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<chapter id="KnownIssues">
<title>Known limitations</title>
<para>This sections describes known problems with VirtualBox
$VBOX_VERSION_STRING. Unless marked otherwise, these issues are planned to
be fixed in later releases.</para>
<itemizedlist>
<listitem>
<para>The following <emphasis role="bold">Guest SMP (multiprocessor)
limitations</emphasis> exist:<itemizedlist>
<listitem>
<para><emphasis role="bold">Poor performance</emphasis> with
32-bit guests on AMD CPUs. This affects mainly Windows and Solaris
guests, but possibly also some Linux kernel revisions. Partially
solved in 3.0.6 for 32 bits Windows NT, 2000, XP and 2003 guests.
Requires 3.0.6 or higher Guest Additions to be installed.</para>
</listitem>
<listitem>
<para><emphasis role="bold">Poor performance</emphasis> with
32-bit guests on certain Intel CPU models that do not include
virtual APIC hardware optimization support. This affects mainly
Windows and Solaris guests, but possibly also some Linux kernel
revisions. Partially solved in 3.0.12 for 32 bits Windows NT,
2000, XP and 2003 guests. Requires 3.0.12 or higher Guest
Additions to be installed.</para>
</listitem>
</itemizedlist></para>
</listitem>
<listitem>
<para><emphasis role="bold">64-bit guests on some 32-bit host systems
with VT-x</emphasis> can cause instabilities to your system. If you
experience this, do not attempt to execute 64-bit guests. Refer to the
VirtualBox user forum for additional information.</para>
</listitem>
<listitem>
<para>For <emphasis role="bold">Direct3D support in Windows
guests</emphasis> to work, the Guest Additions must be installed in
Windows "safe mode". Press F8 when the Windows guest is booting and
select "Safe mode", then install the Guest Additions. Otherwise Windows'
file protection mechanism will interfere with the replacement DLLs
installed by VirtualBox and keep restoring the original Windows system
DLLs.</para>
</listitem>
<listitem>
<para><emphasis role="bold">Guest control.</emphasis> On Windows guests,
a process lauched via the guest control execute support will not be able
to display a graphical user interface <emphasis>unless</emphasis> the
user account under which it is running is currently logged in and has a
desktop session.</para>
<para>Also, to use accounts without or with an empty password, the
guest's group policy must be changed. To do so, open the group policy
editor on the command line by typing
<emphasis>Computer Configuration\Windows Settings\Security
Settings\Local Policies\Security Options</emphasis> and change the value
of <emphasis>Accounts: Limit local account use of blank passwords to
console logon only</emphasis> to <emphasis>Disabled</emphasis>.</para>
</listitem>
<listitem>
<para><emphasis role="bold">Compacting virtual disk images is limited to
VDI files.</emphasis> The <code>VBoxManage modifyhd --compact</code>
command is currently only implemented for VDI files. At the moment the
only way to optimize the size of a virtual disk images in other formats
(VMDK, VHD) is to clone the image and then use the cloned image in the
VM configuration.</para>
</listitem>
<listitem>
<listitem>
<para>OVF localization (multiple languages in one OVF file) is not
yet supported.</para>
</listitem>
<listitem>
<para>Some OVF sections like StartupSection,
DeploymentOptionSection and InstallSection are ignored.</para>
</listitem>
<listitem>
<para>OVF environment documents, including their property sections
and appliance configuration with ISO images, are not yet
supported.</para>
</listitem>
<listitem>
<para>Remote files via HTTP or other mechanisms are not yet
supported.</para>
</listitem>
</itemizedlist></para>
</listitem>
<listitem>
<para>Neither <emphasis role="bold">scale mode</emphasis> nor <emphasis
role="bold">seamless mode</emphasis> work correctly with guests using
OpenGL 3D features (such as with compiz-enabled window managers).</para>
</listitem>
<listitem>
<para>Preserving the aspect ratio in scale mode works only on Windows
hosts and on Mac OS X hosts.</para>
</listitem>
<listitem>
<para>On <emphasis role="bold">Mac OS X hosts,</emphasis> the following
features are not yet implemented: </para>
<para><itemizedlist>
<listitem>
<para>Numlock emulation</para>
</listitem>
<listitem>
<para>CPU frequency metric</para>
</listitem>
<listitem>
<para>Memory ballooning</para>
</listitem>
</itemizedlist></para>
</listitem>
<listitem>
<para><emphasis role="bold">Mac OS X Server guests:</emphasis>
<itemizedlist>
<listitem>
<para>Mac OS X Server guests can only run on a certain host
hardware. For details about license and host hardware limitations,
please see <xref linkend="intro-macosxguests" />.</para>
</listitem>
<listitem>
<para>VirtualBox does not provide Guest Additions for Mac OS X
Server at this time.</para>
</listitem>
<listitem>
<para>The graphics resolution currently defaults to 1024x768 as
Mac OS X Server falls back to the built-in EFI display support.
See <xref linkend="efividmode" /> for more information on how to
change EFI video modes.</para>
</listitem>
<listitem>
<para>Even when idle, Mac OS X Server guests currently burn 100%
CPU. This is a power management issue that will be addressed in a
future release.</para>
</listitem>
<listitem>
<para>Mac OS X Server guests only work with one CPU assigned to
the VM. Support for SMP will be provided in a future
release.</para>
</listitem>
<listitem>
<para>Depending on your system and version of Mac OS X Server, you
might experience guest hangs after some time. This can be fixed by
turning off energy saving (set timeout to "Never") in the system
preferences.</para>
</listitem>
<listitem>
<para>By default, the VirtualBox EFI enables debug output of the
Mac OS X Server kernel to help you diagnose boot problems. Note
that there is a lot of output and not all errors are fatal (they
would also show on your physical Mac). You can turn off these
messages by issuing this command:<screen>VBoxManage setextradata "VM name" "VBoxInternal2/EfiBootArgs" " "</screen>To
revert to the previous behavior, use:<screen>VBoxManage setextradata "VM name" "VBoxInternal2/EfiBootArgs" ""</screen></para>
</listitem>
</itemizedlist></para>
</listitem>
<listitem>
<para><emphasis role="bold">Solaris hosts:</emphasis> <itemizedlist>
<listitem>
<para>There is no support for USB devices connected to Solaris 10
hosts.</para>
</listitem>
<listitem>
<para>USB support on Solaris hosts requires kernel version snv_124
or higher. Webcams and other isochronous devices are known to have
poor performance.</para>
</listitem>
<listitem>
<para>No ACPI information (battery status, power source) is
reported to the guest.</para>
</listitem>
<listitem>
<para>No support for using wireless adapters with bridged
networking.</para>
</listitem>
</itemizedlist></para>
</listitem>
<listitem>
<para><emphasis role="bold">Guest Additions for OS/2.</emphasis> Shared
folders are not yet supported with OS/2 guests. In addition, seamless
windows and automatic guest resizing will probably never be implemented
due to inherent limitations of the OS/2 graphics system.</para>
</listitem>
</itemizedlist>
</chapter>