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<chapter id="guestadditions">
<title>Guest Additions</title>
<para>The previous chapter covered getting started with VirtualBox and
installing operating systems in a virtual machine. For any serious and
interactive use, the VirtualBox Guest Additions will make your life much
easier by providing closer integration between host and guest and improving
the interactive performance of guest systems. This chapter describes the
Guest Additions in detail.</para>
<sect1>
<title>Introduction</title>
<para>As mentioned in <xref linkend="virtintro" />, the Guest Additions
are designed to be installed <emphasis>inside</emphasis> a virtual machine
after the guest operating system has been installed. They consist of
device drivers and system applications that optimize the guest operating
system for better performance and usability. Please see <xref
linkend="guestossupport" /> for details on what guest operating systems
are fully supported with Guest Additions by VirtualBox.</para>
<para>The VirtualBox Guest Additions for all supported guest operating
systems are provided as a single CD-ROM image file which is called
is located in the installation directory of VirtualBox. To install the
Guest Additions for a particular VM, you mount this ISO file in your VM as
a virtual CD-ROM and install from there.</para>
<para>The Guest Additions offer the following features:<glosslist>
<glossentry>
<glossterm>Mouse pointer integration</glossterm>
<glossdef>
<para>To overcome the limitations for mouse support that were
described in <xref linkend="keyb_mouse_normal" />, this provides
you with seamless mouse support. You will only have one mouse
pointer and pressing the Host key is no longer required to "free"
the mouse from being captured by the guest OS. To make this work,
a special mouse driver is installed in the guest that communicates
with the "real" mouse driver on your host and moves the guest
mouse pointer accordingly.</para>
</glossdef>
</glossentry>
<glossentry>
<glossterm>Shared folders</glossterm>
<glossdef>
<para>These provide an easy way to exchange files between the host
and the guest. Much like ordinary Windows network shares, you can
tell VirtualBox to treat a certain host directory as a shared
folder, and VirtualBox will make it available to the guest
operating system as a network share, irrespective of whether guest
actually has a network. For details, please refer to <xref
linkend="sharedfolders" />.</para>
</glossdef>
</glossentry>
<glossentry>
<glossterm>Better video support</glossterm>
<glossdef>
<para>While the virtual graphics card which VirtualBox emulates
for any guest operating system provides all the basic features,
the custom video drivers that are installed with the Guest
Additions provide you with extra high and non-standard video modes
as well as accelerated video performance.</para>
<para>In addition, with Windows, Linux and Solaris guests, you can
resize the virtual machine's window if the Guest Additions are
installed. The video resolution in the guest will be automatically
adjusted (as if you had manually entered an arbitrary resolution
in the guest's display settings). Please see <xref
linkend="intro-resize-window" /> also.</para>
<para>Finally, if the Guest Additions are installed, 3D graphics
and 2D video for guest applications can be accelerated; see <xref
linkend="guestadd-video" />.</para>
</glossdef>
</glossentry>
<glossentry>
<glossterm>Seamless windows</glossterm>
<glossdef>
<para>With this feature, the individual windows that are displayed
on the desktop of the virtual machine can be mapped on the host's
desktop, as if the underlying application was actually running on
the host. See <xref linkend="seamlesswindows" /> for
details.</para>
</glossdef>
</glossentry>
<glossentry>
<glossdef>
<para>The Guest Additions enable you to control and monitor guest
execution in ways other than those mentioned above. The so-called
"guest properties" provide a generic string-based mechanism to
exchange data bits between a guest and a host, some of which have
special meanings for controlling and monitoring the guest; see
<xref linkend="guestadd-guestprops" /> for details.</para>
<para>Additionally, applications can be started in a guest from
the host; see <xref linkend="guestadd-guestcontrol" />.</para>
</glossdef>
</glossentry>
<glossentry>
<glossterm>Time synchronization</glossterm>
<glossdef>
<para>With the Guest Additions installed, VirtualBox can ensure
that the guest's system time is better synchronized with that of
the host.</para>
<para>For various reasons, the time in the guest might run at a
slightly different rate than the time on the host. The host could
be receiving updates via NTP and its own time might not run
linearly. A VM could also be paused, which stops the flow of time
in the guest for a shorter or longer period of time. When the wall
clock time between the guest and host only differs slightly, the
time synchronization service attempts to gradually and smoothly
adjust the guest time in small increments to either "catch up" or
"lose" time. When the difference is too great (e.g., a VM paused
for hours or restored from saved state), the guest time is changed
immediately, without a gradual adjustment.</para>
<para>The Guest Additions will re-synchronize the time regularly.
See <xref linkend="changetimesync" /> for how to configure the
parameters of the time synchronization mechanism.</para>
</glossdef>
</glossentry>
<glossentry>
<glossterm>Shared clipboard</glossterm>
<glossdef>
<para>With the Guest Additions installed, the clipboard of the
guest operating system can optionally be shared with your host
operating system; see <xref linkend="generalsettings" />.</para>
</glossdef>
</glossentry>
<glossentry>
<glossterm>Automated logons (credentials passing)</glossterm>
<glossdef>
<para>For details, please see <xref linkend="autologon" />.</para>
</glossdef>
</glossentry>
</glosslist></para>
<para>Each version of VirtualBox, even minor releases, ship with their own
version of the Guest Additions. While the interfaces through which the
VirtualBox core communicates with the Guest Additions are kept stable so
that Guest Additions already installed in a VM should continue to work
when VirtualBox is upgraded on the host, for best results, it is
recommended to keep the Guest Additions at the same version.</para>
<para>Starting with VirtualBox 3.1, the Windows and Linux Guest Additions
therefore check automatically whether they have to be updated. If the host
is running a newer VirtualBox version than the Guest Additions, a
notification with further instructions is displayed in the guest.</para>
<para>To disable this update check for the Guest Additions of a given
virtual machine, set the value of its
guest property to <computeroutput>0</computeroutput>; see <xref
linkend="guestadd-guestprops" /> for details.</para>
</sect1>
<sect1>
<title>Installing and Maintaining Guest Additions</title>
<para>Guest Additions are available for virtual machines running Windows,
Linux, Solaris or OS/2. The following sections describe the specifics of
each variant in detail.</para>
<sect2 id="additions-windows">
<title>Guest Additions for Windows</title>
<para>The VirtualBox Windows Guest Additions are designed to be
installed in a virtual machine running a Windows operating system. The
following versions of Windows guests are supported:</para>
<itemizedlist>
<listitem>
<para>Microsoft Windows NT 4.0 (any service pack)</para>
</listitem>
<listitem>
<para>Microsoft Windows 2000 (any service pack)</para>
</listitem>
<listitem>
<para>Microsoft Windows XP (any service pack)</para>
</listitem>
<listitem>
<para>Microsoft Windows Server 2003 (any service pack)</para>
</listitem>
<listitem>
<para>Microsoft Windows Server 2008</para>
</listitem>
<listitem>
<para>Microsoft Windows Vista (all editions)</para>
</listitem>
<listitem>
<para>Microsoft Windows 7 (all editions)</para>
</listitem>
<listitem>
<para>Microsoft Windows 8 (all editions)</para>
</listitem>
<listitem>
<para>Microsoft Windows Server 2012</para>
</listitem>
</itemizedlist>
<sect3 id="mountingadditionsiso">
<title>Installation</title>
<para>In the "Devices" menu in the virtual machine's menu bar,
VirtualBox has a handy menu item named "Insert Guest Additions CD image",
which mounts the Guest Additions ISO file inside your virtual machine.
A Windows guest should then automatically start the Guest Additions
installer, which installs the Guest Additions into your Windows
guest. Other guest operating systems (or if automatic start of
software on CD is disabled) need manual start of the installer.</para>
<note>
<para>For the basic Direct3D acceleration to work in a Windows Guest, you
have to install the Guest Additions in "Safe Mode".
This does <emphasis role="bold">not</emphasis> apply to the experimental
WDDM Direct3D video driver available
for Vista and Windows 7 guests, see <xref linkend="KnownIssues" /> for
details.<footnote><para>The experimental WDDM driver was added with
VirtualBox 4.1.</para></footnote></para>
</note>
<para>If you prefer to mount the additions manually, you can perform
the following steps:</para>
<orderedlist>
<listitem>
<para>Start the virtual machine in which you have installed
Windows.</para>
</listitem>
<listitem>
brings up the Virtual Media Manager described in <xref
linkend="vdis" />.</para>
</listitem>
<listitem>
<para>In the Virtual Media Manager, press the "Add" button and
browse your host file system for the
file:<itemizedlist>
<listitem>
<para>On a Windows host, you can find this file in the
VirtualBox installation directory (usually under
<computeroutput>C:\Program
files\Oracle\VirtualBox</computeroutput> ).</para>
</listitem>
<listitem>
<para>On Mac OS X hosts, you can find this file in the
application bundle of VirtualBox. (Right click on the
VirtualBox icon in Finder and choose <emphasis>Show Package
Contents</emphasis>. There it is located in the
folder.)</para>
</listitem>
<listitem>
<para>On a Linux host, you can find this file in the
<computeroutput>additions</computeroutput> folder under
where you installed VirtualBox (normally
</listitem>
<listitem>
<para>On Solaris hosts, you can find this file in the
<computeroutput>additions</computeroutput> folder under
where you installed VirtualBox (normally
</listitem>
</itemizedlist></para>
</listitem>
<listitem>
<para>Back in the Virtual Media Manager, select that ISO file and
press the "Select" button. This will mount the ISO file and
present it to your Windows guest as a CD-ROM.</para>
</listitem>
</orderedlist>
<para>Unless you have the Autostart feature disabled in your Windows
guest, Windows will now autostart the VirtualBox Guest Additions
installation program from the Additions ISO. If the Autostart feature
has been turned off, choose
<para>The installer will add several device drivers to the Windows
driver database and then invoke the hardware detection wizard.</para>
<para>Depending on your configuration, it might display warnings that
the drivers are not digitally signed. You must confirm these in order
to continue the installation and properly install the
Additions.</para>
<para>After installation, reboot your guest operating system to
activate the Additions.</para>
</sect3>
<sect3>
<title>Updating the Windows Guest Additions</title>
<para>Windows Guest Additions can be updated by running the
installation program again, as previously described. This will then
replace the previous Additions drivers with updated versions.</para>
<para>Alternatively, you may also open the Windows Device Manager and
select "Update driver..." for two devices:</para>
<orderedlist>
<listitem>
<para>the VirtualBox Graphics Adapter and</para>
</listitem>
<listitem>
<para>the VirtualBox System Device.</para>
</listitem>
</orderedlist>
<para>For each, choose to provide your own driver and use "Have Disk"
to point the wizard to the CD-ROM drive with the Guest
Additions.</para>
</sect3>
<sect3>
<title>Unattended Installation</title>
<para>As a prerequiste for performing an unattended installation of the
VirtualBox Guest Additions on a Windows guest, there need to be
Oracle CA (Certificate Authority)
certificates installed in order to prevent user intervention popus which
will undermine a silent installation.</para>
<note>On some Windows versions like Windows 2000 and Windows XP the user intervention
popups mentioned above always will be displayed, even after importing the Oracle certificates.</note>
<para>Since VirtualBox 4.2 installing those CA certificates on a Windows
guest can be done in an automated fashion using the
Additions installation CD in the <computeroutput>cert</computeroutput>
folder:</para>
<itemizedlist>
<listitem>
<para>Log in as Administrator on the guest.</para>
</listitem>
<listitem>
<para>Mount the VirtualBox Guest Additions .ISO.</para>
</listitem>
<listitem>
<para>Open a command line window on the guest and change to
the <computeroutput>cert</computeroutput> folder on the VirtualBox
Guest Additions CD.</para>
</listitem>
<listitem>
<para>Do<screen>VBoxCertUtil add-trusted-publisher oracle-vbox.cer --root oracle-vbox.cer</screen></para>
<para>This will install the certificates to the certificate store. When installing the same certificate
more than once, an appropriate error will be displayed.</para>
</listitem>
</itemizedlist>
<para>Prior to VirtualBox 4.2 the Oracle CA certificates need to be imported in more manual style
Vista. For Windows versions before Vista you need to download and install <computeroutput>certutil.exe</computeroutput>
manually. Since the certificates are not accompanied on the VirtualBox Guest Additions CD-ROM
prior to 4.2, these need to get extracted from a signed VirtualBox executable first.</para>
<para>In the following example the needed certificates will be extracted from the VirtualBox
Windows Guest Additions installer on the CD-ROM:</para>
<sect4>
<title>VeriSign Code Signing CA</title>
<itemizedlist>
<listitem>
<para>In the Windows Explorer, right click on VBoxWindowsAdditions-<Architecture>.exe,
click on "Properties"</para>
</listitem>
<listitem>
<para>Go to tab "Digital Signatures", choose "Oracle Corporation" and click on "Details"</para>
</listitem>
<listitem>
<para>In tab "General" click on "View Certificate"</para>
</listitem>
<listitem>
<para>In tab "Certification Path" select "VeriSign Class 3 Public Primary CA"</para>
</listitem>
<listitem>
<para>Click on "View Certificate"</para>
</listitem>
<listitem>
<para>In tab "Details" click on "Copy to File ..."</para>
</listitem>
<listitem>
<para>In the upcoming wizard choose "DER encoded binary X.509 (.CER)"
and save the certificate file to a local path, finish the wizard</para>
</listitem>
<listitem>
<para>Close certificate dialog for "Verisign Class 3 Code Signing
2010 CA"</para>
</listitem>
</itemizedlist>
</sect4>
<sect4>
<title>Oracle Corporation</title>
<itemizedlist>
<listitem>
<para>In the Windows Explorer, right click on VBoxWindowsAdditions-<Architecture>.exe,
click on "Properties"</para>
</listitem>
<listitem>
<para>Go to tab "Digital Signatures", choose "Oracle Corporation" and click on "Details"</para>
</listitem>
<listitem>
<para>In tab "General" click on "View Certificate"</para>
</listitem>
<listitem>
<para>In tab "Details" click on "Copy to File ..."</para>
</listitem>
<listitem>
<para>In the upcoming wizard choose "DER encoded binary X.509 (.CER)"
and save the certificate file to a local path, finish the wizard</para>
</listitem>
<listitem>
<para>Close certificate dialog for "Oracle Corporation"</para>
</listitem>
</itemizedlist>
</sect4>
<para>After exporting the two certificates above they can be imported into the
utility:</para>
<para><computeroutput>certutil -addstore -f Root "<Path to exported
certificate file>"</computeroutput></para>
<para>In order to allow for completely unattended guest installations,
you can specify a command line parameter to the install
launcher:</para>
<para>This automatically installs the right files and drivers for the
corresponding platform (32- or 64-bit).</para>
<note><para>By default on an unattended installation on a Windows 7 or 8
guest, there will be the XPDM graphics driver installed. This graphics
driver does not support Windows Aero / Direct3D on the guest - instead the
experimental WDDM graphics driver needs to be installed. To select this
driver by default, add the command line parameter
<computeroutput>/with_wddm</computeroutput> when invoking the Windows
Guest Additions installer.</para></note>
<note><para>For Windows Aero to run correctly on a guest, the guest's
VRAM size needs to be configured to at least 128 MB.</para></note>
<para>For more options regarding unattended guest installations,
consult the command line help by using the command:</para>
</sect3>
<sect3 id="windows-guest-file-extraction">
<title>Manual file extraction</title>
<para>If you would like to install the files and drivers manually, you
can extract the files from the Windows Guest Additions setup by
typing:</para>
<para>To explicitly extract the Windows Guest Additions for another
platform than the current running one (e.g. 64-bit files on a 32-bit
system), you have to execute the appropriate platform installer
the <computeroutput>/extract</computeroutput> parameter.</para>
</sect3>
</sect2>
<sect2>
<title>Guest Additions for Linux</title>
<para>Like the Windows Guest Additions, the VirtualBox Guest Additions
for Linux are a set of device drivers and system applications which may
be installed in the guest operating system.</para>
<para>The following Linux distributions are officially supported:</para>
<itemizedlist>
<listitem>
<para>Oracle Linux as of version 5 including UEK kernels;</para>
</listitem>
<listitem>
<para>Fedora as of Fedora Core 4;</para>
</listitem>
<listitem>
<para>Redhat Enterprise Linux as of version 3;</para>
</listitem>
<listitem>
<para>SUSE and openSUSE Linux as of version 9;</para>
</listitem>
<listitem>
<para>Ubuntu as of version 5.10.</para>
</listitem>
</itemizedlist>
<para>Many other distributions are known to work with the Guest
Additions.</para>
<para>The version of the Linux kernel supplied by default in SUSE and
openSUSE 10.2, Ubuntu 6.10 (all versions) and Ubuntu 6.06 (server
edition) contains a bug which can cause it to crash during startup when
it is run in a virtual machine. The Guest Additions work in those
distributions.</para>
<para>Note that some Linux distributions already come with all or part of
the VirtualBox Guest Additions. You may choose to keep the distribution's
version of the Guest Additions but these are often not up to date and
limited in functionality, so we recommend replacing them with the
Guest Additions that come with VirtualBox. The VirtualBox Linux Guest
Additions installer tries to detect existing installation and replace
them but depending on how the distribution integrates the Guest
Additions, this may require some manual interaction. It is highly
recommended to take a snapshot of the virtual machine before replacing
pre-installed Guest Additions.</para>
<sect3>
<title>Installing the Linux Guest Additions</title>
<para>The VirtualBox Guest Additions for Linux are provided on the
same virtual CD-ROM file as the Guest Additions for Windows described
above. They also come with an installation program guiding you through
the setup process, although, due to the significant differences between
Linux distributions, installation may be slightly more complex.</para>
<para>Installation generally involves the following steps:</para>
<orderedlist>
<listitem>
<para>Before installing the Guest Additions, you will have to
prepare your guest system for building external kernel modules.
This works similarly as described in <xref
linkend="externalkernelmodules" />, except that this step must now
be performed in your Linux <emphasis>guest</emphasis> instead of
on a Linux host system, as described there.</para>
<para>Again, as with Linux hosts, we recommend using DKMS if it is
available for the guest system. If it is not installed, use this
<screen>sudo apt-get install dkms</screen>
or for Fedora systems: <screen>yum install dkms</screen></para>
<para>Be sure to install DKMS <emphasis>before</emphasis>
installing the Linux Guest Additions. If DKMS is not available
or not installed, the guest kernel modules will need to be
recreated manually whenever the guest kernel is updated using
</para>
</listitem>
<listitem>
<para>Insert the
into your Linux guest's virtual CD-ROM drive, exactly the same way
as described for a Windows guest in <xref
linkend="mountingadditionsiso" />.</para>
</listitem>
<listitem>
<para>Change to the directory where your CD-ROM drive is mounted
and execute as root:</para>
</listitem>
</orderedlist>
<para>For your convenience, we provide the following step-by-step
instructions for freshly installed copies of recent versions of the most
popular Linux distributions. After these preparational steps, you can
execute the VirtualBox Guest Additions installer as described
above.</para>
<sect4>
<title>Ubuntu</title>
<para><orderedlist>
<listitem>
<para>In order to fully update your guest system, open a
terminal and run <screen>apt-get update</screen> as root
followed by <screen>apt-get upgrade</screen></para>
</listitem>
<listitem>
<para>Install DKMS using <screen>apt-get install dkms</screen></para>
</listitem>
<listitem>
<para>Reboot your guest system in order to activate the
updates and then proceed as described above.</para>
</listitem>
</orderedlist></para>
</sect4>
<sect4>
<title>Fedora</title>
<para><orderedlist>
<listitem>
<para>In order to fully update your guest system, open a
terminal and run <screen>yum update</screen></para> as root.
</listitem>
<listitem>
<para>Install DKMS and the GNU C compiler using <screen>yum install dkms</screen>
followed by <screen>yum install gcc</screen></para>
</listitem>
<listitem>
<para>Reboot your guest system in order to activate the
updates and then proceed as described above.</para>
</listitem>
</orderedlist></para>
</sect4>
<sect4>
<title>openSUSE</title>
<para><orderedlist>
<listitem>
<para>In order to fully update your guest system, open a
terminal and run <screen>zypper update</screen></para> as root.
</listitem>
<listitem>
<para>Install the make tool and the GNU C compiler using
<screen>zypper install make gcc</screen></para>
</listitem>
<listitem>
<para>Reboot your guest system in order to activate the
updates.</para>
</listitem>
<listitem>
<para>Find out which kernel you are running using <screen>uname -a</screen>
An example would be
<computeroutput>2.6.31.12-0.2-default</computeroutput> which
refers to the "default" kernel. Then install the correct
kernel development package. In the above example this would be
<screen>zypper install kernel-default-devel</screen></para>
</listitem>
<listitem>
<para>Make sure that your running kernel
(<computeroutput>uname -a</computeroutput>) and the kernel
packages you have installed (<computeroutput>rpm -qa
kernel\*</computeroutput>) have the exact same version number.
Proceed with the installation as described above.</para>
</listitem>
</orderedlist></para>
</sect4>
<sect4>
<title>SuSE Linux Enterprise Desktop (SLED)</title>
<para><orderedlist>
<listitem>
<para>In order to fully update your guest system, open a
terminal and run <screen>zypper update</screen></para> as root.
</listitem>
<listitem>
<para>Install the GNU C compiler using <screen>zypper install gcc</screen></para>
</listitem>
<listitem>
<para>Reboot your guest system in order to activate the
updates.</para>
</listitem>
<listitem>
<para>Find out which kernel you are running using <screen>uname -a</screen>
An example would be
<computeroutput>2.6.27.19-5.1-default</computeroutput> which
refers to the "default" kernel. Then install the correct
kernel development package. In the above example this would be
<screen>zypper install kernel-syms kernel-source</screen></para>
</listitem>
<listitem>
<para>Make sure that your running kernel
(<computeroutput>uname -a</computeroutput>) and the kernel
packages you have installed (<computeroutput>rpm -qa
kernel\*</computeroutput>) have the exact same version number.
Proceed with the installation as described above.</para>
</listitem>
</orderedlist></para>
</sect4>
<sect4>
<title>Mandrake</title>
<para><orderedlist>
<listitem>
<para>Mandrake ships with the VirtualBox Guest Additions which
will be replaced if you follow these steps.</para>
</listitem>
<listitem>
<para>In order to fully update your guest system, open a
terminal and run <screen>urpmi --auto-update</screen></para>
as root.
</listitem>
<listitem>
<para>Reboot your system in order to activate the
updates.</para>
</listitem>
<listitem>
<para>Install DKMS using <screen>urpmi dkms</screen> and make
sure to choose the correct kernel-devel package when asked by
the installer (use <computeroutput>uname -a</computeroutput>
to compare).</para>
</listitem>
</orderedlist></para>
</sect4>
<sect4>
<title>Oracle Linux, Red Hat Enterprise Linux and CentOS</title>
<para><orderedlist>
<listitem>
<para>For versions prior to 6, add <computeroutput>divider=10</computeroutput>
to the kernel boot options in
idle CPU load.</para>
</listitem>
<listitem>
<para>In order to fully update your guest system, open a
terminal and run <screen>yum update</screen></para> as root.
</listitem>
<listitem>
<para>Install the GNU C compiler and the kernel development
packages using <screen>yum install gcc</screen> followed by
<screen>yum install kernel-devel</screen> For Oracle UEK
kernels, use <screen>yum install kernel-uek-devel</screen>
to install the UEK kernel headers.</para>
</listitem>
<listitem>
<para>Reboot your guest system in order to activate the
updates and then proceed as described above.</para>
</listitem>
<listitem>
<para>In case Oracle Linux does not find the
required packages, you either have to install them from a
different source (e.g. DVD) or use Oracle's public Yum server
located at <ulink
</listitem>
</orderedlist></para>
</sect4>
<sect4>
<title>Debian</title>
<para><orderedlist>
<listitem>
<para>In order to fully update your guest system, open a
terminal and run <screen>apt-get update</screen> as root
followed by <screen>apt-get upgrade</screen></para>
</listitem>
<listitem>
<para>Install the make tool and the GNU C compiler using
<screen>apt-get install make gcc</screen></para>
</listitem>
<listitem>
<para>Reboot your guest system in order to activate the
updates.</para>
</listitem>
<listitem>
<para>Determine the exact version of your kernel using
<computeroutput>uname -a</computeroutput> and install the
correct version of the linux-headers package, e.g. using
<screen>apt-get install linux-headers-2.6.26-2-686</screen></para>
</listitem>
</orderedlist></para>
</sect4>
</sect3>
<sect3>
<title>Graphics and mouse integration</title>
<para>In Linux and Solaris guests, VirtualBox graphics and mouse
integration goes through the X Window System. VirtualBox can use
the X.Org variant of the system (or XFree86 version 4.3 which is
identical to the first X.Org release). During the installation process,
the X.Org display server will be set up to use the graphics and mouse
drivers which come with the Guest Additions.</para>
<para>After installing the Guest Additions into a fresh installation of
a supported Linux distribution or Solaris system (many unsupported
systems will work correctly too), the guest's graphics
mode will change to fit the size of the VirtualBox window
on the host when it is resized. You can also ask the guest system to
switch to a particular resolution by sending a "video mode hint" using
the <computeroutput>VBoxManage</computeroutput> tool.</para>
<para>Multiple guest monitors are supported in guests using the X.Org
server version 1.3 (which is part of release 7.3 of the X Window System
version 11) or a later version. The layout of the guest screens can
be adjusted as needed using the tools which come with the guest
operating system.</para>
<para>If you want to understand more about the details of how the
X.Org drivers are set up (in particular if you wish to use them in a
setting which our installer doesn't handle correctly), you should read
<xref linkend="guestxorgsetup" />.</para>
</sect3>
<sect3>
<title>Updating the Linux Guest Additions</title>
<para>The Guest Additions can simply be updated by going through the
installation procedure again with an updated CD-ROM image. This will
replace the drivers with updated versions. You should reboot after
updating the Guest Additions.</para>
</sect3>
<sect3>
<title>Uninstalling the Linux Guest Additions</title>
<para>If you have a version of the Guest Additions installed on your
virtual machine and wish to remove it without installing new ones, you
can do so by inserting the Guest Additions CD image into the virtual
CD-ROM drive as described above and running the installer for the
current Guest Additions with the "uninstall" parameter from the path
that the CD image is mounted on in the guest: <screen>sh /VBoxLinuxAdditions.run uninstall</screen></para>
<para>While this will normally work without issues, you may need to do some
manual cleanup of the guest (particularly of the XFree86Config or
xorg.conf file) in some cases, particularly if the Additions version
installed or the guest operating system were very old, or if you made
your own changes to the Guest Additions setup after you installed
them.</para>
<para>Starting with version 3.1.0, you can uninstall the Additions by
replace
with the correct Guest Additions installation directory.</para>
</sect3>
</sect2>
<sect2>
<title>Guest Additions for Solaris</title>
<para>Like the Windows Guest Additions, the VirtualBox Guest Additions
for Solaris take the form of a set of device drivers and system
applications which may be installed in the guest operating
system.</para>
<para>The following Solaris distributions are officially
supported:</para>
<itemizedlist>
<listitem>
<para>Solaris 11 including Solaris 11 Express;</para>
</listitem>
<listitem>
<para>Solaris 10 (u5 and higher);</para>
</listitem>
</itemizedlist>
<para>Other distributions may work if they are based on comparable
software releases.</para>
<sect3>
<title>Installing the Solaris Guest Additions</title>
<para>The VirtualBox Guest Additions for Solaris are provided on the
same ISO CD-ROM as the Additions for Windows and Linux described
above. They also come with an installation program guiding you through
the setup process.</para>
<para>Installation involves the following steps:</para>
<orderedlist>
<listitem>
<para>Mount the
your Solaris guest's virtual CD-ROM drive, exactly the same way as
described for a Windows guest in <xref
linkend="mountingadditionsiso" />.</para>
<para>If in case the CD-ROM drive on the guest doesn't get mounted
(observed on some versions of Solaris 10), execute as root:</para>
<screen>svcadm restart volfs</screen>
</listitem>
<listitem>
<para>Change to the directory where your CD-ROM drive is mounted
and execute as root:</para>
</listitem>
<listitem>
<para>Choose "1" and confirm installation of the Guest Additions
package. After the installation is complete, re-login to X server
on your guest to activate the X11 Guest Additions.</para>
</listitem>
</orderedlist>
</sect3>
<sect3>
<title>Uninstalling the Solaris Guest Additions</title>
<para>The Solaris Guest Additions can be safely removed by removing
the package from the guest. Open a root terminal session and
execute:</para>
<para><screen>pkgrm SUNWvboxguest</screen></para>
</sect3>
<sect3>
<title>Updating the Solaris Guest Additions</title>
<para>The Guest Additions should be updated by first uninstalling the
existing Guest Additions and then installing the new ones. Attempting
to install new Guest Additions without removing the existing ones is
not possible.</para>
</sect3>
</sect2>
<sect2>
<title>Guest Additions for OS/2</title>
<para>VirtualBox also ships with a set of drivers that improve running
OS/2 in a virtual machine. Due to restrictions of OS/2 itself, this
variant of the Guest Additions has a limited feature set; see <xref
linkend="KnownIssues" /> for details.</para>
<para>The OS/2 Guest Additions are provided on the same ISO CD-ROM as
those for the other platforms. As a result, mount the ISO in OS/2 as
described previously. The OS/2 Guest Additions are located in the
directory <computeroutput>\32bit\OS2</computeroutput>.</para>
<para>As we do not provide an automatic installer at this time, please
directory, which describes how to install the OS/2 Guest Additions
manually.</para>
</sect2>
</sect1>
<sect1 id="sharedfolders">
<title>Shared folders</title>
<para>With the "shared folders" feature of VirtualBox, you can access
files of your host system from within the guest system. This is similar
how you would use network shares in Windows networks -- except that shared
folders do not need require networking, only the Guest Additions. Shared
Folders are supported with Windows (2000 or newer), Linux and Solaris
guests.</para>
<para>Shared folders must physically reside on the
<emphasis>host</emphasis> and are then shared with the guest, which uses a
special file system driver in the Guest Addition to talk to the host. For
Windows guests, shared folders are implemented as a pseudo-network
redirector; for Linux and Solaris guests, the Guest Additions provide a
virtual file system.</para>
<para>To share a host folder with a virtual machine in VirtualBox, you
must specify the path of that folder and choose for it a "share name" that
the guest can use to access it. Hence, first create the shared folder on
the host; then, within the guest, connect to it.</para>
<para>There are several ways in which shared folders can be set up for a
particular virtual machine:<itemizedlist>
<listitem>
<para>In the window of a running VM, you can select "Shared folders"
from the "Devices" menu, or click on the folder icon on the status
bar in the bottom right corner.</para>
</listitem>
<listitem>
<para>If a VM is not currently running, you can configure shared
folders in each virtual machine's "Settings" dialog.</para>
</listitem>
<listitem>
<para>From the command line, you can create shared folders using
VBoxManage, as follows: <screen>VBoxManage sharedfolder add "VM name" --name "sharename" --hostpath "C:\test"</screen></para>
<para>See <xref linkend="vboxmanage-sharedfolder" /> for
details.</para>
</listitem>
</itemizedlist></para>
<para>There are two types of shares:</para>
<orderedlist>
<listitem>
<para>VM shares which are only available to the VM for which they have
been defined;</para>
</listitem>
<listitem>
<para>transient VM shares, which can be added and removed at runtime
and do not persist after a VM has stopped; for these, add the
<computeroutput>--transient</computeroutput> option to the above
command line.</para>
</listitem>
</orderedlist>
by default. To restrict the guest to have read-only access, create a
read-only shared folder. This can either be achieved using the GUI or by
appending the parameter <computeroutput>--readonly</computeroutput> when
creating the shared folder with VBoxManage.</para>
<para>Starting with version 4.0, VirtualBox shared folders also support
symbolic links (<emphasis role="bold">symlinks</emphasis>), under the
following conditions:<orderedlist>
<listitem>
<para>The host operating system must support symlinks (i.e. a Mac,
Linux or Solaris host is required).</para>
</listitem>
<listitem>
<para>Currently only Linux and Solaris Guest Additions support
symlinks.</para>
</listitem>
<listitem>
<para>For security reasons the guest OS is not allowed to create
symlinks by default. If you trust the guest OS to not abuse the
functionality, you can enable creation of symlinks for "sharename"
with:
<screen>VBoxManage setextradata "VM name" VBoxInternal2/SharedFoldersEnableSymlinksCreate/sharename 1</screen></para>
</listitem>
</orderedlist></para>
<sect2 id="sf_mount_manual">
<title>Manual mounting</title>
<para>You can mount the shared folder from inside a VM the same way as
you would mount an ordinary network share:</para>
<para><itemizedlist>
<listitem>
<para>In a Windows guest, shared folders are browseable and
therefore visible in Windows Explorer. So, to attach the host's
shared folder to your Windows guest, open Windows Explorer and
look for it under "My Networking Places" -> "Entire Network"
-> "VirtualBox Shared Folders". By right-clicking on a shared
folder and selecting "Map network drive" from the menu that pops
up, you can assign a drive letter to that shared folder.</para>
<para>Alternatively, on the Windows command line, use the
following:</para>
<screen>net use x: \\vboxsvr\sharename</screen>
<para>While <computeroutput>vboxsvr</computeroutput> is a fixed
name (note that <computeroutput>vboxsrv</computeroutput> would
also work), replace "x:" with the drive letter that you want to
use for the share, and <computeroutput>sharename</computeroutput>
with the share name specified with
<computeroutput>VBoxManage</computeroutput>.</para>
</listitem>
<listitem>
<para>In a Linux guest, use the following command:</para>
<screen>mount -t vboxsf [-o OPTIONS] sharename mountpoint</screen>
<para>To mount a shared folder during boot, add the following
<screen>sharename mountpoint vboxsf defaults 0 0</screen>
</listitem>
<listitem>
<para>In a Solaris guest, use the following command:</para>
<screen>mount -F vboxfs [-o OPTIONS] sharename mountpoint</screen>
<para>Replace <computeroutput>sharename</computeroutput> (use
lowercase) with the share name specified with
<computeroutput>VBoxManage</computeroutput> or the GUI, and
<computeroutput>mountpoint</computeroutput> with the path where
you want the share to be mounted on the guest (e.g.
rules apply, that is, create this directory first if it does not
exist yet.</para>
<para>Here is an example of mounting the shared folder for the
user "jack" on Solaris:</para>
<screen>$ id
uid=5000(jack) gid=1(other)
$ cd ~/mount
$ ls
$</screen>
<para>Beyond the standard options supplied by the
<computeroutput>mount</computeroutput> command, the following are
available:</para>
<screen>iocharset CHARSET</screen>
<para>to set the character set used for I/O operations. Note that
on Linux guests, if the "iocharset" option is not specified then
the Guest Additions driver will attempt to use the character set
specified by the CONFIG_NLS_DEFAULT kernel option. If this option
is not set either then UTF-8 will be used. Also,</para>
<screen>convertcp CHARSET</screen>
<para>is available in order to specify the character set used for
the shared folder name (utf8 by default).</para>
<para>The generic mount options (documented in the mount manual
page) apply also. Especially useful are the options
<computeroutput>uid</computeroutput>,
<computeroutput>gid</computeroutput> and
<computeroutput>mode</computeroutput>, as they allow access by
if root has mounted the filesystem.</para>
</listitem>
</itemizedlist></para>
</sect2>
<sect2 id="sf_mount_auto">
<title>Automatic mounting</title>
<para>Starting with version 4.0, VirtualBox can mount shared folders
automatically, at your option. If automatic mounting is enabled for a
specific shared folder, the Guest Additions will automatically mount
that folder as soon as a user logs into the guest OS. The details depend
on the guest OS type:<itemizedlist>
<listitem>
<para>With <emphasis role="bold">Windows guests,</emphasis> any
auto-mounted shared folder will receive its own drive letter (e.g.
<computeroutput>E:</computeroutput>) depending on the free drive
letters remaining in the guest.</para>
<para>If there no free drive letters left, auto-mounting will
fail; as a result, the number of auto-mounted shared folders is
typically limited to 22 or less with Windows guests.</para>
</listitem>
<listitem>
<para>With <emphasis role="bold">Linux guests,</emphasis>
auto-mounted shared folders are mounted into the
<computeroutput>/media</computeroutput> directory, along with the
prefix <computeroutput>sf_</computeroutput>. For example, the
shared folder <computeroutput>myfiles</computeroutput> would be
Solaris.</para>
<para>The guest property
determines the prefix that is used. Change that guest property to
a value other than "sf" to change that prefix; see <xref
linkend="guestadd-guestprops" /> for details.<note>
<para>Access to auto-mounted shared folders is only
granted to the user group
<computeroutput>vboxsf</computeroutput>, which is created by
the VirtualBox Guest Additions installer. Hence guest users
access or to have read-only access in case the folder is not
mapped writable.</para>
</note></para>
<para>To change the mount directory to something other than
<computeroutput>/media</computeroutput>, you can set the guest
property
</listitem>
<listitem>
<para><emphasis role="bold">Solaris guests</emphasis> behave like
Linux guests except that <computeroutput>/mnt</computeroutput> is
used as the default mount directory instead of
<computeroutput>/media</computeroutput>.</para>
</listitem>
</itemizedlist></para>
<para>To have any changes to auto-mounted shared folders applied while a
VM is running, the guest OS needs to be rebooted. (This applies only to
auto-mounted shared folders, not the ones which are mounted
manually.)</para>
</sect2>
</sect1>
<sect1 id="guestadd-dnd">
<title>Drag'n Drop</title>
<para>Starting with version 5.0, VirtualBox supports to drag'n drop content
from the host to the guest and vice versa. For this to work the latest Guest
Additions must be installed on the guest.</para>
<para>Drag'n drop transparently allows copying or opening files, directories
and even certain clipboard formats from one end to the other, e.g. from the
host to the guest or from the guest to the host. One then can perform drag'n
drop operations between the host and a VM as it would be a native drag'n drop
operation on the host OS.</para>
<para>At the moment drag'n drop is implemented for Windows- and X-Windows-based
systems, both, on host and guest side. As X-Windows sports different drag'n drop
protocols only the most used one, XDND, is supported for now. Applications using
other protocols (such as Motif or OffiX) will not be recognized by VirtualBox.</para>
<para>In context of using drag'n drop the origin of the data is called
<emphasis role="bold">source</emphasis>, that is, where the actual data comes
from and is specified. On the other hand there is the
<emphasis role="bold">target</emphasis>, which specifies where the data from
the source should go to. Transferring data from the source to the target can
the moment only copying of data is supported. Moving or linking is not yet
implemented.</para></footnote></para>
<para>When transferring data from the host to the guest OS, the host in this
case is the source, whereas the guest OS is the target. However, when doing
it the other way around, that is, transferring data from the guest OS to the
host, the guest OS this time became the source and the host is the target.</para>
<para>For security reasons drag'n drop can be configured at runtime
on a per-VM basis either using the "Drag'n'Drop" menu item in the "Devices" menu
of the virtual machine or VBoxManage: The following four modes are available:
<para><mediaobject>
<imageobject>
width="10cm" />
</imageobject>
</mediaobject></para>
<itemizedlist>
<listitem>
<para><emphasis role="bold">Disabled</emphasis> disables the drag'n drop
entirely. This is the default when creating new VMs.</para>
</listitem>
<listitem>
<para><emphasis role="bold">Host To Guest</emphasis> enables performing
drag'n drop operations from the host to the guest only.</para>
</listitem>
<listitem>
<para><emphasis role="bold">Guest To Host</emphasis> enables performing
drag'n drop operations from the guest to the host only.</para>
</listitem>
<listitem>
<para><emphasis role="bold">Bidirectional</emphasis> enables performing
drag'n drop operations to both directions, e.g. from the host to the guest
and vice versa.</para>
</listitem>
</itemizedlist></para>
<note><para>Drag'n drop support depends on the frontend being used; at the
moment only the VirtualBox Manager frontend provides this
functionality.</para></note>
<para>To use VBoxManage for controlling the current drag'n drop mode, see <xref
linkend="vboxmanage" />. The commands <computeroutput>modifyvm</computeroutput>
and <computeroutput>controlvm</computeroutput> allow setting the VM's current
drag'n drop mode via command line.</para>
<sect2 id="guestadd-dnd-formats">
<title>Supported formats</title>
<para>As VirtualBox can run on a variety of host OSes and also supports a wide
range of guests, certain data formats must be translated after those
got transfered over so that the target OS (that is, the side which receiving the
data) is able to handle them in an appropriate manner.</para>
when transferring a file from a Linux guest to a Windows host the Linux-specific
line endings won't be converted to Windows ones.</para></note>
<para>The following formats are handled by the VirtualBox drag'n drop service:
<itemizedlist>
<listitem>
<para><emphasis role="bold">Plain text</emphasis>, from applications such as
text editors, internet browsers and terminal windows</para>
</listitem>
<listitem>
<para><emphasis role="bold">Files</emphasis>, from file managers such
as Windows explorer, Nautilus and Finder</para>
</listitem>
<listitem>
<para><emphasis role="bold">Directories</emphasis>, where the same applies
as for files</para>
</listitem>
</itemizedlist>
</para>
</sect2>
</sect1>
<sect1 id="guestadd-video">
<title>Hardware-accelerated graphics</title>
<sect2 id="guestadd-3d">
<title>Hardware 3D acceleration (OpenGL and Direct3D 8/9)</title>
<para>The VirtualBox Guest Additions contain experimental hardware 3D
support for Windows, Linux and Solaris guests.<footnote>
<para>OpenGL support for Windows guests was added with VirtualBox
2.1; support for Linux and Solaris followed with VirtualBox 2.2.
With VirtualBox 3.0, Direct3D 8/9 support was added for Windows
guests. OpenGL 2.0 is now supported as well.
With VirtualBox 4.1 Windows Aero theme support is added for
Windows Vista and Windows 7 guests (experimental)</para>
</footnote></para>
<para>With this feature, if an application inside your virtual machine
uses 3D features through the OpenGL or Direct3D 8/9 programming
interfaces, instead of emulating them in software (which would be slow),
VirtualBox will attempt to use your host's 3D hardware. This works for
all supported host platforms (Windows, Mac, Linux, Solaris), provided
that your host operating system can make use of your accelerated 3D
hardware in the first place.</para>
<para>The 3D acceleration currently has the following
preconditions:<orderedlist>
<listitem>
<para>It is only available for certain Windows, Linux and Solaris
guests. In particular:<itemizedlist>
<listitem>
<para>3D acceleration with Windows guests requires Windows
2000, Windows XP, Vista or Windows 7. Both OpenGL and
Direct3D 8/9 (not with Windows 2000) are supported
(experimental).</para>
</listitem>
<listitem>
<para>OpenGL on Linux requires kernel 2.6.27 and higher as
well as X.org server version 1.5 and higher. Ubuntu 10.10
and Fedora 14 have been tested and confirmed as
working.</para>
</listitem>
<listitem>
<para>OpenGL on Solaris guests requires X.org server version
1.5 and higher.</para>
</listitem>
</itemizedlist></para>
</listitem>
<listitem>
<para>The Guest Additions must be installed.<note>
<para>For the basic Direct3D acceleration to work in a Windows Guest,
VirtualBox needs to replace Windows system files in the
virtual machine. As a result, the Guest Additions installation
program offers Direct3D acceleration as an option that must
be explicitly enabled. Also, you must install the Guest
Additions in "Safe Mode". This does <emphasis role="bold">not</emphasis>
apply to the experimental WDDM Direct3D video
driver available for Vista and Windows 7 guests,
see <xref linkend="KnownIssues" />
for details.</para></note>
</para>
</listitem>
<listitem>
<para>Because 3D support is still experimental at this time, it is
disabled by default and must be <emphasis role="bold">manually
enabled</emphasis> in the VM settings (see <xref
linkend="generalsettings" />).<note>
<para>
Untrusted guest systems should not be allowed to use
VirtualBox's 3D acceleration features, just as untrusted host
software should not be allowed to use 3D acceleration. Drivers
for 3D hardware are generally too complex to be made properly
secure and any software which is allowed to access them may be
able to compromise the operating system running them. In
addition, enabling 3D acceleration gives the guest direct access
to a large body of additional program code in the VirtualBox
host process which it might conceivably be able to use to crash
the virtual machine.
</para>
</note></para>
</listitem>
</orderedlist></para>
<para>With VirtualBox 4.1, Windows Aero theme support is added for
Windows Vista and Windows 7 guests. To enable Aero theme support,
the experimental VirtualBox WDDM video driver must be installed,
which is available with the Guest Additions installation.
Since the WDDM video driver is still experimental at this time, it is
not installed by default and must be <emphasis role="bold">manually
selected</emphasis> in the Guest Additions installer by answering "No"
int the "Would you like to install basic Direct3D support" dialog
displayed when the Direct3D feature is selected.
<note><para>Unlike the current basic Direct3D support, the WDDM video
driver installation does <emphasis role="bold">not</emphasis> require
the "Safe Mode".</para></note>
<para>The Aero theme is not enabled by default. To enable it<itemizedlist>
<listitem>
<para>In Windows Vista guest: right-click on the desktop, in the
context menu select "Personalize", then select "Windows Color and Appearance"
in the "Personalization" window, in the "Appearance Settings" dialog select
"Windows Aero" and press "OK"</para></listitem>
<listitem>
<para>In Windows 7 guest: right-click on the desktop, in the
context menu select "Personalize" and select any Aero theme
in the "Personalization" window</para></listitem>
</itemizedlist>
</para>
</para>
<para>Technically, VirtualBox implements this by installing an
additional hardware 3D driver inside your guest when the Guest Additions
are installed. This driver acts as a hardware 3D driver and reports to
the guest operating system that the (virtual) hardware is capable of 3D
hardware acceleration. When an application in the guest then requests
hardware acceleration through the OpenGL or Direct3D programming
interfaces, these are sent to the host through a special communication
tunnel implemented by VirtualBox, and then the <emphasis>host</emphasis>
performs the requested 3D operation via the host's programming
interfaces.</para>
</sect2>
<sect2 id="guestadd-2d">
<title>Hardware 2D video acceleration for Windows guests</title>
<para>Starting with version 3.1, the VirtualBox Guest Additions contain
experimental hardware 2D video acceleration support for Windows
guests.</para>
<para>With this feature, if an application (e.g. a video player) inside
your Windows VM uses 2D video overlays to play a movie clip, then
VirtualBox will attempt to use your host's video acceleration hardware
instead of performing overlay stretching and color conversion in
software (which would be slow). This currently works for Windows, Linux
and Mac host platforms, provided that your host operating system can
make use of 2D video acceleration in the first place.</para>
<para>The 2D video acceleration currently has the following
preconditions:<orderedlist>
<listitem>
<para>It is only available for Windows guests (XP or
later).</para>
</listitem>
<listitem>
<para>The Guest Additions must be installed.</para>
</listitem>
<listitem>
<para>Because 2D support is still experimental at this time, it is
disabled by default and must be <emphasis role="bold">manually
enabled</emphasis> in the VM settings (see <xref
linkend="generalsettings" />).</para>
</listitem>
</orderedlist></para>
<para>Technically, VirtualBox implements this by exposing video overlay
DirectDraw capabilities in the Guest Additions video driver. The driver
sends all overlay commands to the host through a special communication
tunnel implemented by VirtualBox. On the host side, OpenGL is then used
to implement color space transformation and scaling</para>
</sect2>
</sect1>
<sect1 id="seamlesswindows">
<title>Seamless windows</title>
<para>With the "seamless windows" feature of VirtualBox, you can have the
windows that are displayed within a virtual machine appear side by side
next to the windows of your host. This feature is supported for the
following guest operating systems (provided that the Guest Additions are
installed):<itemizedlist>
<listitem>
<para>Windows guests (support added with VirtualBox 1.5);</para>
</listitem>
<listitem>
<para>Supported Linux or Solaris guests running the X Window System
(added with VirtualBox 1.6).</para>
</listitem>
</itemizedlist></para>
<para>After seamless windows are enabled (see below), VirtualBox
suppresses the display of the Desktop background of your guest, allowing
you to run the windows of your guest operating system seamlessly next to
the windows of your host:</para>
<para><mediaobject>
<imageobject>
</imageobject>
</mediaobject>To enable seamless mode, after starting the virtual
machine, press the Host key (normally the right control key) together with
"L". This will enlarge the size of the VM's display to the size of your
host screen and mask out the guest operating system's background. To go
back to the "normal" VM display (i.e. to disable seamless windows), press
the Host key and "L" again.</para>
</sect1>
<sect1 id="guestadd-guestprops">
<title>Guest properties</title>
<para>Starting with version 2.1, VirtualBox allows for requesting certain
properties from a running guest, provided that the VirtualBox Guest
Additions are installed and the VM is running. This is good for two
things:<orderedlist>
<listitem>
<para>A number of predefined VM characteristics are automatically
maintained by VirtualBox and can be retrieved on the host, e.g. to
monitor VM performance and statistics.</para>
</listitem>
<listitem>
<para>In addition, arbitrary string data can be exchanged between
guest and host. This works in both directions.</para>
</listitem>
</orderedlist></para>
<para>To accomplish this, VirtualBox establishes a private communication
channel between the VirtualBox Guest Additions and the host, and software
on both sides can use this channel to exchange string data for arbitrary
purposes. Guest properties are simply string keys to which a value is
attached. They can be set (written to) by either the host and the guest,
and they can also be read from both sides.</para>
<para>In addition to establishing the general mechanism of reading and
writing values, a set of predefined guest properties is automatically
maintained by the VirtualBox Guest Additions to allow for retrieving
interesting guest data such as the guest's exact operating system and
service pack level, the installed version of the Guest Additions, users
that are currently logged into the guest OS, network statistics and more.
These predefined properties are all prefixed with
<computeroutput>/VirtualBox/</computeroutput> and organized into a
hierarchical tree of keys.</para>
<para>Some of this runtime information is shown when you select "Session
Information Dialog" from a virtual machine's "Machine" menu.</para>
<para>A more flexible way to use this channel is via the
<computeroutput>VBoxManage guestproperty</computeroutput> command set; see
<xref linkend="vboxmanage-guestproperty" /> for details. For example, to
have <emphasis>all</emphasis> the available guest properties for a given
running VM listed with their respective values, use this:<screen>$ VBoxManage guestproperty enumerate "Windows Vista III"
VirtualBox Command Line Management Interface Version $VBOX_VERSION_MAJOR.$VBOX_VERSION_MINOR.$VBOX_VERSION_BUILD
(C) 2005-$VBOX_C_YEAR $VBOX_VENDOR
All rights reserved.
timestamp: 1229098278843087000, flags:
timestamp: 1229098278950553000, flags:
timestamp: 1229098279122627000, flags:
Guest Additions, timestamp: 1229098279269739000, flags:
timestamp: 1229098279345664000, flags:
Name: /VirtualBox/GuestAdd/Version, value: $VBOX_VERSION_MAJOR.$VBOX_VERSION_MINOR.$VBOX_VERSION_BUILD,
timestamp: 1229098279479515000, flags:
Name: /VirtualBox/GuestAdd/Components/VBoxControl.exe, value: $VBOX_VERSION_MAJOR.$VBOX_VERSION_MINOR.$VBOX_VERSION_BUILDr40720,
timestamp: 1229098279651731000, flags:
Name: /VirtualBox/GuestAdd/Components/VBoxHook.dll, value: $VBOX_VERSION_MAJOR.$VBOX_VERSION_MINOR.$VBOX_VERSION_BUILDr40720,
timestamp: 1229098279804835000, flags:
Name: /VirtualBox/GuestAdd/Components/VBoxDisp.dll, value: $VBOX_VERSION_MAJOR.$VBOX_VERSION_MINOR.$VBOX_VERSION_BUILDr40720,
timestamp: 1229098279880611000, flags:
Name: /VirtualBox/GuestAdd/Components/VBoxMRXNP.dll, value: $VBOX_VERSION_MAJOR.$VBOX_VERSION_MINOR.$VBOX_VERSION_BUILDr40720,
timestamp: 1229098279882618000, flags:
Name: /VirtualBox/GuestAdd/Components/VBoxService.exe, value: $VBOX_VERSION_MAJOR.$VBOX_VERSION_MINOR.$VBOX_VERSION_BUILDr40720,
timestamp: 1229098279883195000, flags:
Name: /VirtualBox/GuestAdd/Components/VBoxTray.exe, value: $VBOX_VERSION_MAJOR.$VBOX_VERSION_MINOR.$VBOX_VERSION_BUILDr40720,
timestamp: 1229098279885027000, flags:
Name: /VirtualBox/GuestAdd/Components/VBoxGuest.sys, value: $VBOX_VERSION_MAJOR.$VBOX_VERSION_MINOR.$VBOX_VERSION_BUILDr40720,
timestamp: 1229098279886838000, flags:
Name: /VirtualBox/GuestAdd/Components/VBoxMouse.sys, value: $VBOX_VERSION_MAJOR.$VBOX_VERSION_MINOR.$VBOX_VERSION_BUILDr40720,
timestamp: 1229098279890600000, flags:
Name: /VirtualBox/GuestAdd/Components/VBoxSF.sys, value: $VBOX_VERSION_MAJOR.$VBOX_VERSION_MINOR.$VBOX_VERSION_BUILDr40720,
timestamp: 1229098279893056000, flags:
Name: /VirtualBox/GuestAdd/Components/VBoxVideo.sys, value: $VBOX_VERSION_MAJOR.$VBOX_VERSION_MINOR.$VBOX_VERSION_BUILDr40720,
timestamp: 1229098279895767000, flags:
timestamp: 1229099826317660000, flags:
timestamp: 1229098455580553000, flags:
timestamp: 1229099826299785000, flags:
timestamp: 1229098151272771000, flags:
timestamp: 1229099826300088000, flags:
timestamp: 1229099826300220000, flags:
timestamp: 1229099826300350000, flags:
timestamp: 1229099826300524000, flags:
timestamp: 1229099826317386000, flags:</screen></para>
<para>To query the value of a single property, use the "get" subcommand
like this:<screen>$ VBoxManage guestproperty get "Windows Vista III" "/VirtualBox/GuestInfo/OS/Product"
VirtualBox Command Line Management Interface Version $VBOX_VERSION_MAJOR.$VBOX_VERSION_MINOR.$VBOX_VERSION_BUILD
(C) 2005-$VBOX_C_YEAR $VBOX_VENDOR
All rights reserved.
Value: Windows Vista Business Edition</screen></para>
<para>To add or change guest properties from the guest, use the tool
<computeroutput>VBoxControl</computeroutput>. This tool is included in the
Guest Additions of VirtualBox 2.2 or later. When started from a Linux
guest, this tool requires root privileges for security reasons:<screen>$ sudo VBoxControl guestproperty enumerate
VirtualBox Guest Additions Command Line Management Interface Version $VBOX_VERSION_MAJOR.$VBOX_VERSION_MINOR.$VBOX_VERSION_BUILD
(C) 2009-$VBOX_C_YEAR $VBOX_VENDOR
All rights reserved.
timestamp: 1265813265835667000, flags: <NULL>
timestamp: 1265813265836305000, flags: <NULL>
...</screen></para>
<para>For more complex needs, you can use the VirtualBox programming
interfaces; see <xref linkend="VirtualBoxAPI" />.</para>
</sect1>
<sect1 id="guestadd-guestcontrol">
<title>Guest control</title>
<para>Starting with version 3.2, the Guest Additions of VirtualBox allow
starting applications inside a VM from the host system.</para>
<para>For this to work, the application needs to be installed inside the
guest; no additional software needs to be installed on the host.
Additionally, text mode output (to stdout and stderr) can be shown on the
host for further processing along with options to specify user credentials
and a timeout value (in milliseconds) to limit time the application is
able to run.</para>
<para>This feature can be used to automate deployment of software within
the guest.</para>
<para>Starting with version 4.0, the Guest Additions for Windows allow for
automatic updating (only already installed Guest Additions 4.0 or later).
Also, copying files from host to the guest as well as remotely creating
guest directories is available.</para>
<para>To use these features, use the VirtualBox command line, see <xref
linkend="vboxmanage-guestcontrol" />.</para>
</sect1>
<sect1>
<title>Memory overcommitment</title>
<para>In server environments with many VMs; the Guest Additions can be
used to share physical host memory between several VMs, reducing the total
amount of memory in use by the VMs. If memory usage is the limiting factor
and CPU resources are still available, this can help with packing more VMs
on each host.</para>
<sect2 id="guestadd-balloon">
<title>Memory ballooning</title>
<para>Starting with version 3.2, the Guest Additions of VirtualBox can
change the amount of host memory that a VM uses while the machine is
running. Because of how this is implemented, this feature is called
"memory ballooning".</para>
<note>
<para>VirtualBox supports memory ballooning only on 64-bit hosts, and
it is not supported on Mac OS X hosts.</para>
</note>
<para>Normally, to change the amount of memory allocated to a virtual
machine, one has to shut down the virtual machine entirely and modify
its settings. With memory ballooning, memory that was allocated for a
virtual machine can be given to another virtual machine without having
to shut the machine down.</para>
<para>When memory ballooning is requested, the VirtualBox Guest
Additions (which run inside the guest) allocate physical memory from the
guest operating system on the kernel level and lock this memory down in
the guest. This ensures that the guest will not use that memory any
longer: no guest applications can allocate it, and the guest kernel will
not use it either. VirtualBox can then re-use this memory and give it to
another virtual machine.</para>
<para>The memory made available through the ballooning mechanism is only
available for re-use by VirtualBox. It is <emphasis>not</emphasis>
returned as free memory to the host. Requesting balloon memory from a
running guest will therefore not increase the amount of free,
unallocated memory on the host. Effectively, memory ballooning is
therefore a memory overcommitment mechanism for multiple virtual
machines while they are running. This can be useful to temporarily start
another machine, or in more complicated environments, for sophisticated
memory management of many virtual machines that may be running in
parallel depending on how memory is used by the guests.</para>
<para>At this time, memory ballooning is only supported through
VBoxManage. Use the following command to increase or decrease the size
of the memory balloon within a running virtual machine that has Guest
Additions installed: <screen>VBoxManage controlvm "VM name" guestmemoryballoon <n></screen>where
<computeroutput>"VM name"</computeroutput> is the name or UUID of the
virtual machine in question and
<computeroutput><n></computeroutput> is the amount of memory to
allocate from the guest in megabytes. See <xref
linkend="vboxmanage-controlvm" /> for more information.</para>
<para>You can also set a default balloon that will automatically be
requested from the VM every time after it has started up with the
following command: <screen>VBoxManage modifyvm "VM name" --guestmemoryballoon <n></screen></para>
<para>By default, no balloon memory is allocated. This is a VM setting,
like other <computeroutput>modifyvm</computeroutput> settings, and
therefore can only be set while the machine is shut down; see <xref
linkend="vboxmanage-modifyvm" />.</para>
</sect2>
<sect2 id="guestadd-pagefusion">
<title>Page Fusion</title>
<para>Whereas memory ballooning simply reduces the amount of RAM that is
available to a VM, Page Fusion works differently: it avoids memory
duplication between several similar running VMs.</para>
<para>In a server environment running several similar VMs (e.g. with
identical operating systems) on the same host, lots of memory pages are
identical. VirtualBox's Page Fusion technology, introduced with
VirtualBox 3.2, is a novel technique to efficiently identify these
identical memory pages and share them between multiple VMs.<note>
<para>VirtualBox supports Page Fusion only on 64-bit hosts, and it
is not supported on Mac OS X hosts. Page Fusion currently works only
with Windows guests (2000 and later).</para>
</note></para>
<para>The more similar the VMs on a given host are, the more efficiently
Page Fusion can reduce the amount of host memory that is in use. It
therefore works best if all VMs on a host run identical operating
systems (e.g. Windows XP Service Pack 2). Instead of having a complete
copy of each operating system in each VM, Page Fusion identifies the
identical memory pages in use by these operating systems and eliminates
the duplicates, sharing host memory between several machines
("deduplication"). If a VM tries to modify a page that has been shared
with other VMs, a new page is allocated again for that VM with a copy of
the shared page ("copy on write"). All this is fully transparent to the
virtual machine.</para>
<para>You may be familiar with this kind of memory overcommitment from
other hypervisor products, which call this feature "page sharing" or
"same page merging". However, Page Fusion differs significantly from
those other solutions, whose approaches have several
drawbacks:<orderedlist>
<listitem>
<para>Traditional hypervisors scan <emphasis>all</emphasis> guest
memory and compute checksums (hashes) for every single memory
page. Then, they look for pages with identical hashes and compare
the entire content of those pages; if two pages produce the same
hash, it is very likely that the pages are identical in content.
This, of course, can take rather long, especially if the system is
not idling. As a result, the additional memory only becomes
available after a significant amount of time (this can be hours or
even days!). Even worse, this kind of page sharing algorithm
generally consumes significant CPU resources and increases the
virtualization overhead by 10-20%.</para>
<para>Page Fusion in VirtualBox uses logic in the VirtualBox Guest
Additions to quickly identify memory cells that are most likely
identical across VMs. It can therefore achieve most of the
possible savings of page sharing almost immediately and with
almost no overhead.</para>
</listitem>
<listitem>
<para>Page Fusion is also much less likely to be confused by
identical memory that it will eliminate just to learn seconds
later that the memory will now change and having to perform a
highly expensive and often service-disrupting reallocation.</para>
</listitem>
</orderedlist></para>
<para>At this time, Page Fusion can only be controlled with VBoxManage,
and only while a VM is shut down. To enable Page Fusion for a VM, use
the following command:<screen>VBoxManage modifyvm "VM name" --pagefusion on</screen></para>
<para>You can observe Page Fusion operation using some metrics.
of fused pages, whereas the per-VM metric
amount of fused memory for a given VM. Please refer to <xref
linkend="metrics" /> for information on how to query metrics.</para>
</sect2>
</sect1>
</chapter>