and then
1777 issue an \path{lvextend}.
1779 In principle, it is possible to continue writing to the volume that
1780 has been cloned (the changes will not be visible to the clones), but
1781 we wouldn't recommend this: have the cloned volume as a `pristine'
1782 file system install that isn't mounted directly by any of the virtual
1783 machines.
1786 \section{Using NFS Root}
1788 First, populate a root filesystem in a directory on the server
1789 machine. This can be on a distinct physical machine, or simply run
1790 within a virtual machine on the same node.
1792 Now configure the NFS server to export this filesystem over the
1793 network by adding a line to \path{/etc/exports}, for instance:
1795 \begin{quote}
1796 \begin{small}
1797 \begin{verbatim}
1798 /export/vm1root 192.0.2.4/24 (rw,sync,no_root_squash)
1799 \end{verbatim}
1800 \end{small}
1801 \end{quote}
1803 Finally, configure the domain to use NFS root. In addition to the
1804 normal variables, you should make sure to set the following values in
1805 the domain's configuration file:
1807 \begin{quote}
1808 \begin{small}
1809 \begin{verbatim}
1810 root = '/dev/nfs'
1811 nfs_server = '2.3.4.5' # substitute IP address of server
1812 nfs_root = '/path/to/root' # path to root FS on the server
1813 \end{verbatim}
1814 \end{small}
1815 \end{quote}
1817 The domain will need network access at boot time, so either statically
1818 configure an IP address using the config variables \path{ip},
1819 \path{netmask}, \path{gateway}, \path{hostname}; or enable DHCP
1820 (\path{dhcp='dhcp'}).
1822 Note that the Linux NFS root implementation is known to have stability
1823 problems under high load (this is not a Xen-specific problem), so this
1824 configuration may not be appropriate for critical servers.
1827 \chapter{CPU Management}
1829 %% KMS Something sage about CPU / processor management.
1831 Xen allows a domain's virtual CPU(s) to be associated with one or more
1832 host CPUs. This can be used to allocate real resources among one or
1833 more guests, or to make optimal use of processor resources when
1834 utilizing dual-core, hyperthreading, or other advanced CPU technologies.
1836 Xen enumerates physical CPUs in a `depth first' fashion. For a system
1837 with both hyperthreading and multiple cores, this would be all the
1838 hyperthreads on a given core, then all the cores on a given socket,
1839 and then all sockets. I.e. if you had a two socket, dual core,
1840 hyperthreaded Xeon the CPU order would be:
1843 \begin{center}
1844 \begin{tabular}{l|l|l|l|l|l|l|r}
1845 \multicolumn{4}{c|}{socket0} & \multicolumn{4}{c}{socket1} \\ \hline
1846 \multicolumn{2}{c|}{core0} & \multicolumn{2}{c|}{core1} &
1847 \multicolumn{2}{c|}{core0} & \multicolumn{2}{c}{core1} \\ \hline
1848 ht0 & ht1 & ht0 & ht1 & ht0 & ht1 & ht0 & ht1 \\
1849 \#0 & \#1 & \#2 & \#3 & \#4 & \#5 & \#6 & \#7 \\
1850 \end{tabular}
1851 \end{center}
1854 Having multiple vcpus belonging to the same domain mapped to the same
1855 physical CPU is very likely to lead to poor performance. It's better to
1856 use `vcpus-set' to hot-unplug one of the vcpus and ensure the others are
1857 pinned on different CPUs.
1859 If you are running IO intensive tasks, its typically better to dedicate
1860 either a hyperthread or whole core to running domain 0, and hence pin
1861 other domains so that they can't use CPU 0. If your workload is mostly
1862 compute intensive, you may want to pin vcpus such that all physical CPU
1863 threads are available for guest domains.
1865 \chapter{Migrating Domains}
1867 \section{Domain Save and Restore}
1869 The administrator of a Xen system may suspend a virtual machine's
1870 current state into a disk file in domain~0, allowing it to be resumed at
1871 a later time.
1873 For example you can suspend a domain called ``VM1'' to disk using the
1874 command:
1875 \begin{verbatim}
1876 # xm save VM1 VM1.chk
1877 \end{verbatim}
1879 This will stop the domain named ``VM1'' and save its current state
1880 into a file called \path{VM1.chk}.
1882 To resume execution of this domain, use the \path{xm restore} command:
1883 \begin{verbatim}
1884 # xm restore VM1.chk
1885 \end{verbatim}
1887 This will restore the state of the domain and resume its execution.
1888 The domain will carry on as before and the console may be reconnected
1889 using the \path{xm console} command, as described earlier.
1891 \section{Migration and Live Migration}
1893 Migration is used to transfer a domain between physical hosts. There
1894 are two varieties: regular and live migration. The former moves a
1895 virtual machine from one host to another by pausing it, copying its
1896 memory contents, and then resuming it on the destination. The latter
1897 performs the same logical functionality but without needing to pause
1898 the domain for the duration. In general when performing live migration
1899 the domain continues its usual activities and---from the user's
1900 perspective---the migration should be imperceptible.
1902 To perform a live migration, both hosts must be running Xen / \xend\ and
1903 the destination host must have sufficient resources (e.g.\ memory
1904 capacity) to accommodate the domain after the move. Furthermore we
1905 currently require both source and destination machines to be on the same
1906 L2 subnet.
1908 Currently, there is no support for providing automatic remote access
1909 to filesystems stored on local disk when a domain is migrated.
1910 Administrators should choose an appropriate storage solution (i.e.\
1911 SAN, NAS, etc.) to ensure that domain filesystems are also available
1912 on their destination node. GNBD is a good method for exporting a
1913 volume from one machine to another. iSCSI can do a similar job, but is
1914 more complex to set up.
1916 When a domain migrates, it's MAC and IP address move with it, thus it is
1917 only possible to migrate VMs within the same layer-2 network and IP
1918 subnet. If the destination node is on a different subnet, the
1919 administrator would need to manually configure a suitable etherip or IP
1920 tunnel in the domain~0 of the remote node.
1922 A domain may be migrated using the \path{xm migrate} command. To live
1923 migrate a domain to another machine, we would use the command:
1925 \begin{verbatim}
1926 # xm migrate --live mydomain destination.ournetwork.com
1927 \end{verbatim}
1929 Without the \path{--live} flag, \xend\ simply stops the domain and
1930 copies the memory image over to the new node and restarts it. Since
1931 domains can have large allocations this can be quite time consuming,
1932 even on a Gigabit network. With the \path{--live} flag \xend\ attempts
1933 to keep the domain running while the migration is in progress, resulting
1934 in typical down times of just 60--300ms.
1936 For now it will be necessary to reconnect to the domain's console on the
1937 new machine using the \path{xm console} command. If a migrated domain
1938 has any open network connections then they will be preserved, so SSH
1939 connections do not have this limitation.
1942 %% Chapter Securing Xen
1943 \chapter{Securing Xen}
1945 This chapter describes how to secure a Xen system. It describes a number
1946 of scenarios and provides a corresponding set of best practices. It
1947 begins with a section devoted to understanding the security implications
1948 of a Xen system.
1951 \section{Xen Security Considerations}
1953 When deploying a Xen system, one must be sure to secure the management
1954 domain (Domain-0) as much as possible. If the management domain is
1955 compromised, all other domains are also vulnerable. The following are a
1956 set of best practices for Domain-0:
1958 \begin{enumerate}
1959 \item \textbf{Run the smallest number of necessary services.} The less
1960 things that are present in a management partition, the better.
1961 Remember, a service running as root in the management domain has full
1962 access to all other domains on the system.
1963 \item \textbf{Use a firewall to restrict the traffic to the management
1964 domain.} A firewall with default-reject rules will help prevent
1965 attacks on the management domain.
1966 \item \textbf{Do not allow users to access Domain-0.} The Linux kernel
1967 has been known to have local-user root exploits. If you allow normal
1968 users to access Domain-0 (even as unprivileged users) you run the risk
1969 of a kernel exploit making all of your domains vulnerable.
1970 \end{enumerate}
1972 \section{Driver Domain Security Considerations}
1973 \label{s:ddsecurity}
1975 Driver domains address a range of security problems that exist regarding
1976 the use of device drivers and hardware. On many operating systems in common
1977 use today, device drivers run within the kernel with the same privileges as
1978 the kernel. Few or no mechanisms exist to protect the integrity of the kernel
1979 from a misbehaving (read "buggy") or malicious device driver. Driver
1980 domains exist to aid in isolating a device driver within its own virtual
1981 machine where it cannot affect the stability and integrity of other
1982 domains. If a driver crashes, the driver domain can be restarted rather than
1983 have the entire machine crash (and restart) with it. Drivers written by
1984 unknown or untrusted third-parties can be confined to an isolated space.
1985 Driver domains thus address a number of security and stability issues with
1986 device drivers.
1988 However, due to limitations in current hardware, a number of security
1989 concerns remain that need to be considered when setting up driver domains (it
1990 should be noted that the following list is not intended to be exhaustive).
1992 \begin{enumerate}
1993 \item \textbf{Without an IOMMU, a hardware device can DMA to memory regions
1994 outside of its controlling domain.} Architectures which do not have an
1995 IOMMU (e.g. most x86-based platforms) to restrict DMA usage by hardware
1996 are vulnerable. A hardware device which can perform arbitrary memory reads
1997 and writes can read/write outside of the memory of its controlling domain.
1998 A malicious or misbehaving domain could use a hardware device it controls
1999 to send data overwriting memory in another domain or to read arbitrary
2000 regions of memory in another domain.
2001 \item \textbf{Shared buses are vulnerable to sniffing.} Devices that share
2002 a data bus can sniff (and possible spoof) each others' data. Device A that
2003 is assigned to Domain A could eavesdrop on data being transmitted by
2004 Domain B to Device B and then relay that data back to Domain A.
2005 \item \textbf{Devices which share interrupt lines can either prevent the
2006 reception of that interrupt by the driver domain or can trigger the
2007 interrupt service routine of that guest needlessly.} A devices which shares
2008 a level-triggered interrupt (e.g. PCI devices) with another device can
2009 raise an interrupt and never clear it. This effectively blocks other devices
2010 which share that interrupt line from notifying their controlling driver
2011 domains that they need to be serviced. A device which shares an
2012 any type of interrupt line can trigger its interrupt continually which
2013 forces execution time to be spent (in multiple guests) in the interrupt
2014 service routine (potentially denying time to other processes within that
2015 guest). System architectures which allow each device to have its own
2016 interrupt line (e.g. PCI's Message Signaled Interrupts) are less
2017 vulnerable to this denial-of-service problem.
2018 \item \textbf{Devices may share the use of I/O memory address space.} Xen can
2019 only restrict access to a device's physical I/O resources at a certain
2020 granularity. For interrupt lines and I/O port address space, that
2021 granularity is very fine (per interrupt line and per I/O port). However,
2022 Xen can only restrict access to I/O memory address space on a page size
2023 basis. If more than one device shares use of a page in I/O memory address
2024 space, the domains to which those devices are assigned will be able to
2025 access the I/O memory address space of each other's devices.
2026 \end{enumerate}
2029 \section{Security Scenarios}
2032 \subsection{The Isolated Management Network}
2034 In this scenario, each node has two network cards in the cluster. One
2035 network card is connected to the outside world and one network card is a
2036 physically isolated management network specifically for Xen instances to
2037 use.
2039 As long as all of the management partitions are trusted equally, this is
2040 the most secure scenario. No additional configuration is needed other
2041 than forcing Xend to bind to the management interface for relocation.
2044 \subsection{A Subnet Behind a Firewall}
2046 In this scenario, each node has only one network card but the entire
2047 cluster sits behind a firewall. This firewall should do at least the
2048 following:
2050 \begin{enumerate}
2051 \item Prevent IP spoofing from outside of the subnet.
2052 \item Prevent access to the relocation port of any of the nodes in the
2053 cluster except from within the cluster.
2054 \end{enumerate}
2056 The following iptables rules can be used on each node to prevent
2057 migrations to that node from outside the subnet assuming the main
2058 firewall does not do this for you:
2060 \begin{verbatim}
2061 # this command disables all access to the Xen relocation
2062 # port:
2063 iptables -A INPUT -p tcp --destination-port 8002 -j REJECT
2065 # this command enables Xen relocations only from the specific
2066 # subnet:
2067 iptables -I INPUT -p tcp -{}-source 192.0.2.0/24 \
2068 --destination-port 8002 -j ACCEPT
2069 \end{verbatim}
2071 \subsection{Nodes on an Untrusted Subnet}
2073 Migration on an untrusted subnet is not safe in current versions of Xen.
2074 It may be possible to perform migrations through a secure tunnel via an
2075 VPN or SSH. The only safe option in the absence of a secure tunnel is to
2076 disable migration completely. The easiest way to do this is with
2077 iptables:
2079 \begin{verbatim}
2080 # this command disables all access to the Xen relocation port
2081 iptables -A INPUT -p tcp -{}-destination-port 8002 -j REJECT
2082 \end{verbatim}
2084 %% Chapter Xen Mandatory Access Control Framework
2085 \chapter{sHype/Xen Access Control}
2086 The Xen mandatory access control framework is an implementation of the
2087 sHype Hypervisor Security Architecture
2088 (www.research.ibm.com/ssd\_shype). It permits or denies communication
2089 and resource access of domains based on a security policy. The
2090 mandatory access controls are enforced in addition to the Xen core
2091 controls, such as memory protection. They are designed to remain
2092 transparent during normal operation of domains (policy-conform
2093 behavior) but to intervene when domains move outside their intended
2094 sharing behavior. This chapter will describe how the sHype access
2095 controls in Xen can be configured to prevent viruses from spilling
2096 over from one into another workload type and secrets from leaking from
2097 one workload type to another. sHype/Xen depends on the correct
2098 behavior of Domain-0 (cf previous chapter).
2100 Benefits of configuring sHype/ACM in Xen include:
2101 \begin{itemize}
2102 \item robust workload and resource protection effective against rogue
2103 user domains
2104 \item simple, platform- and operating system-independent security
2105 policies (ideal for heterogeneous distributed environments)
2106 \item safety net with minimal performance overhead in case operating
2107 system security is missing, does not scale, or fails
2108 \end{itemize}
2110 These benefits are very valuable because today's operating systems
2111 become increasingly complex and often have no or insufficient
2112 mandatory access controls. (Discretionary access controls, supported
2113 by most operating systems, are not effective against viruses or
2114 misbehaving programs.) Where mandatory access control exists (e.g.,
2115 SELinux), they usually deploy platform-specific, complex, and difficult
2116 to understand security policies. Multi-tier applications in business
2117 environments typically require different operating systems
2118 (e.g., AIX, Windows, Linux) in different tiers. Related distributed
2119 transactions and workloads cannot be easily protected on the OS level.
2120 The Xen access control framework steps in to offer a coarse-grained
2121 but very robust and consistent security layer and safety net across
2122 different platforms and operating systems.
2124 To control sharing between domains, Xen mediates all inter-domain
2125 communication (shared memory, events) as well as the access of domains
2126 to resources such as storage disks. Thus, Xen can confine distributed
2127 workloads (domain payloads) by permitting sharing among domains
2128 running the same type of workload and denying sharing between pairs of
2129 domains that run different workload types. We assume that--from a Xen
2130 perspective--only one workload type is running per user domain. To
2131 enable Xen to associate domains and resources with workload types,
2132 security labels including the workload types are attached to domains
2133 and resources. These labels and the hypervisor sHype controls cannot
2134 be manipulated or bypassed by user domains and are effective even
2135 against compromised or rogue domains.
2137 \section{Overview}
2138 This section gives an overview of how workloads can be protected using
2139 the sHype mandatory access control framework in Xen.
2140 Figure~\ref{fig:acmoverview} shows the necessary steps in activating
2141 the Xen workload protection. These steps are described in detail in
2142 Section~\ref{section:acmexample}.
2144 \begin{figure}
2145 \centering
2146 \includegraphics[width=13cm]{figs/acm_overview.eps}
2147 \caption{Overview of activating sHype workload protection in Xen.
2148 Section numbers point to representative examples.}
2149 \label{fig:acmoverview}
2150 \end{figure}
2152 First, the sHype/ACM access control must be enabled in the Xen
2153 distribution and the distribution must be built and installed (cf
2154 Subsection~\ref{subsection:acmexampleconfigure}). Before we can
2155 enforce security, a Xen security policy must be created (cf
2156 Subsection~\ref{subsection:acmexamplecreate}) and deployed (cf
2157 Subsection~\ref{subsection:acmexampleinstall}). This policy defines
2158 the workload types differentiated during access control. It also
2159 defines the rules that compare workload types of domains and resources
2160 to decide about access requests. Workload types are represented by
2161 security labels that can be securely associated to domains and resources (cf
2162 Subsections~\ref{subsection:acmexamplelabeldomains}
2163 and~\ref{subsection:acmexamplelabelresources}). The functioning of
2164 the active sHype/Xen workload protection is demonstrated using simple
2165 resource assignment, and domain creation tests in
2166 Subsection~\ref{subsection:acmexampletest}.
2167 Section~\ref{section:acmpolicy} describes the syntax and semantics of
2168 the sHype/Xen security policy in detail and introduces briefly the
2169 tools that are available to help you create your own sHype security policies.
2171 The next section describes all the necessary steps to create, deploy,
2172 and test a simple workload protection policy. It is meant to enable
2173 Xen users and developers to quickly try out the sHype/Xen workload
2174 protection. Those readers who are interested in learning more about
2175 how the sHype access control in Xen works and how it is configured
2176 using the XML security policy should read Section~\ref{section:acmpolicy}
2177 as well. Section~\ref{section:acmlimitations} concludes this chapter with
2178 current limitations of the sHype implementation for Xen.
2180 \section{Xen Workload Protection Step-by-Step}
2181 \label{section:acmexample}
2183 You are about to configure and deploy the Xen sHype workload protection
2184 by following 5 simple steps:
2185 \begin{itemize}
2186 \item configure and install sHype/Xen
2187 \item create a simple workload protection security policy
2188 \item deploy the sHype/Xen security policy
2189 \item associate domains and resources with workload labels,
2190 \item test the workload protection
2191 \end{itemize}
2192 The essential commands to create and deploy an sHype/Xen security
2193 policy are numbered throughout the following sections. If you want a
2194 quick-guide or return at a later time to go quickly through this
2195 demonstration, simply look for the numbered commands and apply them in
2196 order.
2198 \subsection{Configuring/Building sHype Support into Xen}
2199 \label{subsection:acmexampleconfigure}
2200 First, we need to configure the access control module in Xen and
2201 install the ACM-enabled Xen hypervisor. This step installs security
2202 tools and compiles sHype/ACM controls into the Xen hypervisor.
2204 To enable sHype/ACM in Xen, please edit the Config.mk file in the top
2205 Xen directory.
2207 \begin{verbatim}
2208 (1) In Config.mk
2209 Change: XSM_ENABLE ?= n
2210 To: XSM_ENABLE ?= y
2212 Change: ACM_SECURITY ?= n
2213 To: ACM_SECURITY ?= y
2214 \end{verbatim}
2216 Then install the security-enabled Xen environment as follows:
2218 \begin{verbatim}
2219 (2) # make world
2220 # make install
2221 \end{verbatim}
2223 Reboot into the security-enabled Xen hypervisor.
2225 \begin{verbatim}
2226 (3) # reboot
2227 \end{verbatim}
2229 Xen will boot into the default security policy. After reboot,
2230 you can explore the simple DEFAULT policy.
2231 \begin{scriptsize}
2232 \begin{verbatim}
2233 # xm getpolicy
2234 Supported security subsystems : ACM
2235 Policy name : DEFAULT
2236 Policy type : ACM
2237 Version of XML policy : 1.0
2238 Policy configuration : loaded
2240 # xm labels
2241 SystemManagement
2243 # xm list --label
2244 Name ID Mem VCPUs State Time(s) Label
2245 Domain-0 0 941 1 r----- 38.1 ACM:DEFAULT:SystemManagement
2246 \end{verbatim}
2247 \end{scriptsize}
2249 In this state, no domains can be started.
2250 Now, a policy can be created and loaded into the hypervisor.
2252 \subsection{Creating A WLP Policy in 3 Simple Steps with ezPolicy}
2253 \label{subsection:acmexamplecreate}
2255 We will use the ezPolicy tool to quickly create a policy that protects
2256 workloads. You will need both the Python and wxPython packages to run
2257 this tool. To run the tool in Domain-0, you can download the wxPython
2258 package from www.wxpython.org or use the command \verb|yum install wxPython|
2259 in Redhat/Fedora. To run the tool on MS Windows, you also need to download
2260 the Python package from www.python.org. After these packages are installed,
2261 start the ezPolicy tool with the following command:
2263 \begin{verbatim}
2264 (4) # xensec_ezpolicy
2265 \end{verbatim}
2267 Figure~\ref{fig:acmezpolicy} shows a screen-shot of the tool. The
2268 following steps illustrate how you can create the workload definition
2269 shown in Figure~\ref{fig:acmezpolicy}. You can use \verb|<CTRL>-h| to
2270 pop up a help window at any time. The indicators (a), (b), and (c) in
2271 Figure~\ref{fig:acmezpolicy} show the buttons that are used during the
2272 3 steps of creating a policy:
2273 \begin{enumerate}
2274 \item defining workloads
2275 \item defining run-time conflicts
2276 \item translating the workload definition into an sHype/Xen access
2277 control policy
2278 \end{enumerate}
2280 \paragraph{Defining workloads.} Workloads are defined for each
2281 organization and department that you enter in the left panel.
2283 To ease the transition from an unlabeled to a fully labeled workload-protection
2284 environment, we have added support to sHype/Xen to run unlabeled domains accessing
2285 unlabeled resources in addition to labeled domains accessing labeled resources.
2287 Support for running unlabeled domains on sHype/Xen is enabled by adding the
2288 predefined workload type and label \verb|__UNLABELED__| to the security
2289 policy. (This is a double underscore
2290 followed by the string ''\verb|UNLABELED|'' followed by a double underscore.)
2291 The ezPolicy tool automatically adds this organization-level workload type
2292 to a new workload definition (cf Figure~\ref{fig:acmezpolicy}). It can simply be
2293 deleted from the workload definition if no such support is desired. If unlabeled domains
2294 are supported in the policy, then any domain or resource that has no label will implicitly
2295 inherit this label when access control decisions are made. In effect, unlabeled
2296 domains and resources define a new workload type \verb|__UNLABELED__|, which is
2297 confined from any other labeled workload.
2299 Please use now the ``New Org'' button to add the organization workload types
2300 ``A-Bank'', ``B-Bank'', and ``AutoCorp''.
2302 You can refine an organization to differentiate between multiple
2303 department workloads by right-clicking the organization and selecting
2304 \verb|Add Department| (or selecting an organization and pressing
2305 \verb|<CRTL>-a|). Create department workloads ``SecurityUnderwriting'',
2306 and ``MarketAnalysis'' for the ``A-Bank''. The resulting layout of the
2307 tool should be similar to the left panel shown in
2308 Figure~\ref{fig:acmezpolicy}.
2310 \begin{figure}[htb]
2311 \centering
2312 \includegraphics[width=13cm]{figs/acm_ezpolicy_gui.eps}
2313 \caption{Final layout including workload definition and Run-time Exclusion rules.}
2314 \label{fig:acmezpolicy}
2315 \end{figure}
2317 \paragraph{Defining run-time conflicts.} Workloads that shall be
2318 prohibited from running concurrently on the same hypervisor platform
2319 are grouped into ``Run-time Exclusion rules'' on the right panel of
2320 the window. Cautious users should include the \verb|__UNLABELED__|
2321 workload type in all run-time exclusion rules because any workload
2322 could run inside unlabeled domains.
2324 To prevent A-Bank and B-Bank workloads (including their
2325 departmental workloads) from running simultaneously on the same
2326 hypervisor system, select the organization ``A-Bank'' and, while
2327 pressing the \verb|<CTRL>|-key, select the organization ``B-Bank''.
2328 Being cautious, we also prevent unlabeled workloads from running with
2329 any of those workloads by pressing the \verb|<CTRL>|-key and selecting
2330 ``\_\_UNLABELED\_\_''. Now press the button named ``Create run-time exclusion
2331 rule from selection''. A popup window will ask for the name for this run-time
2332 exclusion rule (enter a name or just hit \verb|<ENTER>|). A rule will
2333 appear on the right panel. The name is used as reference only and does
2334 not affect access control decisions.
2336 Please repeat this process to create another run-time exclusion rule
2337 for the department workloads ``A-Bank.SecurityUnderwriting'',
2338 ``A-Bank.MarketAnalysis''. Also add the ``\_\_UNLABELED\_\_''
2339 workload type to this conflict set.
2341 The resulting layout of your window should be similar to
2342 Figure~\ref{fig:acmezpolicy}. Save this workload definition by
2343 selecting ``Save Workload Definition as ...'' in the ``File'' menu.
2344 This workload definition can be later refined if required.
2346 \paragraph{Translating the workload definition into an sHype/Xen access
2347 control policy.} To translate the workload definition into a access
2348 control policy understood by Xen, please select the ``Save as Xen ACM
2349 Security Policy'' in the ``File'' menu. Enter the following policy
2350 name in the popup window: \verb|mytest|. If you are running ezPolicy in
2351 Domain-0, the resulting policy file mytest\_security-policy.xml will
2352 automatically be placed into the right directory (/etc/xen/acm-security/policies/).
2353 If you run the tool on another system, then you need to copy the
2354 resulting policy file into Domain-0 before continuing. See
2355 Section~\ref{subsection:acmnaming} for naming conventions of security
2356 policies.
2358 \begin{scriptsize}
2359 \textbf{Note:} The support for \verb|__UNLABELED__| domains and
2360 resources is meant to help transitioning from an uncontrolled
2361 environment to a workload-protected environment by starting with
2362 unlabeled domains and resources and then step-by-step labeling domains
2363 and resources. Once all workloads are labeled, the \verb|__UNLABELED__|
2364 type can simply be removed from the Domain-0 label or from the policy
2365 through a policy update. Section~\ref{subsection:acmpolicymanagement} will
2366 show how unlabeled domains can be disabled by updating the
2367 \verb|mytest| policy at run-time.
2368 \end{scriptsize}
2370 \subsection{Deploying a WLP Policy}
2371 \label{subsection:acmexampleinstall}
2372 To deploy the workload protection policy we created in
2373 Section~\ref{subsection:acmexamplecreate}, we create a policy
2374 representation (mytest.bin), load it into the Xen
2375 hypervisor, and configure Xen to also load this policy during
2376 reboot.
2378 The following command translates the source policy representation
2379 into a format that can be loaded into Xen with sHype/ACM support,
2380 activates the policy, and configures this policy for future boot
2381 cycles into the boot sequence. Please refer to the \verb|xm|
2382 man page for further details:
2384 \begin{verbatim}
2385 (5) # xm setpolicy ACM mytest
2386 Successfully set the new policy.
2387 Supported security subsystems : ACM
2388 Policy name : mytest
2389 Policy type : ACM
2390 Version of XML policy : 1.0
2391 Policy configuration : loaded, activated for boot
2392 \end{verbatim}
2394 Alternatively, if installing the policy fails (e.g., because it cannot
2395 identify the Xen boot entry), you can manually install the policy in 3
2396 steps a-c.
2398 (\textit{Alternatively to 5 - step a}) Manually copy the policy binary
2399 file into the boot directory:
2401 \begin{scriptsize}
2402 \begin{verbatim}
2403 # cp /etc/xen/acm-security/policies/mytest.bin /boot/mytest.bin
2404 \end{verbatim}
2405 \end{scriptsize}
2407 (\textit{Alternatively to 5 - step b}) Manually add a module line to your
2408 Xen boot entry so that grub loads this policy file during startup:
2410 \begin{scriptsize}
2411 \begin{verbatim}
2412 title XEN Devel with 2.6.18.8
2413 kernel /xen.gz
2414 module /vmlinuz-2.6.18.8-xen root=/dev/sda3 ro console=tty0
2415 module /initrd-2.6.18.8-xen.img
2416 module /mytest.bin
2417 \end{verbatim}
2418 \end{scriptsize}
2420 (\textit{Alternatively to 5 - step c}) Reboot. Xen will choose the
2421 bootstrap label defined in the policy as Domain-0 label during reboot.
2422 After reboot, you can re-label Domain-0 at run-time,
2423 cf Section~\ref{subsection:acmlabeldom0}.
2425 Assuming that command (5) succeeded or you followed the alternative
2426 instructions above, you should see the new policy and label appear
2427 when listing domains:
2429 \begin{scriptsize}
2430 \begin{verbatim}
2431 # xm list --label
2432 Name ID Mem VCPUs State Time(s) Label
2433 Domain-0 0 941 1 r----- 81.5 ACM:mytest:SystemManagement
2434 \end{verbatim}
2435 \end{scriptsize}
2437 If the security label at the end of the line says ``INACTIVE'' then the
2438 security is not enabled. Verify the previous steps. Note: Domain-0 is
2439 assigned a default label (see \verb|bootstrap| policy attribute
2440 explained in Section~\ref{section:acmpolicy}). All other domains must
2441 be explicitly labeled, which we describe in detail below.
2443 \subsection{Labeling Unmanaged User Domains}
2444 \label{subsection:acmexamplelabeldomains}
2446 Unmanaged domains are started in Xen by using a configuration
2447 file. Please refer to Section~\ref{subsection:acmlabelmanageddomains}
2448 if you are using managed domains.
2450 The following configuration file defines \verb|domain1|:
2452 \begin{scriptsize}
2453 \begin{verbatim}
2454 # cat domain1.xm
2455 kernel= "/boot/vmlinuz-2.6.18.8-xen"
2456 memory = 128
2457 name = "domain1"
2458 vif = ['']
2459 dhcp = "dhcp"
2460 disk = ['file:/home/xen/dom_fc5/fedora.fc5.img,sda1,w', \
2461 'file:/home/xen/dom_fc5/fedora.fc5.swap,sda2,w']
2462 root = "/dev/sda1 ro xencons=tty"
2463 \end{verbatim}
2464 \end{scriptsize}
2466 Every domain must be associated with a security label before it can start
2467 on sHype/Xen. Otherwise, sHype/Xen would not be able to enforce the policy
2468 consistently. Our \verb|mytest| policy is configured so that Xen
2469 assigns a default label \verb|__UNLABELED__| to domains and resources that
2470 have no label and supports them in a controlled manner. Since neither the domain,
2471 nor the resources are (yet) labeled, this domain can start under the \verb|mytest|
2472 policy:
2474 \begin{scriptsize}
2475 \begin{verbatim}
2476 # xm create domain1.xm
2477 Using config file "./domain1.xm".
2478 Started domain domain1
2480 # xm list --label
2481 Name ID Mem VCPUs State Time(s) Label
2482 domain1 1 128 1 -b---- 0.7 ACM:mytest:__UNLABELED__
2483 Domain-0 0 875 1 r----- 84.6 ACM:mytest:SystemManagement
2484 \end{verbatim}
2485 \end{scriptsize}
2487 Please shutdown domain1 so that we can move it into the protection
2488 domain of workload \verb|A-Bank|.
2490 \begin{scriptsize}
2491 \begin{verbatim}
2492 # xm shutdown domain1
2493 (wait some seconds until the domain has shut down)
2495 #xm list --label
2496 Name ID Mem VCPUs State Time(s) Label
2497 Domain-0 0 875 1 r----- 86.4 ACM:mytest:SystemManagement
2498 \end{verbatim}
2499 \end{scriptsize}
2501 We assume that the processing in domain1 contributes to the \verb|A-Bank| workload.
2502 We explore now how to transition this domain into the ``A-Bank'' workload-protection.
2503 The following command prints all domain labels available in the active policy:
2505 \begin{scriptsize}
2506 \begin{verbatim}
2507 # xm labels
2508 A-Bank
2509 A-Bank.MarketAnalysis
2510 A-Bank.SecurityUnderwriting
2511 AutoCorp
2512 B-Bank
2513 SystemManagement
2514 __UNLABELED__
2515 \end{verbatim}
2516 \end{scriptsize}
2518 Now label \verb|domain1| with the A-Bank label and another \verb|domain2|
2519 with the B-Bank label. Please refer to the xm man page for
2520 further information.
2522 \begin{verbatim}
2523 (6) # xm addlabel A-Bank dom domain1.xm
2524 # xm addlabel B-Bank dom domain2.xm
2525 \end{verbatim}
2527 Let us try to start the domain again:
2529 \begin{scriptsize}
2530 \begin{verbatim}
2531 # xm create domain1.xm
2532 Using config file "./domain1.xm".
2533 Error: VM's access to block device 'file:/home/xen/dom_fc5/fedora.fc5.img' denied
2534 \end{verbatim}
2535 \end{scriptsize}
2537 This error indicates that \verb|domain1|, if started, would not be able to
2538 access its image and swap files because they are not labeled. This
2539 makes sense because to confine workloads, access of domains to
2540 resources must be controlled. Otherwise, domains that are not allowed
2541 to communicate or run simultaneously could share data through storage
2542 resources.
2544 \subsection{Labeling Resources}
2545 \label{subsection:acmexamplelabelresources}
2546 You can use the \verb|xm labels type=res| command to list available
2547 resource labels. Let us assign the A-Bank resource label to the
2548 \verb|domain1| image file representing \verb|/dev/sda1| and to its swap file:
2550 \begin{verbatim}
2551 (7) # xm addlabel A-Bank res \
2552 file:/home/xen/dom_fc5/fedora.fc5.img
2554 # xm addlabel A-Bank res \
2555 file:/home/xen/dom_fc5/fedora.fc5.swap
2556 \end{verbatim}
2558 The following command lists all labeled resources on the system, e.g.,
2559 to lookup or verify the labeling:
2561 \begin{scriptsize}
2562 \begin{verbatim}
2563 # xm resources
2564 file:/home/xen/dom_fc5/fedora.fc5.swap
2565 type: ACM
2566 policy: mytest
2567 label: A-Bank
2568 file:/home/xen/dom_fc5/fedora.fc5.img
2569 type: ACM
2570 policy: mytest
2571 label: A-Bank
2572 \end{verbatim}
2573 \end{scriptsize}
2575 Starting \verb|domain1| will now succeed:
2577 \begin{scriptsize}
2578 \begin{verbatim}
2579 # xm create domain1.xm
2580 Using config file "./domain1.xm".
2581 Started domain domain1
2583 # xm list --label
2584 Name ID Mem VCPUs State Time(s) Label
2585 domain1 3 128 1 -b---- 0.8 ACM:mytest:A-Bank
2586 Domain-0 0 875 1 r----- 90.9 ACM:mytest:SystemManagement
2587 \end{verbatim}
2588 \end{scriptsize}
2590 Currently, if a labeled resource is moved to another location, the
2591 label must first be manually removed, and after the move re-attached
2592 using the xm commands \verb|rmlabel| and \verb|addlabel|
2593 respectively. Please see Section~\ref{section:acmlimitations} for
2594 further details.
2596 \begin{verbatim}
2597 (8) Label the resources of domain2 as B-Bank
2598 but please do not start this domain yet.
2599 \end{verbatim}
2601 \subsection{Testing The Xen Workload Protection}
2602 \label{subsection:acmexampletest}
2604 We are about to demonstrate the sHype/Xen workload protection by verifying
2605 \begin{itemize}
2606 \item that user domains with conflicting workloads cannot run
2607 simultaneously
2608 \item that user domains cannot access resources of workloads other than the
2609 one they are associated with
2610 \item that user domains cannot exchange network packets if they are not
2611 associated with the same workload type (not yet supported in Xen)
2612 \end{itemize}
2614 \paragraph{Test 1: Run-time exclusion rules.} We assume that \verb|domain1|
2615 with the A-Bank label is still running. While \verb|domain1| is running,
2616 the run-time exclusion set of our policy implies that \verb|domain2| cannot
2617 start because the label of \verb|domain1| includes the CHWALL type A-Bank
2618 and the label of \verb|domain2| includes the CHWALL type B-Bank. The
2619 run-time exclusion rule of our policy enforces that A-Bank and
2620 B-Bank cannot run at the same time on the same hypervisor platform.
2621 Once domain1 is stopped, saved, or migrated to another platform,
2622 \verb|domain2| can start. Once \verb|domain2| is started, however,
2623 \verb|domain1| can no longer start or resume on this system. When creating the
2624 Chinese Wall types for the workload labels, the ezPolicy tool policy
2625 translation component ensures that department workloads inherit all the
2626 organization types (and with it any organization exclusions).
2628 \begin{scriptsize}
2629 \begin{verbatim}
2630 # xm list --label
2631 Name ID Mem VCPUs State Time(s) Label
2632 domain1 3 128 1 -b---- 0.8 ACM:mytest:A-Bank
2633 Domain-0 0 875 1 r----- 90.9 ACM:mytest:SystemManagement
2635 # xm create domain2.xm
2636 Using config file "./domain2.xm".
2637 Error: 'Domain in conflict set with running domains'
2639 # xm shutdown domain1
2640 (wait some seconds until domain 1 is shut down)
2642 # xm list --label
2643 Name ID Mem VCPUs State Time(s) Label
2644 Domain-0 0 873 1 r----- 95.3 ACM:mytest:SystemManagement
2646 # xm create domain2.xm
2647 Using config file "./domain2.xm".
2648 Started domain domain2
2650 # xm list --label
2651 Name ID Mem VCPUs State Time(s) Label
2652 domain2 5 164 1 -b---- 0.3 ACM:mytest:B-Bank
2653 Domain-0 0 839 1 r----- 96.4 ACM:mytest:SystemManagement
2655 # xm create domain1.xm
2656 Using config file "domain1.xm".
2657 Error: 'Domain in conflict with running domains'
2659 # xm shutdown domain2
2660 # xm list --label
2661 Name ID Mem VCPUs State Time(s) Label
2662 Domain-0 0 839 1 r----- 97.8 ACM:mytest:SystemManagement
2663 \end{verbatim}
2664 \end{scriptsize}
2666 You can verify that domains with AutoCorp label can run together with
2667 domains labeled A-Bank or B-Bank.
2669 \paragraph{Test2: Resource access.} In this test, we will re-label the
2670 swap file for \verb|domain1| with the \verb|B-Bank| resource label. In a
2671 real environment, the swap file must be sanitized (scrubbed/zeroed) before
2672 it is reassigned to prevent data leaks from the A-Bank to the B-Bank workload
2673 through the swap file.
2675 We expect that \verb|domain1| will no longer start because it cannot access
2676 this resource. This test checks the sharing abilities of domains, which are
2677 defined by the Simple Type Enforcement Policy component.
2679 \begin{scriptsize}
2680 \begin{verbatim}
2681 # xm rmlabel res file:/home/xen/dom_fc5/fedora.fc5.swap
2683 # xm addlabel B-Bank res file:/home/xen/dom_fc5/fedora.fc5.swap
2685 # xm resources
2686 file:/home/xen/dom_fc5/fedora.fc5.swap
2687 type: ACM
2688 policy: mytest
2689 label: B-Bank
2690 file:/home/xen/dom_fc5/fedora.fc5.img
2691 type: ACM
2692 policy: mytest
2693 label: A-Bank
2695 # xm create domain1.xm
2696 Using config file "./domain1.xm".
2697 Error:
2698 VM's access to block device 'file:/home/xen/dom_fc5/fedora.fc5.swap' denied
2699 \end{verbatim}
2700 \end{scriptsize}
2702 The resource authorization checks are performed before the domain is actually started
2703 so that failures during the startup are prevented. A domain is only started if all
2704 the resources specified in its configuration are accessible.
2706 \paragraph{Test 3: Communication.} In this test we would verify that
2707 two domains with labels A-Bank and B-Bank cannot exchange network packets
2708 by using the 'ping' connectivity test. It is also related to the STE
2709 policy. {\bf Note:} sHype/Xen does control direct communication between
2710 domains. However, domains associated with different workloads can
2711 currently still communicate through the Domain-0 virtual network. We
2712 are working on the sHype/ACM controls for local and remote network
2713 traffic through Domain-0. Please monitor the xen-devel mailing list
2714 for updated information.
2717 \subsection{Labeling Domain-0 --or-- Restricting System Authorization}
2718 \label{subsection:acmlabeldom0}
2719 The major use case for explicitly labeling or relabeling Domain-0 is to restrict
2720 or extend which workload types can run on a virtualized Xen system. This enables
2721 flexible partitioning of the physical infrastructure as well as the workloads
2722 running on it in a multi-platform environment.
2724 In case no Domain-0 label is explicitly stated, we automatically assigned Domain-0
2725 the \verb|SystemManagement| label, which includes all STE (workload) types that
2726 are known to the policy. In effect, the Domain-0 label authorizes the Xen system
2727 to run only those workload types, whose STE types are included in the Domain-0
2728 label. Hence, choosing the \verb|SystemManagement| label for Domain-0 permits any
2729 labeled domain to run. Resetting the label for Domain-0 at boot or run-time to
2730 a label with a subset of the known STE workload types restricts which user domains
2731 can run on this system. If Domain-0 is relabeled at run-time, then the new label
2732 must at least include all STE types of those domains that are currently running.
2733 The operation fails otherwise. This requirement ensures that the system remains
2734 in a valid security configuration after re-labelling.
2736 Restricting the Domain-0 authorization through the label creates a flexible
2737 policy-driven way to strongly partition the physical infrastructure and the
2738 workloads running on it. This partitioning will be automatically enforced during
2739 migration, start, or resume of domains and simplifies the security management
2740 considerably. Strongly competing workloads can be forced to run on separate physical
2741 infrastructure and become less depend on the domain isolation capabilities
2742 of the hypervisor.
2744 First, we relabel the swap image back to A-Bank and then start up domain1:
2745 \begin{scriptsize}
2746 \begin{verbatim}
2747 # xm rmlabel res file:/home/xen/dom_fc5/fedora.fc5.swap
2749 # xm addlabel A-Bank res file:/home/xen/dom_fc5/fedora.fc5.swap
2751 # xm create domain1.xm
2752 Using config file "./domain1.xm".
2753 Started domain domain1
2755 # xm list --label
2756 Name ID Mem VCPUs State Time(s) Label
2757 domain1 7 128 1 -b---- 0.7 ACM:mytest:A-Bank
2758 Domain-0 0 839 1 r----- 103.1 ACM:mytest:SystemManagement
2759 \end{verbatim}
2760 \end{scriptsize}
2762 The following command will restrict the Xen system to only run STE types
2763 included in the A-Bank label.
2765 \begin{scriptsize}
2766 \begin{verbatim}
2767 # xm addlabel A-Bank mgt Domain-0
2768 Successfully set the label of domain 'Domain-0' to 'A-Bank'.
2770 # xm list --label
2771 Name ID Mem VCPUs State Time(s) Label
2772 Domain-0 0 839 1 r----- 103.7 ACM:mytest:A-Bank
2773 domain1 7 128 1 -b---- 0.7 ACM:mytest:A-Bank
2775 \end{verbatim}
2776 \end{scriptsize}
2778 In our example policy in Figure~\ref{fig:acmxmlfileb}, this means that
2779 only \verb|A-Bank| domains and workloads (types) can run after the
2780 successful completion of this command because the \verb|A-Bank| label
2781 includes only a single STE type, namely \verb|A-Bank|. This command
2782 fails if any running domain has an STE type in its label that is not
2783 included in the A-Bank label.
2785 If we now label a domain3 with AutoCorp, it cannot start because Domain-0 is
2786 no longer authorized to run the workload type \verb|AutoCorp|.
2787 \begin{scriptsize}
2788 \begin{verbatim}
2789 # xm addlabel AutoCorp dom domain3.xm
2790 (remember to label its resources, too)
2792 # xm create domain3.xm
2793 Using config file "./domain3.xm".
2794 Error: VM is not authorized to run.
2796 # xm list --label
2797 Name ID Mem VCPUs State Time(s) Label
2798 Domain-0 0 839 1 r----- 104.7 ACM:mytest:A-Bank
2799 domain1 7 128 1 -b---- 0.7 ACM:mytest:A-Bank
2800 \end{verbatim}
2801 \end{scriptsize}
2803 At this point, unlabeled domains cannot start either. Let domain4.xm
2804 describe an unlabeled domain, then trying to start domain4
2805 will fail:
2806 \begin{scriptsize}
2807 \begin{verbatim}
2808 # xm getlabel dom domain4.xm
2809 Error: 'Domain not labeled'
2811 # xm create domain4.xm
2812 Using config file "./domain4.xm".
2813 Error: VM is not authorized to run.
2814 \end{verbatim}
2815 \end{scriptsize}
2817 Relabeling Domain-0 with the SystemManagement label will enable domain3 to start.
2818 \begin{scriptsize}
2819 \begin{verbatim}
2820 # xm addlabel SystemManagement mgt Domain-0
2821 Successfully set the label of domain 'Domain-0' to 'SystemManagement'.
2823 # xm list --label
2824 Name ID Mem VCPUs State Time(s) Label
2825 domain1 7 128 1 -b---- 0.8 ACM:mytest:A-Bank
2826 Domain-0 0 839 1 r----- 106.6 ACM:mytest:SystemManagement
2828 # xm create domain3.xm
2829 Using config file "./domain3.xm".
2830 Started domain domain3
2832 # xm list --label
2833 Name ID Mem VCPUs State Time(s) Label
2834 domain1 7 128 1 -b---- 0.8 ACM:mytest:A-Bank
2835 domain3 8 164 1 -b---- 0.3 ACM:mytest:AutoCorp
2836 Domain-0 0 711 1 r----- 107.6 ACM:mytest:SystemManagement
2837 \end{verbatim}
2838 \end{scriptsize}
2841 \subsection{Labeling Managed User Domains}
2842 \label{subsection:acmlabelmanageddomains}
2844 Xend has been extended with functionality to manage domains along with their
2845 configuration information. Such domains are configured and started via Xen-API
2846 calls. Since managed domains do not have an associated xm configuration file,
2847 the existing \verb|addlabel| command, which adds the security label into a
2848 domain's configuration file, will not work for such managed domains.
2850 Therefore, we have extended the \verb|xm addlabel| and \verb|xm rmlabel|
2851 subcommands to enable adding security labels to and removing security
2852 labels from managed domain configurations. The following example shows how
2853 the \verb|A-Bank| label can be assigned to the xend-managed
2854 domain configuration of \verb|domain1|. Removing labels from managed user
2855 domain configurations works similarly.
2857 Below, we show a dormant configuration of the managed domain1
2858 with ID \verb|"-1"| and state \verb|"-----"| before labeling:
2859 \begin{scriptsize}
2860 \begin{verbatim}
2861 # xm list --label
2862 Name ID Mem VCPUs State Time(s) Label
2863 domain1 -1 128 1 ------ 0.0 ACM:mytest:__UNLABELED__
2864 Domain-0 0 711 1 r----- 128.4 ACM:mytest:SystemManagement
2865 \end{verbatim}
2866 \end{scriptsize}
2868 Now we label the managed domain:
2869 \begin{scriptsize}
2870 \begin{verbatim}
2871 # xm addlabel A-Bank mgt domain1
2872 Successfully set the label of the dormant domain 'domain1' to 'A-Bank'.
2873 \end{verbatim}
2874 \end{scriptsize}
2876 After labeling, you can see that the security label is part of the
2877 domain configuration:
2878 \begin{scriptsize}
2879 \begin{verbatim}
2880 # xm list --label
2881 Name ID Mem VCPUs State Time(s) Label
2882 domain1 -1 128 1 ------ 0.0 ACM:mytest:A-Bank
2883 Domain-0 0 711 1 r----- 129.7 ACM:mytest:SystemManagement
2884 \end{verbatim}
2885 \end{scriptsize}
2887 This command extension does not support relabeling of individual running user domains
2888 for several reasons. For one, because of the difficulty to revoke resources
2889 in cases where a running domain's new label does not permit access to resources
2890 that were accessible under the old label. Another reason is that changing the
2891 label of a single domain of a workload is rarely a good choice and will affect
2892 the workload isolation properties of the overall workload.
2894 However, the name and contents of the label associated with running domains can
2895 be indirectly changed through a global policy change, which will update the whole
2896 workload consistently (domains and resources), cf.
2897 Section~\ref{subsection:acmpolicymanagement}.
2899 \section{Xen Access Control Policy}
2900 \label{section:acmpolicy}
2902 This section describes the sHype/Xen access control policy in detail.
2903 It gives enough information to enable the reader to write custom
2904 access control policies and to use the available Xen policy tools. The
2905 policy language is expressive enough to specify most symmetric access
2906 relationships between domains and resources efficiently.
2908 The Xen access control policy consists of two policy components. The
2909 first component, called Simple Type Enforcement (STE) policy, controls
2910 the sharing between running domains, i.e., communication or access to
2911 shared resources. The second component, called Chinese Wall (CHWALL)
2912 policy, controls which domains can run simultaneously on the same
2913 virtualized platform. The CHWALL and STE policy components complement
2914 each other. The XML policy file includes all information
2915 needed by Xen to enforce those policies.
2917 Figures~\ref{fig:acmxmlfilea} and \ref{fig:acmxmlfileb} show the fully
2918 functional but very simple example Xen security policy that is created
2919 by ezPolicy as shown in Figure~\ref{fig:acmezpolicy}. The policy can
2920 distinguish the 6 workload types shown in lines 11-17 in
2921 Fig.~\ref{fig:acmxmlfilea}. The whole XML Security Policy consists of
2922 four parts:
2923 \begin{enumerate}
2924 \item Policy header including the policy name
2925 \item Simple Type Enforcement block
2926 \item Chinese Wall Policy block
2927 \item Label definition block
2928 \end{enumerate}
2930 \begin{figure}
2931 \begin{scriptsize}
2932 \begin{verbatim}
2933 01 <?xml version="1.0" ?>
2934 02 <!-- Auto-generated by ezPolicy -->
2935 03 <SecurityPolicyDefinition ...">
2936 04 <PolicyHeader>
2937 05 <PolicyName>mytest</PolicyName>
2938 06 <Date>Mon Nov 19 22:51:56 2007</Date>
2939 07 <Version>1.0</Version>
2940 08 </PolicyHeader>
2941 09 <SimpleTypeEnforcement>
2942 10 <SimpleTypeEnforcementTypes>
2943 11 <Type>SystemManagement</Type>
2944 12 <Type>__UNLABELED__</Type>
2945 13 <Type>A-Bank</Type>
2946 14 <Type>A-Bank.SecurityUnderwriting</Type>
2947 15 <Type>A-Bank.MarketAnalysis</Type>
2948 16 <Type>B-Bank</Type>
2949 17 <Type>AutoCorp</Type>
2950 18 </SimpleTypeEnforcementTypes>
2951 19 </SimpleTypeEnforcement>
2952 20 <ChineseWall priority="PrimaryPolicyComponent">
2953 21 <ChineseWallTypes>
2954 22 <Type>SystemManagement</Type>
2955 23 <Type>__UNLABELED__</Type>
2956 24 <Type>A-Bank</Type>
2957 25 <Type>A-Bank.SecurityUnderwriting</Type>
2958 26 <Type>A-Bank.MarketAnalysis</Type>
2959 27 <Type>B-Bank</Type>
2960 28 <Type>AutoCorp</Type>
2961 29 </ChineseWallTypes>
2962 30 <ConflictSets>
2963 31 <Conflict name="RER">
2964 32 <Type>A-Bank</Type>
2965 33 <Type>B-Bank</Type>
2966 34 <Type>__UNLABELED__</Type>
2967 35 </Conflict>
2968 36 <Conflict name="RER">
2969 37 <Type>A-Bank.MarketAnalysis</Type>
2970 38 <Type>A-Bank.SecurityUnderwriting</Type>
2971 39 <Type>__UNLABELED__</Type>
2972 40 </Conflict>
2973 41 </ConflictSets>
2974 42 </ChineseWall>
2975 \end{verbatim}
2976 \end{scriptsize}
2977 \caption{Example XML security policy file -- Part I: Types and Rules Definition.}
2978 \label{fig:acmxmlfilea}
2979 \end{figure}
2981 \subsection{Policy Header and Policy Name}
2982 \label{subsection:acmnaming}
2983 Lines 1-2 (cf Figure~\ref{fig:acmxmlfilea}) include the usual XML
2984 header. The security policy definition starts in Line 3 and refers to
2985 the policy schema. The XML-Schema definition for the Xen policy can be
2986 found in the file
2987 \textit{/etc/xen/acm-security/policies/security-policy.xsd}. Examples
2988 for security policies can be found in the example subdirectory. The
2989 acm-security directory is only installed if ACM security is configured
2990 during installation (cf Section~\ref{subsection:acmexampleconfigure}).
2992 The \verb|Policy Header| spans lines 4-8. It includes a date field and
2993 defines the policy name \verb|mytest| as well
2994 as the version of the XML. It can also include optional fields that are
2995 not shown and are for future use (see schema definition).
2997 The policy name serves two purposes: First, it provides a unique name
2998 for the security policy. This name is also exported by the Xen
2999 hypervisor to the Xen management tools in order to ensure that both
3000 the Xen hypervisor and Domain-0 enforce the same policy.
3001 We plan to extend the policy name with a
3002 digital fingerprint of the policy contents to better protect this
3003 correlation. Second, it implicitly points the xm tools to the
3004 location where the XML policy file is stored on the Xen system.
3005 Replacing the colons in the policy name by slashes yields the local
3006 path to the policy file starting from the global policy directory
3007 \verb|/etc/xen/acm-security/policies|. The last part of the policy
3008 name is the prefix for the XML policy file name, completed by
3009 \verb|-security_policy.xml|. Our example policy with the name
3010 \verb|mytest| can be found in the XML policy file named
3011 \verb|mytest-security_policy.xml| that is stored under the global
3012 policy directory. Another, preinstalled example policy named
3013 \verb|example.test| can be found in the \verb|test-security_policy.xml|
3014 under \verb|/etc/xen/acm-security/policies/example|.
3016 \subsection{Simple Type Enforcement Policy Component}
3018 The Simple Type Enforcement (STE) policy controls which domains can
3019 communicate or share resources. This way, Xen can enforce confinement
3020 of workload types by confining the domains running those workload
3021 types and their resources. The mandatory access control framework
3022 enforces its policy when
3023 domains access intended communication or cooperation means (shared
3024 memory, events, shared resources such as block devices). It builds on
3025 top of the core hypervisor isolation, which restricts the ways of
3026 inter-communication to those intended means. STE does not protect or
3027 intend to protect from covert channels in the hypervisor or hardware;
3028 this is an orthogonal problem that can be mitigated by using the
3029 Run-time Exclusion rules described above or by fixing the problem leading
3030 to those covert channels in the core hypervisor or hardware platform.
3032 Xen controls sharing between domains on the resource and domain level
3033 because this is the abstraction the hypervisor and its management
3034 understand naturally. While this is coarse-grained, it is also very
3035 reliable and robust and it requires minimal changes to implement
3036 mandatory access controls in the hypervisor. It enables platform- and
3037 operating system-independent policies as part of a layered security
3038 approach.
3040 Lines 11-17 (cf Figure~\ref{fig:acmxmlfilea}) define the Simple Type
3041 Enforcement policy component. Essentially, they define the workload
3042 type names \verb|SystemManagement|, \verb|A-Bank|,
3043 \verb|AutoCorp| etc. that are available in the STE policy component. The
3044 policy rules are implicit: Xen permits two domains to communicate with
3045 each other if and only if their security labels have at least one STE type in
3046 common. Similarly, Xen permits a user domain to access a
3047 resource if and only if the labels of the domain and the resource
3048 have at least one STE workload type in common.
3050 \subsection{Chinese Wall Policy Component}
3052 The Chinese Wall security policy interpretation of sHype enables users
3053 to prevent certain workloads from running simultaneously on the same
3054 hypervisor platform. Run-time Exclusion rules (RER), also called
3055 Conflict Sets or Anti-Collocation rules, define a set of workload types
3056 that are not permitted to run simultaneously on the same virtualized
3057 platform. Of all the workloads specified in a Run-time
3058 Exclusion rule, at most one type can run on the same hypervisor
3059 platform at a time. Run-time Exclusion Rules implement a less
3060 rigorous variant of the original Chinese Wall security component. They
3061 do not implement the *-property of the policy, which would require to
3062 restrict also types that are not part of an exclusion rule once they
3063 are running together with a type in an exclusion rule
3064 (http://www.gammassl.co.uk/topics/chinesewall.html provides more information
3065 on the original Chinese Wall policy).
3067 Xen considers the \verb|ChineseWallTypes| part of the label for the
3068 enforcement of the Run-time Exclusion rules. It is illegal to define
3069 labels including conflicting Chinese Wall types.
3071 Lines 20-41 (cf Figure~\ref{fig:acmxmlfilea}) define the Chinese Wall
3072 policy component. Lines 22-28 define the known Chinese Wall types,
3073 which coincide here with the STE types defined above. This usually
3074 holds if the criteria for sharing among domains and sharing of the
3075 hardware platform are the same. Lines 30-41 define one Run-time
3076 Exclusion rules, the first of which is depicted below:
3078 \begin{scriptsize}
3079 \begin{verbatim}
3080 31 <Conflict name="RER">
3081 32 <Type>A-Bank</Type>
3082 33 <Type>B-Bank</Type>
3083 34 <Type>__UNLABELED__</Type>
3084 35 </Conflict>
3085 \end{verbatim}
3086 \end{scriptsize}
3088 Based on this rule, Xen enforces that only one of the types
3089 \verb|A-Bank|, \verb|B-Bank|, or \verb|__UNLABELED__| will run
3090 on a single hypervisor platform at a time. For example, once a domain assigned a
3091 \verb|A-Bank| workload type is started, domains with the
3092 \verb|B-Bank| type or unlabeled domains will be denied to start.
3093 When the former domain stops and no other domains with the \verb|A-Bank|
3094 type are running, then domains with the \verb|B-Bank| type or unlabeled domains
3095 can start.
3097 Xen maintains reference counts on each running workload type to keep
3098 track of which workload types are running. Every time a domain starts
3099 or resumes, the reference count on those Chinese Wall types that are
3100 referenced in the domain's label are incremented. Every time a domain
3101 is destroyed or saved, the reference counts of its Chinese Wall types
3102 are decremented. sHype in Xen fully supports migration and live-migration,
3103 which is subject to access control the same way as saving a domain on
3104 the source platform and resuming it on the destination platform.
3106 Here are some reasons why users might want to restrict workloads or domains
3107 from sharing the system hardware simultaneously:
3109 \begin{itemize}
3110 \item Imperfect resource management or control might enable a compromised
3111 user domain to starve other domains and the workload running in them.
3112 \item Redundant user domains might run the same workload to increase
3113 availability; such domains should not run on the same hardware to
3114 avoid single points of failure.
3115 \item Imperfect Xen core domain isolation might enable two rogue
3116 domains running different workload types to use unintended and
3117 unknown ways (covert channels) to exchange some bits of information.
3118 This way, they bypass the policed Xen access control mechanisms. Such
3119 imperfections cannot be completely eliminated and are a result of
3120 trade-offs between security and other design requirements. For a
3121 simple example of a covert channel see
3122 http://www.multicians.org/timing-chn.html. Such covert channels
3123 exist also between workloads running on different platforms if they
3124 are connected through networks. The Xen Chinese Wall policy provides
3125 an approximated ``air-gap'' between selected workload types.
3126 \end{itemize}
3128 \subsection{Security Labels}
3130 To enable Xen to associate domains with workload types running in
3131 them, each domain is assigned a security label that includes the
3132 workload types of the domain.
3134 \begin{figure}[htb]
3135 \begin{tabular*}{\textwidth}{@{\extracolsep{\fill}}l|l}
3136 \begin{minipage}{0.475\textwidth}
3137 \begin{tiny}
3138 \begin{verbatim}
3139 <SecurityLabelTemplate>
3140 <SubjectLabels bootstrap="SystemManagement">
3141 <VirtualMachineLabel>
3142 <Name>SystemManagement</Name>
3143 <SimpleTypeEnforcementTypes>
3144 <Type>SystemManagement</Type>
3145 <Type>__UNLABELED__</Type>
3146 <Type>A-Bank</Type>
3147 <Type>A-Bank.SecurityUnderwriting</Type>
3148 <Type>A-Bank.MarketAnalysis</Type>
3149 <Type>B-Bank</Type>
3150 <Type>AutoCorp</Type>
3151 </SimpleTypeEnforcementTypes>
3152 <ChineseWallTypes>
3153 <Type>SystemManagement</Type>
3154 </ChineseWallTypes>
3155 </VirtualMachineLabel>
3156 <VirtualMachineLabel>
3157 <Name>__UNLABELED__</Name>
3158 <SimpleTypeEnforcementTypes>
3159 <Type>__UNLABELED__</Type>
3160 </SimpleTypeEnforcementTypes>
3161 <ChineseWallTypes>
3162 <Type>__UNLABELED__</Type>
3163 </ChineseWallTypes>
3164 </VirtualMachineLabel>
3165 <VirtualMachineLabel>
3166 <Name>A-Bank</Name>
3167 <SimpleTypeEnforcementTypes>
3168 <Type>A-Bank</Type>
3169 </SimpleTypeEnforcementTypes>
3170 <ChineseWallTypes>
3171 <Type>A-Bank</Type>
3172 </ChineseWallTypes>
3173 </VirtualMachineLabel>
3174 <VirtualMachineLabel>
3175 <Name>A-Bank.SecurityUnderwriting</Name>
3176 <SimpleTypeEnforcementTypes>
3177 <Type>A-Bank.SecurityUnderwriting</Type>
3178 </SimpleTypeEnforcementTypes>
3179 <ChineseWallTypes>
3180 <Type>A-Bank</Type>
3181 <Type>A-Bank.SecurityUnderwriting</Type>
3182 </ChineseWallTypes>
3183 </VirtualMachineLabel>
3184 <VirtualMachineLabel>
3185 <Name>A-Bank.MarketAnalysis</Name>
3186 <SimpleTypeEnforcementTypes>
3187 <Type>A-Bank.MarketAnalysis</Type>
3188 </SimpleTypeEnforcementTypes>
3189 <ChineseWallTypes>
3190 <Type>A-Bank</Type>
3191 <Type>A-Bank.MarketAnalysis</Type>
3192 </ChineseWallTypes>
3193 </VirtualMachineLabel>
3194 <VirtualMachineLabel>
3195 <Name>B-Bank</Name>
3196 <SimpleTypeEnforcementTypes>
3197 <Type>B-Bank</Type>
3198 </SimpleTypeEnforcementTypes>
3199 <ChineseWallTypes>
3200 <Type>B-Bank</Type>
3201 </ChineseWallTypes>
3202 </VirtualMachineLabel>
3203 \end{verbatim}
3204 \end{tiny}
3205 \end{minipage} &
3206 \begin{minipage}{0.475\textwidth}
3207 \begin{tiny}
3208 \begin{verbatim}
3209 <VirtualMachineLabel>
3210 <Name>AutoCorp</Name>
3211 <SimpleTypeEnforcementTypes>
3212 <Type>AutoCorp</Type>
3213 </SimpleTypeEnforcementTypes>
3214 <ChineseWallTypes>
3215 <Type>AutoCorp</Type>
3216 </ChineseWallTypes>
3217 </VirtualMachineLabel>
3218 </SubjectLabels>
3219 <ObjectLabels>
3220 <ResourceLabel>
3221 <Name>SystemManagement</Name>
3222 <SimpleTypeEnforcementTypes>
3223 <Type>SystemManagement</Type>
3224 </SimpleTypeEnforcementTypes>
3225 </ResourceLabel>
3226 <ResourceLabel>
3227 <Name>__UNLABELED__</Name>
3228 <SimpleTypeEnforcementTypes>
3229 <Type>__UNLABELED__</Type>
3230 </SimpleTypeEnforcementTypes>
3231 </ResourceLabel>
3232 <ResourceLabel>
3233 <Name>A-Bank</Name>
3234 <SimpleTypeEnforcementTypes>
3235 <Type>A-Bank</Type>
3236 </SimpleTypeEnforcementTypes>
3237 </ResourceLabel>
3238 <ResourceLabel>
3239 <Name>A-Bank.SecurityUnderwriting</Name>
3240 <SimpleTypeEnforcementTypes>
3241 <Type>A-Bank.SecurityUnderwriting</Type>
3242 </SimpleTypeEnforcementTypes>
3243 </ResourceLabel>
3244 <ResourceLabel>
3245 <Name>A-Bank.MarketAnalysis</Name>
3246 <SimpleTypeEnforcementTypes>
3247 <Type>A-Bank.MarketAnalysis</Type>
3248 </SimpleTypeEnforcementTypes>
3249 </ResourceLabel>
3250 <ResourceLabel>
3251 <Name>B-Bank</Name>
3252 <SimpleTypeEnforcementTypes>
3253 <Type>B-Bank</Type>
3254 </SimpleTypeEnforcementTypes>
3255 </ResourceLabel>
3256 <ResourceLabel>
3257 <Name>AutoCorp</Name>
3258 <SimpleTypeEnforcementTypes>
3259 <Type>AutoCorp</Type>
3260 </SimpleTypeEnforcementTypes>
3261 </ResourceLabel>
3262 </ObjectLabels>
3263 </SecurityLabelTemplate>
3264 </SecurityPolicyDefinition>
3273 \end{verbatim}
3274 \end{tiny}
3275 \end{minipage}
3276 \end{tabular*}
3277 \caption{Example XML security policy file -- Part II: Label Definition.}
3278 \label{fig:acmxmlfileb}
3279 \end{figure}
3280 % DO NOT MODIFY WHITESPACE ABOVE, it balances the columns
3281 The \verb|SecurityLabelTemplate| (cf Figure~\ref{fig:acmxmlfileb}) defines
3282 the security labels that can be associated with domains and resources when
3283 this policy is active (use the \verb|xm labels type=any| command described in
3284 Section~\ref{subsection:acmexamplelabeldomains} to list all available labels).
3286 The domain labels include
3287 Chinese Wall types while resource labels do not include Chinese Wall types.
3288 The \verb|SubjectLabels| policy section defines the labels that can be
3289 assigned to domains. The VM label
3290 \verb|A-Bank.SecurityUnderwriting| in Figure~\ref{fig:acmxmlfileb})
3291 associates the domain that carries it with the workload STE type
3292 \verb|A-Bank.SecurityUnderwriting| and with the CHWALL types \verb|A-Bank|
3293 and \verb|A-Bank.SecurityUnderwriting|. The ezPolicy tool
3294 assumes that any department workload will inherit any conflict set that
3295 is specified for its organization, i.e., if \verb|B-Bank| is running, not
3296 only \verb|A-Bank| but also all its departmental workloads are prevented
3297 from running by this first run-time exclusion set. The separation of STE
3298 and CHWALL types in the label definition ensures that
3299 all departmental workloads are isolated from each other and from their generic
3300 organization workloads, while they are sharing CHWALL types to
3301 simplify the formulation of run-time exclusion sets.
3303 The \verb|bootstrap| attribute of the \verb|<SubjectLabels>| XML node
3304 in our example policy shown in Figure~\ref{fig:acmxmlfileb} names
3305 the label \verb|SystemManagement| as the label that Xen will assign
3306 to Domain-0 at boot time (if this policy is installed as boot policy). The
3307 label of Domain-0 can be persistently changed at run-time with the
3308 \verb|addlabel| command, which adds an overriding option to the grub.conf
3309 boot entry (cf Section~\ref{subsection:acmlabeldom0}).
3310 All user domains are assigned labels according to their domain configuration
3311 (see Section~\ref{subsection:acmexamplelabeldomains} for examples of
3312 how to label domains).
3314 The \verb|ObjectLabels| depicted in Figure~\ref{fig:acmxmlfileb} can be
3315 assigned to resources when this policy is active.
3317 In general, user domains should be assigned labels that have only a
3318 single SimpleTypeEnforcement workload type. This way, workloads remain
3319 confined even if user domains become rogue. Any domain that is
3320 assigned a label with multiple STE types must be trusted to keep
3321 information belonging to the different STE types separate (confined).
3322 For example, Domain-0 is assigned the bootstrap label
3323 \verb|SystemManagement|, which includes all existing STE types.
3324 Therefore, Domain-0 must take care not to enable unauthorized
3325 information flow (eg. through block devices or virtual networking)
3326 between domains or resources that are assigned different STE types.
3328 Security administrators simply use the name of a label (specified in
3329 the \verb|<Name>| field) to associate a label with a domain (cf.
3330 Section~\ref{subsection:acmexamplelabeldomains}). The types inside the
3331 label are used by the Xen access control enforcement. While the name
3332 can be arbitrarily chosen (as long as it is unique), it is advisable
3333 to choose the label name in accordance to the security types included.
3334 Similarly, the STE and CHWALL types should be named according to the
3335 workloads they represent. While the XML representation of the label
3336 in the above example seems unnecessary flexible, labels in general
3337 must be able to include multiple types.
3339 We assume in the following example, that \verb|A-Bank.SecurityUnderwriting| and
3340 \verb|A-Bank.MarketAnalysis| workloads use virtual disks that are provided
3341 by a virtual I/O domain hosting a physical storage device and carrying
3342 the following label:
3344 \begin{scriptsize}
3345 \begin{verbatim}
3346 <VirtualMachineLabel>
3347 <Name>VIOServer</Name>
3348 <SimpleTypeEnforcementTypes>
3349 <Type>A-Bank</Type>
3350 <Type>A-Bank.SecurityUnderwriting</Type>
3351 <Type>A-Bank.MarketAnalysis</Type>
3352 <Type>VIOServer</Type>
3353 </SimpleTypeEnforcementTypes>
3354 <ChineseWallTypes>
3355 <Type>VIOServer</Type>
3356 </ChineseWallTypes>
3357 </VirtualMachineLabel>
3358 \end{verbatim}
3359 \end{scriptsize}
3361 This Virtual I/O domain (VIO) exports its virtualized disks by
3362 communicating to all domains labeled with the
3363 \verb|A-Bank.SecurityUnderwriting|, the \verb|A-Bank|, or the
3364 \verb|A-Bank.MarketAnalysis| label. This requires the
3365 VIO domain to carry those STE types. In addition, this label includes a
3366 new \verb|VIOServer| type that can be used to restrict direct access to the
3367 physical storage resource to the VIODomain.
3369 In this example, the confinement of these A-Bank workloads depends on the
3370 VIO domain that must keep the data of those different workloads separate.
3371 The virtual disks are labeled as well to keep track of their assignments
3372 to workload types (see Section~\ref{subsection:acmexamplelabelresources}
3373 for labeling resources) and enforcement functions inside the VIO
3374 domain must ensure that the labels of the domain mounting a virtual
3375 disk and the virtual disk label share a common STE type. The VIO label
3376 carrying its own VIOServer CHWALL type introduces the flexibility to
3377 permit the trusted VIO server to run together with \verb|A-Bank.SecurityUnderwriting|
3378 or \verb|A-Bank.MarketAnalysis| workloads.
3380 Alternatively, a system that has two hard-drives does not need a VIO
3381 domain but can directly assign one hardware storage device to each of
3382 the workloads if the platform offers an IO-MMU, cf
3383 Section~\ref{s:ddsecurity}. Sharing hardware through virtualized devices
3384 is a trade-off between the amount of trusted code (size of the trusted
3385 computing base) and the amount of acceptable over-provisioning. This
3386 holds both for peripherals and for system platforms.
3389 \subsection{Managing sHype/Xen Security Policies at Run-time}
3390 \label{subsection:acmpolicymanagement}
3392 \subsubsection{Removing the sHype/Xen Security Policy}
3393 When resetting the policy, no labeled domains can be running.
3394 Please stop or shutdown all running labeled domains. Then you can reset
3395 the policy to the default policy using the \verb|resetpolicy| command:
3397 \begin{scriptsize}
3398 \begin{verbatim}
3399 # xm getpolicy
3400 Supported security subsystems : ACM
3401 Policy name : mytest
3402 Policy type : ACM
3403 Version of XML policy : 1.0
3404 Policy configuration : loaded, activated for boot
3406 # xm resetpolicy
3407 Successfully reset the system's policy.
3409 # xm getpolicy
3410 Supported security subsystems : ACM
3411 Policy name : DEFAULT
3412 Policy type : ACM
3413 Version of XML policy : 1.0
3414 Policy configuration : loaded
3416 # xm resources
3417 file:/home/xen/dom_fc5/fedora.fc5.swap
3418 type: INV_ACM
3419 policy: mytest
3420 label: A-Bank
3421 file:/home/xen/dom_fc5/fedora.fc5.img
3422 type: INV_ACM
3423 policy: mytest
3424 label: A-Bank
3425 \end{verbatim}
3426 \end{scriptsize}
3428 As the \verb|xm resources| output shows, all resource labels have
3429 invalidated type information but their semantics remain associated
3430 with the resources so that they can later on either be relabeled
3431 with semantically equivalent labels or sanitized and reused
3432 (storage resources).
3434 At this point, the system is in the same initial state as after
3435 configuring XSM and sHype/ACM and rebooting the system without
3436 a specific policy. No user domains can run.
3438 \subsubsection{Changing to a Different sHype/Xen Security Policy}
3439 The easiest way to change to a different, unrelated policy is to reset the system
3440 policy and then set the new policy. Please consider that the existing
3441 domain and resource labels become invalid at this point. Please refer
3442 to the next section for an example of how to seamlessly update an
3443 active policy at run-time without invalidating labels.
3445 \begin{scriptsize}
3446 \begin{verbatim}
3447 # xm resetpolicy
3448 Successfully reset the system's policy.
3450 # xm setpolicy ACM example.test
3451 Successfully set the new policy.
3452 Supported security subsystems : ACM
3453 Policy name : example.test
3454 Policy type : ACM
3455 Version of XML policy : 1.0
3456 Policy configuration : loaded, activated for boot
3458 # xm labels
3459 CocaCola
3460 PepsiCo
3461 SystemManagement
3462 VIO
3463 # xm list --label
3464 Name ID Mem VCPUs State Time(s) Label
3465 Domain-0 0 873 1 r----- 56.3 ACM:example.test:SystemManagement
3467 # xm resetpolicy
3468 Successfully reset the system's policy.
3470 # xm getpolicy
3471 Supported security subsystems : ACM
3472 Policy name : DEFAULT
3473 Policy type : ACM
3474 Version of XML policy : 1.0
3475 Policy configuration : loaded
3477 # xm list --label
3478 Name ID Mem VCPUs State Time(s) Label
3479 Domain-0 0 873 1 r----- 57.2 ACM:DEFAULT:SystemManagement
3481 # xm setpolicy ACM mytest
3482 Successfully set the new policy.
3483 Supported security subsystems : ACM
3484 Policy name : mytest
3485 Policy type : ACM
3486 Version of XML policy : 1.0
3487 Policy configuration : loaded, activated for boot
3489 # xm labels
3490 A-Bank
3491 A-Bank.MarketAnalysis
3492 A-Bank.SecurityUnderwriting
3493 AutoCorp
3494 B-Bank
3495 SystemManagement
3496 __UNLABELED__
3498 # xm list --label
3499 Name ID Mem VCPUs State Time(s) Label
3500 Domain-0 0 873 1 r----- 58.0 ACM:mytest:SystemManagement
3501 \end{verbatim}
3502 \end{scriptsize}
3504 The described way of changing policies by resetting the existing
3505 policy is useful for testing different policies. For real deployment
3506 environments, a policy update as described in the following section
3507 is more appropriate and can be applied seamlessly at run-time while
3508 user domains are running.
3510 \subsubsection{Update an sHype/Xen Security Policy at Run-time}
3512 Once an ACM security policy is activated (loaded into the Xen
3513 hypervisor), the policy may be updated at run-time without the
3514 need to re-boot the system. The XML update-policy contains several
3515 additional information fields that are required to safely link the
3516 new policy contents to the old policy and ensure a consistent
3517 transformation of the system security state from the old to the
3518 new policy. Those additional fields are required for policies that
3519 are updating an existing policy at run-time.
3521 The major benefit of policy updates is the ability to add, delete,
3522 or rename workload types, labels, and conflict sets (run-time
3523 exclusion rules) to accommodate changes in the managed virtual
3524 environment without the need to reboot the Xen system. When a
3525 new policy renames labels of the current policy, the labels
3526 attached to resources and domains are automatically updated
3527 during a successful policy update.
3529 We have manually crafted an update policy for the \verb|mytest|
3530 security policy and stored it in the file mytest\_update-security\_policy.xml
3531 in the policies directory. We will discuss this policy in detail before
3532 using it to update a running sHype/Xen system. The following figures contain
3533 the whole contents of the update policy file.
3535 Figure~\ref{fig:acmupdateheader} shows the policy
3536 header of an update-policy and the new \verb|FromPolicy| XML
3537 node. For the policy update to succeed, the policy name and the
3538 policy version fields of the \verb|FromPolicy| XML node must
3539 exactly match those of the currently enforced policy. This
3540 ensures a controlled update path of the policy.
3542 \begin{figure}[htb]
3543 \begin{scriptsize}
3544 \begin{verbatim}
3545 <?xml version="1.0" encoding="UTF-8"?>
3546 <!-- Auto-generated by ezPolicy -->
3547 <SecurityPolicyDefinition xmlns="http://www.ibm.com"
3548 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
3549 xsi:schemaLocation="http://www.ibm.com ../../security_policy.xsd ">
3550 <PolicyHeader>
3551 <PolicyName>mytest</PolicyName>
3552 <Date>Tue Nov 27 21:53:45 2007</Date>
3553 <Version>1.1</Version>
3554 <FromPolicy>
3555 <PolicyName>mytest</PolicyName>
3556 <Version>1.0</Version>
3557 </FromPolicy>
3558 </PolicyHeader>
3559 \end{verbatim}
3560 \end{scriptsize}
3561 \caption{XML security policy update -- Part I: Updated Policy Header.}
3562 \label{fig:acmupdateheader}
3563 \end{figure}
3565 The version number of the new policy, which is shown in the
3566 node following the \verb|Date| node, must be a logical increment
3567 to the current policy's version. Therefore at least the minor
3568 number of the policy version must be incremented. This ensures
3569 that a policy update is applied only to exactly the policy for
3570 which this update was created and minimizes unforseen side-effects
3571 of policy updates.
3573 \paragraph{Types and Conflic Sets}
3574 The type names and the assignment of types to labels or conflict
3575 sets (run-time exclusion rules) can
3576 simply be changed consistently throughout the policy. Types,
3577 as opposed to labels, are not directly associated or referenced
3578 outside the policy so they do not need to carry their history
3579 in a ``From'' field. The figure below shows the update for the
3580 types and conflict sets. The \verb|__UNLABELED__| type is removed
3581 to disable support for running unlabeled domains. Additionally,
3582 we have renamed the two \verb|A-Bank| department types with
3583 abbreviated names \verb|A-Bank.SU| and \verb|A-Bank.MA|. You
3584 can also see how those type names are
3585 consistently changed within the conflict set definition.
3587 \begin{figure}[htb]
3588 \begin{scriptsize}
3589 \begin{verbatim}
3590 <SimpleTypeEnforcement>
3591 <SimpleTypeEnforcementTypes>
3592 <Type>SystemManagement</Type>
3593 <Type>A-Bank</Type>
3594 <Type>A-Bank.SU</Type>
3595 <Type>A-Bank.MA</Type>
3596 <Type>B-Bank</Type>
3597 <Type>AutoCorp</Type>
3598 </SimpleTypeEnforcementTypes>
3599 </SimpleTypeEnforcement>
3601 <ChineseWall priority="PrimaryPolicyComponent">
3602 <ChineseWallTypes>
3603 <Type>SystemManagement</Type>
3604 <Type>A-Bank</Type>
3605 <Type>A-Bank.SU</Type>
3606 <Type>A-Bank.MA</Type>
3607 <Type>B-Bank</Type>
3608 <Type>AutoCorp</Type>
3609 </ChineseWallTypes>
3611 <ConflictSets>
3612 <Conflict name="RER">
3613 <Type>A-Bank</Type>
3614 <Type>B-Bank</Type>
3615 </Conflict>
3616 <Conflict name="RER">
3617 <Type>A-Bank.MA</Type>
3618 <Type>A-Bank.SU</Type>
3619 </Conflict>
3620 </ConflictSets>
3621 </ChineseWall>
3622 \end{verbatim}
3623 \end{scriptsize}
3624 \caption{XML security policy update -- Part II: Updated Types and Conflict Sets.}
3625 \label{fig:acmupdatetypesnrules}
3626 \end{figure}
3628 In the same way, new types can be introduced and new conflict sets
3629 can be defined by simply adding the types or conflict sets to the
3630 update policy.
3632 \paragraph{Labels} Virtual machine and resource labels of an existing policy can be
3633 deleted through a policy update simply by omitting them in the
3634 update-policy. However, if a currently running virtual machine
3635 or a currently used resource is labeled with a label not stated
3636 in the update-policy, then the policy update is rejected. This
3637 ensures that a policy update leaves the system in a consistent
3638 security state.
3640 A policy update also enables the renaming of virtual machine and
3641 resource labels. Linking the old label name with the new label
3642 name is achieved through the \verb|from| attribute in the
3643 \verb|VirtualMachineLabel| or \verb|ResourceLabel| nodes in the
3644 update-policy. Figure~\ref{fig:acmupdatelabels} shown how subject
3645 and resource labels
3646 are updated from their old name \verb|A-Bank.SecurityUnterwriting|
3647 to their new name \verb|A-Bank.SU| using the \verb|from| attribute.
3649 \begin{figure}[htb]
3650 \begin{tabular*}{\textwidth}{@{\extracolsep{\fill}}l|l}
3651 \begin{minipage}{0.475\textwidth}
3652 \begin{tiny}
3653 \begin{verbatim}
3654 <SecurityLabelTemplate>
3655 <SubjectLabels bootstrap="SystemManagement">
3656 <VirtualMachineLabel>
3657 <Name>SystemManagement</Name>
3658 <SimpleTypeEnforcementTypes>
3659 <Type>SystemManagement</Type>
3660 <Type>A-Bank</Type>
3661 <Type>A-Bank.SU</Type>
3662 <Type>A-Bank.MA</Type>
3663 <Type>B-Bank</Type>
3664 <Type>AutoCorp</Type>
3665 </SimpleTypeEnforcementTypes>
3666 <ChineseWallTypes>
3667 <Type>SystemManagement</Type>
3668 </ChineseWallTypes>
3669 </VirtualMachineLabel>
3670 <VirtualMachineLabel>
3671 <Name>A-Bank-WL</Name>
3672 <SimpleTypeEnforcementTypes>
3673 <Type>SystemManagement</Type>
3674 <Type>A-Bank</Type>
3675 <Type>A-Bank.SU</Type>
3676 <Type>A-Bank.MA</Type>
3677 </SimpleTypeEnforcementTypes>
3678 <ChineseWallTypes>
3679 <Type>SystemManagement</Type>
3680 </ChineseWallTypes>
3681 </VirtualMachineLabel>
3682 <VirtualMachineLabel>
3683 <Name>A-Bank</Name>
3684 <SimpleTypeEnforcementTypes>
3685 <Type>A-Bank</Type>
3686 </SimpleTypeEnforcementTypes>
3687 <ChineseWallTypes>
3688 <Type>A-Bank</Type>
3689 </ChineseWallTypes>
3690 </VirtualMachineLabel>
3691 <VirtualMachineLabel>
3692 <Name from="A-Bank.SecurityUnderwriting">
3693 A-Bank.SU</Name>
3694 <SimpleTypeEnforcementTypes>
3695 <Type>A-Bank.SU</Type>
3696 </SimpleTypeEnforcementTypes>
3697 <ChineseWallTypes>
3698 <Type>A-Bank</Type>
3699 <Type>A-Bank.SU</Type>
3700 </ChineseWallTypes>
3701 </VirtualMachineLabel>
3702 <VirtualMachineLabel>
3703 <Name from="A-Bank.MarketAnalysis">
3704 A-Bank.MA</Name>
3705 <SimpleTypeEnforcementTypes>
3706 <Type>A-Bank.MA</Type>
3707 </SimpleTypeEnforcementTypes>
3708 <ChineseWallTypes>
3709 <Type>A-Bank</Type>
3710 <Type>A-Bank.MA</Type>
3711 </ChineseWallTypes>
3712 </VirtualMachineLabel>
3713 \end{verbatim}
3714 \end{tiny}
3715 \end{minipage} &
3716 \begin{minipage}{0.475\textwidth}
3717 \begin{tiny}
3718 \begin{verbatim}
3719 <VirtualMachineLabel>
3720 <Name>B-Bank</Name>
3721 <SimpleTypeEnforcementTypes>
3722 <Type>B-Bank</Type>
3723 </SimpleTypeEnforcementTypes>
3724 <ChineseWallTypes>
3725 <Type>B-Bank</Type>
3726 </ChineseWallTypes>
3727 </VirtualMachineLabel>
3728 <VirtualMachineLabel>
3729 <Name>AutoCorp</Name>
3730 <SimpleTypeEnforcementTypes>
3731 <Type>AutoCorp</Type>
3732 </SimpleTypeEnforcementTypes>
3733 <ChineseWallTypes>
3734 <Type>AutoCorp</Type>
3735 </ChineseWallTypes>
3736 </VirtualMachineLabel>
3737 </SubjectLabels>
3739 <ObjectLabels>
3740 <ResourceLabel>
3741 <Name>SystemManagement</Name>
3742 <SimpleTypeEnforcementTypes>
3743 <Type>SystemManagement</Type>
3744 </SimpleTypeEnforcementTypes>
3745 </ResourceLabel>
3746 <ResourceLabel>
3747 <Name>A-Bank</Name>
3748 <SimpleTypeEnforcementTypes>
3749 <Type>A-Bank</Type>
3750 </SimpleTypeEnforcementTypes>
3751 </ResourceLabel>
3752 <ResourceLabel>
3753 <Name from="A-Bank.SecurityUnderwriting">
3754 A-Bank.SU</Name>
3755 <SimpleTypeEnforcementTypes>
3756 <Type>A-Bank.SU</Type>
3757 </SimpleTypeEnforcementTypes>
3758 </ResourceLabel>
3759 <ResourceLabel>
3760 <Name from="A-Bank.MarketAnalysis">
3761 A-Bank.MA</Name>
3762 <SimpleTypeEnforcementTypes>
3763 <Type>A-Bank.MA</Type>
3764 </SimpleTypeEnforcementTypes>
3765 </ResourceLabel>
3766 <ResourceLabel>
3767 <Name>B-Bank</Name>
3768 <SimpleTypeEnforcementTypes>
3769 <Type>B-Bank</Type>
3770 </SimpleTypeEnforcementTypes>
3771 </ResourceLabel>
3772 <ResourceLabel>
3773 <Name>AutoCorp</Name>
3774 <SimpleTypeEnforcementTypes>
3775 <Type>AutoCorp</Type>
3776 </SimpleTypeEnforcementTypes>
3777 </ResourceLabel>
3778 </ObjectLabels>
3779 </SecurityLabelTemplate>
3780 </SecurityPolicyDefinition>
3781 \end{verbatim}
3782 \end{tiny}
3783 \end{minipage}
3784 \end{tabular*}
3785 \caption{XML security policy update -- Part III: Updated Label Definition.}
3786 \label{fig:acmupdatelabels}
3787 \end{figure}
3788 % DO NOT MODIFY WHITESPACE ABOVE, it balances the columns
3790 The updated label definition also includes a new label \verb|A-Bank-WL|
3791 that includes all STE types related to A-Bank. Its CHWALL type
3792 is \verb|SystemManagement|. This indicates that this label is designed
3793 as Domain-0 label. A Xen system can be restricted to only run A-Bank
3794 related workloads by relabeling Domain-0 with the \verb|A-Bank-WL| label.
3796 We assume that the update-policy shown in
3797 Figures~\ref{fig:acmupdateheader}, \ref{fig:acmupdatetypesnrules}
3798 and \ref{fig:acmupdatelabels}
3799 is stored in the XML file mytest\_update-security\_policy.xml located
3800 in the ACM policy directory. See Section~\ref{subsection:acmnaming}
3801 for information about policy names and locations.
3803 The following \verb|xm setpolicy| command updates the active ACM
3804 security policy at run-time.
3806 \begin{scriptsize}
3807 \begin{verbatim}
3808 # xm list --label
3809 Name ID Mem VCPUs State Time(s) Label
3810 domain1 2 128 1 -b---- 0.6 ACM:mytest:A-Bank
3811 domain4 3 164 1 -b---- 0.3 ACM:mytest:A-Bank.SecurityUnderwriting
3812 Domain-0 0 711 1 r----- 71.8 ACM:mytest:SystemManagement
3814 # xm resources
3815 file:/home/xen/dom_fc5/fedora.fc5.swap
3816 type: ACM
3817 policy: mytest
3818 label: A-Bank
3819 file:/home/xen/dom_fc5/fedora.fc5.img
3820 type: ACM
3821 policy: mytest
3822 label: A-Bank
3824 # xm setpolicy ACM mytest_update
3825 Successfully set the new policy.
3826 Supported security subsystems : ACM
3827 Policy name : mytest
3828 Policy type : ACM
3829 Version of XML policy : 1.1
3830 Policy configuration : loaded, activated for boot
3832 # xm list --label
3833 Name ID Mem VCPUs State Time(s) Label
3834 domain1 2 128 1 -b---- 0.7 ACM:mytest:A-Bank
3835 domain4 3 164 1 -b---- 0.3 ACM:mytest:A-Bank.SU
3836 Domain-0 0 711 1 r----- 72.8 ACM:mytest:SystemManagement
3838 # xm labels
3839 A-Bank
3840 A-Bank-WL
3841 A-Bank.MA
3842 A-Bank.SU
3843 AutoCorp
3844 B-Bank
3846 # xm resources
3847 file:/home/xen/dom_fc5/fedora.fc5.swap
3848 type: ACM
3849 policy: mytest
3850 label: A-Bank
3851 file:/home/xen/dom_fc5/fedora.fc5.img
3852 type: ACM
3853 policy: mytest
3854 label: A-Bank
3855 \end{verbatim}
3856 \end{scriptsize}
3858 After successful completion of this command, \verb|xm list --label|
3859 shows that the labels of running domains changed to their new names.
3860 \verb|xm labels| shows that new labels \verb|A-Bank.SU| and \verb|A-Bank.AM|
3861 are now available in the policy. The resource labels remain valid after
3862 the successful update as \verb|xm resources| confirms.
3864 The \verb|setpolicy| command fails if the new policy is inconsistent
3865 with the current one or the policy is inconsistent internally (e.g., types
3866 are renamed in the type definition but not in the label definition part of
3867 the policy). In this case, the old policy remains active.
3869 After relabeling Domain-0 with the new \verb|A-Bank-WL| label, we can no
3870 longer run domains labeled \verb|B-Bank| or \verb|AutoCorp| since their
3871 STE types are not a subset of the new Domain-0 label.
3873 \begin{scriptsize}
3874 \begin{verbatim}
3875 # xm addlabel A-Bank-WL mgt Domain-0
3876 Successfully set the label of domain 'Domain-0' to 'A-Bank-WL'.
3878 # xm list --label
3879 Name ID Mem VCPUs State Time(s) Label
3880 domain1 2 128 1 -b---- 0.8 ACM:mytest:A-Bank
3881 Domain-0 0 711 1 r----- 74.5 ACM:mytest:A-Bank-WL
3882 domain4 3 164 1 -b---- 0.3 ACM:mytest:A-Bank.SU
3884 # xm getlabel dom domain3.xm
3885 policytype=ACM,policy=mytest,label=AutoCorp
3887 # xm create domain3.xm
3888 Using config file "./domain3.xm".
3889 Error: VM is not authorized to run.
3891 # xm addlabel SystemManagement mgt Domain-0
3892 Successfully set the label of domain 'Domain-0' to 'SystemManagement'.
3894 # xm list --label
3895 Name ID Mem VCPUs State Time(s) Label
3896 domain1 2 128 1 -b---- 0.8 ACM:mytest:A-Bank
3897 domain4 3 164 1 -b---- 0.3 ACM:mytest:A-Bank.SU
3898 Domain-0 0 709 1 r----- 76.4 ACM:mytest:SystemManagement
3900 # xm create domain3.xm
3901 Using config file "./domain3.xm".
3902 Started domain domain3
3904 # xm list --label
3905 Name ID Mem VCPUs State Time(s) Label
3906 domain1 2 128 1 -b---- 0.8 ACM:mytest:A-Bank
3907 domain4 3 164 1 -b---- 0.3 ACM:mytest:A-Bank.SU
3908 domain3 4 164 1 -b---- 0.3 ACM:mytest:AutoCorp
3909 Domain-0 0 547 1 r----- 77.5 ACM:mytest:SystemManagement
3910 \end{verbatim}
3911 \end{scriptsize}
3913 In the same manner, you can add new labels to support new workloads and
3914 add, delete, or rename workload types (STE and/or CHWALL types) simply
3915 by changing the composition of labels. Another use case is to add new
3916 workload types to the current Domain-0 label to enable them to run.
3917 Conflict sets (run-time exclusion rules) can be simply omitted or added.
3918 The policy and label changes become active at once and new workloads
3919 can be run in protected mode without rebooting the Xen system.
3921 In all these cases, if any running user domain would--under the new policy--not
3922 be allowed to run or would not be allowed to access any of the resources
3923 it currently uses, then the policy update is rejected. In this case, you
3924 can stop domains that conflict with the new policy and update the policy
3925 afterwards. The old policy remains active until a policy update succeeds
3926 or Xen is re-booted into a new policy.
3928 \subsection{Tools For Creating sHype/Xen Security Policies}
3929 To create a security policy for Xen, you can use one of the following
3930 tools:
3931 \begin{itemize}
3932 \item \verb|ezPolicy| GUI tool -- start writing policies
3933 \item \verb|xensec_gen| tool -- refine policies created with \verb|ezPolicy|
3934 \item text or XML editor
3935 \end{itemize}
3937 We use the \verb|ezPolicy| tool in
3938 Section~\ref{subsection:acmexamplecreate} to quickly create a workload
3939 protection policy. If desired, the resulting XML policy file can be
3940 loaded into the \verb|xensec_gen| tool to refine it. It can also be
3941 directly edited using an XML editor. Any XML policy file is verified
3942 against the security policy schema when it is translated (see
3943 Subsection~\ref{subsection:acmexampleinstall}).
3945 \section{Current Limitations}
3946 \label{section:acmlimitations}
3948 The sHype/ACM configuration for Xen is work in progress. There is
3949 ongoing work for protecting virtualized resources and planned and
3950 ongoing work for protecting access to remote resources and domains.
3951 The following sections describe limitations of some of the areas into
3952 which access control is being extended.
3954 \subsection{Network Traffic}
3955 Local and remote network traffic is currently not controlled.
3956 Solutions to add sHype/ACM policy enforcement to the virtual network
3957 exist but need to be discussed before they can become part of Xen.
3958 Subjecting external network traffic to the ACM security policy is work
3959 in progress. Manually setting up filters in domain 0 is required for
3960 now but does not scale well.
3962 \subsection{Resource Access and Usage Control}
3964 Enforcing the security policy across multiple hypervisor systems and
3965 on access to remote shared resources is work in progress. Extending
3966 access control to new types of resources is ongoing work (e.g. network
3967 storage).
3969 On a single Xen system, information about the association of resources
3970 and security labels is stored in
3971 \verb|/var/lib/xend/security/policies/resource_labels|. This file relates
3972 a full resource path with a security label. This association is weak
3973 and will break if resources are moved or renamed without adapting the
3974 label file. Improving the protection of label-resource relationships
3975 is ongoing work.
3977 Controlling resource usage and enforcing resource limits in general is
3978 ongoing work in the Xen community.
3980 \subsection{Domain Migration}
3982 Labels on domains are enforced during domain migration and the
3983 destination hypervisor will ensure that the domain label is valid and
3984 the domain is permitted to run (considering the Chinese Wall policy
3985 rules) before it accepts the migration. However, the network between
3986 the source and destination hypervisor as well as both hypervisors must
3987 be trusted. Architectures and prototypes exist that both protect the
3988 network connection and ensure that the hypervisors enforce access
3989 control consistently but patches are not yet available for the main
3990 stream.
3992 \subsection{Covert Channels}
3994 The sHype access control aims at system independent security policies.
3995 It builds on top of the core hypervisor isolation. Any covert channels
3996 that exist in the core hypervisor or in the hardware (e.g., shared
3997 processor cache) will be inherited. If those covert channels are not
3998 the result of trade-offs between security and other system properties,
3999 then they are most effectively minimized or eliminated where they are
4000 caused. sHype offers however some means to mitigate their impact, e.g.,
4001 run-time exclusion rules (cf Section~\ref{subsection:acmexamplecreate})
4002 or limiting the system authorization (cf Section~\ref{subsection:acmlabeldom0}).
4005 \part{Reference}
4007 %% Chapter Build and Boot Options
4008 \chapter{Build and Boot Options}
4010 This chapter describes the build- and boot-time options which may be
4011 used to tailor your Xen system.
4013 \section{Top-level Configuration Options}
4015 Top-level configuration is achieved by editing one of two
4016 files: \path{Config.mk} and \path{Makefile}.
4018 The former allows the overall build target architecture to be
4019 specified. You will typically not need to modify this unless
4020 you are cross-compiling. Additional configuration options are
4021 documented in the \path{Config.mk} file.
4023 The top-level \path{Makefile} is chiefly used to customize the set of
4024 kernels built. Look for the line:
4025 \begin{quote}
4026 \begin{verbatim}
4027 KERNELS ?= linux-2.6-xen0 linux-2.6-xenU
4028 \end{verbatim}
4029 \end{quote}
4031 Allowable options here are any kernels which have a corresponding
4032 build configuration file in the \path{buildconfigs/} directory.
4036 \section{Xen Build Options}
4038 Xen provides a number of build-time options which should be set as
4039 environment variables or passed on make's command-line.
4041 \begin{description}
4042 \item[verbose=y] Enable debugging messages when Xen detects an
4043 unexpected condition. Also enables console output from all domains.
4044 \item[debug=y] Enable debug assertions. Implies {\bf verbose=y}.
4045 (Primarily useful for tracing bugs in Xen).
4046 \item[debugger=y] Enable the in-Xen debugger. This can be used to
4047 debug Xen, guest OSes, and applications.
4048 \item[perfc=y] Enable performance counters for significant events
4049 within Xen. The counts can be reset or displayed on Xen's console
4050 via console control keys.
4051 \end{description}
4054 \section{Xen Boot Options}
4055 \label{s:xboot}
4057 These options are used to configure Xen's behaviour at runtime. They
4058 should be appended to Xen's command line, either manually or by
4059 editing \path{grub.conf}.
4061 \begin{description}
4062 \item [ noreboot ] Don't reboot the machine automatically on errors.
4063 This is useful to catch debug output if you aren't catching console
4064 messages via the serial line.
4065 \item [ nosmp ] Disable SMP support. This option is implied by
4066 `ignorebiostables'.
4067 \item [ watchdog ] Enable NMI watchdog which can report certain
4068 failures.
4069 \item [ noirqbalance ] Disable software IRQ balancing and affinity.
4070 This can be used on systems such as Dell 1850/2850 that have
4071 workarounds in hardware for IRQ-routing issues.
4072 \item [ badpage=$<$page number$>$,$<$page number$>$, \ldots ] Specify
4073 a list of pages not to be allocated for use because they contain bad
4074 bytes. For example, if your memory tester says that byte 0x12345678
4075 is bad, you would place `badpage=0x12345' on Xen's command line.
4076 \item [ serial\_tx\_buffer=$<$size$>$ ] Size of serial transmit
4077 buffers. Default is 16kB.
4078 \item [ com1=$<$baud$>$,DPS,$<$io\_base$>$,$<$irq$>$
4079 com2=$<$baud$>$,DPS,$<$io\_base$>$,$<$irq$>$ ] \mbox{}\\
4080 Xen supports up to two 16550-compatible serial ports. For example:
4081 `com1=9600, 8n1, 0x408, 5' maps COM1 to a 9600-baud port, 8 data
4082 bits, no parity, 1 stop bit, I/O port base 0x408, IRQ 5. If some
4083 configuration options are standard (e.g., I/O base and IRQ), then
4084 only a prefix of the full configuration string need be specified. If
4085 the baud rate is pre-configured (e.g., by the bootloader) then you
4086 can specify `auto' in place of a numeric baud rate.
4087 \item [ console=$<$specifier list$>$ ] Specify the destination for Xen
4088 console I/O. This is a comma-separated list of, for example:
4089 \begin{description}
4090 \item[ vga ] Use VGA console (until domain 0 boots, unless {\bf
4091 vga=...keep } is specified).
4092 \item[ com1 ] Use serial port com1.
4093 \item[ com2H ] Use serial port com2. Transmitted chars will have the
4094 MSB set. Received chars must have MSB set.
4095 \item[ com2L] Use serial port com2. Transmitted chars will have the
4096 MSB cleared. Received chars must have MSB cleared.
4097 \end{description}
4098 The latter two examples allow a single port to be shared by two
4099 subsystems (e.g.\ console and debugger). Sharing is controlled by
4100 MSB of each transmitted/received character. [NB. Default for this
4101 option is `com1,vga']
4102 \item [ vga=$<$mode$>$(,keep) ] The mode is one of the following options:
4103 \begin{description}
4104 \item[ ask ] Display a vga menu allowing manual selection of video
4105 mode.
4106 \item[ current ] Use existing vga mode without modification.
4107 \item[ text-$<$mode$>$ ] Select text-mode resolution, where mode is
4108 one of 80x25, 80x28, 80x30, 80x34, 80x43, 80x50, 80x60.
4109 \item[ gfx-$<$mode$>$ ] Select VESA graphics mode
4110 $<$width$>$x$<$height$>$x$<$depth$>$ (e.g., `vga=gfx-1024x768x32').
4111 \item[ mode-$<$mode$>$ ] Specify a mode number as discovered by `vga
4112 ask'. Note that the numbers are displayed in hex and hence must be
4113 prefixed by `0x' here (e.g., `vga=mode-0x0335').
4114 \end{description}
4115 The mode may optionally be followed by `{\bf,keep}' to cause Xen to keep
4116 writing to the VGA console after domain 0 starts booting (e.g., `vga=text-80x50,keep').
4117 \item [ no-real-mode ] (x86 only) Do not execute real-mode bootstrap
4118 code when booting Xen. This option should not be used except for
4119 debugging. It will effectively disable the {\bf vga} option, which
4120 relies on real mode to set the video mode.
4121 \item [ edid=no,force ] (x86 only) Either force retrieval of monitor
4122 EDID information via VESA DDC, or disable it (edid=no). This option
4123 should not normally be required except for debugging purposes.
4124 \item [ edd=off,on,skipmbr ] (x86 only) Control retrieval of Extended
4125 Disc Data (EDD) from the BIOS during boot.
4126 \item [ console\_to\_ring ] Place guest console output into the
4127 hypervisor console ring buffer. This is disabled by default.
4128 When enabled, both hypervisor output and guest console output
4129 is available from the ring buffer. This can be useful for logging
4130 and/or remote presentation of console data.
4131 \item [ sync\_console ] Force synchronous console output. This is
4132 useful if you system fails unexpectedly before it has sent all
4133 available output to the console. In most cases Xen will
4134 automatically enter synchronous mode when an exceptional event
4135 occurs, but this option provides a manual fallback.
4136 \item [ conswitch=$<$switch-char$><$auto-switch-char$>$ ] Specify how
4137 to switch serial-console input between Xen and DOM0. The required
4138 sequence is CTRL-$<$switch-char$>$ pressed three times. Specifying
4139 the backtick character disables switching. The
4140 $<$auto-switch-char$>$ specifies whether Xen should auto-switch
4141 input to DOM0 when it boots --- if it is `x' then auto-switching is
4142 disabled. Any other value, or omitting the character, enables
4143 auto-switching. [NB. Default switch-char is `a'.]
4144 \item [ loglvl=$<$level$>/<$level$>$ ]
4145 Specify logging level. Messages of the specified severity level (and
4146 higher) will be printed to the Xen console. Valid levels are `none',
4147 `error', `warning', `info', `debug', and `all'. The second level
4148 specifier is optional: it is used to specify message severities
4149 which are to be rate limited. Default is `loglvl=warning'.
4150 \item [ guest\_loglvl=$<$level$>/<$level$>$ ] As for loglvl, but
4151 applies to messages relating to guests. Default is
4152 `guest\_loglvl=none/warning'.
4153 \item [ console\_timestamps ]
4154 Adds a timestamp prefix to each line of Xen console output.
4155 \item [ nmi=xxx ]
4156 Specify what to do with an NMI parity or I/O error. \\
4157 `nmi=fatal': Xen prints a diagnostic and then hangs. \\
4158 `nmi=dom0': Inform DOM0 of the NMI. \\
4159 `nmi=ignore': Ignore the NMI.
4160 \item [ mem=xxx ] Set the physical RAM address limit. Any RAM
4161 appearing beyond this physical address in the memory map will be
4162 ignored. This parameter may be specified with a B, K, M or G suffix,
4163 representing bytes, kilobytes, megabytes and gigabytes respectively.
4164 The default unit, if no suffix is specified, is kilobytes.
4165 \item [ dom0\_mem=$<$specifier list$>$ ] Set the amount of memory to
4166 be allocated to domain 0. This is a comma-separated list containing
4167 the following optional components:
4168 \begin{description}
4169 \item[ min:$<$min\_amt$>$ ] Minimum amount to allocate to domain 0
4170 \item[ max:$<$min\_amt$>$ ] Maximum amount to allocate to domain 0
4171 \item[ $<$amt$>$ ] Precise amount to allocate to domain 0
4172 \end{description}
4173 Each numeric parameter may be specified with a B, K, M or
4174 G suffix, representing bytes, kilobytes, megabytes and gigabytes
4175 respectively; if no suffix is specified, the parameter defaults to
4176 kilobytes. Negative values are subtracted from total available
4177 memory. If $<$amt$>$ is not specified, it defaults to all available
4178 memory less a small amount (clamped to 128MB) for uses such as DMA
4179 buffers.
4180 \item [ dom0\_vcpus\_pin ] Pins domain 0 VCPUs on their respective
4181 physical CPUS (default=false).
4182 \item [ tbuf\_size=xxx ] Set the size of the per-cpu trace buffers, in
4183 pages (default 0).
4184 \item [ sched=xxx ] Select the CPU scheduler Xen should use. The
4185 current possibilities are `credit' (default), and `sedf'.
4186 \item [ apic\_verbosity=debug,verbose ] Print more detailed
4187 information about local APIC and IOAPIC configuration.
4188 \item [ lapic ] Force use of local APIC even when left disabled by
4189 uniprocessor BIOS.
4190 \item [ nolapic ] Ignore local APIC in a uniprocessor system, even if
4191 enabled by the BIOS.
4192 \item [ apic=bigsmp,default,es7000,summit ] Specify NUMA platform.
4193 This can usually be probed automatically.
4194 \item [ dma\_bits=xxx ] Specify width of DMA addresses in bits. This
4195 is used in NUMA systems to prevent this special DMA memory from
4196 being exhausted in one node when remote nodes have available memory.
4197 \end{description}
4199 In addition, the following options may be specified on the Xen command
4200 line. Since domain 0 shares responsibility for booting the platform,
4201 Xen will automatically propagate these options to its command line.
4202 These options are taken from Linux's command-line syntax with
4203 unchanged semantics.
4205 \begin{description}
4206 \item [ acpi=off,force,strict,ht,noirq,\ldots ] Modify how Xen (and
4207 domain 0) parses the BIOS ACPI tables.
4208 \item [ acpi\_skip\_timer\_override ] Instruct Xen (and domain~0) to
4209 ignore timer-interrupt override instructions specified by the BIOS
4210 ACPI tables.
4211 \item [ noapic ] Instruct Xen (and domain~0) to ignore any IOAPICs
4212 that are present in the system, and instead continue to use the
4213 legacy PIC.
4214 \end{description}
4217 \section{XenLinux Boot Options}
4219 In addition to the standard Linux kernel boot options, we support:
4220 \begin{description}
4221 \item[ xencons=xxx ] Specify the device node to which the Xen virtual
4222 console driver is attached. The following options are supported:
4223 \begin{center}
4224 \begin{tabular}{l}
4225 `xencons=off': disable virtual console \\
4226 `xencons=tty': attach console to /dev/tty1 (tty0 at boot-time) \\
4227 `xencons=ttyS': attach console to /dev/ttyS0 \\
4228 `xencons=xvc': attach console to /dev/xvc0
4229 \end{tabular}
4230 \end{center}
4231 The default is ttyS for dom0 and xvc for all other domains.
4232 \end{description}
4235 %% Chapter Further Support
4236 \chapter{Further Support}
4238 If you have questions that are not answered by this manual, the
4239 sources of information listed below may be of interest to you. Note
4240 that bug reports, suggestions and contributions related to the
4241 software (or the documentation) should be sent to the Xen developers'
4242 mailing list (address below).
4245 \section{Other Documentation}
4247 For developers interested in porting operating systems to Xen, the
4248 \emph{Xen Interface Manual} is distributed in the \path{docs/}
4249 directory of the Xen source distribution.
4252 \section{Online References}
4254 The official Xen web site can be found at:
4255 \begin{quote} {\tt http://www.xensource.com}
4256 \end{quote}
4258 This contains links to the latest versions of all online
4259 documentation, including the latest version of the FAQ.
4261 Information regarding Xen is also available at the Xen Wiki at
4262 \begin{quote} {\tt http://wiki.xensource.com/xenwiki/}\end{quote}
4263 The Xen project uses Bugzilla as its bug tracking system. You'll find
4264 the Xen Bugzilla at http://bugzilla.xensource.com/bugzilla/.
4267 \section{Mailing Lists}
4269 There are several mailing lists that are used to discuss Xen related
4270 topics. The most widely relevant are listed below. An official page of
4271 mailing lists and subscription information can be found at \begin{quote}
4272 {\tt http://lists.xensource.com/} \end{quote}
4274 \begin{description}
4275 \item[xen-devel@lists.xensource.com] Used for development
4276 discussions and bug reports. Subscribe at: \\
4277 {\small {\tt http://lists.xensource.com/xen-devel}}
4278 \item[xen-users@lists.xensource.com] Used for installation and usage
4279 discussions and requests for help. Subscribe at: \\
4280 {\small {\tt http://lists.xensource.com/xen-users}}
4281 \item[xen-announce@lists.xensource.com] Used for announcements only.
4282 Subscribe at: \\
4283 {\small {\tt http://lists.xensource.com/xen-announce}}
4284 \item[xen-changelog@lists.xensource.com] Changelog feed
4285 from the unstable and 2.0 trees - developer oriented. Subscribe at: \\
4286 {\small {\tt http://lists.xensource.com/xen-changelog}}
4287 \end{description}
4291 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
4293 \appendix
4295 \chapter{Unmodified (HVM) guest domains in Xen with Hardware support for Virtualization}
4297 Xen supports guest domains running unmodified guest operating systems using
4298 virtualization extensions available on recent processors. Currently processors
4299 featuring the Intel Virtualization Extension (Intel-VT) or the AMD extension
4300 (AMD-V) are supported. The technology covering both implementations is
4301 called HVM (for Hardware Virtual Machine) in Xen. More information about the
4302 virtualization extensions are available on the respective websites:
4303 {\small {\tt http://www.intel.com/technology/computing/vptech}}
4306 {\small {\tt http://www.amd.com/us-en/assets/content\_type/white\_papers\_and\_tech\_docs/24593.pdf}}
4308 \section{Building Xen with HVM support}
4310 The following packages need to be installed in order to build Xen with HVM support. Some Linux distributions do not provide these packages by default.
4312 \begin{tabular}{lp{11.0cm}}
4313 {\bfseries Package} & {\bfseries Description} \\
4315 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.
4317 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}} \\
4319 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.
4321 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}}
4324 {\scriptsize {\tt http://www.rpmfind.net/linux/rpm2html/search.php?query=SDL-devel\&submit=Search}} \\
4326 \end{tabular}
4328 \section{Configuration file for unmodified HVM guests}
4330 The Xen installation includes a sample configuration file, {\small {\tt /etc/xen/xmexample.hvm}}. There are comments describing all the options. In addition to the common options that are the same as those for paravirtualized guest configurations, HVM guest configurations have the following settings:
4332 \begin{tabular}{lp{11.0cm}}
4334 {\bfseries Parameter} & {\bfseries Description} \\
4336 kernel & The HVM firmware loader, {\small {\tt /usr/lib/xen/boot/hvmloader}}\\
4338 builder & The domain build function. The HVM domain uses the 'hvm' builder.\\
4340 acpi & Enable HVM guest ACPI, default=1 (enabled)\\
4342 apic & Enable HVM guest APIC, default=1 (enabled)\\
4344 pae & Enable HVM guest PAE, default=1 (enabled)\\
4346 hap & Enable hardware-assisted paging support, such as AMD-V's nested paging
4347 or Intel\textregistered VT's extended paging. If available, Xen will
4348 use hardware-assisted paging instead of shadow paging for this guest's memory
4349 management.\\
4351 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 HVM NIC. If no type is specified, vbd is used, as with paravirtualized guests.\\
4353 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 HVM guest's disk, each disk entry is of the form
4355 {\small {\tt phy:UNAME,ioemu:DEV,MODE,}}
4357 where UNAME is the host device file, 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 HVM disk. If not adding ioemu, it uses vbd like paravirtualized guests.
4359 If using disk image file, its form should be like
4361 {\small {\tt file:FILEPATH,ioemu:DEV,MODE}}
4363 Optical devices can be emulated by appending cdrom to the device type
4365 {\small {\tt ',hdc:cdrom,r'}}
4367 If using more than one disk, there should be a comma between each disk entry. For example:
4369 {\scriptsize {\tt disk = ['file:/var/images/image1.img,ioemu:hda,w', 'phy:hda1,hdb1,w', 'file:/var/images/install1.iso,hdc:cdrom,r']}}\\
4371 boot & Boot from floppy (a), hard disk (c) or CD-ROM (d). For example, to boot from CD-ROM and fallback to HD, the entry should be:
4373 boot='dc'\\
4375 device\_model & The device emulation tool for HVM guests. This parameter should not be changed.\\
4377 sdl & Enable SDL library for graphics, default = 0 (disabled)\\
4379 vnc & Enable VNC library for graphics, default = 1 (enabled)\\
4381 vncconsole & Enable spawning of the vncviewer (only valid when vnc=1), default = 0 (disabled)
4383 If vnc=1 and vncconsole=0, user can use vncviewer to manually connect HVM from remote. For example:
4385 {\small {\tt vncviewer domain0\_IP\_address:HVM\_domain\_id}} \\
4387 serial & Enable redirection of HVM serial output to pty device\\
4389 \end{tabular}
4391 \begin{tabular}{lp{10cm}}
4393 usb & Enable USB support without defining a specific USB device.
4394 This option defaults to 0 (disabled) unless the option usbdevice is
4395 specified in which case this option then defaults to 1 (enabled).\\
4397 usbdevice & Enable USB support and also enable support for the given
4398 device. Devices that can be specified are {\small {\tt mouse}} (a PS/2 style
4399 mouse), {\small {\tt tablet}} (an absolute pointing device) and
4400 {\small {\tt host:id1:id2}} (a physical USB device on the host machine whose
4401 ids are {\small {\tt id1}} and {\small {\tt id2}}). The advantage
4402 of {\small {\tt tablet}} is that Windows guests will automatically recognize
4403 and support this device so specifying the config line
4405 {\small
4406 \begin{verbatim}
4407 usbdevice='tablet'
4408 \end{verbatim}
4411 will create a mouse that works transparently with Windows guests under VNC.
4412 Linux doesn't recognize the USB tablet yet so Linux guests under VNC will
4413 still need the Summagraphics emulation.
4414 Details about mouse emulation are provided in section \textbf{A.4.3}.\\
4416 localtime & Set the real time clock to local time [default=0, that is, set to UTC].\\
4418 soundhw & Enable sound card support and specify the hardware to emulate. Values can be sb16, es1370 or all. Default is none.\\
4420 full-screen & Start in full screen.\\
4422 nographic & Another way to redirect serial output. If enabled, no 'sdl' or 'vnc' can work. Not recommended.\\
4424 \end{tabular}
4427 \section{Creating virtual disks from scratch}
4428 \subsection{Using physical disks}
4429 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.
4431 \subsection{Using disk image files}
4432 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 HVM 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.
4434 \subsubsection*{To create the image file:}
4435 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).
4437 {\small {\tt \# dd if=/dev/zero of=hd.img bs=1M count=0 seek=1024}}
4439 \subsubsection*{To directly install Linux OS into an image file using a HVM guest:}
4441 Install Xen and create HVM with the original image file with booting from CD-ROM. Then it is just like a normal Linux OS installation. The HVM configuration file should have a stanza for the CD-ROM as well as a boot device specification:
4443 {\small {\tt disk=['file:/var/images/your-hd.img,hda,w', ',hdc:cdrom,r' ]
4444 boot='d'}}
4446 If this method does not succeed, you can choose the following method of copying an installed Linux OS into an image file.
4448 \subsubsection*{To copy a installed OS into an image file:}
4449 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.
4451 \begin{enumerate}
4452 \item {\bfseries Install a normal Linux OS on the host machine}\\
4453 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/}}.
4455 \item {\bfseries Make the partition table}\\
4456 The image file will be treated as hard disk, so you should make the partition table in the image file. For example:
4458 {\scriptsize {\tt \# losetup /dev/loop0 hd.img\\
4459 \# fdisk -b 512 -C 4096 -H 16 -S 32 /dev/loop0\\
4460 press 'n' to add new partition\\
4461 press 'p' to choose primary partition\\
4462 press '1' to set partition number\\
4463 press "Enter" keys to choose default value of "First Cylinder" parameter.\\
4464 press "Enter" keys to choose default value of "Last Cylinder" parameter.\\
4465 press 'w' to write partition table and exit\\
4466 \# losetup -d /dev/loop0}}
4468 \item {\bfseries Make the file system and install grub}\\
4469 {\scriptsize {\tt \# ln -s /dev/loop0 /dev/loop\\
4470 \# losetup /dev/loop0 hd.img\\
4471 \# losetup -o 16384 /dev/loop1 hd.img\\
4472 \# mkfs.ext3 /dev/loop1\\
4473 \# mount /dev/loop1 /mnt\\
4474 \# mkdir -p /mnt/boot/grub\\
4475 \# cp /boot/grub/stage* /boot/grub/e2fs\_stage1\_5 /mnt/boot/grub\\
4476 \# umount /mnt\\
4477 \# grub\\
4478 grub> device (hd0) /dev/loop\\
4479 grub> root (hd0,0)\\
4480 grub> setup (hd0)\\
4481 grub> quit\\
4482 \# rm /dev/loop\\
4483 \# losetup -d /dev/loop0\\
4484 \# losetup -d /dev/loop1}}
4486 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.
4488 \item {\bfseries Copy the OS files to the image}\\
4489 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.
4491 {\scriptsize {\tt \# lomount -t ext3 -diskimage hd.img -partition 1 /mnt/guest\\
4492 \# cp -ax /var/guestos/\{root,dev,var,etc,usr,bin,sbin,lib\} /mnt/guest\\
4493 \# mkdir /mnt/guest/\{proc,sys,home,tmp\}}}
4495 \item {\bfseries Edit the {\small {\tt /etc/fstab}} of the guest image}\\
4496 The fstab should look like this:
4498 {\scriptsize {\tt \# vim /mnt/guest/etc/fstab\\
4499 /dev/hda1 / ext3 defaults 1 1\\
4500 none /dev/pts devpts gid=5,mode=620 0 0\\
4501 none /dev/shm tmpfs defaults 0 0\\
4502 none /proc proc defaults 0 0\\
4503 none /sys sysfs efaults 0 0}}
4505 \item {\bfseries umount the image file}\\
4506 {\small {\tt \# umount /mnt/guest}}
4507 \end{enumerate}
4509 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.
4511 \section{HVM Guests}
4512 \subsection{Editing the Xen HVM config file}
4513 Make a copy of the example HVM configuration file {\small {\tt /etc/xen/xmexample.hvm}} and edit the line that reads
4515 {\small {\tt disk = [ 'file:/var/images/\emph{min-el3-i386.img},hda,w' ]}}
4517 replacing \emph{min-el3-i386.img} with the name of the guest OS image file you just made.
4519 \subsection{Creating HVM guests}
4520 Simply follow the usual method of creating the guest, providing the filename of your HVM configuration file:\\
4522 {\small {\tt \# xend start\\
4523 \# xm create /etc/xen/hvmguest.hvm}}
4525 In the default configuration, VNC is on and SDL is off. Therefore VNC windows will open when HVM guests are created. If you want to use SDL to create HVM guests, set {\small {\tt sdl=1}} in your HVM configuration file. You can also turn off VNC by setting {\small {\tt vnc=0}}.
4527 \subsection{Mouse issues, especially under VNC}
4528 Mouse handling when using VNC is a little problematic.
4529 The problem is that the VNC viewer provides a virtual pointer which is
4530 located at an absolute location in the VNC window and only absolute
4531 coordinates are provided.
4532 The HVM device model converts these absolute mouse coordinates
4533 into the relative motion deltas that are expected by the PS/2
4534 mouse driver running in the guest.
4535 Unfortunately,
4536 it is impossible to keep these generated mouse deltas
4537 accurate enough for the guest cursor to exactly match
4538 the VNC pointer.
4539 This can lead to situations where the guest's cursor
4540 is in the center of the screen and there's no way to
4541 move that cursor to the left
4542 (it can happen that the VNC pointer is at the left
4543 edge of the screen and,
4544 therefore,
4545 there are no longer any left mouse deltas that
4546 can be provided by the device model emulation code.)
4548 To deal with these mouse issues there are 4 different
4549 mouse emulations available from the HVM device model:
4551 \begin{description}
4552 \item[PS/2 mouse over the PS/2 port.]
4553 This is the default mouse
4554 that works perfectly well under SDL.
4555 Under VNC the guest cursor will get
4556 out of sync with the VNC pointer.
4557 When this happens you can re-synchronize
4558 the guest cursor to the VNC pointer by
4559 holding down the
4560 \textbf{left-ctl}
4561 and
4562 \textbf{left-alt}
4563 keys together.
4564 While these keys are down VNC pointer motions
4565 will not be reported to the guest so
4566 that the VNC pointer can be moved
4567 to a place where it is possible
4568 to move the guest cursor again.
4570 \item[Summagraphics mouse over the serial port.]
4571 The device model also provides emulation
4572 for a Summagraphics tablet,
4573 an absolute pointer device.
4574 This emulation is provided over the second
4575 serial port,
4576 \textbf{/dev/ttyS1}
4577 for Linux guests and
4578 \textbf{COM2}
4579 for Windows guests.
4580 Unfortunately,
4581 neither Linux nor Windows provides
4582 default support for the Summagraphics
4583 tablet so the guest will have to be
4584 manually configured for this mouse.
4586 \textbf{Linux configuration.}
4588 First,
4589 configure the GPM service to use the Summagraphics tablet.
4590 This can vary between distributions but,
4591 typically,
4592 all that needs to be done is modify the file
4593 \path{/etc/sysconfig/mouse} to contain the lines:
4595 {\small
4596 \begin{verbatim}
4597 MOUSETYPE="summa"
4598 XMOUSETYPE="SUMMA"
4599 DEVICE=/dev/ttyS1
4600 \end{verbatim}
4603 and then restart the GPM daemon.
4605 Next,
4606 modify the X11 config
4607 \path{/etc/X11/xorg.conf}
4608 to support the Summgraphics tablet by replacing
4609 the input device stanza with the following:
4611 {\small
4612 \begin{verbatim}
4613 Section "InputDevice"
4614 Identifier "Mouse0"
4615 Driver "summa"
4616 Option "Device" "/dev/ttyS1"
4617 Option "InputFashion" "Tablet"
4618 Option "Mode" "Absolute"
4619 Option "Name" "EasyPen"
4620 Option "Compatible" "True"
4621 Option "Protocol" "Auto"
4622 Option "SendCoreEvents" "on"
4623 Option "Vendor" "GENIUS"
4624 EndSection
4625 \end{verbatim}
4628 Restart X and the X cursor should now properly
4629 track the VNC pointer.
4632 \textbf{Windows configuration.}
4634 Get the file
4635 \path{http://www.cad-plan.de/files/download/tw2k.exe}
4636 and execute that file on the guest,
4637 answering the questions as follows:
4639 \begin{enumerate}
4640 \item When the program asks for \textbf{model},
4641 scroll down and select \textbf{SummaSketch (MM Compatible)}.
4643 \item When the program asks for \textbf{COM Port} specify \textbf{com2}.
4645 \item When the programs asks for a \textbf{Cursor Type} specify
4646 \textbf{4 button cursor/puck}.
4648 \item The guest system will then reboot and,
4649 when it comes back up,
4650 the guest cursor will now properly track
4651 the VNC pointer.
4652 \end{enumerate}
4654 \item[PS/2 mouse over USB port.]
4655 This is just the same PS/2 emulation except it is
4656 provided over a USB port.
4657 This emulation is enabled by the configuration flag:
4658 {\small
4659 \begin{verbatim}
4660 usbdevice='mouse'
4661 \end{verbatim}
4664 \item[USB tablet over USB port.]
4665 The USB tablet is an absolute pointing device
4666 that has the advantage that it is automatically
4667 supported under Windows guests,
4668 although Linux guests still require some
4669 manual configuration.
4670 This mouse emulation is enabled by the
4671 configuration flag:
4672 {\small
4673 \begin{verbatim}
4674 usbdevice='tablet'
4675 \end{verbatim}
4678 \textbf{Linux configuration.}
4680 Unfortunately,
4681 there is no GPM support for the
4682 USB tablet at this point in time.
4683 If you intend to use a GPM pointing
4684 device under VNC you should
4685 configure the guest for Summagraphics
4686 emulation.
4688 Support for X11 is available by following
4689 the instructions at\\
4690 \verb+http://stz-softwaretechnik.com/~ke/touchscreen/evtouch.html+\\
4691 with one minor change.
4692 The
4693 \path{xorg.conf}
4694 given in those instructions
4695 uses the wrong values for the X \& Y minimums and maximums,
4696 use the following config stanza instead:
4698 {\small
4699 \begin{verbatim}
4700 Section "InputDevice"
4701 Identifier "Tablet"
4702 Driver "evtouch"
4703 Option "Device" "/dev/input/event2"
4704 Option "DeviceName" "touchscreen"
4705 Option "MinX" "0"
4706 Option "MinY" "0"
4707 Option "MaxX" "32256"
4708 Option "MaxY" "32256"
4709 Option "ReportingMode" "Raw"
4710 Option "Emulate3Buttons"
4711 Option "Emulate3Timeout" "50"
4712 Option "SendCoreEvents" "On"
4713 EndSection
4714 \end{verbatim}
4717 \textbf{Windows configuration.}
4719 Just enabling the USB tablet in the
4720 guest's configuration file is sufficient,
4721 Windows will automatically recognize and
4722 configure device drivers for this
4723 pointing device.
4725 \end{description}
4727 \subsection{USB Support}
4728 There is support for an emulated USB mouse,
4729 an emulated USB tablet
4730 and physical low speed USB devices
4731 (support for high speed USB 2.0 devices is
4732 still under development).
4734 \begin{description}
4735 \item[USB PS/2 style mouse.]
4736 Details on the USB mouse emulation are
4737 given in sections
4738 \textbf{A.2}
4739 and
4740 \textbf{A.4.3}.
4741 Enabling USB PS/2 style mouse emulation
4742 is just a matter of adding the line
4744 {\small
4745 \begin{verbatim}
4746 usbdevice='mouse'
4747 \end{verbatim}
4750 to the configuration file.
4751 \item[USB tablet.]
4752 Details on the USB tablet emulation are
4753 given in sections
4754 \textbf{A.2}
4755 and
4756 \textbf{A.4.3}.
4757 Enabling USB tablet emulation
4758 is just a matter of adding the line
4760 {\small
4761 \begin{verbatim}
4762 usbdevice='tablet'
4763 \end{verbatim}
4766 to the configuration file.
4767 \item[USB physical devices.]
4768 Access to a physical (low speed) USB device
4769 is enabled by adding a line of the form
4771 {\small
4772 \begin{verbatim}
4773 usbdevice='host:vid:pid'
4774 \end{verbatim}
4777 into the the configuration file.\footnote{
4778 There is an alternate
4779 way of specifying a USB device that
4780 uses the syntax
4781 \textbf{host:bus.addr}
4782 but this syntax suffers from
4783 a major problem that makes
4784 it effectively useless.
4785 The problem is that the
4786 \textbf{addr}
4787 portion of this address
4788 changes every time the USB device
4789 is plugged into the system.
4790 For this reason this addressing
4791 scheme is not recommended and
4792 will not be documented further.
4794 \textbf{vid}
4795 and
4796 \textbf{pid}
4797 are a
4798 product id and
4799 vendor id
4800 that uniquely identify
4801 the USB device.
4802 These ids can be identified
4803 in two ways:
4805 \begin{enumerate}
4806 \item Through the control window.
4807 As described in section
4808 \textbf{A.4.6}
4809 the control window
4810 is activated by pressing
4811 \textbf{ctl-alt-2}
4812 in the guest VGA window.
4813 As long as USB support is
4814 enabled in the guest by including
4815 the config file line
4816 {\small
4817 \begin{verbatim}
4818 usb=1
4819 \end{verbatim}
4821 then executing the command
4822 {\small
4823 \begin{verbatim}
4824 info usbhost
4825 \end{verbatim}
4827 in the control window
4828 will display a list of all
4829 usb devices and their ids.
4830 For example,
4831 this output:
4832 {\small
4833 \begin{verbatim}
4834 Device 1.3, speed 1.5 Mb/s
4835 Class 00: USB device 04b3:310b
4836 \end{verbatim}
4838 was created from a USB mouse with
4839 vendor id
4840 \textbf{04b3}
4841 and product id
4842 \textbf{310b}.
4843 This device could be made available
4844 to the HVM guest by including the
4845 config file entry
4846 {\small
4847 \begin{verbatim}
4848 usbdevice='host:04be:310b'
4849 \end{verbatim}
4852 It is also possible to
4853 enable access to a USB
4854 device dynamically through
4855 the control window.
4856 The control window command
4857 {\small
4858 \begin{verbatim}
4859 usb_add host:vid:pid
4860 \end{verbatim}
4862 will also allow access to a
4863 USB device with vendor id
4864 \textbf{vid}
4865 and product id
4866 \textbf{pid}.
4867 \item Through the
4868 \path{/proc} file system.
4869 The contents of the pseudo file
4870 \path{/proc/bus/usb/devices}
4871 can also be used to identify
4872 vendor and product ids.
4873 Looking at this file,
4874 the line starting with
4875 \textbf{P:}
4876 has a field
4877 \textbf{Vendor}
4878 giving the vendor id and
4879 another field
4880 \textbf{ProdID}
4881 giving the product id.
4882 The contents of
4883 \path{/proc/bus/usb/devices}
4884 for the example mouse is as
4885 follows:
4886 {\small
4887 \begin{verbatim}
4888 T: Bus=01 Lev=01 Prnt=01 Port=01 Cnt=02 Dev#= 3 Spd=1.5 MxCh= 0
4889 D: Ver= 2.00 Cls=00(>ifc ) Sub=00 Prot=00 MxPS= 8 #Cfgs= 1
4890 P: Vendor=04b3 ProdID=310b Rev= 1.60
4891 C:* #Ifs= 1 Cfg#= 1 Atr=a0 MxPwr=100mA
4892 I: If#= 0 Alt= 0 #EPs= 1 Cls=03(HID ) Sub=01 Prot=02 Driver=(none)
4893 E: Ad=81(I) Atr=03(Int.) MxPS= 4 Ivl=10ms
4894 \end{verbatim}
4896 Note that the
4897 \textbf{P:}
4898 line correctly identifies the
4899 vendor id and product id
4900 for this mouse as
4901 \textbf{04b3:310b}.
4902 \end{enumerate}
4903 There is one other issue to
4904 be aware of when accessing a
4905 physical USB device from the guest.
4906 The Dom0 kernel must not have
4907 a device driver loaded for
4908 the device that the guest wishes
4909 to access.
4910 This means that the Dom0
4911 kernel must not have that
4912 device driver compiled into
4913 the kernel or,
4914 if using modules,
4915 that driver module must
4916 not be loaded.
4917 Note that this is the device
4918 specific USB driver that must
4919 not be loaded,
4920 either the
4921 \textbf{UHCI}
4922 or
4923 \textbf{OHCI}
4924 USB controller driver must
4925 still be loaded.
4927 Going back to the USB mouse
4928 as an example,
4929 if \textbf{lsmod}
4930 gives the output:
4932 {\small
4933 \begin{verbatim}
4934 Module Size Used by
4935 usbmouse 4128 0
4936 usbhid 28996 0
4937 uhci_hcd 35409 0
4938 \end{verbatim}
4941 then the USB mouse is being
4942 used by the Dom0 kernel and is
4943 not available to the guest.
4944 Executing the command
4945 \textbf{rmmod usbhid}\footnote{
4946 Turns out the
4947 \textbf{usbhid}
4948 driver is the significant
4949 one for the USB mouse,
4950 the presence or absence of
4951 the module
4952 \textbf{usbmouse}
4953 has no effect on whether or
4954 not the guest can see a USB mouse.}
4955 will remove the USB mouse
4956 driver from the Dom0 kernel
4957 and the mouse will now be
4958 accessible by the HVM guest.
4960 Be aware the the Linux USB
4961 hotplug system will reload
4962 the drivers if a USB device
4963 is removed and plugged back
4964 in.
4965 This means that just unloading
4966 the driver module might not
4967 be sufficient if the USB device
4968 is removed and added back.
4969 A more reliable technique is
4970 to first
4971 \textbf{rmmod}
4972 the driver and then rename the
4973 driver file in the
4974 \path{/lib/modules}
4975 directory,
4976 just to make sure it doesn't get
4977 reloaded.
4978 \end{description}
4980 \subsection{Destroy HVM guests}
4981 HVM guests can be destroyed in the same way as can paravirtualized guests. We recommend that you shut-down the guest using the guest OS' provided method, for Linux, type the command
4983 {\small {\tt poweroff}}
4985 in the HVM guest's console, for Windows use Start -> Shutdown first to prevent
4986 data loss. Depending on the configuration the guest will be automatically
4987 destroyed, otherwise execute the command
4989 {\small {\tt xm destroy \emph{vmx\_guest\_id} }}
4991 at the Domain0 console.
4993 \subsection{HVM window (X or VNC) Hot Key}
4994 If you are running in the X environment after creating a HVM guest, an X window is created. There are several hot keys for control of the HVM guest that can be used in the window.
4996 {\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 HVM guest.\\
4997 {\bfseries Ctrl+Alt+1} switches back to HVM guest's VGA.\\
4998 {\bfseries Ctrl+Alt+3} switches to serial port output. It captures serial output from the HVM guest. It works only if the HVM guest was configured to use the serial port. \\
5000 \chapter{Vnets - Domain Virtual Networking}
5002 Xen optionally supports virtual networking for domains using {\em vnets}.
5003 These emulate private LANs that domains can use. Domains on the same
5004 vnet can be hosted on the same machine or on separate machines, and the
5005 vnets remain connected if domains are migrated. Ethernet traffic
5006 on a vnet is tunneled inside IP packets on the physical network. A vnet is a virtual
5007 network and addressing within it need have no relation to addressing on
5008 the underlying physical network. Separate vnets, or vnets and the physical network,
5009 can be connected using domains with more than one network interface and
5010 enabling IP forwarding or bridging in the usual way.
5012 Vnet support is included in \texttt{xm} and \xend:
5013 \begin{verbatim}
5014 # xm vnet-create <config>
5015 \end{verbatim}
5016 creates a vnet using the configuration in the file \verb|<config>|.
5017 When a vnet is created its configuration is stored by \xend and the vnet persists until it is
5018 deleted using
5019 \begin{verbatim}
5020 # xm vnet-delete <vnetid>
5021 \end{verbatim}
5022 The vnets \xend knows about are listed by
5023 \begin{verbatim}
5024 # xm vnet-list
5025 \end{verbatim}
5026 More vnet management commands are available using the
5027 \texttt{vn} tool included in the vnet distribution.
5029 The format of a vnet configuration file is
5030 \begin{verbatim}
5031 (vnet (id <vnetid>)
5032 (bridge <bridge>)
5033 (vnetif <vnet interface>)
5034 (security <level>))
5035 \end{verbatim}
5036 White space is not significant. The parameters are:
5037 \begin{itemize}
5038 \item \verb|<vnetid>|: vnet id, the 128-bit vnet identifier. This can be given
5039 as 8 4-digit hex numbers separated by colons, or in short form as a single 4-digit hex number.
5040 The short form is the same as the long form with the first 7 fields zero.
5041 Vnet ids must be non-zero and id 1 is reserved.
5043 \item \verb|<bridge>|: the name of a bridge interface to create for the vnet. Domains
5044 are connected to the vnet by connecting their virtual interfaces to the bridge.
5045 Bridge names are limited to 14 characters by the kernel.
5047 \item \verb|<vnetif>|: the name of the virtual interface onto the vnet (optional). The
5048 interface encapsulates and decapsulates vnet traffic for the network and is attached
5049 to the vnet bridge. Interface names are limited to 14 characters by the kernel.
5051 \item \verb|<level>|: security level for the vnet (optional). The level may be one of
5052 \begin{itemize}
5053 \item \verb|none|: no security (default). Vnet traffic is in clear on the network.
5054 \item \verb|auth|: authentication. Vnet traffic is authenticated using IPSEC
5055 ESP with hmac96.
5056 \item \verb|conf|: confidentiality. Vnet traffic is authenticated and encrypted
5057 using IPSEC ESP with hmac96 and AES-128.
5058 \end{itemize}
5059 Authentication and confidentiality are experimental and use hard-wired keys at present.
5060 \end{itemize}
5061 When a vnet is created its configuration is stored by \xend and the vnet persists until it is
5062 deleted using \texttt{xm vnet-delete <vnetid>}. The interfaces and bridges used by vnets
5063 are visible in the output of \texttt{ifconfig} and \texttt{brctl show}.
5065 \section{Example}
5066 If the file \path{vnet97.sxp} contains
5067 \begin{verbatim}
5068 (vnet (id 97) (bridge vnet97) (vnetif vnif97)
5069 (security none))
5070 \end{verbatim}
5071 Then \texttt{xm vnet-create vnet97.sxp} will define a vnet with id 97 and no security.
5072 The bridge for the vnet is called vnet97 and the virtual interface for it is vnif97.
5073 To add an interface on a domain to this vnet set its bridge to vnet97
5074 in its configuration. In Python:
5075 \begin{verbatim}
5076 vif="bridge=vnet97"
5077 \end{verbatim}
5078 In sxp:
5079 \begin{verbatim}
5080 (dev (vif (mac aa:00:00:01:02:03) (bridge vnet97)))
5081 \end{verbatim}
5082 Once the domain is started you should see its interface in the output of \texttt{brctl show}
5083 under the ports for \texttt{vnet97}.
5085 To get best performance it is a good idea to reduce the MTU of a domain's interface
5086 onto a vnet to 1400. For example using \texttt{ifconfig eth0 mtu 1400} or putting
5087 \texttt{MTU=1400} in \texttt{ifcfg-eth0}.
5088 You may also have to change or remove cached config files for eth0 under
5089 \texttt{/etc/sysconfig/networking}. Vnets work anyway, but performance can be reduced
5090 by IP fragmentation caused by the vnet encapsulation exceeding the hardware MTU.
5092 \section{Installing vnet support}
5093 Vnets are implemented using a kernel module, which needs to be loaded before
5094 they can be used. You can either do this manually before starting \xend, using the
5095 command \texttt{vn insmod}, or configure \xend to use the \path{network-vnet}
5096 script in the xend configuration file \texttt{/etc/xend/xend-config.sxp}:
5097 \begin{verbatim}
5098 (network-script network-vnet)
5099 \end{verbatim}
5100 This script insmods the module and calls the \path{network-bridge} script.
5102 The vnet code is not compiled and installed by default.
5103 To compile the code and install on the current system
5104 use \texttt{make install} in the root of the vnet source tree,
5105 \path{tools/vnet}. It is also possible to install to an installation
5106 directory using \texttt{make dist}. See the \path{Makefile} in
5107 the source for details.
5109 The vnet module creates vnet interfaces \texttt{vnif0002},
5110 \texttt{vnif0003} and \texttt{vnif0004} by default. You can test that
5111 vnets are working by configuring IP addresses on these interfaces
5112 and trying to ping them across the network. For example, using machines
5113 hostA and hostB:
5114 \begin{verbatim}
5115 hostA# ifconfig vnif0004 192.0.2.100 up
5116 hostB# ifconfig vnif0004 192.0.2.101 up
5117 hostB# ping 192.0.2.100
5118 \end{verbatim}
5120 The vnet implementation uses IP multicast to discover vnet interfaces, so
5121 all machines hosting vnets must be reachable by multicast. Network switches
5122 are often configured not to forward multicast packets, so this often
5123 means that all machines using a vnet must be on the same LAN segment,
5124 unless you configure vnet forwarding.
5126 You can test multicast coverage by pinging the vnet multicast address:
5127 \begin{verbatim}
5128 # ping -b 224.10.0.1
5129 \end{verbatim}
5130 You should see replies from all machines with the vnet module running.
5131 You can see if vnet packets are being sent or received by dumping traffic
5132 on the vnet UDP port:
5133 \begin{verbatim}
5134 # tcpdump udp port 1798
5135 \end{verbatim}
5137 If multicast is not being forwarded between machines you can configure
5138 multicast forwarding using vn. Suppose we have machines hostA on 192.0.2.200
5139 and hostB on 192.0.2.211 and that multicast is not forwarded between them.
5140 We use vn to configure each machine to forward to the other:
5141 \begin{verbatim}
5142 hostA# vn peer-add hostB
5143 hostB# vn peer-add hostA
5144 \end{verbatim}
5145 Multicast forwarding needs to be used carefully - you must avoid creating forwarding
5146 loops. Typically only one machine on a subnet needs to be configured to forward,
5147 as it will forward multicasts received from other machines on the subnet.
5149 %% Chapter Glossary of Terms moved to glossary.tex
5150 \chapter{Glossary of Terms}
5152 \begin{description}
5154 \item[Domain] A domain is the execution context that contains a
5155 running {\bf virtual machine}. The relationship between virtual
5156 machines and domains on Xen is similar to that between programs and
5157 processes in an operating system: a virtual machine is a persistent
5158 entity that resides on disk (somewhat like a program). When it is
5159 loaded for execution, it runs in a domain. Each domain has a {\bf
5160 domain ID}.
5162 \item[Domain 0] The first domain to be started on a Xen machine.
5163 Domain 0 is responsible for managing the system.
5165 \item[Domain ID] A unique identifier for a {\bf domain}, analogous to
5166 a process ID in an operating system.
5168 \item[Full virtualization] An approach to virtualization which
5169 requires no modifications to the hosted operating system, providing
5170 the illusion of a complete system of real hardware devices.
5172 \item[Hypervisor] An alternative term for {\bf VMM}, used because it
5173 means `beyond supervisor', since it is responsible for managing
5174 multiple `supervisor' kernels.
5176 \item[Live migration] A technique for moving a running virtual machine
5177 to another physical host, without stopping it or the services
5178 running on it.
5180 \item[Paravirtualization] An approach to virtualization which requires
5181 modifications to the operating system in order to run in a virtual
5182 machine. Xen uses paravirtualization but preserves binary
5183 compatibility for user space applications.
5185 \item[Shadow pagetables] A technique for hiding the layout of machine
5186 memory from a virtual machine's operating system. Used in some {\bf
5187 VMMs} to provide the illusion of contiguous physical memory, in
5188 Xen this is used during {\bf live migration}.
5190 \item[Virtual Block Device] Persistent storage available to a virtual
5191 machine, providing the abstraction of an actual block storage device.
5192 {\bf VBD}s may be actual block devices, filesystem images, or
5193 remote/network storage.
5195 \item[Virtual Machine] The environment in which a hosted operating
5196 system runs, providing the abstraction of a dedicated machine. A
5197 virtual machine may be identical to the underlying hardware (as in
5198 {\bf full virtualization}, or it may differ, as in {\bf
5199 paravirtualization}).
5201 \item[VMM] Virtual Machine Monitor - the software that allows multiple
5202 virtual machines to be multiplexed on a single physical machine.
5204 \item[Xen] Xen is a paravirtualizing virtual machine monitor,
5205 developed primarily by the Systems Research Group at the University
5206 of Cambridge Computer Laboratory.
5208 \item[XenLinux] A name for the port of the Linux kernel that
5209 runs on Xen.
5211 \end{description}
5214 \end{document}
5217 %% Other stuff without a home
5219 %% Instructions Re Python API
5221 %% Other Control Tasks using Python
5222 %% ================================
5224 %% A Python module 'Xc' is installed as part of the tools-install
5225 %% process. This can be imported, and an 'xc object' instantiated, to
5226 %% provide access to privileged command operations:
5228 %% # import Xc
5229 %% # xc = Xc.new()
5230 %% # dir(xc)
5231 %% # help(xc.domain_create)
5233 %% In this way you can see that the class 'xc' contains useful
5234 %% documentation for you to consult.
5236 %% A further package of useful routines (xenctl) is also installed:
5238 %% # import xenctl.utils
5239 %% # help(xenctl.utils)
5241 %% You can use these modules to write your own custom scripts or you
5242 %% can customise the scripts supplied in the Xen distribution.
5246 % Explain about AGP GART
5249 %% If you're not intending to configure the new domain with an IP
5250 %% address on your LAN, then you'll probably want to use NAT. The
5251 %% 'xen_nat_enable' installs a few useful iptables rules into domain0
5252 %% to enable NAT. [NB: We plan to support RSIP in future]
5256 %% Installing the file systems from the CD
5257 %% =======================================
5259 %% If you haven't got an existing Linux installation onto which you
5260 %% can just drop down the Xen and Xenlinux images, then the file
5261 %% systems on the CD provide a quick way of doing an install. However,
5262 %% you would be better off in the long run doing a proper install of
5263 %% your preferred distro and installing Xen onto that, rather than
5264 %% just doing the hack described below:
5266 %% Choose one or two partitions, depending on whether you want a
5267 %% separate /usr or not. Make file systems on it/them e.g.:
5268 %% mkfs -t ext3 /dev/hda3
5269 %% [or mkfs -t ext2 /dev/hda3 && tune2fs -j /dev/hda3 if using an old
5270 %% version of mkfs]
5272 %% Next, mount the file system(s) e.g.:
5273 %% mkdir /mnt/root && mount /dev/hda3 /mnt/root
5274 %% [mkdir /mnt/usr && mount /dev/hda4 /mnt/usr]
5276 %% To install the root file system, simply untar /usr/XenDemoCD/root.tar.gz:
5277 %% cd /mnt/root && tar -zxpf /usr/XenDemoCD/root.tar.gz
5279 %% You'll need to edit /mnt/root/etc/fstab to reflect your file system
5280 %% configuration. Changing the password file (etc/shadow) is probably a
5281 %% good idea too.
5283 %% To install the usr file system, copy the file system from CD on
5284 %% /usr, though leaving out the "XenDemoCD" and "boot" directories:
5285 %% cd /usr && cp -a X11R6 etc java libexec root src bin dict kerberos
5286 %% local sbin tmp doc include lib man share /mnt/usr
5288 %% If you intend to boot off these file systems (i.e. use them for
5289 %% domain 0), then you probably want to copy the /usr/boot
5290 %% directory on the cd over the top of the current symlink to /boot
5291 %% on your root filesystem (after deleting the current symlink)
5292 %% i.e.:
5293 %% cd /mnt/root ; rm boot ; cp -a /usr/boot .