source: vbox/trunk/doc/manual/en_US/user_BasicConcepts.xml@ 75866

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<chapter id="BasicConcepts">

  <title>Configuring Virtual Machines</title>

  <para>
    Whereas <xref linkend="Introduction" /> gave you a quick
    introduction to VirtualBox and how to get your first virtual machine
    running, the following chapter describes in detail how to configure
    virtual machines.
  </para>

  <para>
    You have considerable latitude in deciding what virtual hardware
    will be provided to the guest. The virtual hardware can be used for
    communicating with the host system or with other guests. For
    instance, if you provide VirtualBox with the image of a CD-ROM in an
    ISO file, VirtualBox can present this image to a guest system as if
    it were a physical CD-ROM. Similarly, you can give a guest system
    access to the real network via its virtual network card, and, if you
    so choose, give the host system, other guests, or computers on the
    Internet access to the guest system.
  </para>

  <sect1 id="guestossupport">

    <title>Supported Guest Operating Systems</title>

    <para>
      Since VirtualBox is designed to provide a generic virtualization
      environment for x86 systems, it may run operating systems of any
      kind, even those not listed here. However, the focus is to
      optimize VirtualBox for the following guest systems:
    </para>

    <itemizedlist>

      <listitem>
        <para>
          <emphasis role="bold">Windows NT 4.0:</emphasis>
        </para>

        <para>
          All versions, editions and service packs are fully supported.
          However, there are some issues with older service packs. We
          recommend that you install service pack 6a. Guest Additions
          are available with a limited feature set.
        </para>
      </listitem>

      <listitem>
        <para>
          <emphasis role="bold">Windows 2000/XP/Server 2003/Vista/Server
          2008/7/8/8.1/10 RTM 10240/Server 2012:</emphasis>
        </para>

        <para>
          All versions, editions and service packs are fully supported,
          including 64-bit versions, under the preconditions listed
          below. Guest Additions are available. Windows 8 and later
          requires hardware virtualization to be enabled.
        </para>
      </listitem>

      <listitem>
        <para>
          <emphasis role="bold">DOS/Windows 3.x/95/98/ME:</emphasis>
        </para>

        <para>
          Limited testing has been performed. Use beyond legacy
          installation mechanisms is not recommended. Guest Additions
          are not available.
        </para>
      </listitem>

      <listitem>
        <para>
          <emphasis role="bold">Linux 2.4:</emphasis>
        </para>

        <para>
          Limited support.
        </para>
      </listitem>

      <listitem>
        <para>
          <emphasis role="bold">Linux 2.6:</emphasis>
        </para>

        <para>
          All versions and editions are fully supported, both 32-bit and
          64-bit. Guest Additions are available.
        </para>

        <para>
          We strongly recommend using a Linux kernel version of 2.6.13
          or later for best performance.
        </para>

        <note>
          <para>
            Certain Linux kernel releases have bugs that prevent them
            from executing in a virtual environment. See
            <xref
                linkend="ts_linux-buggy" />.
          </para>
        </note>
      </listitem>

      <listitem>
        <para>
          <emphasis role="bold">Linux 3.x and later:</emphasis>
        </para>

        <para>
          All versions and editions are fully supported, both 32-bit and
          64-bit. Guest Additions are available.
        </para>
      </listitem>

      <listitem>
        <para>
          <emphasis role="bold"> Solaris 10u6 and higher, Solaris 11,
          including Solaris 11 Express:</emphasis>
        </para>

        <para>
          Fully supported. 64-bit, prior to Solaris 11 11/11, and also
          32 32-bit. Guest Additions are available.
        </para>
      </listitem>

      <listitem>
        <para>
          <emphasis role="bold">FreeBSD:</emphasis>
        </para>

        <para>
          Requires hardware virtualization to be enabled. Limited
          support. Guest Additions are not available yet.
        </para>
      </listitem>

      <listitem>
        <para>
          <emphasis role="bold"> OpenBSD:</emphasis>
        </para>

        <para>
          Requires hardware virtualization to be enabled. Versions 3.7
          and later are supported. Guest Additions are not available
          yet.
        </para>
      </listitem>

      <listitem>
        <para>
          <emphasis role="bold">OS/2 Warp 4.5:</emphasis>
        </para>

        <para>
          Requires hardware virtualization to be enabled. We officially
          support MCP2 only. Other OS/2 versions may or may not work.
          Guest Additions are available with a limited feature set. See
          <xref linkend="KnownIssues" />.
        </para>
      </listitem>

      <listitem>
        <para>
          <emphasis role="bold">Mac OS X:</emphasis>
        </para>

        <para>
          VirtualBox 3.2 added experimental support for Mac OS X guests,
          but this comes with restrictions. See
          <xref linkend="intro-macosxguests"/> and also
          <xref linkend="KnownIssues" />.
        </para>
      </listitem>

    </itemizedlist>

    <sect2 id="intro-macosxguests">

      <title>Mac OS X Guests</title>

      <para>
        Starting with version 3.2, VirtualBox has experimental support
        for Mac OS X guests. This allows you to install and execute
        unmodified versions of Mac OS X on supported host hardware.
      </para>

      <para>
        Whereas competing solutions perform modifications to the Mac OS
        X install DVDs, such as a different boot loader and replaced
        files, VirtualBox is the first product to provide the modern PC
        architecture expected by OS X without requiring any "hacks".
      </para>

      <para>
        You should be aware of a number of important issues before
        attempting to install a Mac OS X guest:
      </para>

      <itemizedlist>

        <listitem>
          <para>
            Mac OS X is commercial, licensed software and contains
            <emphasis role="bold">both license and technical
            restrictions</emphasis> that limit its use to certain
            hardware and usage scenarios. It is important that you
            understand and obey these restrictions.
          </para>

          <para>
            In particular, for most versions of Mac OS X, Apple
            prohibits installing them on non-Apple hardware.
          </para>

          <para>
            These license restrictions are also enforced on a technical
            level. Mac OS X verifies whether it is running on Apple
            hardware, and most DVDs that come with Apple hardware even
            check for an exact model. These restrictions are
            <emphasis>not</emphasis> circumvented by VirtualBox and
            continue to apply.
          </para>
        </listitem>

        <listitem>
          <para>
            Only <emphasis role="bold">CPUs</emphasis> known and tested
            by Apple are supported. As a result, if your Intel CPU is
            newer than the build of Mac OS X, or if you have a non-Intel
            CPU, it will most likely panic during bootup with an
            "Unsupported CPU" exception. It is generally best to use the
            Mac OS X DVD that came with your Apple hardware.
          </para>
        </listitem>

        <listitem>
          <para>
            The Mac OS X installer expects the harddisk to be
            <emphasis role="bold">partitioned</emphasis> so when it does
            not offer a selection, you have to start the Disk Utility
            from the Tools menu and partition the hard disk. Then close
            the Disk Utility and proceed with the installation.
          </para>
        </listitem>

        <listitem>
          <para>
            In addition, as Mac OS X support in VirtualBox is currently
            still experimental, see also <xref linkend="KnownIssues" />.
          </para>
        </listitem>

      </itemizedlist>

    </sect2>

    <sect2 id="intro-64bitguests">

      <title>64-bit Guests</title>

      <para>
        VirtualBox supports 64-bit guest operating systems, even on
        32-bit host operating systems,

        <footnote>

          <para>
            64-bit guest support was added with VirtualBox 2.0; support
            for 64-bit guests on 32-bit hosts was added with VirtualBox
            2.1.
          </para>

        </footnote>

        provided that the following conditions are met:
      </para>

      <itemizedlist>

        <listitem>
          <para>
            You need a 64-bit processor with hardware virtualization
            support. See <xref linkend="hwvirt" />.
          </para>
        </listitem>

        <listitem>
          <para>
            You must enable hardware virtualization for the particular
            VM for which you want 64-bit support. Software
            virtualization is not supported for 64-bit VMs.
          </para>
        </listitem>

        <listitem>
          <para>
            If you want to use 64-bit guest support on a 32-bit host
            operating system, you must also select a 64-bit operating
            system for the particular VM. Since supporting 64 bits on
            32-bit hosts incurs additional overhead, VirtualBox only
            enables this support upon explicit request.
          </para>

          <para>
            On 64-bit hosts, which typically come with hardware
            virtualization support, 64-bit guest operating systems are
            always supported regardless of settings. So you can simply
            install a 64-bit operating system in the guest.
          </para>
        </listitem>

      </itemizedlist>

      <para>
        <warning>
          <para>
            On any host, you should enable <emphasis role="bold">I/O
            APIC</emphasis> for virtual machines that you intend to use
            in 64-bit mode. This is especially true for 64-bit Windows
            VMs. See <xref linkend="settings-general-advanced" />. In
            addition, for 64-bit Windows guests, you should make sure
            that the VM uses the <emphasis role="bold">Intel networking
            device</emphasis>, since there is no 64-bit driver support
            for the AMD PCNet card. See
            <xref
          linkend="nichardware" />.
          </para>
        </warning>
      </para>

      <para>
        If you use the <emphasis role="bold">Create VM </emphasis>
        wizard of the VirtualBox graphical user interface, see
        <xref linkend="gui-createvm" />, VirtualBox will automatically
        use the correct settings for each selected 64-bit operating
        system type.
      </para>

    </sect2>

  </sect1>

  <sect1 id="basic-unattended">

    <title>Unattended Guest Installation</title>

    <para>
      VirtualBox is able to automatically install a guest by providing
      the installation medium as well as a few parameters like the name
      of the default user.
    </para>

    <para>
      To perform an unattended guest installation, a VM has to be
      prepared. A VM can be created using the GUI as described in
      <xref
    linkend="gui-createvm" /> or by using VBoxManage as
      described in <xref linkend="vboxmanage-createvm" />. In general
      it's sufficient to chose the type of the guest operating system
      and to use the proposed defaults for that operating system. See
      the following sections on how to change the VM settings for
      certain needs.
    </para>

    <para>
      After the VM was created, the VM has to be prepared for unattended
      guest execution use VBoxManage, see
      <xref
    linkend="vboxmanage-unattended" />. During this step
      VirtualBox scans the installation medium and changes certain
      parameters for a seamless installation as a guest running on
      VirtualBox.
    </para>

    <para>
      Once the preparation phase was successfully finished, the VM can
      be started either from the GUI or from VBoxManage, see
      <xref
    linkend="vboxmanage-startvm" />. The VM will now perform
      the automatic installation. Please note that the boot order was
      changed during the preparation phase by giving the virtual hard
      disk the highest priority. As the disk is normally empty before an
      automatic installation is started, the VM will boot from the
      virtual DVD drive as next available boot medium and the
      installation will start. If, for some reason, the virtual hard
      disk contains a bootable operating system then the installation
      will not start unless the boot order was manually changed by
      pressing F12 during the BIOS splash screen.
    </para>

  </sect1>

  <sect1 id="emul-hardware">

    <title>Emulated Hardware</title>

    <para>
      VirtualBox virtualizes nearly all hardware of the host. Depending
      on a VM's configuration, the guest will see the following virtual
      hardware:
    </para>

    <itemizedlist>

      <listitem>
        <para>
          <emphasis role="bold">Input devices.</emphasis> By default,
          VirtualBox emulates a standard PS/2 keyboard and mouse. These
          devices are supported by almost all past and present operating
          systems.
        </para>

        <para>
          In addition, VirtualBox can provide virtual USB input devices
          to avoid having to capture mouse and keyboard, as described in
          <xref
          linkend="keyb_mouse_normal" />.
        </para>
      </listitem>

      <listitem>
        <para>
          <emphasis role="bold">Graphics.</emphasis> The VirtualBox
          graphics device (sometimes referred to as VGA device) is,
          unlike nearly all other emulated devices, not based on any
          physical counterpart. It is a simple, synthetic device which
          provides compatibility with standard VGA and several extended
          registers used by the VESA BIOS Extensions (VBE).
        </para>
      </listitem>

      <listitem>
        <para>
          <emphasis role="bold">Storage.</emphasis> VirtualBox currently
          emulates the standard ATA interface found on Intel PIIX3/PIIX4
          chips, the SATA (AHCI) interface, and two SCSI adapters (LSI
          Logic and BusLogic). See
          <xref linkend="harddiskcontrollers" /> for details. Whereas
          providing one of these would be enough for VirtualBox by
          itself, this multitude of storage adapters is required for
          compatibility with other hypervisors. Windows is particularly
          picky about its boot devices, and migrating VMs between
          hypervisors is very difficult or impossible if the storage
          controllers are different.
        </para>
      </listitem>

      <listitem>
        <para>
          <emphasis role="bold">Networking.</emphasis> See
          <xref
          linkend="nichardware" />.
        </para>
      </listitem>

      <listitem>
        <para>
          <emphasis role="bold">USB.</emphasis> VirtualBox emulates
          three USB host controllers: xHCI, EHCI, and OHCI. While xHCI
          handles all USB transfer speeds, only guest operating systems
          released approximately after 2011 support xHCI. Note that for
          Windows 7 guests, 3rd party drivers must be installed for xHCI
          support.
        </para>

        <para>
          Older operating systems typically support OHCI and EHCI. The
          two controllers are needed because OHCI only handles USB low-
          and full-speed devices (both USB 1.x and 2.0), while EHCI only
          handles high-speed devices (USB 2.0 only).
        </para>

        <para>
          The emulated USB controllers do not communicate directly with
          devices on the host but rather with a virtual USB layer which
          abstracts the USB protocol and allows the use of remote USB
          devices.
        </para>
      </listitem>

      <listitem>
        <para>
          <emphasis role="bold">Audio.</emphasis> See
          <xref
          linkend="settings-audio" />.
        </para>
      </listitem>

    </itemizedlist>

  </sect1>

  <sect1 id="generalsettings">

    <title>General Settings</title>

    <para>
      In the Settings window, under
      <emphasis role="bold">General</emphasis>, you can configure the
      most fundamental aspects of the virtual machine such as memory and
      essential hardware. There are three tabs: Basic, Advanced and
      Description.
    </para>

    <sect2 id="settings-basic">

      <title>Basic Tab</title>

      <para>
        In the Basic tab of the General settings category, you can find
        these settings:
      </para>

      <itemizedlist>

        <listitem>
          <para>
            <emphasis role="bold">Name:</emphasis> The name under which
            the VM is shown in the list of VMs in the main window. Under
            this name, VirtualBox also saves the VM's configuration
            files. By changing the name, VirtualBox renames these files
            as well. As a result, you can only use characters which are
            allowed in your host operating system's file names.
          </para>

          <para>
            Note that internally, VirtualBox uses unique identifiers
            (UUIDs) to identify virtual machines. You can display these
            with <computeroutput>VBoxManage</computeroutput>.
          </para>
        </listitem>

        <listitem>
          <para>
            <emphasis role="bold">Operating system/version:</emphasis>
            The type of the guest operating system that is, or will be,
            installed in the VM. This is the same setting that was
            specified in the "New Virtual Machine" wizard. See
            <xref
            linkend="gui-createvm" />.
          </para>

          <para>
            Whereas the default settings of a newly created VM depend on
            the selected operating system type, changing the type later
            has no effect on VM settings. This value is purely
            informational and decorative.
          </para>
        </listitem>

      </itemizedlist>

    </sect2>

    <sect2 id="settings-general-advanced">

      <title>Advanced Tab</title>

      <para>
        The following settings are available in the Advanced tab:
      </para>

      <itemizedlist>

        <listitem>
          <para>
            <emphasis role="bold">Snapshot Folder:</emphasis> By
            default, VirtualBox saves snapshot data together with your
            other VirtualBox configuration data. See
            <xref
              linkend="vboxconfigdata" />. With this
            setting, you can specify any other folder for each VM.
          </para>
        </listitem>

        <listitem>
          <para>
            <emphasis role="bold">Shared Clipboard:</emphasis> You can
            select here whether the clipboard of the guest operating
            system should be shared with that of your host. If you
            select <emphasis role="bold">Bidirectional</emphasis>, then
            VirtualBox will always make sure that both clipboards
            contain the same data. If you select
            <emphasis role="bold">Host to Guest</emphasis> or
            <emphasis role="bold">Guest to Host</emphasis>, then
            VirtualBox will only ever copy clipboard data in one
            direction.
          </para>

          <para>
            Clipboard sharing requires that the VirtualBox Guest
            Additions be installed. In such a case, this setting has no
            effect. See <xref linkend="guestadditions" />.
          </para>

          <para>
            The shared clipboard is disabled by default. See
            <xref linkend="security_clipboard"/> for an explanation.
            This setting can be changed at any time using the "Shared
            Clipboard" menu item in the "Devices" menu of the virtual
            machine.
          </para>
        </listitem>

        <listitem>
          <para>
            <emphasis role="bold">Drag and Drop:</emphasis> This setting
            enables support for drag and drop. Select an object, such as
            a file, from the host or guest and directly copy or open it
            on the guest or host. Multiple per-VM drag and drop modes
            allow restricting access in either direction.
          </para>

          <para>
            For drag and drop to work the Guest Additions need to be
            installed on the guest.
          </para>

          <note>
            <para>
              Drag and drop is disabled by default. This setting can be
              changed at any time using the <emphasis role="bold">Drag
              and Drop</emphasis> menu item in the Devices menu of the
              virtual machine.
            </para>
          </note>

          <para>
            See <xref linkend="guestadd-dnd"/>.

            <footnote>

              <para>
                Experimental support for drag and drop was added with
                VirtualBox 4.2.
              </para>

            </footnote>
          </para>
        </listitem>

      </itemizedlist>

    </sect2>

    <sect2 id="settings-description">

      <title>Description Tab</title>

      <para>
        Here you can enter any description for your virtual machine, if
        you want. This has no effect on the functionality of the
        machine, but you may find this space useful to note down things
        like the configuration of a virtual machine and the software
        that has been installed into it.
      </para>

      <para>
        To insert a line break into the description text field, press
        <emphasis>Shift+Enter</emphasis>.
      </para>

    </sect2>

  </sect1>

  <sect1 id="settings-system">

    <title>System Settings</title>

    <para>
      The System category groups various settings that are related to
      the basic hardware that is presented to the virtual machine.
    </para>

    <note>
      <para>
        As the activation mechanism of Microsoft Windows is sensitive to
        hardware changes, if you are changing hardware settings for a
        Windows guest, some of these changes may trigger a request for
        another activation with Microsoft.
      </para>
    </note>

    <sect2 id="settings-motherboard">

      <title>Motherboard Tab</title>

      <para>
        On the Motherboard tab, you can influence virtual hardware that
        would normally be on the motherboard of a real computer.
      </para>

      <itemizedlist>

        <listitem>
          <para>
            <emphasis role="bold">Base memory:</emphasis> Sets the
            amount of RAM that is allocated and given to the VM when it
            is running. The specified amount of memory will be requested
            from the host operating system, so it must be available or
            made available as free memory on the host when attempting to
            start the VM and will not be available to the host while the
            VM is running. This is the same setting that was specified
            in the "New Virtual Machine" wizard, as described in
            <xref linkend="gui-createvm" />.
          </para>

          <para>
            Generally, it is possible to change the memory size after
            installing the guest operating system. But you must not
            reduce the memory to an amount where the operating system
            would no longer boot.
          </para>
        </listitem>

        <listitem>
          <para>
            <emphasis role="bold">Boot order:</emphasis> Determines the
            order in which the guest operating system will attempt to
            boot from the various virtual boot devices. Analogous to a
            real PC's BIOS setting, VirtualBox can tell a guest OS to
            start from the virtual floppy, the virtual CD/DVD drive, the
            virtual hard drive (each of these as defined by the other VM
            settings), the network, or none of these.
          </para>

          <para>
            If you select <emphasis role="bold">Network</emphasis>, the
            VM will attempt to boot from a network via the PXE
            mechanism. This needs to be configured in detail on the
            command line. See
            <xref
              linkend="vboxmanage-modifyvm" />.
          </para>
        </listitem>

        <listitem>
          <para>
            <emphasis role="bold">Chipset:</emphasis> You can select
            which chipset will be presented to the virtual machine.
            Before VirtualBox 4.0, PIIX3 was the only available option
            here. For modern guest operating systems such as Mac OS X,
            that old chipset is no longer well supported. As a result,
            VirtualBox 4.0 introduced an emulation of the more modern
            ICH9 chipset, which supports PCI express, three PCI buses,
            PCI-to-PCI bridges and Message Signaled Interrupts (MSI).
            This allows modern operating systems to address more PCI
            devices and no longer requires IRQ sharing. Using the ICH9
            chipset it is also possible to configure up to 36 network
            cards, up to 8 network adapters with PIIX3. Note that the
            ICH9 support is experimental and not recommended for guest
            operating systems which do not require it.
          </para>
        </listitem>

        <listitem>
          <para>
            <emphasis role="bold">Pointing Device:</emphasis> The
            default virtual pointing devices for older guests is the
            traditional PS/2 mouse. If set to <emphasis>USB
            tablet</emphasis>, VirtualBox reports to the virtual machine
            that a USB tablet device is present and communicates mouse
            events to the virtual machine through this device. The third
            setting is a <emphasis>USB Multi-Touch Tablet</emphasis>
            which is suited for recent Windows guests.
          </para>

          <para>
            Using the virtual USB tablet has the advantage that
            movements are reported in absolute coordinates, instead of
            as relative position changes. This allows VirtualBox to
            translate mouse events over the VM window into tablet events
            without having to "capture" the mouse in the guest as
            described in
            <xref
              linkend="keyb_mouse_normal" />. This
            makes using the VM less tedious even if Guest Additions are
            not installed.

            <footnote>

              <para>
                The virtual USB tablet was added with VirtualBox 3.2.
                Depending on the guest operating system selected, this
                is now enabled by default for new virtual machines.
              </para>

            </footnote>
          </para>
        </listitem>

        <listitem>
          <para>
            <emphasis role="bold">Enable I/O APIC:</emphasis> Advanced
            Programmable Interrupt Controllers (APICs) are a newer x86
            hardware feature that have replaced old-style Programmable
            Interrupt Controllers (PICs) in recent years. With an I/O
            APIC, operating systems can use more than 16 interrupt
            requests (IRQs) and therefore avoid IRQ sharing for improved
            reliability.
          </para>

          <note>
            <para>
              Enabling the I/O APIC is <emphasis>required</emphasis> for
              64-bit guest operating systems, especially Windows Vista.
              It is also required if you want to use more than one
              virtual CPU in a virtual machine.
            </para>
          </note>

          <para>
            However, software support for I/O APICs has been unreliable
            with some operating systems other than Windows. Also, the
            use of an I/O APIC slightly increases the overhead of
            virtualization and therefore slows down the guest OS a
            little.
          </para>

          <warning>
            <para>
              All Windows operating systems starting with Windows 2000
              install different kernels depending on whether an I/O APIC
              is available. As with ACPI, the I/O APIC therefore
              <emphasis>must not be turned off after
              installation</emphasis> of a Windows guest OS. Turning it
              on after installation will have no effect however.
            </para>
          </warning>
        </listitem>

        <listitem>
          <para>
            <emphasis role="bold">Enable EFI:</emphasis> Enables
            Extensible Firmware Interface (EFI), which replaces the
            legacy BIOS and may be useful for certain advanced use
            cases. See <xref linkend="efi" />.
          </para>
        </listitem>

        <listitem>
          <para>
            <emphasis role="bold">Hardware clock in UTC time:</emphasis>
            If checked, VirtualBox will report the system time in UTC
            format to the guest instead of local (host) time. This
            affects how the virtual real-time clock (RTC) operates and
            may be useful for Unix-like guest operating systems, which
            typically expect the hardware clock to be set to UTC.
          </para>
        </listitem>

      </itemizedlist>

      <para>
        In addition, you can turn off the <emphasis role="bold">Advanced
        Configuration and Power Interface (ACPI)</emphasis> which
        VirtualBox presents to the guest operating system by default.
        ACPI is the current industry standard to allow operating systems
        to recognize hardware, configure motherboards and other devices
        and manage power. As all modern PCs contain this feature and
        Windows and Linux have been supporting it for years, it is also
        enabled by default in VirtualBox. It can only be turned off on
        the command line. See
        <xref
      linkend="vboxmanage-modifyvm" />.
      </para>

      <warning>
        <para>
          All Windows operating systems starting with Windows 2000
          install different kernels depending on whether ACPI is
          available, so ACPI <emphasis>must not be turned off</emphasis>
          after installation of a Windows guest OS. Turning it on after
          installation will have no effect however.
        </para>
      </warning>

    </sect2>

    <sect2 id="settings-processor">

      <title>Processor Tab</title>

      <para>
        On the Processor tab, you can set how many virtual
        <emphasis role="bold">CPU cores</emphasis> the guest operating
        systems should see. Starting with version 3.0, VirtualBox
        supports symmetrical multiprocessing (SMP) and can present up to
        32 virtual CPU cores to each virtual machine.
      </para>

      <para>
        You should not, however, configure virtual machines to use more
        CPU cores than are available physically (real cores, no
        hyperthreads).
      </para>

      <para>
        On this tab you can also set the <emphasis role="bold">CPU
        execution cap</emphasis>. This setting limits the amount of time
        a host CPU spends to emulate a virtual CPU. The default setting
        is 100% meaning that there is no limitation. A setting of 50%
        implies a single virtual CPU can use up to 50% of a single host
        CPU. Note that limiting the execution time of the virtual CPUs
        may induce guest timing problems.
      </para>

      <para>
        In addition, the <emphasis role="bold">Enable PAE/NX</emphasis>
        setting determines whether the PAE and NX capabilities of the
        host CPU will be exposed to the virtual machine. PAE stands for
        "Physical Address Extension". Normally, if enabled and supported
        by the operating system, then even a 32-bit x86 CPU can access
        more than 4 GB of RAM. This is made possible by adding another 4
        bits to memory addresses, so that with 36 bits, up to 64 GB can
        be addressed. Some operating systems, such as Ubuntu Server,
        require PAE support from the CPU and cannot be run in a virtual
        machine without it.
      </para>

      <para>
        With virtual machines running modern server operating systems,
        VirtualBox also supports CPU hot-plugging. For details, see
        <xref linkend="cpuhotplug" />.
      </para>

    </sect2>

    <sect2 id="settings-acceleration">

      <title>Acceleration Tab</title>

      <para>
        On this page, you can determine whether and how VirtualBox
        should use hardware virtualization extensions that your host CPU
        may support. This is the case with most CPUs built after 2006.
      </para>

      <para>
        You can select for each virtual machine individually whether
        VirtualBox should use software or hardware virtualization.

        <footnote>

          <para>
            Prior to VirtualBox version 2.2, software virtualization was
            the default; starting with version 2.2, VirtualBox will
            enable hardware virtualization by default for new virtual
            machines that you create. Existing virtual machines are not
            automatically changed for compatibility reasons, and the
            default can of course be changed for each virtual machine.
          </para>

        </footnote>
      </para>

      <para>
        In most cases, the default settings will be fine; VirtualBox
        will have picked sensible defaults depending on the operating
        system that you selected when you created the virtual machine.
        In certain situations, however, you may want to change these
        preconfigured defaults.
      </para>

      <para>
        Advanced users may be interested in technical details about
        software vs. hardware virtualization. See
        <xref
      linkend="hwvirt" />.
      </para>

      <para>
        If your host's CPU supports the <emphasis role="bold">nested
        paging</emphasis> (AMD-V) or
        <emphasis role="bold">EPT</emphasis> (Intel VT-x) features, then
        you can expect a significant performance increase by enabling
        nested paging in addition to hardware virtualization. For
        technical details, see <xref linkend="nestedpaging" />.
      </para>

      <para>
        Starting with version 5.0, VirtualBox provides
        paravirtualization interfaces to improve time-keeping accuracy
        and performance of guest operating systems. The options
        available are documented under the
        <computeroutput>paravirtprovider</computeroutput> option in
        <xref linkend="vboxmanage-modifyvm" />. For further details on
        the paravirtualization providers, see
        <xref linkend="gimproviders" />.
      </para>

    </sect2>

  </sect1>

  <sect1 id="settings-display">

    <title>Display Settings</title>

    <itemizedlist>

      <listitem>
        <para>
          <emphasis role="bold">Video memory size:</emphasis> Sets the
          size of the memory provided by the virtual graphics card
          available to the guest, in MB. As with the main memory, the
          specified amount will be allocated from the host's resident
          memory. Based on the amount of video memory, higher
          resolutions and color depths may be available.
        </para>

        <para>
          The GUI will show a warning if the amount of video memory is
          too small to be able to switch the VM into full screen mode.
          The minimum value depends on the number of virtual monitors,
          the screen resolution and the color depth of the host display
          as well as of the activation of <emphasis>3D
          acceleration</emphasis> and <emphasis>2D video
          acceleration</emphasis>. A rough estimate is (<emphasis>color
          depth</emphasis> / 8) x <emphasis>vertical pixels</emphasis> x
          <emphasis>horizontal pixels</emphasis> x <emphasis>number of
          screens</emphasis> = <emphasis>number of bytes</emphasis>.
          Like said above, there might be extra memory required for any
          activated display acceleration setting.
        </para>
      </listitem>

      <listitem>
        <para>
          <emphasis role="bold">Monitor count:</emphasis> With this
          setting VirtualBox can provide more than one virtual monitor
          to a virtual machine. If a guest operating system, such as
          Windows, supports multiple attached monitors, VirtualBox can
          pretend that multiple virtual monitors are present.

          <footnote>

            <para>
              Multiple monitor support was added with VirtualBox 3.2.
            </para>

          </footnote>

          Up to eight such virtual monitors are supported.
        </para>

        <para>
          The output of the multiple monitors are displayed on the host
          in multiple VM windows which are running side by side.
        </para>

        <para>
          However, in full screen and seamless mode, they use the
          available physical monitors attached to the host. As a result,
          for full screen and seamless modes to work with multiple
          monitors, you will need at least as many physical monitors as
          you have virtual monitors configured, or VirtualBox will
          report an error. You can configure the relationship between
          guest and host monitors using the view menu by pressing Host
          key + Home when you are in full screen or seamless mode.
        </para>

        <para>
          See also <xref linkend="KnownIssues" />.
        </para>
      </listitem>

      <listitem>
        <para>
          <emphasis role="bold">Enable 3D acceleration:</emphasis> If a
          virtual machine has Guest Additions installed, you can select
          here whether the guest should support accelerated 3D graphics.
          See <xref linkend="guestadd-3d" />.
        </para>
      </listitem>

      <listitem>
        <para>
          <emphasis role="bold">Enable 2D video acceleration:</emphasis>
          If a virtual machine with Microsoft Windows has Guest
          Additions installed, you can select here whether the guest
          should support accelerated 2D video graphics. See
          <xref
          linkend="guestadd-2d" />.
        </para>
      </listitem>

      <listitem>
        <para>
          <emphasis role="bold">Remote display:</emphasis> On the
          <emphasis role="bold">Remote Display</emphasis> tab, if the
          VirtualBox Remote Display Extension (VRDE) is installed, you
          can enable the VRDP server that is built into VirtualBox. This
          enables you to connect to the console of the virtual machine
          remotely with any standard RDP viewer, such as
          <computeroutput>mstsc.exe</computeroutput> that comes with
          Microsoft Windows. On Linux and Solaris systems you can use
          the standard open source
          <computeroutput>rdesktop</computeroutput> program. These
          features are described in <xref linkend="vrde" />.
        </para>
      </listitem>

      <listitem>
        <para>
          <emphasis role="bold">Capture:</emphasis> On the
          <emphasis role="bold">Capture</emphasis> tab you can
          enable video and audio capturing, as well as changing related options
          for this VM. Note that these features can also be enabled/disabled
          while the VM is being executed.
        </para>
      </listitem>

    </itemizedlist>

  </sect1>

  <sect1 id="settings-storage">

    <title>Storage Settings</title>

    <para>
      The Storage category in the VM settings enables you to connect
      virtual hard disk, CD/DVD, and floppy images and drives to your
      virtual machine.
    </para>

    <para>
      In a real PC, so-called "storage controllers" connect physical
      disk drives to the rest of the computer. Similarly, VirtualBox
      presents virtual storage controllers to a virtual machine. Under
      each controller, the virtual devices, such as hard disks, CD/DVD
      or floppy drives, attached to the controller are shown.

      <note>
        <para>
          This section can only give you a quick introduction to the
          VirtualBox storage settings. Since VirtualBox gives you an
          enormous wealth of options in this area, we have dedicated an
          entire chapter of this User Manual to explaining all the
          details. See <xref
        linkend="storage" />.
        </para>
      </note>
    </para>

    <para>
      If you have used the <emphasis role="bold">Create VM</emphasis>
      wizard to create a machine, you will normally see something like
      the following:
    </para>

    <para>
      <mediaobject>
        <imageobject>
          <imagedata align="center" fileref="images/vm-settings-harddisk.png"
                     width="10cm" />
        </imageobject>
      </mediaobject>
    </para>

    <para>
      Depending on the guest operating system type that you selected
      when you created the VM, the typical layout of storage devices in
      a new VM is as follows:
    </para>

    <itemizedlist>

      <listitem>
        <para>
          You will see an <emphasis role="bold">IDE
          controller</emphasis>, to which a virtual CD/DVD drive has
          been attached to the "secondary master" port of the IDE
          controller.
        </para>
      </listitem>

      <listitem>
        <para>
          You will also see a <emphasis role="bold">SATA
          controller</emphasis>, which is a more modern type of storage
          controller for higher hard disk data throughput, to which the
          virtual hard disks are attached. Initially you will normally
          have one such virtual disk, but as you can see in the above
          screenshot, you can have more than one. Each is represented by
          a disk image file, VDI files in this case.
        </para>
      </listitem>

    </itemizedlist>

    <para>
      If you created your VM with an older version of VirtualBox, the
      default storage layout may differ. You might then only have an IDE
      controller to which both the CD/DVD drive and the hard disks have
      been attached. This might also apply if you selected an older
      operating system type when you created the VM. Since older
      operating systems do not support SATA without additional drivers,
      VirtualBox will make sure that no such devices are present
      initially. See <xref
    linkend="harddiskcontrollers" />.
    </para>

    <para>
      VirtualBox also provides a <emphasis role="bold">floppy
      controller</emphasis>. You cannot add devices other than floppy
      drives to this controller. Virtual floppy drives, like virtual
      CD/DVD drives, can be connected to either a host floppy drive, if
      you have one, or a disk image, which in this case must be in RAW
      format.
    </para>

    <para>
      You can modify these media attachments freely. For example, if you
      wish to copy some files from another virtual disk that you
      created, you can connect that disk as a second hard disk, as in
      the above screenshot. You could also add a second virtual CD/DVD
      drive, or change where these items are attached. The following
      options are available:
    </para>

    <itemizedlist>

      <listitem>
        <para>
          To <emphasis role="bold">add another virtual hard disk, or a
          CD/DVD or floppy drive</emphasis>, select the storage
          controller to which it should be added (IDE, SATA, SCSI, SAS,
          floppy controller) and then click on the
          <emphasis role="bold">Add Disk</emphasis> button below the
          tree. You can then either select <emphasis role="bold">Add
          CD/DVD Device</emphasis> or <emphasis role="bold">Add Hard
          Disk</emphasis>. If you clicked on a floppy controller, you
          can add a floppy drive instead. Alternatively, right-click on
          the storage controller and select a menu item there.
        </para>

        <para>
          On the right part of the window, you can then set the
          following:
        </para>

        <orderedlist>

          <listitem>
            <para>
              You can then select to which
              <emphasis
                role="bold">device
              slot</emphasis> of the controller the virtual disk should
              be connected to. IDE controllers have four slots which
              have traditionally been called "primary master", "primary
              slave", "secondary master" and "secondary slave". By
              contrast, SATA and SCSI controllers offer you up to 30
              slots to which virtual devices can be attached.
            </para>
          </listitem>

          <listitem>
            <para>
              You can select which <emphasis role="bold">image
              file</emphasis> to use.
            </para>

            <itemizedlist>

              <listitem>
                <para>
                  For virtual hard disks, a button with a drop-down list
                  appears on the right, offering you to either select a
                  <emphasis role="bold">virtual hard disk
                  file</emphasis> using a standard file dialog or to
                  <emphasis role="bold">create a new hard
                  disk</emphasis> (image file). The latter option
                  displays the <emphasis role="bold">Create New
                  Disk</emphasis> wizard, described in
                  <xref
                      linkend="gui-createvm" />.
                </para>

                <para>
                  For details on the image file types that are
                  supported, see
                  <xref
                      linkend="vdidetails" />.
                </para>
              </listitem>

              <listitem>
                <para>
                  For virtual CD/DVD drives, the image files will
                  typically be in the standard ISO format instead. Most
                  commonly, you will select this option when installing
                  an operating system from an ISO file that you have
                  obtained from the Internet. For example, most Linux
                  distributions are available in this way.
                </para>

                <para>
                  For virtual CD/DVD drives, the following additional
                  options are available:
                </para>

                <itemizedlist>

                  <listitem>
                    <para>
                      If you select <emphasis role="bold">Host
                      Drive</emphasis> from the list, then the physical
                      device of the host computer is connected to the
                      VM, so that the guest operating system can read
                      from and write to your physical device. This is,
                      for instance, useful if you want to install
                      Windows from a real installation CD. In this case,
                      select your host drive from the drop-down list
                      presented.
                    </para>

                    <para>
                      If you want to write (burn) CDs or DVDs using the
                      host drive, you need to also enable the
                      <emphasis role="bold">Passthrough</emphasis>
                      option. See <xref linkend="storage-cds" />.
                    </para>
                  </listitem>

                  <listitem>
                    <para>
                      If you select <emphasis role="bold">Remove Disk
                      from Virtual Drive</emphasis>, VirtualBox will
                      present an empty CD/DVD drive to the guest into
                      which no media has been inserted.
                    </para>
                  </listitem>

                </itemizedlist>
              </listitem>

            </itemizedlist>
          </listitem>

        </orderedlist>
      </listitem>

      <listitem>
        <para>
          To <emphasis role="bold">remove an attachment</emphasis>,
          either select it and click on the
          <emphasis role="bold">Remove</emphasis> icon at the bottom, or
          right-click on it and select the menu item.
        </para>
      </listitem>

    </itemizedlist>

    <para>
      Removable media, such as CD/DVDs and floppies, can be changed
      while the guest is running. Since the Settings dialog is not
      available at that time, you can also access these settings from
      the <emphasis role="bold">Devices</emphasis> menu of your virtual
      machine window.
    </para>

  </sect1>

  <sect1 id="settings-audio">

    <title>Audio Settings</title>

    <para>
      The Audio section in a virtual machine's Settings window
      determines whether the VM will see a sound card connected, and
      whether the audio output should be heard on the host system.
    </para>

    <para>
      If audio is enabled for a guest, you can choose between the
      emulation of an Intel AC'97 controller, an Intel HD Audio
      controller

      <footnote>

        <para>
          Intel HD Audio support was added with VirtualBox 4.0 because
          Windows 7 and later (as well as 64-bit Windows Vista) do not
          support the Intel AC'97 controller out of the box.
        </para>

      </footnote>

      or a SoundBlaster 16 card. In any case, you can select what audio
      driver VirtualBox will use on the host.
    </para>

    <para>
      On a Linux host, depending on your host configuration, you can
      also select between the OSS, ALSA, or the PulseAudio subsystem. On
      newer Linux distributions, the PulseAudio subsystem should be
      preferred.
    </para>

    <para>
      Since VirtualBox 5.0 only OSS is supported on Solaris hosts. The
      "Solaris Audio" audio backend is no longer supported on Solaris
      hosts.
    </para>

  </sect1>

  <sect1 id="settings-network">

    <title>Network Settings</title>

    <para>
      The Network section in a virtual machine's Settings window enables
      you to configure how VirtualBox presents virtual network cards to
      your VM, and how they operate.
    </para>

    <para>
      When you first create a virtual machine, VirtualBox by default
      enables one virtual network card and selects the Network Address
      Translation (NAT) mode for it. This way the guest can connect to
      the outside world using the host's networking and the outside
      world can connect to services on the guest which you choose to
      make visible outside of the virtual machine.
    </para>

    <para>
      This default setup is good for the majority of VirtualBox users.
      However, VirtualBox is extremely flexible in how it can virtualize
      networking. It supports many virtual network cards per virtual
      machine, the first four of which can be configured in detail in
      the Manager window. Additional network cards can be configured on
      the command line with VBoxManage.
    </para>

    <para>
      Because of the vast array of options available, we have dedicated
      an entire chapter of this manual to discussing networking
      configuration. See <xref linkend="networkingdetails" />.
    </para>

  </sect1>

  <sect1 id="serialports">

    <title>Serial Ports</title>

    <para>
      VirtualBox fully supports virtual serial ports in a virtual
      machine in an easy-to-use manner.

      <footnote>

        <para>
          Serial port support was added with VirtualBox 1.5.
        </para>

      </footnote>
    </para>

    <para>
      Ever since the original IBM PC, personal computers have been
      equipped with one or two serial ports, also called COM ports by
      DOS and Windows. Serial ports were commonly used with modems, and
      some computer mice used to be connected to serial ports before USB
      became commonplace.
    </para>

    <para>
      While serial ports are no longer as ubiquitous as they used to be,
      there are still some important uses left for them. For example,
      serial ports can be used to set up a primitive network over a
      null-modem cable, in case Ethernet is not available. Also, serial
      ports are indispensable for system programmers needing to do
      kernel debugging, since kernel debugging software usually
      interacts with developers over a serial port. With virtual serial
      ports, system programmers can do kernel debugging on a virtual
      machine instead of needing a real computer to connect to.
    </para>

    <para>
      If a virtual serial port is enabled, the guest operating system
      sees a standard 16550A compatible UART device. Both receiving and
      transmitting data is supported. How this virtual serial port is
      then connected to the host is configurable, and the details depend
      on your host operating system.
    </para>

    <para>
      You can use either the graphical user interface or the
      command-line <computeroutput>VBoxManage</computeroutput> tool to
      set up virtual serial ports. For the latter, see
      <xref
    linkend="vboxmanage-modifyvm" /> for information on the
      <computeroutput>--uart</computeroutput> and
      <computeroutput>--uartmode</computeroutput> options.
    </para>

    <para>
      In either case, you can configure up to four virtual serial ports
      per virtual machine. For each such device, you will need to
      determine the following:
    </para>

    <orderedlist>

      <listitem>
        <para>
          What kind of serial port the virtual machine should see, by
          selecting an I/O base address and interrupt (IRQ). For these,
          we recommend you use the traditional values, as follows:

          <footnote>

            <para>
              See, for example,
              <ulink
              url="http://en.wikipedia.org/wiki/COM_(hardware_interface)">http://en.wikipedia.org/wiki/COM_(hardware_interface)</ulink>.
            </para>

          </footnote>
        </para>

        <itemizedlist>

          <listitem>
            <para>
              COM1: I/O base 0x3F8, IRQ 4
            </para>
          </listitem>

          <listitem>
            <para>
              COM2: I/O base 0x2F8, IRQ 3
            </para>
          </listitem>

          <listitem>
            <para>
              COM3: I/O base 0x3E8, IRQ 4
            </para>
          </listitem>

          <listitem>
            <para>
              COM4: I/O base 0x2E8, IRQ 3
            </para>
          </listitem>

        </itemizedlist>
      </listitem>

      <listitem>
        <para>
          Then, you will need to determine what this virtual port should
          be connected to. For each virtual serial port, you have the
          following options:
        </para>

        <itemizedlist>

          <listitem>
            <para>
              You can configure the virtual serial port to be
              "disconnected". This means that the guest will see the
              device, but it will behave as if no cable had been
              connected to it.
            </para>
          </listitem>

          <listitem>
            <para>
              You can connect the virtual serial port to a physical
              serial port on your host. On a Windows host, this will be
              a name like <computeroutput>COM1</computeroutput>. On
              Linux or Solaris hosts, it will be a device node like
              <computeroutput>/dev/ttyS0</computeroutput>. VirtualBox
              will then simply redirect all data received from and sent
              to the virtual serial port to the physical device.
            </para>
          </listitem>

          <listitem>
            <para>
              You can tell VirtualBox to connect the virtual serial port
              to a software pipe on the host. This depends on your host
              operating system, as follows:
            </para>

            <itemizedlist>

              <listitem>
                <para>
                  On a Windows host, data will be sent and received
                  through a named pipe. The pipe name must be in the
                  format
                  <computeroutput>\\.\pipe\&lt;name&gt;</computeroutput>
                  where <computeroutput>&lt;name&gt;</computeroutput>
                  should identify the virtual machine but may be freely
                  chosen.
                </para>
              </listitem>

              <listitem>
                <para>
                  On a Mac, Linux, or Solaris host, a local domain
                  socket is used instead. The socket filename must be
                  chosen such that the user running VirtualBox has
                  sufficient privileges to create and write to it. The
                  <computeroutput>/tmp</computeroutput> directory is
                  often a good candidate.
                </para>

                <para>
                  On Linux there are various tools which can connect to
                  a local domain socket or create one in server mode.
                  The most flexible tool is
                  <computeroutput>socat</computeroutput> and is
                  available as part of many distributions.
                </para>
              </listitem>

            </itemizedlist>

            <para>
              In this case, you can configure whether VirtualBox should
              create the named pipe (or, on non-Windows hosts, the local
              domain socket) itself or whether VirtualBox should assume
              that the pipe or socket exists already. With the
              <computeroutput>VBoxManage</computeroutput> command-line
              options, this is referred to as "server" or "client" mode,
              respectively.
            </para>

            <para>
              For a direct connection between two virtual machines,
              corresponding to a null-modem cable, simply configure one
              VM to create a pipe/socket and another to attach to it.
            </para>
          </listitem>

          <listitem>
            <para>
              You can send the virtual serial port output to a file.
              This option is very useful for capturing diagnostic output
              from a guest. Any file may be used for this purpose, as
              long as the user running VirtualBox has sufficient
              privileges to create and write to the file.
            </para>
          </listitem>

          <listitem>
            <para>
              TCP Socket: Useful for forwarding serial traffic over
              TCP/IP, acting as a server, or it can act as a TCP client
              connecting to other servers. It allows a remote machine to
              directly connect to the guest's serial port via TCP.
            </para>

            <itemizedlist>

              <listitem>
                <para>
                  TCP Server: Uncheck the <emphasis>Connect to existing
                  pipe/socket</emphasis> checkbox and specify the
                  <emphasis role="bold"><computeroutput>port</computeroutput></emphasis>
                  number. Typically 23 or 2023. Note that on UNIX-like
                  systems you will have to use a port a number greater
                  than 1024 for regular users.
                </para>

                <para>
                  The client can use software such as
                  <computeroutput>PuTTY</computeroutput> or the
                  <computeroutput>telnet</computeroutput> command line
                  tool to access the TCP Server.
                </para>
              </listitem>

              <listitem>
                <para>
                  TCP Client: To create a virtual null-modem cable over
                  the Internet or LAN, the other side can connect via
                  TCP by specifying
                  <computeroutput>hostname:port</computeroutput>. The
                  TCP socket will act in client mode if you check the
                  <emphasis role="bold">Connect to existing
                  pipe/socket</emphasis> checkbox.
                </para>
              </listitem>

            </itemizedlist>
          </listitem>

        </itemizedlist>
      </listitem>

    </orderedlist>

    <para>
      Up to four serial ports can be configured per virtual machine, but
      you can pick any port numbers out of the above. However, serial
      ports cannot reliably share interrupts; if both ports are to be
      used at the same time, they must use different interrupt levels,
      for example COM1 and COM2, but not COM1 and COM3.
    </para>

  </sect1>

  <sect1 id="usb-support">

    <title>USB Support</title>

    <sect2 id="settings-usb">

      <title>USB Settings</title>

      <para>
        The USB section in a virtual machine's Settings window enables
        you to configure VirtualBox's sophisticated USB support.
      </para>

      <para>
        VirtualBox can enable virtual machines to access the USB devices
        on your host directly. To achieve this, VirtualBox presents the
        guest operating system with a virtual USB controller. As soon as
        the guest system starts using a USB device, it will appear as
        unavailable on the host.
      </para>

      <note>
        <itemizedlist>

          <listitem>
            <para>
              Be careful with USB devices that are currently in use on
              the host! For example, if you allow your guest to connect
              to your USB hard disk that is currently mounted on the
              host, when the guest is activated, it will be disconnected
              from the host without a proper shutdown. This may cause
              data loss.
            </para>
          </listitem>

          <listitem>
            <para>
              Solaris hosts have a few known limitations regarding USB
              support. See <xref linkend="KnownIssues" />.
            </para>
          </listitem>

        </itemizedlist>
      </note>

      <para>
        In addition to allowing a guest access to your local USB
        devices, VirtualBox even allows your guests to connect to remote
        USB devices by use of the VirtualBox Remote Desktop Extension
        (VRDE). See <xref linkend="usb-over-rdp" />.
      </para>

      <para>
        In the Settings dialog, you can first configure whether USB is
        available in the guest at all, and then choose the level of USB
        support: OHCI for USB 1.1, EHCI (which will also enable OHCI)
        for USB 2.0, or xHCI for all USB speeds.
      </para>

      <note>
        <para>
          The xHCI and EHCI controllers are shipped as a VirtualBox
          extension package, which must be installed separately. See
          <xref
          linkend="intro-installing" />.
        </para>
      </note>

      <para>
        When USB support is enabled for a VM, you can determine in
        detail which devices will be automatically attached to the
        guest. For this, you can create so-called "filters" by
        specifying certain properties of the USB device. USB devices
        with a matching filter will be automatically passed to the guest
        once they are attached to the host. USB devices without a
        matching filter can be passed manually to the guest, for example
        by using the <emphasis role="bold">Devices</emphasis>,
        <emphasis role="bold">USB</emphasis> menu.
      </para>

      <para>
        Clicking on the <emphasis role="bold">+</emphasis> button to the
        right of the <emphasis role="bold">USB Device Filters</emphasis>
        window creates a new filter. You can give the filter a name, for
        later reference, and specify the filter criteria. The more
        criteria you specify, the more precisely devices will be
        selected. For instance, if you specify only a vendor ID of 046d,
        all devices produced by Logitech will be available to the guest.
        If you fill in all fields, on the other hand, the filter will
        only apply to a particular device model from a particular
        vendor, and not even to other devices of the same type with a
        different revision and serial number.
      </para>

      <para>
        In detail, the following criteria are available:
      </para>

      <itemizedlist>

        <listitem>
          <para>
            <emphasis role="bold">Vendor and product ID</emphasis>. With
            USB, each vendor of USB products carries an identification
            number that is unique world-wide, called the
            <emphasis>vendor ID</emphasis>. Similarly, each line of
            products is assigned a <emphasis>product ID</emphasis>
            number. Both numbers are commonly written in hexadecimal
            (that is, they are composed of the numbers 0-9 and the
            letters A-F), and a colon separates the vendor from the
            product ID. For example,
            <computeroutput>046d:c016</computeroutput> stands for
            Logitech as a vendor, and the M-UV69a Optical Wheel Mouse
            product.
          </para>

          <para>
            Alternatively, you can also specify
            <emphasis
          role="bold">Manufacturer</emphasis> and
            <emphasis
          role="bold">Product</emphasis> by name.
          </para>

          <para>
            To list all the USB devices that are connected to your host
            machine with their respective vendor IDs and product IDs,
            use the following command:

<screen>VBoxManage list usbhost</screen>
          </para>

          <para>
            On Windows, you can also see all USB devices that are
            attached to your system in the Device Manager. On Linux, you
            can use the <computeroutput>lsusb</computeroutput> command.
          </para>
        </listitem>

        <listitem>
          <para>
            <emphasis role="bold">Serial number</emphasis>. While vendor
            ID and product ID are quite specific to identify USB
            devices, if you have two identical devices of the same brand
            and product line, you will also need their serial numbers to
            filter them out correctly.
          </para>
        </listitem>

        <listitem>
          <para>
            <emphasis role="bold">Remote</emphasis>. This setting
            specifies whether the device will be local only, remote only
            (such as over VRDP), or either.
          </para>
        </listitem>

      </itemizedlist>

      <para>
        On a Windows host, you will need to unplug and reconnect a USB
        device to use it after creating a filter for it.
      </para>

      <para>
        As an example, you could create a new USB filter and specify a
        vendor ID of 046d (Logitech, Inc), a manufacturer index of 1,
        and "not remote". Then any USB devices on the host system
        produced by Logitech, Inc with a manufacturer index of 1 will be
        visible to the guest system.
      </para>

      <para>
        Several filters can select a single device. For example, a
        filter which selects all Logitech devices, and one which selects
        a particular webcam.
      </para>

      <para>
        You can deactivate filters without deleting them by clicking in
        the checkbox next to the filter name.
      </para>

    </sect2>

    <sect2 id="usb-implementation-notes">

      <title>Implementation Notes for Windows and Linux Hosts</title>

      <para>
        On Windows hosts, a kernel mode device driver provides USB proxy
        support. It implements both a USB monitor, which allows
        VirtualBox to capture devices when they are plugged in, and a
        USB device driver to claim USB devices for a particular virtual
        machine. As opposed to VirtualBox versions before 1.4.0, system
        reboots are no longer necessary after installing the driver.
        Also, you no longer need to replug devices for VirtualBox to
        claim them.
      </para>

      <para>
        On newer Linux hosts, VirtualBox accesses USB devices through
        special files in the file system. When VirtualBox is installed,
        these are made available to all users in the
        <computeroutput>vboxusers</computeroutput> system group. In
        order to be able to access USB from guest systems, make sure
        that you are a member of this group.
      </para>

      <para>
        On older Linux hosts, USB devices are accessed using the
        <computeroutput>usbfs</computeroutput> file system. Therefore,
        the user executing VirtualBox needs read and write permission to
        the USB file system. Most distributions provide a group (e.g.
        <computeroutput>usbusers</computeroutput>) which the VirtualBox
        user needs to be added to. Also, VirtualBox can only proxy to
        virtual machines USB devices which are not claimed by a Linux
        host USB driver. The <computeroutput>Driver=</computeroutput>
        entry in <computeroutput>/proc/bus/usb/devices</computeroutput>
        will show you which devices are currently claimed. See also
        <xref
      linkend="ts_usb-linux" /> for details about
        <computeroutput>usbfs</computeroutput>.
      </para>

    </sect2>

  </sect1>

  <sect1 id="shared-folders">

    <title>Shared Folders</title>

    <para>
      Shared folders enable you to easily exchange data between a
      virtual machine and your host. This feature requires that the
      VirtualBox Guest Additions be installed in a virtual machine and
      is described in detail in <xref linkend="sharedfolders" />.
    </para>

  </sect1>

  <sect1 id="user-interface">

    <title>User Interface</title>

    <para>
      The User Interface section allows you to change certain aspects of
      the user interface of this VM.
    </para>

    <itemizedlist>

      <listitem>
        <para>
          <emphasis role="bold">Menu Bar:</emphasis> This widget enables
          you to disable menus by clicking on the menu to release it,
          menu entries by unchecking the checkbox of the entry to
          disable it and the complete menu bar by unchecking the
          rightmost checkbox.
        </para>
      </listitem>

      <listitem>
        <para>
          <emphasis role="bold">Mini ToolBar:</emphasis> In full screen
          or seamless mode, VirtualBox can display a small toolbar that
          contains some of the items that are normally available from
          the virtual machine's menu bar. This toolbar reduces itself to
          a small gray line unless you move the mouse over it. With the
          toolbar, you can return from full screen or seamless mode,
          control machine execution or enable certain devices. If you do
          not want to see the toolbar, disable this setting.
        </para>

        <para>
          The second setting enables you to show the toolbar at the top
          of the screen, instead of showing it at the bottom.
        </para>
      </listitem>

      <listitem>
        <para>
          <emphasis role="bold">Status Bar:</emphasis> This widget
          allows you to disable icons on the status bar by unchecking
          the checkbox of an icon to disable it, to rearrange icons by
          dragging and dropping the icon, and to disable the complete
          status bar by unchecking the leftmost checkbox.
        </para>
      </listitem>

    </itemizedlist>

  </sect1>

  <sect1 id="efi">

    <title>Alternative Firmware (EFI)</title>

    <para>
      Starting with release 3.1, VirtualBox includes experimental
      support for the Extensible Firmware Interface (EFI), which is a
      new industry standard intended to eventually replace the legacy
      BIOS as the primary interface for bootstrapping computers and
      certain system services later.
    </para>

    <para>
      By default, VirtualBox uses the BIOS firmware for virtual
      machines. To use EFI for a given virtual machine, you can enable
      EFI in the machine's Settings dialog. See
      <xref linkend="settings-motherboard" />. Alternatively, use the
      <computeroutput>VBoxManage</computeroutput> command line interface
      as follows:
    </para>

<screen>VBoxManage modifyvm "VM name" --firmware efi</screen>

    <para>
      To switch back to using the BIOS:
    </para>

<screen>VBoxManage modifyvm "VM name" --firmware bios</screen>

    <para>
      One notable user of EFI is Apple's Mac OS X, but more recent
      Linuxes and Windows, starting with Vista, offer special versions
      that can be booted using EFI as well.
    </para>

    <para>
      Another possible use of EFI in VirtualBox is development and
      testing of EFI applications, without booting any OS.
    </para>

    <para>
      Note that the VirtualBox EFI support is experimental and will be
      enhanced as EFI matures and becomes more widespread. Mac OS X,
      Linux, and newer Windows guests are known to work fine. Windows 7
      guests are unable to boot with the VirtualBox EFI implementation.
    </para>

    <sect2 id="efividmode">

      <title>Video Modes in EFI</title>

      <para>
        EFI provides two distinct video interfaces: GOP (Graphics Output
        Protocol) and UGA (Universal Graphics Adapter). Modern operating
        systems, such as Mac OS X, generally use GOP, while some older
        ones still use UGA. VirtualBox provides a configuration option
        to control the graphics resolution for both interfaces, making
        the difference mostly irrelevant for users.
      </para>

      <para>
        The default resolution is 1024x768. To select a graphics
        resolution for EFI, use the following
        <computeroutput>VBoxManage</computeroutput> command:
      </para>

<screen>VBoxManage setextradata "VM name" VBoxInternal2/EfiGraphicsResolution HxV</screen>

      <para>
        Determine the horizontal resolution H and the vertical
        resolution V from the following list of default resolutions:
      </para>

      <variablelist>

        <varlistentry>
          <term>
            VGA
          </term>

          <listitem>
            <para>
              640x480, 32bpp, 4:3
            </para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>
            SVGA
          </term>

          <listitem>
            <para>
              800x600, 32bpp, 4:3
            </para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>
            XGA
          </term>

          <listitem>
            <para>
              1024x768, 32bpp, 4:3
            </para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>
            XGA+
          </term>

          <listitem>
            <para>
              1152x864, 32bpp, 4:3
            </para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>
            HD
          </term>

          <listitem>
            <para>
              1280x720, 32bpp, 16:9
            </para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>
            WXGA
          </term>

          <listitem>
            <para>
              1280x800, 32bpp, 16:10
            </para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>
            SXGA
          </term>

          <listitem>
            <para>
              1280x1024, 32bpp, 5:4
            </para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>
            SXGA+
          </term>

          <listitem>
            <para>
              1400x1050, 32bpp, 4:3
            </para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>
            WXGA+
          </term>

          <listitem>
            <para>
              1440x900, 32bpp, 16:10
            </para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>
            HD+
          </term>

          <listitem>
            <para>
              1600x900, 32bpp, 16:9
            </para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>
            UXGA
          </term>

          <listitem>
            <para>
              1600x1200, 32bpp, 4:3
            </para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>
            WSXGA+
          </term>

          <listitem>
            <para>
              1680x1050, 32bpp, 16:10
            </para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>
            Full HD
          </term>

          <listitem>
            <para>
              1920x1080, 32bpp, 16:9
            </para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>
            WUXGA
          </term>

          <listitem>
            <para>
              1920x1200, 32bpp, 16:10
            </para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>
            DCI 2K
          </term>

          <listitem>
            <para>
              2048x1080, 32bpp, 19:10
            </para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>
            Full HD+
          </term>

          <listitem>
            <para>
              2160x1440, 32bpp, 3:2
            </para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>
            Unnamed
          </term>

          <listitem>
            <para>
              2304x1440, 32bpp, 16:10
            </para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>
            QHD
          </term>

          <listitem>
            <para>
              2560x1440, 32bpp, 16:9
            </para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>
            WQXGA
          </term>

          <listitem>
            <para>
              2560x1600, 32bpp, 16:10
            </para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>
            QWXGA+
          </term>

          <listitem>
            <para>
              2880x1800, 32bpp, 16:10
            </para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>
            QHD+
          </term>

          <listitem>
            <para>
              3200x1800, 32bpp, 16:9
            </para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>
            WQSXGA
          </term>

          <listitem>
            <para>
              3200x2048, 32bpp, 16:10
            </para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>
            4K UHD
          </term>

          <listitem>
            <para>
              3840x2160, 32bpp, 16:9
            </para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>
            WQUXGA
          </term>

          <listitem>
            <para>
              3840x2400, 32bpp, 16:10
            </para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>
            DCI 4K
          </term>

          <listitem>
            <para>
              4096x2160, 32bpp, 19:10
            </para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>
            HXGA
          </term>

          <listitem>
            <para>
              4096x3072, 32bpp, 4:3
            </para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>
            UHD+
          </term>

          <listitem>
            <para>
              5120x2880, 32bpp, 16:9
            </para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>
            WHXGA
          </term>

          <listitem>
            <para>
              5120x3200, 32bpp, 16:10
            </para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>
            WHSXGA
          </term>

          <listitem>
            <para>
              6400x4096, 32bpp, 16:10
            </para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>
            HUXGA
          </term>

          <listitem>
            <para>
              6400x4800, 32bpp, 4:3
            </para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>
            8K UHD2
          </term>

          <listitem>
            <para>
              7680x4320, 32bpp, 16:9
            </para>
          </listitem>
        </varlistentry>

      </variablelist>

      <para>
        If this list of default resolution does not cover your needs,
        see <xref linkend="customvesa" />. Note that the color depth
        value specified in a custom video mode must be specified (8, 16,
        24 and 32 are accepted), but it is silently assumed to be 32 by
        EFI.
      </para>

      <para>
        The EFI default video resolution settings can only be changed
        when the VM is powered off.
      </para>

    </sect2>

    <sect2 id="efibootargs">

      <title>Specifying Boot Arguments</title>

      <para>
        It is currently not possible to manipulate EFI variables from
        within a running guest. For example, setting the "boot-args"
        variable by running the <computeroutput>nvram</computeroutput>
        tool in a Mac OS X guest will not work. As an alternative way,
        "VBoxInternal2/EfiBootArgs" extradata can be passed to a VM in
        order to set the "boot-args" variable. To change the "boot-args"
        EFI variable:

<screen>VBoxManage setextradata "VM name" VBoxInternal2/EfiBootArgs &lt;value&gt;</screen>
      </para>

    </sect2>

  </sect1>

</chapter>