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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
      <computeroutput>gpedit.msc</computeroutput>, open the key
      <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>
      <para><emphasis role="bold">OVF import/export:</emphasis><itemizedlist>
          <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>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>
