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<chapter>

<title>Remote virtual machines</title>

<sect1>

<title id="vrde">Remote display (VRDP support)</title>

<para>VirtualBox can display virtual machines remotely, meaning that a

virtual machine can execute on one machine even though the machine will be

displayed on a second computer, and the machine will be controlled from

there as well, as if the virtual machine was running on that second

computer.</para>

<para>For maximum flexibility, starting with VirtualBox 4.0, VirtualBox

implements remote machine display through a generic extension interface,

the VirtualBox Remote Desktop Extension (VRDE). The base open-source

VirtualBox package only provides this interface, while implementations can

be supplied by third parties with VirtualBox extension packages, which

must be installed separately from the base package. See <xref

linkend="intro-installing" /> for more information.</para>

<para>Oracle provides support for the <emphasis role="bold">VirtualBox

Remote Display Protocol (VRDP)</emphasis> in such a VirtualBox extension

package. When this package is installed, VirtualBox versions 4.0 and later

support VRDP the same way as binary (non-open-source) versions of

VirtualBox before 4.0 did.</para>

<para>VRDP is a backwards-compatible extension to Microsoft's Remote

Desktop Protocol (RDP). Typically graphics updates and audio are sent from

the remote machine to the client, while keyboard and mouse events are sent

back. As a result, you can use any standard RDP client to control the

remote VM.</para>

<para>Even when the extension is installed, the VRDP server is disabled by

default. It can easily be enabled on a per-VM basis either in the

VirtualBox Manager in the "Display" settings (see <xref

linkend="settings-display" />) or with

<computeroutput>VBoxManage</computeroutput>:<screen>VBoxManage modifyvm "VM name" --vrde on</screen></para>

<para>If you use <computeroutput>VBoxHeadless</computeroutput> (described

further below), VRDP support will be automatically enabled since

VBoxHeadless has no other means of output.</para>

<sect2 id="rdp-viewers">

<title>Common third-party RDP viewers</title>

<para>Since VRDP is backwards-compatible to RDP, you can use any

standard RDP viewer to connect to such a remote virtual machine

(examples follow below). For this to work, you must specify the

<emphasis role="bold">IP address</emphasis> of your

<emphasis>host</emphasis> system (not of the virtual machine!) as the

server address to connect to, as well as the <emphasis role="bold">port

number</emphasis> that the RDP server is using.</para>

<para>By default, VRDP uses TCP port

<computeroutput>3389</computeroutput>. You will need to change the

default port if you run more than one VRDP server, since the port can

only be used by one server at a time; you might also need to change it

on Windows hosts since the default port might already be used by the RDP

server that is built into Windows itself. Ports 5000 through 5050 are

typically not used and might be a good choice.</para>

<para>The port can be changed either in the "Display" settings of the

graphical user interface or with

<computeroutput>--vrdeport</computeroutput> option of the

<computeroutput>VBoxManage modifyvm</computeroutput> command. You can

specify a comma-separated list of ports or ranges of ports. Use a dash

between two port numbers to specify a range. The VRDP server will bind

to <emphasis role="bold">one</emphasis> of available ports from the

specified list. For example, <computeroutput>VBoxManage modifyvm "VM

name" --vrdeport 5000,5010-5012</computeroutput> will configure the

server to bind to one of the ports 5000, 5010, 5011 or 5012. See <xref

linkend="vboxmanage-modifyvm" /> for details.</para>

<para>The actual port used by a running VM can be either queried with

<computeroutput>VBoxManage showvminfo</computeroutput> command or seen

in the GUI on the "Runtime" tab of the "Session Information Dialog",

which is accessible via the "Machine" menu of the VM window.</para>

<para>Here follow examples for the most common RDP viewers:<itemizedlist>

<listitem>

<para>On Windows, you can use the Microsoft Terminal Services

Connector (<computeroutput>mstsc.exe</computeroutput>) that ships

with Windows. You can start it by bringing up the "Run" dialog

(press the Windows key and "R") and typing "mstsc". You can also

find it under "Start" -&gt; "All Programs" -&gt; "Accessories"

-&gt; "Remote Desktop Connection". If you use the "Run" dialog,

you can type in options directly:<screen>mstsc 1.2.3.4[:3389]</screen></para>

<para>Replace "1.2.3.4" with the host IP address, and 3389 with a

different port if necessary.</para>

<note>

<para>When connecting to localhost in order to test the

connection, the addresses

<computeroutput>localhost</computeroutput> and

<computeroutput>127.0.0.1</computeroutput> might not work using

<computeroutput>mstsc.exe</computeroutput>. Instead, the address

<computeroutput>127.0.0.2[:3389]</computeroutput> has to be

used.</para>

</note>

</listitem>

<listitem>

<para>On other systems, you can use the standard open-source

<computeroutput>rdesktop</computeroutput> program. This ships with

most Linux distributions, but VirtualBox also comes with a

modified variant of rdesktop for remote USB support (see <xref

linkend="usb-over-rdp" /> below).</para>

<para>With rdesktop, use a command line such as the

following:<screen>rdesktop -a 16 -N 1.2.3.4:3389</screen></para>

<para>As said for the Microsoft viewer above, replace "1.2.3.4"

with the host IP address, and 3389 with a different port if

necessary. The <computeroutput>-a 16</computeroutput> option

requests a color depth of 16 bits per pixel, which we recommend.

(For best performance, after installation of the guest operating

system, you should set its display color depth to the same value).

The <computeroutput>-N</computeroutput> option enables use of the

NumPad keys.</para>

</listitem>

<listitem>

<para>If you run the KDE desktop, you might prefer

<computeroutput>krdc</computeroutput>, the KDE RDP viewer. The

command line would look like this:<screen>krdc --window --high-quality rdp:/1.2.3.4[:3389]</screen></para>

<para>Again, replace "1.2.3.4" with the host IP address, and 3389

with a different port if necessary. The "rdp:/" bit is required

with krdc to switch it into RDP mode.</para>

</listitem>

<listitem>

<para>With Sun Ray thin clients you can use

<computeroutput>uttsc</computeroutput>, which is part of the

Sun Ray Windows Connector package. See the corresponding

documentation for details.</para>

</listitem>

</itemizedlist></para>

</sect2>

<sect2 id="vboxheadless">

<title>VBoxHeadless, the remote desktop server</title>

<para>While any VM started from the VirtualBox Manager is capable of

running virtual machines remotely, it is not convenient to have to run

the full-fledged GUI if you never want to have VMs displayed locally in

the first place. In particular, if you are running server hardware whose

only purpose is to host VMs, and all your VMs are supposed to run

remotely over VRDP, then it is pointless to have a graphical user

interface on the server at all -- especially since, on a Linux or

Solaris host, the VirtualBox manager comes with dependencies on the Qt

and SDL libraries. This is inconvenient if you would rather not have the

X Window system on your server at all.</para>

<para>VirtualBox therefore comes with yet another front-end called

<computeroutput>VBoxHeadless</computeroutput>, which produces no visible

output on the host at all, but instead only delivers VRDP data. This

front-end has no dependencies on the X Window system on Linux and

Solaris hosts.<footnote>

<para>Before VirtualBox 1.6, the headless server was called

<computeroutput>VBoxVRDP</computeroutput>. For the sake of backwards

compatibility, the VirtualBox installation still installs an

executable with that name as well.</para>

</footnote></para>

<para>To start a virtual machine with

<computeroutput>VBoxHeadless</computeroutput>, you have two

options:</para>

<itemizedlist>

<listitem>

<para>You can use <screen>VBoxManage startvm "VM name" --type headless</screen>The

extra <computeroutput>--type</computeroutput> option causes

VirtualBox to use <computeroutput>VBoxHeadless</computeroutput> as

the front-end to the internal virtualization engine instead of the

Qt front-end.</para>

</listitem>

<listitem>

<para>The alternative is to use

<computeroutput>VBoxHeadless</computeroutput> directly, as

follows:<screen>VBoxHeadless --startvm &lt;uuid|name&gt;</screen></para>

<para>This way of starting the VM is preferred because you can see

more detailed error messages, especially for early failures before

the VM execution is started. If you have trouble with

<computeroutput>VBoxManage startvm</computeroutput>, it can help

greatly to start <computeroutput>VBoxHeadless</computeroutput>

directly to diagnose the problem cause.</para>

</listitem>

</itemizedlist>

<para>Note that when you use

<computeroutput>VBoxHeadless</computeroutput> to start a VM, since the

headless server has no other means of output, the VRDP server will

<emphasis>always</emphasis> be enabled, regardless of whether you had

enabled the VRDP server in the VM's settings. If this is undesirable

(for example because you want to access the VM via

<computeroutput>ssh</computeroutput> only), start the VM like

this:<screen>VBoxHeadless --startvm &lt;uuid|name&gt; --vrde=off</screen>To

have the VRDP server enabled depending on the VM configuration, as the

other front-ends would, use this:<screen>VBoxHeadless --startvm &lt;uuid|name&gt; --vrde=config</screen></para>

</sect2>

<sect2>

<title>Step by step: creating a virtual machine on a headless

server</title>

<para>The following instructions may give you an idea how to create a

virtual machine on a headless server over a network connection. We will

create a virtual machine, establish an RDP connection and install a

guest operating system -- all without having to touch the headless

server. All you need is the following:</para>

<para><orderedlist>

<listitem>

<para>VirtualBox on a server machine with a supported host

operating system. The VirtualBox extension pack for the VRDP

server must be installed (see the previous section). For the

following example, we will assume a Linux server.</para>

</listitem>

<listitem>

<para>An ISO file accessible from the server, containing the

installation data for the guest operating system to install (we

will assume Windows XP in the following example).</para>

</listitem>

<listitem>

<para>A terminal connection to that host through which you can

access a command line (e.g. via

<computeroutput>ssh</computeroutput>).</para>

</listitem>

<listitem>

<para>An RDP viewer on the remote client; see <xref

linkend="rdp-viewers" /> above for examples.</para>

</listitem>

</orderedlist>Note again that on the server machine, since we will

only use the headless server, neither Qt nor SDL nor the X Window system

will be needed.</para>

<para><orderedlist>

<listitem>

<para>On the headless server, create a new virtual machine:</para>

<screen>VBoxManage createvm --name "Windows XP" --ostype WindowsXP --register</screen>

<para>Note that if you do not specify

<computeroutput>--register</computeroutput>, you will have to

manually use the <computeroutput>registervm</computeroutput>

command later.</para>

<para>Note further that you do not need to specify

<computeroutput>--ostype</computeroutput>, but doing so selects

some sane default values for certain VM parameters, for example

the RAM size and the type of the virtual network device. To get a

complete list of supported operating systems you can use</para>

<screen>VBoxManage list ostypes</screen>

</listitem>

<listitem>

<para>Make sure the settings for this VM are appropriate for the

guest operating system that we will install. For example:<screen>VBoxManage modifyvm "Windows XP" --memory 256 --acpi on --boot1 dvd --nic1 nat</screen></para>

</listitem>

<listitem>

<para>Create a virtual hard disk for the VM (in this case, 10GB in

size):<screen>VBoxManage createhd --filename "WinXP.vdi" --size 10000</screen></para>

</listitem>

<listitem>

<para>Add an IDE Controller to the new VM:<screen>VBoxManage storagectl "Windows XP" --name "IDE Controller"

--add ide --controller PIIX4</screen></para>

</listitem>

<listitem>

<para>Set the VDI file created above as the first virtual hard

disk of the new VM:<screen>VBoxManage storageattach "Windows XP" --storagectl "IDE Controller"

--port 0 --device 0 --type hdd --medium "WinXP.vdi"</screen></para>

</listitem>

<listitem>

<para>Attach the ISO file that contains the operating system

installation that you want to install later to the virtual

machine, so the machine can boot from it:<screen>VBoxManage storageattach "Windows XP" --storagectl "IDE Controller"

--port 0 --device 1 --type dvddrive --medium /full/path/to/iso.iso</screen></para>

</listitem>

<listitem>

<para>Start the virtual machine using VBoxHeadless:<screen>VBoxHeadless --startvm "Windows XP"</screen></para>

<para>If everything worked, you should see a copyright notice. If,

instead, you are returned to the command line, then something went

wrong.</para>

</listitem>

<listitem>

<para>On the client machine, fire up the RDP viewer and try to

connect to the server (see <xref linkend="rdp-viewers" /> above

for how to use various common RDP viewers).</para>

<para>You should now be seeing the installation routine of your

guest operating system remotely in the RDP viewer.</para>

</listitem>

</orderedlist></para>

</sect2>

<sect2 id="usb-over-rdp">

<title>Remote USB</title>

<para>As a special feature on top of the VRDP support, VirtualBox

supports remote USB devices over the wire as well. That is, the

VirtualBox guest that runs on one computer can access the USB devices of

the remote computer on which the VRDP data is being displayed the same

way as USB devices that are connected to the actual host. This allows

for running virtual machines on a VirtualBox host that acts as a server,

where a client can connect from elsewhere that needs only a network

adapter and a display capable of running an RDP viewer. When USB devices

are plugged into the client, the remote VirtualBox server can access

them.</para>

<para>For these remote USB devices, the same filter rules apply as for

other USB devices, as described with <xref linkend="settings-usb" />.

All you have to do is specify "Remote" (or "Any") when setting up these

rules.</para>

<para>Accessing remote USB devices is only possible if the RDP client

supports this extension. On Linux and Solaris hosts, the VirtualBox

installation provides a suitable VRDP client called

<computeroutput>rdesktop-vrdp</computeroutput>. Recent versions of

<computeroutput>uttsc</computeroutput>, a client tailored for the use

with Sun Ray thin clients, also support accessing remote USB devices.

RDP clients for other platforms will be provided in future VirtualBox

versions.</para>

<para>To make a remote USB device available to a VM,

<computeroutput>rdesktop-vrdp</computeroutput> should be started as

follows:<screen>rdesktop-vrdp -r usb -a 16 -N my.host.address</screen>Note

that <computeroutput>rdesktop-vrdp</computeroutput> can access USB

devices only through <computeroutput>/proc/bus/usb</computeroutput>.

Please refer to <xref linkend="ts_usb-linux" /> for further details on how

to properly set up the permissions. Furthermore it is advisable to

disable automatic loading of any host driver on the remote host which

might work on USB devices to ensure that the devices are accessible by

the RDP client. If the setup was properly done on the remote host,

plug/unplug events are visible on the VBox.log file of the VM.</para>

</sect2>

<sect2 id="vbox-auth">

<title>RDP authentication</title>

<para>For each virtual machine that is remotely accessible via RDP, you

can individually determine if and how client connections are

authenticated. For this, use <computeroutput>VBoxManage

modifyvm</computeroutput> command with the

<computeroutput>--vrdeauthtype</computeroutput> option; see <xref

linkend="vboxmanage-modifyvm" /> for a general introduction. Three

methods of authentication are available:<itemizedlist>

<listitem>

<para>The "null" method means that there is no authentication at

all; any client can connect to the VRDP server and thus the

virtual machine. This is, of course, very insecure and only to be

recommended for private networks.</para>

</listitem>

<listitem>

<para>The "external" method provides external authentication

through a special authentication library. VirtualBox ships with

two such authentication libraries:<orderedlist>

<listitem>

<para>The default authentication library,

<computeroutput>VBoxAuth</computeroutput>, authenticates

against user credentials of the hosts. Depending on the host

platform, this means:<itemizedlist>

<listitem>

<para>On Linux hosts,

<computeroutput>VBoxAuth.so</computeroutput>

authenticates users against the host's PAM

system.</para>

</listitem>

<listitem>

<para>On Windows hosts,

<computeroutput>VBoxAuth.dll</computeroutput>

authenticates users against the host's WinLogon

system.</para>

</listitem>

<listitem>

<para>On Mac OS X hosts,

<computeroutput>VBoxAuth.dylib</computeroutput>

authenticates users against the host's directory

service.<footnote>

<para>Support for Mac OS X was added in version

3.2.</para>

</footnote></para>

</listitem>

</itemizedlist></para>

<para>In other words, the "external" method per default

performs authentication with the user accounts that exist on

the host system. Any user with valid authentication

credentials is accepted, i.e. the username does not have to

correspond to the user running the VM.</para>

</listitem>

<listitem>

<para>An additional library called

<computeroutput>VBoxAuthSimple</computeroutput> performs

authentication against credentials configured in the

"extradata" section of a virtual machine's XML settings

file. This is probably the simplest way to get

authentication that does not depend on a running and

supported guest (see below). The following steps are

required:<orderedlist>

<listitem>

<para>Enable

<computeroutput>VBoxAuthSimple</computeroutput> with

the following command:</para>

<para><screen>VBoxManage setproperty vrdeauthlibrary "VBoxAuthSimple"</screen></para>

</listitem>

<listitem>

<para>To enable the library for a particular VM, you

must then switch authentication to external:<screen>VBoxManage modifyvm &lt;vm&gt; --vrdeauthtype external</screen></para>

<para>Replace

<computeroutput>&lt;vm&gt;</computeroutput> with the

VM name or UUID.</para>

</listitem>

<listitem>

<para>You will then need to configure users and

passwords by writing items into the machine's

extradata. Since the XML machine settings file, into

whose "extradata" section the password needs to be

written, is a plain text file, VirtualBox uses hashes

to encrypt passwords. The following command must be

used:<screen>VBoxManage setextradata &lt;vm&gt; "VBoxAuthSimple/users/&lt;user&gt;" &lt;hash&gt;</screen></para>

<para>Replace

<computeroutput>&lt;vm&gt;</computeroutput> with the

VM name or UUID,

<computeroutput>&lt;user&gt;</computeroutput> with the

user name who should be allowed to log in and

<computeroutput>&lt;hash&gt;</computeroutput> with the

encrypted password. As an example, to obtain the hash

value for the password "secret", you can use the

following command:<screen>VBoxManage internalcommands passwordhash "secret"</screen></para>

<para>This will print

<screen>2bb80d537b1da3e38bd30361aa855686bde0eacd7162fef6a25fe97bf527a25b</screen>

You can then use VBoxManage setextradata to store this

value in the machine's "extradata" section.</para>

<para>As example, combined together, to set the

password for the user "john" and the machine "My VM"

to "secret", use this command:<screen>VBoxManage setextradata "My VM" "VBoxAuthSimple/users/john"

2bb80d537b1da3e38bd30361aa855686bde0eacd7162fef6a25fe97bf527a25b</screen></para>

</listitem>

</orderedlist></para>

</listitem>

</orderedlist></para>

</listitem>

<listitem>

<para>Finally, the "guest" authentication method performs

authentication with a special component that comes with the Guest

Additions; as a result, authentication is not performed on the

host, but with the <emphasis>guest</emphasis> user

accounts.</para>

<para>This method is currently still in testing and not yet

supported.</para>

</listitem>

</itemizedlist></para>

<para>In addition to the methods described above, you can replace the

default "external" authentication module with any other module. For

this, VirtualBox provides a well-defined interface that allows you to

write your own authentication module. This is described in detail in the

VirtualBox Software Development Kit (SDK) reference; please see <xref

linkend="VirtualBoxAPI" /> for details.</para>

</sect2>

<sect2 id="vrde-crypt">

<title>RDP encryption</title>

<para>RDP features data stream encryption, which is based on the RC4

symmetric cipher (with keys up to 128bit). The RC4 keys are being

replaced in regular intervals (every 4096 packets).</para>

<para>RDP provides different authentication methods:<orderedlist>

<listitem>

<para>Historically, RDP4 authentication was used, with which the

RDP client does not perform any checks in order to verify the

identity of the server it connects to. Since user credentials can

be obtained using a "man in the middle" (MITM) attack, RDP4

authentication is insecure and should generally not be

used.</para>

</listitem>

<listitem>

<para>RDP5.1 authentication employs a server certificate for which

the client possesses the public key. This way it is guaranteed

that the server possess the corresponding private key. However, as

this hard-coded private key became public some years ago, RDP5.1

authentication is also insecure.</para>

</listitem>

<listitem>

<para>RDP5.2 authentication uses the Enhanced RDP Security, which

means that an external security protocol is used to secure the

connection. RDP4 and RDP5.1 use Standard RDP Security.

The VRDP server supports Enhanced RDP Security with TLS protocol and,

as a part of TLS handshake, sends the server certificate to the

client.</para>

<para>The <computeroutput>Security/Method</computeroutput> VRDE

property sets the desired security method, which is used for a

connection. Valid values are:<itemizedlist>

<listitem>

<para>

<computeroutput>Negotiate</computeroutput> - both Enhanced (TLS)

and Standard RDP Security connections are allowed. The security

method is negotiated with the client. This is the default setting.

</para>

</listitem>

<listitem>

<para>

<computeroutput>RDP</computeroutput> - only Standard RDP Security

is accepted.</para>

</listitem>

<listitem>

<para>

<computeroutput>TLS</computeroutput> - only Enhanced RDP Security

is accepted. The client must support TLS.</para>

</listitem>

</itemizedlist>

For example the following command allows a client to use either Standard

or Enhanced RDP Security connection:

<screen>vboxmanage modifyvm "VM name" --vrdeproperty "Security/Method=negotiate"</screen>

</para>

<para>If the <computeroutput>Security/Method</computeroutput> property is

set to either <computeroutput>Negotiate</computeroutput> or

<computeroutput>TLS</computeroutput>, the TLS protocol will be automatically

used by the server, if the client supports TLS. However, in order to use TLS

the server must possess the Server Certificate, the Server Private Key and the

Certificate Authority (CA) Certificate. The following example shows how to

generate a server certificate.<orderedlist>

<listitem>

Create a CA self signed certificate:

<screen>openssl req -new -x509 -days 365 -extensions v3_ca \

-keyout ca_key_private.pem -out ca_cert.pem</screen>

</listitem>

<listitem>

Generate a server private key and a request for signing:

<screen>openssl genrsa -out server_key_private.pem

openssl req -new -key server_key_private.pem -out server_req.pem</screen>

</listitem>

<listitem>

Generate the server certificate:

<screen>openssl x509 -req -days 365 -in server_req.pem \

-CA ca_cert.pem -CAkey ca_key_private.pem -set_serial 01 -out server_cert.pem</screen>

</listitem>

</orderedlist>

The server must be configured to access the required files:

<screen>vboxmanage modifyvm "VM name" \

--vrdeproperty "Security/CACertificate=path/ca_cert.pem"</screen>

<screen>vboxmanage modifyvm "VM name" \

--vrdeproperty "Security/ServerCertificate=path/server_cert.pem"</screen>

<screen>vboxmanage modifyvm "VM name" \

--vrdeproperty "Security/ServerPrivateKey=path/server_key_private.pem"</screen>

</para>

</listitem>

</orderedlist></para>

<para>As the client that connects to the server determines what type

of encryption will be used, with rdesktop, the Linux RDP viewer, use the

<computeroutput>-4</computeroutput> or

<computeroutput>-5</computeroutput> options.</para>

</sect2>

<sect2 id="vrde-multiconnection">

<title>Multiple connections to the VRDP server</title>

<para>The VRDP server of VirtualBox supports multiple simultaneous

connections to the same running VM from different clients. All connected

clients see the same screen output and share a mouse pointer and

keyboard focus. This is similar to several people using the same

computer at the same time, taking turns at the keyboard.</para>

<para>The following command enables multiple connection mode: <screen>VBoxManage modifyvm "VM name" --vrdemulticon on</screen></para>

</sect2>

<sect2 id="vrde-multimonitor">

<title>Multiple remote monitors</title>

<para>To access two or more remote VM displays you have to enable the

VRDP multiconnection mode (see <xref

linkend="vrde-multiconnection" />).</para>

<para>The RDP client can select the virtual monitor number to connect to

using the <computeroutput>domain</computeroutput> logon parameter

(<computeroutput>-d</computeroutput>). If the parameter ends with

<computeroutput>@</computeroutput> followed by a number, VirtualBox

interprets this number as the screen index. The primary guest screen is

selected with <computeroutput>@1</computeroutput>, the first secondary

screen is <computeroutput>@2</computeroutput>, etc.</para>

<para>The Microsoft RDP6 client does not let you specify a separate

domain name. Instead, use

<computeroutput>domain\username</computeroutput> in the

<computeroutput>Username:</computeroutput> field -- for example,

<computeroutput>@2\name</computeroutput>.

<computeroutput>name</computeroutput> must be supplied, and must be the

name used to log in if the VRDP server is set up to require credentials.

If it is not, you may use any text as the username.</para>

</sect2>

<sect2 id="vrde-videochannel">

<title>VRDP video redirection</title>

<para>Starting with VirtualBox 3.2, the VRDP server can redirect video

streams from the guest to the RDP client. Video frames are compressed

using the JPEG algorithm allowing a higher compression ratio than

standard RDP bitmap compression methods. It is possible to increase the

compression ratio by lowering the video quality.</para>

<para>The VRDP server automatically detects video streams in a guest as

frequently updated rectangular areas. As a result, this method works

with any guest operating system without having to install additional

software in the guest; in particular, the Guest Additions are not

required.</para>

<para>On the client side, however, currently only the Windows 7 Remote

Desktop Connection client supports this feature. If a client does not

support video redirection, the VRDP server falls back to regular bitmap

updates.</para>

<para>The following command enables video redirection: <screen>VBoxManage modifyvm "VM name" --vrdevideochannel on</screen></para>

<para>The quality of the video is defined as a value from 10 to 100

percent, representing a JPEG compression level (where lower numbers mean

lower quality but higher compression). The quality can be changed using

the following command: <screen>VBoxManage modifyvm "VM name" --vrdevideochannelquality 75</screen></para>

</sect2>

<sect2 id="vrde-customization">

<title>VRDP customization</title>

<para>With VirtualBox 4.0 it is possible to disable display output,

mouse and keyboard input, audio, remote USB or clipboard individually in

the VRDP server.</para>

<para>The following commands change corresponding server

settings:</para>

<screen>VBoxManage modifyvm "VM name" --vrdeproperty Client/DisableDisplay=1

VBoxManage modifyvm "VM name" --vrdeproperty Client/DisableInput=1

VBoxManage modifyvm "VM name" --vrdeproperty Client/DisableUSB=1

VBoxManage modifyvm "VM name" --vrdeproperty Client/DisableAudio=1

VBoxManage modifyvm "VM name" --vrdeproperty Client/DisableClipboard=1

VBoxManage modifyvm "VM name" --vrdeproperty Client/DisableUpstreamAudio=1</screen>

<para>To reenable a feature use a similar command without the trailing

1. For example: <screen>VBoxManage modifyvm "VM name" --vrdeproperty Client/DisableDisplay=</screen></para>

<para>These properties were introduced with VirtualBox 3.2.10. However,

in the 3.2.x series, it was necessary to use the following commands to

alter these settings instead:</para>

<screen>VBoxManage setextradata "VM name" "VRDP/Feature/Client/DisableDisplay" 1

VBoxManage setextradata "VM name" "VRDP/Feature/Client/DisableInput" 1

VBoxManage setextradata "VM name" "VRDP/Feature/Client/DisableUSB" 1

VBoxManage setextradata "VM name" "VRDP/Feature/Client/DisableAudio" 1

VBoxManage setextradata "VM name" "VRDP/Feature/Client/DisableClipboard" 1</screen>

<para>To reenable a feature use a similar command without the trailing

1. For example: <screen>VBoxManage setextradata "VM name" "VRDP/Feature/Client/DisableDisplay"</screen></para>

</sect2>

</sect1>

<sect1 id="teleporting">

<title>Teleporting</title>

<para>Starting with version 3.1, VirtualBox supports "teleporting" -- that

is, moving a virtual machine over a network from one VirtualBox host to

another, while the virtual machine is running. This works regardless of

the host operating system that is running on the hosts: you can teleport

virtual machines between Solaris and Mac hosts, for example.</para>

<para>Teleporting requires that a machine be currently running on one

host, which is then called the <emphasis role="bold">"source"</emphasis>.

The host to which the virtual machine will be teleported will then be

called the <emphasis role="bold">"target"</emphasis>; the machine on the

target is then configured to wait for the source to contact the target.

The machine's running state will then be transferred from the source to

the target with minimal downtime.</para>

<para>Teleporting happens over any TCP/IP network; the source and the

target only need to agree on a TCP/IP port which is specified in the

teleporting settings.</para>

<para>At this time, there are a few prerequisites for this to work,

however:<orderedlist>

<listitem>

<para>On the target host, you must configure a virtual machine in

VirtualBox with exactly the same hardware settings as the machine on

the source that you want to teleport. This does not apply to

settings which are merely descriptive, such as the VM name, but

obviously for teleporting to work, the target machine must have the

same amount of memory and other hardware settings. Otherwise

teleporting will fail with an error message.</para>

</listitem>

<listitem>

<para>The two virtual machines on the source and the target must

share the same storage (hard disks as well as floppy and CD/DVD

images). This means that they either use the same iSCSI targets or

that the storage resides somewhere on the network and both hosts

have access to it via NFS or SMB/CIFS.</para>

<para>This also means that neither the source nor the target machine

can have any snapshots.</para>

</listitem>

</orderedlist></para>

<para>Then perform the following steps:<orderedlist>

<listitem>

<para>On the <emphasis>target</emphasis> host, configure the virtual

machine to wait for a teleport request to arrive when it is started,

instead of actually attempting to start the machine. This is done

with the following VBoxManage command:<screen>VBoxManage modifyvm &lt;targetvmname&gt; --teleporter on --teleporterport &lt;port&gt;</screen></para>

<para>where <computeroutput>&lt;targetvmname&gt;</computeroutput> is

the name of the virtual machine on the target host and

<computeroutput>&lt;port&gt;</computeroutput> is a TCP/IP port

number to be used on both the source and the target hosts. For

example, use 6000. For details, see <xref

linkend="vboxmanage-modifyvm-teleport" />.</para>

</listitem>

<listitem>

<para>Start the VM on the target host. You will see that instead of

actually running, it will show a progress dialog. indicating that it

is waiting for a teleport request to arrive.</para>

</listitem>

<listitem>

<para>Start the machine on the <emphasis>source</emphasis> host as

usual. When it is running and you want it to be teleported, issue

the following command on the source host:<screen>VBoxManage controlvm &lt;sourcevmname&gt; teleport --host &lt;targethost&gt; --port &lt;port&gt;</screen></para>

<para>where <computeroutput>&lt;sourcevmname&gt;</computeroutput> is

the name of the virtual machine on the source host (the machine that

is currently running),

<computeroutput>&lt;targethost&gt;</computeroutput> is the host or

IP name of the target host on which the machine is waiting for the

teleport request, and <computeroutput>&lt;port&gt;</computeroutput>

must be the same number as specified in the command on the target

host. For details, see <xref

linkend="vboxmanage-controlvm" />.</para>

</listitem>

</orderedlist></para>

<para>For testing, you can also teleport machines on the same host; in

that case, use "localhost" as the hostname on both the source and the

target host.<note>

<para>In rare cases, if the CPUs of the source and the target are very

different, teleporting can fail with an error message, or the target

may hang. This may happen especially if the VM is running application

software that is highly optimized to run on a particular CPU without

correctly checking that certain CPU features are actually present.

VirtualBox filters what CPU capabilities are presented to the guest

operating system. Advanced users can attempt to restrict these virtual

CPU capabilities with the <computeroutput>VBoxManage --modifyvm

--cpuid</computeroutput> command; see <xref

linkend="vboxmanage-modifyvm-teleport" />.</para>

</note></para>

</sect1>

</chapter>