<htmlxmlns="http://www.w3.org/1999/xhtml"><head><metahttp-equiv="Content-Type"content="text/html; charset=ISO-8859-1"/><linkrel="stylesheet"type="text/css"href="libvirt.css"/><linkrel="SHORTCUT ICON"href="/32favicon.png"/><title>Releases</title></head><body><divid="container"><divid="intro"><divid="adjustments"></div><divid="pageHeader"></div><divid="content2"><h1class="style1">Releases</h1><p>Here is the list of official releases, however since it is early on in the
development of libvirt, it is preferable when possible to just use the <ahref="downloads.html">CVS version or snapshot</a>, contact the mailing list
and check the <ahref="ChangeLog.html">ChangeLog</a> to gauge progresses.</p><h3>0.2.2: Apr 17 2007</h3><ul><li>Documentation: fix errors due to Amaya (with Simon Hernandez),
virsh uses kB not bytes (Atsushi SAKAI), add command line help to
<li>bug fixes: VCPU info breakages on xen 3.0.3, xenDaemonListDomains buffer overflow (Daniel Berrange), reference count bug when creating Xen domains (Daniel Berrange).</li>
<li>improvements: support graphic framebuffer for Xen paravirt (Daniel Berrange), VNC listen IP range support (Daniel Berrange), support for default Xen config files and inactive domains of 3.0.4 (Daniel Berrange).</li>
<p>When running in a Xen environment, programs using libvirt have to execute
in "Domain 0", which is the primary Linux OS loaded on the machine. That OS
kernel provides most if not all of the actual drivers used by the set of
domains. It also runs the Xen Store, a database of informations shared by the
hypervisor, the kernels, the drivers and the xen daemon. Xend. The xen daemon
supervise the control and execution of the sets of domains. The hypervisor,
drivers, kernels and daemons communicate though a shared system bus
implemented in the hypervisor. The figure below tries to provide a view of
this environment:</p>
<imgsrc="architecture.gif"alt="The Xen architecture"/><p>The library can be initialized in 2 ways depending on the level of
priviledge of the embedding program. If it runs with root access,
virConnectOpen() can be used, it will use three different ways to connect to
the Xen infrastructure:</p>
<ul><li>a connection to the Xen Daemon though an HTTP RPC layer</li>
<li>a read/write connection to the Xen Store</li>
<li>use Xen Hypervisor calls</li>
<li>when used as non-root libvirt connect to a proxy daemon running
as root and providing read-only support</li>
</ul><p>The library will usually interact with the Xen daemon for any operation
changing the state of the system, but for performance and accuracy reasons
may talk directly to the hypervisor when gathering state informations at
least when possible (i.e. when the running program using libvirt has root
priviledge access).</p>
<p>If it runs without root access virConnectOpenReadOnly() should be used to
connect to initialize the library. It will then fork a libvirt_proxy
program running as root and providing read_only access to the API, this is
then only useful for reporting and monitoring.</p>
<h3><aname="QEmu"id="QEmu">Libvirt QEmu and KVM support</a></h3>
<p>The model for QEmu and KVM is completely similar, basically KVM is based
on QEmu for the process controlling a new domain, only small details differs
between the two. In both case the libvirt API is provided by a controlling
process forked by libvirt in the background and which launch and control the
QEmu or KVM process. That program called libvirt_qemud talks though a specific
protocol to the library, and connects to the console of the QEmu process in
order to control and report on its status. Libvirt tries to expose all the
emulations models of QEmu, the selection is done when creating the new
domain, by specifying the architecture and machine type targetted.</p>
<p>The code controlling the QEmu process is available in the
<code>qemud/</code> directory.</p>
<h3><aname="drivers"id="drivers">the driver based architecture</a></h3>
<p>As the previous section explains, libvirt can communicate using different
channels with the current hypervisor, and should also be able to use
different kind of hypervisor. To simplify the internal design, code, ease
maintainance and simplify the support of other virtualization engine the
internals have been structured as one core component, the libvirt.c module
acting as a front-end for the library API and a set of hypvisor drivers
defining a common set of routines. That way the Xen Daemon accces, the Xen
Store one, the Hypervisor hypercall are all isolated in separate C modules
implementing at least a subset of the common operations defined by the
drivers present in driver.h:</p>
<ul><li>xend_internal: implements the driver functions though the Xen
Daemon</li>
<li>xs_internal: implements the subset of the driver availble though the
Xen Store</li>
<li>xen_internal: provide the implementation of the functions possible via
direct hypervisor access</li>
<li>proxy_internal: provide read-only Xen access via a proxy, the proxy code
is in the <code>proxy/</code>directory.</li>
<li>xm_internal: provide support for Xen defined but not running
domains.</li>
<li>qemu_internal: implement the driver functions for QEmu and
KVM virtualization engines. It also uses a qemud/ specific daemon
which interracts with the QEmu process to implement libvirt API.</li>
<li>test: this is a test driver useful for regression tests of the
front-end part of libvirt.</li>
</ul><p>Note that a given driver may only implement a subset of those functions,
(for example saving a Xen domain state to disk and restoring it is only
possible though the Xen Daemon), in that case the driver entry points for
unsupported functions are initialized to NULL.</p>
<p></p>
<p>The latest versions of libvirt can be found on the <ahref="ftp://libvirt.org/libvirt/">libvirt.org</a> server ( <ahref="http://libvirt.org/sources/">HTTP</a>, <ahref="ftp://libvirt.org/libvirt/">FTP</a>). You will find there the released
versions as well as <ahref="http://libvirt.org/sources/libvirt-cvs-snapshot.tar.gz">snapshot
tarballs</a> updated from CVS head every hour</p>
<p>Anonymous <ahref="http://ximbiot.com/cvs/cvshome/docs/">CVS</a> is also
</domain></pre><p>There is a few things to notice specifically for HVM domains:</p><ul><li>the optional <code><features></code> block is used to enable
certain guest CPU / system features. For HVM guests the following
<li>the <code><os></code> block description is very different, first
it indicates that the type is 'hvm' for hardware virtualization, then
instead of a kernel, boot and command line arguments, it points to an os
boot loader which will extract the boot informations from the boot device
specified in a separate boot element. The <code>dev</code> attribute on
the <code>boot</code> tag can be one of:
<ul><li><code>fd</code> - boot from first floppy device</li>
<li><code>hd</code> - boot from first harddisk device</li>
<li><code>cdrom</code> - boot from first cdrom device</li>
</ul></li>
<li>the <code><devices></code> section includes an emulator entry
pointing to an additional program in charge of emulating the devices</li>
<li>the disk entry indicates in the dev target section that the emulation
for the drive is the first IDE disk device hda. The list of device names
supported is dependant on the Hypervisor, but for Xen it can be any IDE
device <code>hda</code>-<code>hdd</code>, or a floppy device
<code>fda</code>, <code>fdb</code>. The <code><disk></code> element
also supports a 'device' attribute to indicate what kinda of hardware to
emulate. The following values are supported:
<ul><li><code>floppy</code> - a floppy disk controller</li>
<li><code>disk</code> - a generic hard drive (the default it
omitted)</li>
<li><code>cdrom</code> - a CDROM device</li>
</ul>
For Xen 3.0.2 and earlier a CDROM device can only be emulated on the
<code>hdc</code> channel, while for 3.0.3 and later, it can be emulated
on any IDE channel.</li>
<li>the <code><devices></code> section also include at least one
entry for the graphic device used to render the os. Currently there is
just 2 types possible 'vnc' or 'sdl'. If the type is 'vnc', then an
additional <code>port</code> attribute will be present indicating the TCP
port on which the VNC server is accepting client connections.</li>
</ul><p>It is likely that the HVM description gets additional optional elements
and attributes as the support for fully virtualized domain expands,
especially for the variety of devices emulated and the graphic support
options offered.</p><h3><aname="KVM1"id="KVM1">KVM domain (added in 0.2.0)</a></h3><p>Support for the <ahref="http://kvm.qumranet.com/">KVM virtualization</a>
is provided in recent Linux kernels (2.6.20 and onward). This requires
specific hardware with acceleration support and the availability of the
special version of the <ahref="http://fabrice.bellard.free.fr/qemu/">QEmu</a> binary. Since this
relies on QEmu for the machine emulation like fully virtualized guests the
XML description is quite similar, here is a simple example:</p><pre><domain <spanstyle="color: #FF0000; background-color: #FFFFFF">type='kvm'</span>>
</domain></pre><p>The specific points to note if using KVM are:</p><ul><li>the top level domain element carries a type of 'kvm'</li>
<li>the <devices> emulator points to the special qemu binary required
for KVM</li>
<li>networking interface definitions definitions are somewhat different due
to a different model from Xen see below</li>
</ul><p>except those points the options should be quite similar to Xen HVM
ones.</p><h3><aname="Net1"id="Net1">Networking options for QEmu and KVM (added in 0.2.0)</a></h3><p>The networking support in the QEmu and KVM case is more flexible, and
support a variety of options:</p><ol><li>Userspace SLIRP stack
<p>Provides a virtual LAN with NAT to the outside world. The virtual
network has DHCP & DNS services and will give the guest VM addresses
starting from <code>10.0.2.15</code>. The default router will be
<code>10.0.2.2</code> and the DNS server will be <code>10.0.2.3</code>.
This networking is the only option for unprivileged users who need their
VMs to have outgoing access. Example configs are:</p>
<pre><interface type='user'/></pre>
<pre>
<interface type='user'>
<mac address="11:22:33:44:55:66:/>
</interface>
</pre>
</li>
<li>Virtual network
<p>Provides a virtual network using a bridge device in the host.
Depending on the virtual network configuration, the network may be
totally isolated,NAT'ing to aan explicit network device, or NAT'ing to
the default route. DHCP and DNS are provided on the virtual network in
all cases and the IP range can be determined by examining the virtual
network config with '<code>virsh net-dumpxml <network
name></code>'. There is one virtual network called'default' setup out
of the box which does NAT'ing to the default route and has an IP range of
<code>192.168.22.0/255.255.255.0</code>. Each guest will have an
associated tun device created with a name of vnetN, which can also be
overriden with the <target> element. Example configs are:</p>
<pre><interface type='network'>
<source network='default'/>
</interface>
<interface type='network'>
<source network='default'/>
<target dev='vnet7'/>
<mac address="11:22:33:44:55:66:/>
</interface>
</pre>
</li>
<li>Bridge to to LAN
<p>Provides a bridge from the VM directly onto the LAN. This assumes
there is a bridge device on the host which has one or more of the hosts
physical NICs enslaved. The guest VM will have an associated tun device
created with a name of vnetN, which can also be overriden with the
<target> element. The tun device will be enslaved to the bridge.
The IP range / network configuration is whatever is used on the LAN. This
provides the guest VM full incoming & outgoing net access just like a
physical machine. Examples include:</p>
<pre><interface type='bridge'>
<source dev='br0'/>
</interface>
<interface type='bridge'>
<source dev='br0'/>
<target dev='vnet7'/>
<mac address="11:22:33:44:55:66:/>
</interface><interface type='bridge'>
<source dev='br0'/>
<target dev='vnet7'/>
<mac address="11:22:33:44:55:66:/>
</interface></pre>
</li>
<li>Generic connection to LAN
<p>Provides a means for the administrator to execute an arbitrary script
to connect the guest's network to the LAN. The guest will have a tun
device created with a name of vnetN, which can also be overriden with the
<target> element. After creating the tun device a shell script will
be run which is expected to do whatever host network integration is
required. By default this script is called /etc/qemu-ifup but can be
overriden.</p>
<pre><interface type='ethernet'/>
<interface type='ethernet'>
<target dev='vnet7'/>
<script path='/etc/qemu-ifup-mynet'/>
</interface></pre>
</li>
<li>Multicast tunnel
<p>A multicast group is setup to represent a virtual network. Any VMs
whose network devices are in the same multicast group can talk to each
other even across hosts. This mode is also available to unprivileged
users. There is no default DNS or DHCP support and no outgoing network
access. To provide outgoing network access, one of the VMs should have a
2nd NIC which is connected to one of the first 4 network types and do the
appropriate routing. The multicast protocol is compatible with that used
by user mode linux guests too. The source address used must be from the
multicast address block.</p>
<pre><interface type='mcast'>
<source address='230.0.0.1' port='5558'/>
</interface></pre>
</li>
<li>TCP tunnel
<p>A TCP client/server architecture provides a virtual network. One VM
provides the server end of the netowrk, all other VMS are configured as
clients. All network traffic is routed between the VMs via the server.
This mode is also available to unprivileged users. There is no default
DNS or DHCP support and no outgoing network access. To provide outgoing
network access, one of the VMs should have a 2nd NIC which is connected
to one of the first 4 network types and do the appropriate routing.</p>
<p>Example server config:</p>
<pre><interface type='server'>
<source address='192.168.0.1' port='5558'/>
</interface></pre>
<p>Example client config:</p>
<pre><interface type='client'>
<source address='192.168.0.1' port='5558'/>
</interface></pre>
</li>
</ol><p>To be noted, options 2, 3, 4 are also supported by Xen VMs, so it is
possible to use these configs to have networking with both Xen &
QEMU/KVMs connected to each other.</p><h3>Q<aname="QEmu1"id="QEmu1">Emu domain (added in 0.2.0)</a></h3><p>Libvirt support for KVM and QEmu is the same code base with only minor
changes. The configuration is as a result nearly identical, the only changes
are related to QEmu ability to emulate <ahref="http://www.qemu.org/status.html">various CPU type and hardware
platforms</a>, and kqemu support (QEmu own kernel accelerator when the
emulated CPU is i686 as well as the target machine):</p><pre><domain <spanstyle="color: #FF0000; background-color: #FFFFFF">type='qemu'</span>>
</domain></pre><p>The difference here are:</p><ul><li>the value of type on top-level domain, it's 'qemu' or kqemu if asking
for <ahref="http://www.qemu.org/kqemu-tech.html">kernel assisted
acceleration</a></li>
<li>the os type block defines the architecture to be emulated, and
optionally the machine type, see the discovery API below</li>
<li>the emulator string must point to the right emulator for that
architecture</li>
</ul><h3><aname="Capa1"id="Capa1">Discovering virtualization capabilities (Added in 0.2.1)</a></h3><p>As new virtualization engine support gets added to libvirt, and to handle
cases like QEmu supporting a variety of emulations, a query interface has
been added in 0.2.1 allowing to list the set of supported virtualization
capabilities on the host:</p><pre> char * virConnectGetCapabilities (virConnectPtr conn);</pre><p>The value returned is an XML document listing the virtualization
capabilities of the host and virtualization engine to which
<code>@conn</code> is connected. One can test it using <code>virsh</code>
command line tool command '<code>capabilities</code>', it dumps the XML
associated to the current connection. For example in the case of a 64 bits
machine with hardware virtualization capabilities enabled in the chip and
</capabilities></pre><p>The fist block (in red) indicates the host hardware capbilities, currently
it is limited to the CPU properties but other information may be available,
it shows the CPU architecture, and the features of the chip (the feature
block is similar to what you will find in a Xen fully virtualized domain
description).</p><p>The second block (in blue) indicates the paravirtualization support of the
Xen support, you will see the os_type of xen to indicate a paravirtual
kernel, then architecture informations and potential features.</p><p>The third block (in green) gives similar informations but when running a
32 bit OS fully virtualized with Xen using the hvm support.</p><p>This section is likely to be updated and augmented in the future, see <ahref="https://www.redhat.com/archives/libvir-list/2007-March/msg00215.html">the
discussion</a> which led to the capabilities format in the mailing-list
archives.</p></div></div><divclass="linkList2"><divclass="llinks2"><h3class="links2"><span>main menu</span></h3><ul><li><ahref="index.html">Home</a></li><li><ahref="news.html">Releases</a></li><li><ahref="python.html">Binding for Python</a></li><li><ahref="errors.html">Handling of errors</a></li><li><ahref="FAQ.html">FAQ</a></li><li><ahref="bugs.html">Reporting bugs and getting help</a></li><li><ahref="html/index.html">API Menu</a></li><li><ahref="examples/index.html">C code examples</a></li><li><ahref="ChangeLog.html">Recent Changes</a></li></ul></div><divclass="llinks2"><h3class="links2"><span>related links</span></h3><ul><li><ahref="https://www.redhat.com/archives/libvir-list/">Mail archive</a></li><li><ahref="https://bugzilla.redhat.com/bugzilla/buglist.cgi?product=Fedora+Core&component=libvirt&bug_status=NEW&bug_status=ASSIGNED&bug_status=REOPENED&bug_status=MODIFIED&short_desc_type=allwordssubstr&short_desc=&long_desc_type=allwordssubstr">Open bugs</a></li><li><ahref="http://virt-manager.et.redhat.com/">virt-manager</a></li><li><ahref="http://search.cpan.org/~danberr/Sys-Virt-0.1.0/">Perl bindings</a></li><li><ahref="http://www.cl.cam.ac.uk/Research/SRG/netos/xen/index.html">Xen project</a></li><li><formaction="search.php"enctype="application/x-www-form-urlencoded"method="get"><inputname="query"type="text"size="12"value="Search..."/><inputname="submit"type="submit"value="Go"/></form></li><li><ahref="http://xmlsoft.org/"><imgsrc="Libxml2-Logo-90x34.gif"alt="Made with Libxml2 Logo"/></a></li></ul><pclass="credits">Graphics and design by <ahref="mail:dfong@redhat.com">Diana Fong</a></p></div></div><divid="bottom"><pclass="p1"></p></div></div></body></html>
