Update domain XML docs

This commit is contained in:
Daniel P. Berrange 2008-05-08 14:20:07 +00:00
parent 7b21582e2d
commit 979edb4a64
4 changed files with 1502 additions and 438 deletions

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Thu May 8 10:19:11 EST 2008 Daniel P. Berrange <berrange@redhat.com>
* docs/page.xsl: Fix detection of sub-headings
* docs/domain.html, docs/domain.html.in: Re-write content to
reflect current domain XML format
Thu May 8 07:51:11 EST 2008 Daniel P. Berrange <berrange@redhat.com>
* src/auth.html.in, src/auth.html: Fix policykit config docs

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</div>
<div id="content">
<h1>Domain XML format</h1>
<p>This section describes the XML format used to represent domains, there are
variations on the format based on the kind of domains run and the options
used to launch them:</p>
<h3 id="Normal"><a name="Normal1" id="Normal1">Normal paravirtualized Xen
guests</a>:</h3>
<p>The root element must be called <code>domain</code> with no namespace, the
<code>type</code> attribute indicates the kind of hypervisor used, 'xen' is
the default value. The <code>id</code> attribute gives the domain id at
runtime (not however that this may change, for example if the domain is saved
to disk and restored). The domain has a few children whose order is not
significant:</p>
<ul><li>name: the domain name, preferably ASCII based</li><li>memory: the maximum memory allocated to the domain in kilobytes</li><li>vcpu: the number of virtual cpu configured for the domain</li><li>os: a block describing the Operating System, its content will be
dependent on the OS type
<ul><li>type: indicate the OS type, always linux at this point</li><li>kernel: path to the kernel on the Domain 0 filesystem</li><li>initrd: an optional path for the init ramdisk on the Domain 0
filesystem</li><li>cmdline: optional command line to the kernel</li><li>root: the root filesystem from the guest viewpoint, it may be
passed as part of the cmdline content too</li></ul></li><li>devices: a list of <code>disk</code>, <code>interface</code> and
<code>console</code> descriptions in no special order</li></ul>
<p>The format of the devices and their type may grow over time, but the
following should be sufficient for basic use:</p>
<p>A <code>disk</code> device indicates a block device, it can have two
values for the type attribute either 'file' or 'block' corresponding to the 2
options available at the Xen layer. It has two mandatory children, and one
optional one in no specific order:</p>
<ul><li>source with a file attribute containing the path in Domain 0 to the
file or a dev attribute if using a block device, containing the device
name ('hda5' or '/dev/hda5')</li><li>target indicates in a dev attribute the device where it is mapped in
the guest</li><li>readonly an optional empty element indicating the device is
read-only</li><li>shareable an optional empty element indicating the device
can be used read/write with other domains</li></ul>
<p>An <code>interface</code> element describes a network device mapped on the
guest, it also has a type whose value is currently 'bridge', it also have a
number of children in no specific order:</p>
<ul><li>source: indicating the bridge name</li><li>mac: the optional mac address provided in the address attribute</li><li>ip: the optional IP address provided in the address attribute</li><li>script: the script used to bridge the interface in the Domain 0</li><li>target: and optional target indicating the device name.</li></ul>
<p>A <code>console</code> element describes a serial console connection to
the guest. It has no children, and a single attribute <code>tty</code> which
provides the path to the Pseudo TTY on which the guest console can be
accessed</p>
<p>Life cycle actions for the domain can also be expressed in the XML format,
they drive what should be happening if the domain crashes, is rebooted or is
poweroff. There is various actions possible when this happen:</p>
<ul><li>destroy: The domain is cleaned up (that's the default normal processing
in Xen)</li><li>restart: A new domain is started in place of the old one with the same
configuration parameters</li><li>preserve: The domain will remain in memory until it is destroyed
manually, it won't be running but allows for post-mortem debugging</li><li>rename-restart: a variant of the previous one but where the old domain
is renamed before being saved to allow a restart</li></ul>
<p>The following could be used for a Xen production system:</p>
<pre>&lt;domain&gt;
...
&lt;on_reboot&gt;restart&lt;/on_reboot&gt;
&lt;on_poweroff&gt;destroy&lt;/on_poweroff&gt;
&lt;on_crash&gt;rename-restart&lt;/on_crash&gt;
...
&lt;/domain&gt;</pre>
<p>While the format may be extended in various ways as support for more
hypervisor types and features are added, it is expected that this core subset
will remain functional in spite of the evolution of the library.</p>
<h3 id="Fully">
<a name="Fully1" id="Fully1">Fully virtualized guests</a>
</h3>
<p>There is a few things to notice specifically for HVM domains:</p>
<ul><li>the optional <code>&lt;features&gt;</code> block is used to enable
certain guest CPU / system features. For HVM guests the following
features are defined:
<ul><li><code>pae</code> - enable PAE memory addressing</li><li><code>apic</code> - enable IO APIC</li><li><code>acpi</code> - enable ACPI bios</li></ul></li><li>the optional <code>&lt;clock&gt;</code> element is used to specify
whether the emulated BIOS clock in the guest is synced to either
<code>localtime</code> or <code>utc</code>. In general Windows will
want <code>localtime</code> while all other operating systems will
want <code>utc</code>. The default is thus <code>utc</code></li><li>the <code>&lt;os&gt;</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 information 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>&lt;devices&gt;</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 dependent 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>&lt;disk&gt;</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>&lt;devices&gt;</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>
<ul><li>
<a href="#elements">Element and attribute overview</a>
<ul><li>
<a href="#elementsMetadata">General metadata</a>
</li><li>
<a href="#elementsOS">Operating system booting</a>
<ul><li>
<a href="#elementsOSBIOS">BIOS bootloader</a>
</li><li>
<a href="#elementsOSBootloader">Host bootloader</a>
</li><li>
<a href="#elementsOSKernel">Direct kernel boot</a>
</li></ul>
</li><li>
<a href="#elementsResources">Basic resources</a>
</li><li>
<a href="#elementsLifecycle">Lifecycle control</a>
</li><li>
<a href="#elementsFeatures">Hypervisor features</a>
</li><li>
<a href="#elementsTime">Time keeping</a>
</li><li>
<a href="#elementsDevices">Devices</a>
<ul><li>
<a href="#elementsDisks">Hard drives, floppy disks, CDROMs</a>
</li><li>
<a href="#elementsNICS">Network interfaces</a>
<ul><li>
<a href="#elementsNICSVirtual">Virtual network</a>
</li><li>
<a href="#elementsNICSBridge">Bridge to to LAN</a>
</li><li>
<a href="#elementsNICSSlirp">Userspace SLIRP stack</a>
</li><li>
<a href="#elementsNICSEthernet">Generic ethernet connection</a>
</li><li>
<a href="#elementsNICSMulticast">Multicast tunnel</a>
</li><li>
<a href="#elementsNICSTCP">TCP tunnel</a>
</li></ul>
</li><li>
<a href="#elementsInput">Input devices</a>
</li><li>
<a href="#elementsGraphics">Graphical framebuffers</a>
</li><li>
<a href="#elementsConsole">Consoles, serial &amp; parallel devices</a>
<ul><li>
<a href="#elementsCharSTDIO">Domain logfile</a>
</li><li>
<a href="#elementsCharFle">Device logfile</a>
</li><li>
<a href="#elementsCharVC">Virtual console</a>
</li><li>
<a href="#elementsCharNull">Null device</a>
</li><li>
<a href="#elementsCharPTY">Pseudo TTY</a>
</li><li>
<a href="#elementsCharHost">Host device proxy</a>
</li><li>
<a href="#elementsCharTCP">TCP client/server</a>
</li><li>
<a href="#elementsCharUDP">UDP network console</a>
</li><li>
<a href="#elementsCharUNIX">UNIX domain socket client/server</a>
</li></ul>
</li></ul>
</li></ul>
</li><li>
<a href="#examples">Example configs</a>
</li></ul>
<p>
This section describes the XML format used to represent domains, there are
variations on the format based on the kind of domains run and the options
used to launch them. For hypervisor specific details consult the
<a href="drivers.html">driver docs</a>
</p>
<h2>
<a name="elements" id="elements">Element and attribute overview</a>
</h2>
<p>
The root element required for all virtual machines is
named <code>domain</code>. It has two attributes, the
<code>type</code> specifies the hypervisor used for running
the domain. The allowed values are driver specific, but
include "xen", "kvm", "qemu", "lxc" and "kqemu". The
second attribute is <code>id</code> which is a unique
integer identifier for the running guest machine. Inactive
machines have no id value.
</p>
<h3>
<a name="Net1" id="Net1">Networking interface options</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 &amp; 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>&lt;interface type='user'/&gt;</pre>
<pre>
&lt;interface type='user'&gt;
&lt;mac address="11:22:33:44:55:66"/&gt;
&lt;/interface&gt;
</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 an 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 &lt;network
name&gt;</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
overridden with the &lt;target&gt; element. Example configs are:</p>
<pre>&lt;interface type='network'&gt;
&lt;source network='default'/&gt;
&lt;/interface&gt;
<a name="elementsMetadata" id="elementsMetadata">General metadata</a>
</h3>
<pre>
&lt;domain type='xen' id='3'&gt;
&lt;name&gt;fv0&lt;/name&gt;
&lt;uuid&gt;4dea22b31d52d8f32516782e98ab3fa0&lt;/uuid&gt;
...</pre>
<dl><dt><code>name</code></dt><dd>The content of the <code>name</code> element provides
a short name for the virtual machine. This name should
consist only of alpha-numeric characters and is required
to be unique within the scope of a single host. It is
often used to form the filename for storing the persistent
configuration file. <span class="since">Since 0.0.1</span></dd><dt><code>uuid</code></dt><dd>The content of the <code>uuid</code> element provides
a globally unique identifier for the virtual machine.
The format must be RFC 4122 compliant, eg <code>3e3fce45-4f53-4fa7-bb32-11f34168b82b</code>.
If omitted when defining/creating a new machine, a random
UUID is generated. <span class="since">Since 0.0.1</span></dd></dl>
<h3>
<a name="elementsOS" id="elementsOS">Operating system booting</a>
</h3>
<p>
There are a number of different ways to boot virtual machines
each with their own pros and cons.
</p>
<h4>
<a name="elementsOSBIOS" id="elementsOSBIOS">BIOS bootloader</a>
</h4>
<p>
Booting via the BIOS is available for hypervisors supporting
full virtualization. In this case the BIOS has a boot order
priority (floppy, harddisk, cdrom, network) determining where
to obtain/find the boot image.
</p>
<pre>
...
&lt;os&gt;
&lt;type&gt;hvm&lt;/type&gt;
&lt;loader&gt;/usr/lib/xen/boot/hvmloader&lt;/loader&gt;
&lt;boot dev='hd'/&gt;
&lt;/os&gt;
...</pre>
<dl><dt><code>type</code></dt><dd>The content of the <code>type</code> element specifies the
type of operating system to be booted in the virtual machine.
<code>hvm</code> indicates that the OS is one designed to run
on bare metal, so requires full virtualization. <code>linux</code>
(badly named!) refers to an OS that supports the Xen 3 hypervisor
guest ABI. There are also two optional attributes, <code>arch</code>
specifying the CPU architecture to virtualization, and <code>machine</code>
refering to the machine type. The <a href="formatcaps.html">Capabilities XML</a>
provides details on allowed values for these. <span class="since">Since 0.0.1</span></dd><dt><code>loader</code></dt><dd>The optional <code>loader</code> tag refers to a firmware blob
used to assist the domain creation process. At this time, it is
only needed by Xen fullyvirtualized domains. <span class="since">Since 0.1.0</span></dd><dt><code>boot</code></dt><dd>The <code>dev</code> attribute takes one of the values "fd", "hd",
"cdrom" or "network" and is used to specify the next boot device
to consider. The <code>boot</code> element can be repeated multiple
times to setup a priority list of boot devices to try in turn.
<span class="since">Since 0.1.3</span>
</dd></dl>
<h4>
<a name="elementsOSBootloader" id="elementsOSBootloader">Host bootloader</a>
</h4>
<p>
Hypervisors employing paravirtualization do not usually emulate
a BIOS, and instead the host is responsible to kicking off the
operating system boot. This may use a pseduo-bootloader in the
host to provide an interface to choose a kernel for the guest.
An example is <code>pygrub</code> with Xen.
</p>
<pre>
...
&lt;bootloader&gt;/usr/bin/pygrub&lt;/bootloader&gt;
&lt;bootloader_args&gt;--append single&lt;/bootloader_args&gt;
...</pre>
<dl><dt><code>bootloader</code></dt><dd>The content of the <code>bootloader</code> element provides
a fullyqualified path to the bootloader executable in the
host OS. This bootloader will be run to choose which kernel
to boot. The required output of the bootloader is dependant
on the hypervisor in use. <span class="since">Since 0.1.0</span></dd><dt><code>bootloader_args</code></dt><dd>The optional <code>bootloader_args</code> element allows
command line arguments to be passed to the bootloader.
<span class="since">Since 0.2.3</span>
</dd></dl>
<h4>
<a name="elementsOSKernel" id="elementsOSKernel">Direct kernel boot</a>
</h4>
<p>
When installing a new guest OS it is often useful to boot directly
from a kernel and initrd stored in the host OS, allowing command
line arguments to be passed directly to the installer. This capability
is usually available for both para and full virtualized guests.
</p>
<pre>
...
&lt;os&gt;
&lt;type&gt;hvm&lt;/type&gt;
&lt;loader&gt;/usr/lib/xen/boot/hvmloader&lt;/loader&gt;
&lt;kernel&gt;/root/f8-i386-vmlinuz&lt;/kernel&gt;
&lt;initrd&gt;/root/f8-i386-initrd&lt;/initrd&gt;
&lt;cmdline&gt;console=ttyS0 ks=http://example.com/f8-i386/os/&lt;/cmdline&gt;
&lt;/os&gt;
...</pre>
<dl><dt><code>type</code></dt><dd>This element has the same semantics as described earlier in the
<a href="#elementsOSBIOS">BIOS boot section</a></dd><dt><code>type</code></dt><dd>This element has the same semantics as described earlier in the
<a href="#elementsOSBIOS">BIOS boot section</a></dd><dt><code>kernel</code></dt><dd>The contents of this element specify the fully-qualified path
to the kernel image in the host OS.</dd><dt><code>initrd</code></dt><dd>The contents of this element specify the fully-qualified path
to the (optional) ramdisk image in the host OS.</dd><dt><code>cmdline</code></dt><dd>The contents of this element specify arguments to be passed to
the kernel (or installer) at boottime. This is often used to
specify an alternate primary console (eg serial port), or the
installation media source / kickstart file</dd></dl>
<h3>
<a name="elementsResources" id="elementsResources">Basic resources</a>
</h3>
<pre>
...
&lt;memory&gt;524288&lt;/memory&gt;
&lt;currentMemory&gt;524288&lt;/currentMemory&gt;
&lt;vcpu&gt;1&lt;/vcpu&gt;
...</pre>
<dl><dt><code>memory</code></dt><dd>The maximum allocation of memory for the guest at boot time.
The units for this value are bytes</dd><dt><code>currentMemory</code></dt><dd>The actual allocation of memory for the guest. This value
be less than the maximum allocation, to allow for ballooning
up the guests memory on the fly. If this is omitted, it defaults
to the same value as the <code>memory<code> element</code></code></dd><dt><code>vcpu</code></dt><dd>The content of this element defines the number of virtual
CPUs allocated for the guest OS.</dd></dl>
<h3>
<a name="elementsLifecycle" id="elementsLifecycle">Lifecycle control</a>
</h3>
<p>
It is sometimes neccessary to override the default actions taken
when a guest OS triggers a lifecycle operation. The following
collections of elements allow the actions to be specified. A
common use case is to force a reboot to be treated as a poweroff
when doing the initial OS installation. This allows the VM to be
re-configured for the first post-install bootup.
</p>
<pre>
...
&lt;on_poweroff&gt;destroy&lt;/on_poweroff&gt;
&lt;on_reboot&gt;restart&lt;/on_reboot&gt;
&lt;on_crash&gt;restart&lt;/on_crash&gt;
...</pre>
<dl><dt><code>on_poweroff</code></dt><dd>The content of this element specifies the action to take when
the guest requests a poweroff.</dd><dt><code>on_poweroff</code></dt><dd>The content of this element specifies the action to take when
the guest requests a reboot.</dd><dt><code>on_poweroff</code></dt><dd>The content of this element specifies the action to take when
the guest crashes.</dd></dl>
<p>
Each of these states allow for the same four possible actions.
</p>
<dl><dt><code>destroy</code></dt><dd>The domain will be terminated completely and all resources
released</dd><dt><code>restart</code></dt><dd>The domain will be terminated, and then restarted with
the same configuration</dd><dt><code>preserve</code></dt><dd>The domain will be terminated, and its resource preserved
to allow analysis.</dd><dt><code>rename-restart</code></dt><dd>The domain will be terminated, and then restarted with
a new name</dd></dl>
<h3>
<a name="elementsFeatures" id="elementsFeatures">Hypervisor features</a>
</h3>
<p>
Hypervisors may allow certain CPU / machine features to be
toggled on/off.
</p>
<pre>
...
&lt;features&gt;
&lt;pae/&gt;
&lt;acpi/&gt;
&lt;apic/&gt;
&lt;/features&gt;
...</pre>
<p>
All features are listed within the <code>features</code>
element, omitting a togglable feature tag turns it off.
The available features can be found by asking
for the <a href="formatcaps.html">capabilities XML</a>,
but a common set for fully virtualized domains are:
</p>
<dl><dt><code>pae</code></dt><dd>Physical address extension mode allows 32-bit guests
to address more than 4 GB of memory.</dd><dt><code>acpi</code></dt><dd>ACPI is useful for power management, for example, with
KVM guests it is required for graceful shutdown to work.
</dd></dl>
<h3>
<a name="elementsTime" id="elementsTime">Time keeping</a>
</h3>
<p>
The guest clock is typically initialized from the host clock.
Most operating systems expect the hardware clock to be kept
in UTC, and this is the default. Windows, however, expects
it to be in so called 'localtime'.
</p>
<pre>
...
&lt;clock sync="localtime"/&gt;
...</pre>
<dl><dt><code>clock</code></dt><dd>The <code>sync</code> attribute takes either "utc" or
"localtime" to specify how the guest clock is initialized
in relation to the host OS.
</dd></dl>
<h3>
<a name="elementsDevices" id="elementsDevices">Devices</a>
</h3>
<p>
The final set of XML elements are all used to descibe devices
provided to the guest domain. All devices occur as children
of the main <code>devices</code> element.
<span class="since">Since 0.1.3</span>
</p>
<pre>
...
&lt;devices&gt;
&lt;emulator&gt;/usr/lib/xen/bin/qemu-dm&lt;/emulator&gt;
...</pre>
<dl><dt><code>emulator</code></dt><dd>
The contents of the <code>emulator</code> element specify
the fully qualified path to the device model emulator binary.
The <a href="formatcaps.html">capabilities XML</a> specifies
the recommended default emulator to use for each particular
domain type / architecture combination.
</dd></dl>
<h4>
<a name="elementsDisks" id="elementsDisks">Hard drives, floppy disks, CDROMs</a>
</h4>
<p>
Any device that looks like a disk, be it a floppy, harddisk,
cdrom, or paravirtualized driver is specified via the <code>disk</code>
element.
</p>
<pre>
...
&lt;disk type='file'&gt;
&lt;driver name="tap" type="aio"&gt;
&lt;source file='/var/lib/xen/images/fv0'/&gt;
&lt;target dev='hda' bus='ide'/&gt;
&lt;/disk&gt;
...</pre>
<dl><dt><code>disk</code></dt><dd>The <code>disk</code> element is the main container for describing
disks. The <code>type</code> attribute is either "file" or "block"
and refers to the underlying source for the disk. The optional
<code>device</code> attribute indicates how the disk is to be exposed
to the guest OS. Possible values for this attribute are "floppy", "disk"
and "cdrom", defaulting to "disk".
<span class="since">Since 0.0.3; "device" attribute since 0.1.4</span></dd><dt><code>source</code></dt><dd>If the disk <code>type</code> is "file", then the <code>file</code> attribute
specifies the fully-qualified path to the file holding the disk. If the disk
<code>type</code> is "block", then the <code>dev</code> attribute specifies
the path to the host device to serve as the disk. <span class="since">Since 0.0.3</span></dd><dt><code>target</code></dt><dd>The <code>target</code> element controls the bus / device under which the
disk is exposed to the guest OS. The <code>dev</code> attribute indicates
the "logical" device name. The actual device name specified is not guarenteed to map to
the device name in the guest OS. Treat it as a device ordering hint.
The optional <code>bus</code> attribute specifies the type of disk device
to emulate; possible values are driver specific, with typical values being
"ide", "scsi", "virtio", "xen". If omitted, the bus type is inferred from
the style of the device name. eg, a device named 'sda' will typically be
exported using a SCSI bus.
<span class="since">Since 0.0.3; <code>bus</code> attribute since 0.4.3</span></dd><dt><code>driver</code></dt><dd>If the hypervisor supports multiple backend drivers, then the optional
<code>driver</code> element allows them to be selected. The <code>name</code>
attribute is the primary backend driver name, while the optional <code>type</code>
attribute provides the sub-type. <span class="since">Since 0.1.8</span>
</dd></dl>
<h4>
<a name="elementsNICS" id="elementsNICS">Network interfaces</a>
</h4>
<pre>
...
&lt;interface type='bridge'&gt;
&lt;source bridge='xenbr0'/&gt;
&lt;mac address='00:16:3e:5d:c7:9e'/&gt;
&lt;script path='vif-bridge'/&gt;
&lt;/interface&gt;
...</pre>
<h5>
<a name="elementsNICSVirtual" id="elementsNICSVirtual">Virtual network</a>
</h5>
<p>
<strong><em>
This is the recommended config for general guest connectivity on
hosts with dynamic / wireless networking configs
</em></strong>
</p>
<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 an 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 [networkname]</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
overridden with the &lt;target&gt; element.
</p>
<pre>
...
&lt;interface type='network'&gt;
&lt;source network='default'/&gt;
&lt;/interface&gt;
...
&lt;interface type='network'&gt;
&lt;source network='default'/&gt;
&lt;target dev='vnet7'/&gt;
&lt;mac address="11:22:33:44:55:66"/&gt;
&lt;/interface&gt;
...</pre>
<h5>
<a name="elementsNICSBridge" id="elementsNICSBridge">Bridge to to LAN</a>
</h5>
<p>
<strong><em>
This is the recommended config for general guest connectivity on
hosts with static wired networking configs
</em></strong>
</p>
<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 overridden with the
&lt;target&gt; 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 &amp; outgoing net access just like a
physical machine.
</p>
<pre>
...
&lt;interface type='bridge'&gt;
&lt;source bridge='br0'/&gt;
&lt;/interface&gt;
&lt;interface type='network'&gt;
&lt;source network='default'/&gt;
&lt;target dev='vnet7'/&gt;
&lt;mac address="11:22:33:44:55:66"/&gt;
&lt;/interface&gt;
</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 overridden with the
&lt;target&gt; 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 &amp; outgoing net access just like a
physical machine. Examples include:</p>
<pre>&lt;interface type='bridge'&gt;
&lt;source bridge='br0'/&gt;
&lt;/interface&gt;
&lt;interface type='bridge'&gt;
&lt;source bridge='br0'/&gt;
&lt;target dev='vnet7'/&gt;
&lt;mac address="11:22:33:44:55:66"/&gt;
&lt;/interface&gt;</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 overridden with the
&lt;target&gt; 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
overridden.</p>
<pre>&lt;interface type='ethernet'/&gt;
&lt;interface type='ethernet'&gt;
&lt;target dev='vnet7'/&gt;
&lt;script path='/etc/qemu-ifup-mynet'/&gt;
&lt;/interface&gt;</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>&lt;interface type='mcast'&gt;
&lt;source address='230.0.0.1' port='5558'/&gt;
&lt;/interface&gt;</pre>
</li><li>TCP tunnel
<p>A TCP client/server architecture provides a virtual network. One VM
provides the server end of the network, 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>&lt;interface type='server'&gt;
&lt;source address='192.168.0.1' port='5558'/&gt;
&lt;/interface&gt;</pre>
<p>Example client config:</p>
<pre>&lt;interface type='client'&gt;
&lt;source address='192.168.0.1' port='5558'/&gt;
&lt;/interface&gt;</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 &amp;
QEMU/KVMs connected to each other.</p>
<h2>Example configs</h2>
&lt;interface type='bridge'&gt;
&lt;source bridge='br0'/&gt;
&lt;target dev='vnet7'/&gt;
&lt;mac address="11:22:33:44:55:66"/&gt;
&lt;/interface&gt;
...</pre>
<h5>
<a name="elementsNICSSlirp" id="elementsNICSSlirp">Userspace SLIRP stack</a>
</h5>
<p>
Provides a virtual LAN with NAT to the outside world. The virtual
network has DHCP &amp; 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.
</p>
<pre>
...
&lt;interface type='user'/&gt;
...
&lt;interface type='user'&gt;
&lt;mac address="11:22:33:44:55:66"/&gt;
&lt;/interface&gt;
...</pre>
<h5>
<a name="elementsNICSEthernet" id="elementsNICSEthernet">Generic ethernet connection</a>
</h5>
<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 overridden with the
&lt;target&gt; 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
overridden.
</p>
<pre>
...
&lt;interface type='ethernet'/&gt;
...
&lt;interface type='ethernet'&gt;
&lt;target dev='vnet7'/&gt;
&lt;script path='/etc/qemu-ifup-mynet'/&gt;
&lt;/interface&gt;
...</pre>
<h5>
<a name="elementsNICSMulticast" id="elementsNICSMulticast">Multicast tunnel</a>
</h5>
<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>
...
&lt;interface type='mcast'&gt;
&lt;source address='230.0.0.1' port='5558'/&gt;
&lt;/interface&gt;
...</pre>
<h5>
<a name="elementsNICSTCP" id="elementsNICSTCP">TCP tunnel</a>
</h5>
<p>
A TCP client/server architecture provides a virtual network. One VM
provides the server end of the network, 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>
<pre>
...
&lt;interface type='server'&gt;
&lt;source address='192.168.0.1' port='5558'/&gt;
&lt;/interface&gt;
...
&lt;interface type='client'&gt;
&lt;source address='192.168.0.1' port='5558'/&gt;
&lt;/interface&gt;
...</pre>
<h4>
<a name="elementsInput" id="elementsInput">Input devices</a>
</h4>
<p>
Input devices allow interaction with the graphical framebuffer in the guest
virtual machine. When enabling the framebuffer, an input device is automatically
provided. It may be possible to add additional devices explicitly, for example,
to provide a graphics tablet for absolute cursor movement.
</p>
<pre>
...
&lt;input type='mouse' bus='usb'/&gt;
...</pre>
<dl><dt><code>input</code></dt><dd>The <code>input</code> element has one madatory attribute, the <code>type</code>
whose value can be either 'mouse' or 'tablet'. The latter provides absolute
cursor movement, while the former uses relative movement. The optional
<code>bus</code> attribute can be used to refine the exact device type.
It takes values "xen" (paravirtualized), "ps2" and "usb".</dd></dl>
<h4>
<a name="elementsGraphics" id="elementsGraphics">Graphical framebuffers</a>
</h4>
<p>
A graphics device allows for graphical interaction with the
guest OS. A guest will typically have either a framebuffer
or a text console configured to allow interaction with the
admin.
</p>
<pre>
...
&lt;graphics type='vnc' port='5904'/&gt;
...</pre>
<dl><dt><code>graphics</code></dt><dd>The <code>graphics</code> element has a mandatory <code>type</code>
attribute which takes the value "sdl" or "vnc". The former displays
a window on the host desktop, while the latter activates a VNC server.
If the latter is used the <code>port</code> attributes specifies the
TCP port number (with -1 indicating that it should be auto-allocated).
The <code>listen</code> attribute is an IP address for the server to
listen on. The <code>password</code> attribute provides a VNC password
in clear text.</dd></dl>
<h4>
<a name="elementsConsole" id="elementsConsole">Consoles, serial &amp; parallel devices</a>
</h4>
<p>
A character device provides a way to interact with the virtual machine.
Paravirtualized consoles, serial ports and parallel ports are all
classed as character devices and so represented using the same syntax.
</p>
<pre>
...
&lt;parallel type='pty'&gt;
&lt;source path='/dev/pts/2'/&gt;
&lt;target port='0'/&gt;
&lt;/parallel&gt;
&lt;serial type='pty'&gt;
&lt;source path='/dev/pts/3'/&gt;
&lt;target port='0'/&gt;
&lt;/serial&gt;
&lt;console type='pty'&gt;
&lt;source path='/dev/pts/4'/&gt;
&lt;target port='0'/&gt;
&lt;/console&gt;
&lt;/devices&gt;
&lt;/domain&gt;</pre>
<dl><dt><code>parallel</code></dt><dd>Represents a parallel port</dd><dt><code>serial</code></dt><dd>Represents a serial port</dd><dt><code>console</code></dt><dd>Represents the primary console. This can be the paravirtualized
console with Xen guests, or duplicates the primary serial port
for fully virtualized guests without a paravirtualized console.</dd><dt><code>source</code></dt><dd>The attributes available for the <code>source</code> element
vary according to the <code>type</code> attribute on the parent
tag. Allowed variations will be described below</dd><dt><code>target</code></dt><dd>The port number of the character device is specified via the
<code>port</code> attribute, numbered starting from 1. There is
usually only one console device, and 0, 1 or 2 serial devices
or parallel devices.
</dd></dl>
<h5>
<a name="elementsCharSTDIO" id="elementsCharSTDIO">Domain logfile</a>
</h5>
<p>
This disables all input on the character device, and sends output
into the virtual machine's logfile
</p>
<pre>
...
&lt;console type='stdio'&gt;
&lt;target port='1'&gt;
&lt;/console&gt;
...</pre>
<h5>
<a name="elementsCharFle" id="elementsCharFle">Device logfile</a>
</h5>
<p>
A file is opened and all data sent to the character
device is written to the file.
</p>
<pre>
...
&lt;serial type="file"&gt;
&lt;source path="/var/log/vm/vm-serial.log"/&gt;
&lt;target port="1"/&gt;
&lt;/serial&gt;
...</pre>
<h5>
<a name="elementsCharVC" id="elementsCharVC">Virtual console</a>
</h5>
<p>
Connects the character device to the graphical framebuffer in
a virtual console. This is typically accessed via a special
hotkey sequence such as "ctrl+alt+3"
</p>
<pre>
...
&lt;serial type='vc'&gt;
&lt;target port="1"/&gt;
&lt;/serial&gt;
...</pre>
<h5>
<a name="elementsCharNull" id="elementsCharNull">Null device</a>
</h5>
<p>
Connects the character device to the void. No data is ever
provided to the input. All data written is discarded.
</p>
<pre>
...
&lt;serial type='null'&gt;
&lt;target port="1"/&gt;
&lt;/serial&gt;
...</pre>
<h5>
<a name="elementsCharPTY" id="elementsCharPTY">Pseudo TTY</a>
</h5>
<p>
A Pseudo TTY is allocated using /dev/ptmx. A suitable client
such as 'virsh console' can connect to interact with the
serial port locally.
</p>
<pre>
...
&lt;serial type="pty"&gt;
&lt;source path="/dev/pts/3"/&gt;
&lt;target port="1"/&gt;
&lt;/serial&gt;
...</pre>
<p>
NB special case if &lt;console type='pty'&gt;, then the TTY
path is also duplicated as an attribute tty='/dv/pts/3'
on the top level &lt;console&gt; tag. This provides compat
with existing syntax for &lt;console&gt; tags.
</p>
<h5>
<a name="elementsCharHost" id="elementsCharHost">Host device proxy</a>
</h5>
<p>
The character device is passed through to the underlying
physical character device. The device types must match,
eg the emulated serial port should only be connected to
a host serial port - dont connect a serial port to a parallel
port.
</p>
<pre>
...
&lt;serial type="dev"&gt;
&lt;source path="/dev/ttyS0"/&gt;
&lt;target port="1"/&gt;
&lt;/serial&gt;
...</pre>
<h5>
<a name="elementsCharTCP" id="elementsCharTCP">TCP client/server</a>
</h5>
<p>
The character device acts as a TCP client connecting to a
remote server, or as a server waiting for a client connection.
</p>
<pre>
...
&lt;serial type="tcp"&gt;
&lt;source mode="connect" host="0.0.0.0" service="2445"/&gt;
&lt;wiremode type="telnet"/&gt;
&lt;target port="1"/&gt;
&lt;/serial&gt;
...</pre>
<h5>
<a name="elementsCharUDP" id="elementsCharUDP">UDP network console</a>
</h5>
<p>
The character device acts as a UDP netconsole service,
sending and receiving packets. This is a lossy service.
</p>
<pre>
...
&lt;serial type="udp"&gt;
&lt;source mode="bind" host="0.0.0.0" service="2445"/&gt;
&lt;source mode="connect" host="0.0.0.0" service="2445"/&gt;
&lt;target port="1"/&gt;
&lt;/serial&gt;
...</pre>
<h5>
<a name="elementsCharUNIX" id="elementsCharUNIX">UNIX domain socket client/server</a>
</h5>
<p>
The character device acts as a UNIX domain socket server,
accepting connections from local clients.
</p>
<pre>
...
&lt;serial type="unix"&gt;
&lt;source mode="bind" path="/tmp/foo"/&gt;
&lt;target port="1"/&gt;
&lt;/serial&gt;
...</pre>
<h2>
<a name="examples" id="examples">Example configs</a>
</h2>
<p>
Example configurations for each driver are provide on the
driver specific pages listed below

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