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http://www.xen.org/

What is Xen?
============

Xen is a Virtual Machine Monitor (VMM) originally developed by the
Systems Research Group of the University of Cambridge Computer
Laboratory, as part of the UK-EPSRC funded XenoServers project.  Xen
is freely-distributable Open Source software, released under the GNU
GPL. Since its initial public release, Xen has grown a large
development community, spearheaded by xen.org (http://www.xen.org).

The 4.3 release offers a number of improvements, including NUMA
scheduling affinity, openvswitch integration, and defaulting to
qemu-xen rather than qemu-traditional for non-stubdom guests.
(qemu-xen is kept very close to the upstream project.)  We also have a
number of updates to vTPM, and improvements to XSM and Flask to allow
greater disaggregation.  Additionally, 4.3 contains a basic version of
Xen for the new ARM server architecture, both 32- and 64-bit.  And as
always, there are a number of performance, stability, and security
improvements under-the hood.

This file contains some quick-start instructions to install Xen on
your system. For more information see http:/www.xen.org/ and
http://wiki.xen.org/

Quick-Start Guide
=================

First, there are a number of prerequisites for building a Xen source
release. Make sure you have all the following installed, either by
visiting the project webpage or installing a pre-built package
provided by your OS distributor:
    * GCC v4.1 or later
    * GNU Make
    * GNU Binutils
    * Development install of zlib (e.g., zlib-dev)
    * Development install of Python v2.3 or later (e.g., python-dev)
    * Development install of curses (e.g., libncurses-dev)
    * Development install of openssl (e.g., openssl-dev)
    * Development install of x11 (e.g. xorg-x11-dev)
    * Development install of uuid (e.g. uuid-dev)
    * Development install of yajl (e.g. libyajl-dev)
    * Development install of libaio (e.g. libaio-dev) version 0.3.107 or
      greater.
    * Development install of GLib v2.0 (e.g. libglib2.0-dev)
    * Development install of Pixman (e.g. libpixman-1-dev)
    * pkg-config
    * bridge-utils package (/sbin/brctl)
    * iproute package (/sbin/ip)
    * udev
    * GNU bison and GNU flex
    * GNU gettext
    * 16-bit x86 assembler, loader and compiler (dev86 rpm or bin86 & bcc debs)
    * ACPI ASL compiler (iasl)

In addition to the above there are a number of optional build
prerequisites. Omitting these will cause the related features to be
disabled at compile time:
    * Development install of Ocaml (e.g. ocaml-nox and
      ocaml-findlib). Required to build ocaml components which
      includes the alternative ocaml xenstored.
    * cmake (if building vtpm stub domains)
    * markdown
    * figlet (for generating the traditional Xen start of day banner)
    * systemd daemon development files

Second, you need to acquire a suitable kernel for use in domain 0. If
possible you should use a kernel provided by your OS distributor. If
no suitable kernel is available from your OS distributor then refer to
http://wiki.xen.org/wiki/XenDom0Kernels for suggestions for
suitable kernels to use.
If you are looking to compile a Dom0 kernel from source, please refer to
http://wiki.xen.org/wiki/XenParavirtOps.

[NB. Unless noted otherwise, all the following steps should be
performed with root privileges.]

1. Download and untar the source tarball file. This will be a
   file named xen-unstable-src.tgz, or xen-$version-src.tgz.
   You can also pull the current version from the mercurial
   repository at http://xenbits.xen.org/

    # tar xzf xen-unstable-src.tgz

   Assuming you are using the unstable tree, this will
   untar into xen-unstable. The rest of the instructions
   use the unstable tree as an example, substitute the
   version for unstable.

2. cd to xen-unstable (or whatever you sensibly rename it to).

3. For the very first build, or if you want to destroy build trees,
   perform the following steps:

    # ./configure
    # make world
    # make install

   If you want, you can run ./configure --help to see the list of
   options available options when building and installing Xen.

   This will create and install onto the local machine. It will build
   the xen binary (xen.gz), the tools and the documentation.

   You can override the destination for make install by setting DESTDIR
   to some value.

4. To rebuild an existing tree without modifying the config:
    # make dist

   This will build and install xen, tools, and docs into the local dist/
   directory.

   You can override the destination for make install by setting DISTDIR
   to some value.

   make install and make dist differ in that make install does the
   right things for your local machine (installing the appropriate
   version of udev scripts, for example), but make dist includes all
   versions of those scripts, so that you can copy the dist directory
   to another machine and install from that distribution.

xenstore: xenstored and oxenstored
====================================

Xen uses a configuration database called xenstore [0] to maintain configuration
and status information shared between domains. A daemon is implemented as part
of xenstore to act as an interface for access to the database for dom0 and
guests. Two xenstored daemons are supported, one written in C which we refer
to as the xenstored (sometimes referred to as cxenstored), and another written
in Ocaml called oxenstored. Details for xenstore and the different
implementations can be found on the wiki's xenstore reference guide [1] and
the xenstored [2] page. You can choose which xenstore you want to enable as
default on a system through configure:

	./configure --with-xenstored=xenstored
	./configure --with-xenstored=oxenstored

By default oxenstored will be used if the ocaml development tools are found.
If you enable oxenstored the xenstored will still be built and installed,
the xenstored used can be changed through the configuration file:

/etc/sysconfig/xencommons
or
/etc/default/xencommons

You can change the preferred xenstored you want to use in the configuration
but since we cannot stop the daemon a reboot will be required to make the
change take effect.

[0] http://wiki.xen.org/wiki/XenStore
[1] http://wiki.xen.org/wiki/XenStoreReference
[2] http://wiki.xen.org/wiki/Xenstored

Systemd support
===============

If you have systemd development packages installed you can build binaries
with systemd support. Systemd support is enabled by default if you have
systemd development libraries present. If you want to force enable systemd to
ensure you build binaries with systemd support you can use the --enable-systemd
flag. Likewise if you want to force disable systemd you can use:

	./configure --disable-systemd

For more details refer to the xen xenstored systemd wiki page [3].

[3] http://wiki.xen.org/wiki/Xenstored#xenstored_systemd_support

Python Runtime Libraries
========================

Xend (the Xen daemon) has the following runtime dependencies:

    * Python 2.3 or later.
      In some distros, the XML-aspects to the standard library
      (xml.dom.minidom etc) are broken out into a separate python-xml package.
      This is also required.
      In more recent versions of Debian and Ubuntu the XML-aspects are included
      in the base python package however (python-xml has been removed
      from Debian in squeeze and from Ubuntu in intrepid).

          URL:    http://www.python.org/
          Debian: python

    * For optional SSL support, pyOpenSSL:
          URL:    http://pyopenssl.sourceforge.net/
          Debian: python-pyopenssl

    * For optional PAM support, PyPAM:
          URL:    http://www.pangalactic.org/PyPAM/
          Debian: python-pam

    * For optional XenAPI support in XM, lxml:
          URL:    http://lxml.de/
          Debian: python-lxml
          YUM:    python-lxml


Intel(R) Trusted Execution Technology Support
=============================================

Intel's technology for safer computing, Intel(R) Trusted Execution Technology
(Intel(R) TXT), defines platform-level enhancements that provide the building
blocks for creating trusted platforms.  For more information, see
http://www.intel.com/technology/security/.

Intel(R) TXT support is provided by the Trusted Boot (tboot) module in
conjunction with minimal logic in the Xen hypervisor.

Tboot is an open source, pre- kernel/VMM module that uses Intel(R) TXT to
perform a measured and verified launch of an OS kernel/VMM.

The Trusted Boot module is available from
http://sourceforge.net/projects/tboot.  This project hosts the code in a
mercurial repo at http://tboot.sourceforge.net/hg/tboot.hg and contains
tarballs of the source.  Instructions in the tboot README describe how
to modify grub.conf to use tboot to launch Xen.

There are optional targets as part of Xen's top-level makefile that will
download and build tboot: install-tboot, build-tboot, dist-tboot, clean-tboot.
These will download the latest tar file from the SourceForge site using wget,
then build/install/dist according to Xen's settings.

Required Kernel modules
======================

Xen has a set of Kernel modules which the init scripts ensure to load before
before starting Xen guests. The list of modules are maintained in one place:

  * config/$(XEN_OS).modules

For more details refer to:

http://wiki.xen.org/wiki/Category:Host_Configuration#Kernel_modules