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7 Remote virtual machines
7.1.8 Multiple remote monitors
To access two or more remote VM displays you have to enable the VRDP multiconnection mode
(see chapter 7.1.7, Multiple connections to the VRDP server, page 108).
The RDP client can select the virtual monitor number to connect to using the domain logon
parameter (-d). If the parameter ends with @ followed by a number, VirtualBox interprets this
number as the screen index. The primary guest screen is selected with @1, the first secondary
screen is @2, etc.
The Microsoft RDP6 client does not let you specify a separate domain name. Instead, use
domain\username in the Username: field – for example, @2\name. name 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.
7.1.9 VRDP video redirection
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.
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.
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.
The following command enables video redirection:
VBoxManage modifyvm "VM name" --vrdevideochannel on
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:
VBoxManage modifyvm "VM name" --vrdevideochannelquality 75
7.1.10 VRDP customization
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.
The following commands change corresponding server settings:
VBoxManage
VBoxManage
VBoxManage
VBoxManage
VBoxManage
VBoxManage
modifyvm
modifyvm
modifyvm
modifyvm
modifyvm
modifyvm
"VM
"VM
"VM
"VM
"VM
"VM
name"
name"
name"
name"
name"
name"
--vrdeproperty
--vrdeproperty
--vrdeproperty
--vrdeproperty
--vrdeproperty
--vrdeproperty
Client/DisableDisplay=1
Client/DisableInput=1
Client/DisableUSB=1
Client/DisableAudio=1
Client/DisableClipboard=1
Client/DisableUpstreamAudio=1
To reenable a feature use a similar command without the trailing 1. For example:
VBoxManage modifyvm "VM name" --vrdeproperty Client/DisableDisplay=
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:
VBoxManage
VBoxManage
VBoxManage
VBoxManage
VBoxManage
setextradata
setextradata
setextradata
setextradata
setextradata
"VM
"VM
"VM
"VM
"VM
name"
name"
name"
name"
name"
"VRDP/Feature/Client/DisableDisplay" 1
"VRDP/Feature/Client/DisableInput" 1
"VRDP/Feature/Client/DisableUSB" 1
"VRDP/Feature/Client/DisableAudio" 1
"VRDP/Feature/Client/DisableClipboard" 1
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