(SMP).</
emphasis> VirtualBox can present up to 32 virtual CPUs to
a virtual machine, irrespective of how many CPU cores are actually
present in your host.</
para>
<
para><
emphasis role="bold">USB 2.0 device support.</
emphasis>
VirtualBox implements a virtual USB controller and allows you to
connect arbitrary USB devices to your virtual machines without
having to install device-specific drivers on the host. USB support
is not limited to certain device categories. For details, see
<
xref linkend="settings-usb" />.</
para>
<
para><
emphasis role="bold">Hardware compatibility.</
emphasis>
VirtualBox virtualizes a vast array of virtual devices, among them
many devices that are typically provided by other virtualization
platforms. That includes IDE, SCSI and SATA hard disk controllers,
several virtual network cards and sound cards, virtual serial and
parallel ports and an
Input/
Output Advanced Programmable Interrupt
Controller (I/O APIC), which is found in many modern PC systems.
This eases cloning of PC images from real machines and importing
of third-party virtual machines into VirtualBox.</
para>
<
para><
emphasis role="bold">Full ACPI support.</
emphasis> The
Advanced Configuration and Power Interface (ACPI) is fully
supported by VirtualBox. This eases cloning of PC images from real
machines or third-party virtual machines into VirtualBox. With its
unique <
emphasis role="bold">ACPI power status support,</
emphasis>
VirtualBox can even report to ACPI-aware guest operating systems
the power status of the host. For mobile systems running on
battery, the guest can thus enable energy saving and notify the
user of the remaining power (
e.g. in fullscreen modes).</
para>
<
para><
emphasis role="bold">Multiscreen resolutions.</
emphasis>
VirtualBox virtual machines support screen resolutions many times
that of a physical screen, allowing them to be spread over a large
number of screens attached to the host system.</
para>
<
para><
emphasis role="bold">Built-in iSCSI support.</
emphasis>
This unique feature allows you to connect a virtual machine
directly to an iSCSI storage server without going through the host
system. The VM accesses the iSCSI target directly without the
extra overhead that is required for virtualizing hard disks in
container files. For details, see <
xref linkend="storage-iscsi" />.</
para>
<
para><
emphasis role="bold">PXE Network boot.</
emphasis> The
integrated virtual network cards of VirtualBox fully support
remote booting via the Preboot Execution Environment (PXE).</
para>
<
para><
emphasis role="bold">Multigeneration branched
snapshots.</
emphasis> VirtualBox can save arbitrary snapshots of the
state of the virtual machine. You can go back in time and revert the
virtual machine to any such snapshot and start an alternative VM
configuration from there, effectively creating a whole snapshot tree.
For details, see <
xref linkend="snapshots" />. You can delete
snapshots while the virtual machine is running.</
para>
<
para><
emphasis role="bold">Clean architecture; unprecedented
modularity.</
emphasis> VirtualBox has an extremely modular design with
well-defined internal programming interfaces and a clean separation of
client and server code. This makes it easy to control it from several
interfaces at once: for example, you can start a VM simply by clicking
on a button in the VirtualBox graphical user interface and then
control that machine from the command line, or even remotely. See
<
xref linkend="frontends" /> for details.</
para>
<
para>Due to its modular architecture, VirtualBox can also expose its
full functionality and configurability through a comprehensive
<
emphasis role="bold">software development kit (SDK),</
emphasis> which
allows for integrating every aspect of VirtualBox with other software
systems. Please see <
xref linkend="VirtualBoxAPI" /> for
<
para><
emphasis role="bold">Remote machine display.</
emphasis> You can
run any virtual machine in a special VirtualBox program that acts as a
server for the VirtualBox Remote Desktop Protocol (VRDP), a
backward-compatible extension of the standard Remote Desktop Protocol.
With this unique feature, VirtualBox provides high-performance remote
access to any virtual machine.</
para>
<
para>VirtualBox's VRDP support does not rely on the RDP server that
is built into Microsoft Windows. Instead, a custom VRDP server has
been built directly into the virtualization layer. As a result, it
works with any operating system (even in text mode) and does not
require application support in the virtual machine either.</
para>
<
para>VRDP support is described in detail in <
xref linkend="vrdp" />.</
para>
<
para>On top of this special capacity, VirtualBox offers you more
unique features:<
itemizedlist>
<
para><
emphasis role="bold">Extensible RDP
authentication.</
emphasis> VirtualBox already supports Winlogon
on Windows and PAM on Linux for RDP authentication. In addition,
it includes an easy-to-use SDK which allows you to create
arbitrary interfaces for other methods of authentication; see
<
xref linkend="vbox-authenticate-sdk" /> for details.</
para>
<
para><
emphasis role="bold">USB over RDP.</
emphasis> Via RDP
virtual channel support, VirtualBox also allows you to connect
arbitrary USB devices locally to a virtual machine which is
running remotely on a VirtualBox RDP server; see <
xref linkend="usb-over-rdp" /> for details.</
para>
<
title id="hostossupport">Supported host operating systems</
title>
<
para>Currently, VirtualBox runs on the following host operating
<
para><
emphasis role="bold">Windows</
emphasis> hosts:<
itemizedlist>
<
para>Windows XP, all service packs (32-bit)</
para>
<
para>Windows Server 2003 (32-bit)</
para>
<
para>Windows Vista (32-bit and 64-bit<
footnote>
<
para>Support for 64-bit Windows was added with VirtualBox
<
para>Windows Server 2008 (32-bit and 64-bit)</
para>
<
para>Windows 7 (32-bit and 64-bit)</
para>
<
para><
emphasis role="bold">Mac OS X</
emphasis> hosts:<
footnote>
<
para>Preliminary Mac OS X support (beta stage) was added with
VirtualBox 1.4, full support with 1.6. Mac OS X 10.4 (Tiger)
support was removed with VirtualBox 3.1.</
para>
<
para>10.5 (Leopard, 32-bit)</
para>
<
para>10.6 (Snow Leopard, 32-bit and 64-bit)</
para>
<
para>Intel hardware is required; please see <
xref linkend="KnownIssues" /> also.</
para>
<
para><
emphasis role="bold">Linux</
emphasis> hosts (32-bit and
<
para>Support for 64-bit Linux was added with VirtualBox
</
footnote>). Among others, this includes:<
itemizedlist>
<
para>Ubuntu 6.06 ("Dapper Drake"), 6.10 ("Edgy Eft"), 7.04
("Feisty Fawn"), 7.10 ("Gutsy Gibbon"), 8.04 ("Hardy Heron"),
8.10 ("Intrepid Ibex"), 9.04 ("Jaunty Jackalope"), 9.10 ("Karmic
Koala"), 10.04 ("Lucid Lynx").</
para>
<
para>Debian
GNU/
Linux 3.1 ("sarge"), 4.0 ("etch") and 5.0
<
para>Oracle Enterprise Linux 4 and 5</
para>
<
para>Redhat Enterprise Linux 4 and 5</
para>
<
para>Fedora Core 4 to 12</
para>
<
para>Gentoo Linux</
para>
<
para>SUSE Linux 9 and 10, openSUSE 10.3, 11.0, 11.1,
<
para>Mandriva 2007.1, 2008.0, 2009.1, 2010.0</
para>
<
para>It should be possible to use VirtualBox on most systems based on
Linux kernel 2.6 using either the VirtualBox installer or by doing a
manual installation; see <
xref linkend="install-linux-host" />.</
para>
<
para>Note that starting with VirtualBox 2.1, Linux 2.4-based host
operating systems are no longer supported.</
para>
<
para><
emphasis role="bold">Solaris</
emphasis> hosts (32-bit and
<
para>Support for OpenSolaris was added with VirtualBox
</
footnote>) are supported with the restrictions listed in <
xref linkend="KnownIssues" />:<
itemizedlist>
<
para>OpenSolaris (2008.05 and higher, "Nevada" build 86 and
<
para>Solaris 10 (u8 and higher)</
para>
<
title>Installing and starting VirtualBox</
title>
<
para>VirtualBox comes in many different packages, and <
emphasis role="bold">installation</
emphasis> depends on your host platform. If you
have installed software before, installation should be straightforward as
on each host platform, VirtualBox uses the installation method that is
most common and easy to use. If you run into trouble or have special
requirements, please refer to <
xref linkend="installation" /> for details
about the various installation methods.</
para>
<
para>After installation, you can start VirtualBox as
<
para>On a Windows host, in the standard "Programs" menu, click on
the item in the "VirtualBox" group. On Vista or Windows 7, you can
also type "VirtualBox" in the search box of the "Start" menu.</
para>
<
para>On a Mac OS X host, in the Finder, double-click on the
"VirtualBox" item in the "Applications" folder. (You may want to
drag this item onto your Dock.)</
para>
<
para>On a Linux or Solaris host, depending on your desktop
environment, a "VirtualBox" item may have been placed in either the
"System" or "System Tools" group of your "Applications" menu.
Alternatively, you can type
<
computeroutput>VirtualBox</
computeroutput> in a terminal.</
para>
<
para>When you start VirtualBox for the first time, a window like the
following should come up:</
para>
</
mediaobject>On the left, you can see a pane that will later list all
your virtual machines. Since you have not created any, the list is empty.
A row of buttons above it allows you to create new VMs and work on
existing VMs, once you have some. The pane on the right displays the
properties of the virtual machine currently selected, if any. Again, since
you don't have any machines yet, the pane displays a welcome
<
para>To give you an idea what VirtualBox might look like later, after you
have created many machines, here's another example:</
para>
<
sect1 id="gui-createvm">
<
title>Creating your first virtual machine</
title>
<
para>Click on the "New" button at the top of the VirtualBox window. A
wizard will pop up to guide you through setting up a new virtual machine
</
mediaobject>On the following pages, the wizard will ask you for the
bare minimum of information that is needed to create a VM, in
<
para>A <
emphasis role="bold">name</
emphasis> for your VM, and the
<
emphasis role="bold">type of operating system</
emphasis> (OS) you
<
para>The name is what you will later see in the VirtualBox main
window, and what your settings will be stored under. It is purely
informational, but once you have created a few VMs, you will
appreciate if you have given your VMs informative names. "My VM"
probably is therefore not as useful as "Windows XP SP2".</
para>
<
para>For "Operating System Type", select the operating system that
you want to install later. Depending on your selection, VirtualBox
will enable or disable certain VM settings that your guest operating
system may require. This is particularly important for 64-bit guests
(see <
xref linkend="intro-64bitguests" />). It is therefore
recommended to always set it to the correct value.</
para>
<
para>The <
emphasis role="bold">amount of memory (RAM)</
emphasis>
that the virtual machine should have for itself. Every time a
virtual machine is started, VirtualBox will allocate this much
memory from your host machine and present it to the guest operating
system, which will report this size as the (virtual) computer's
<
para>Choose this setting carefully! The memory you give to the
VM will not be available to your host OS while the VM is
running, so do not specify more than you can spare. For example,
if your host machine has 1 GB of RAM and you enter 512 MB as the
amount of RAM for a particular virtual machine, while that VM is
running, you will only have 512 MB left for all the other
software on your host. If you run two VMs at the same time, even
more memory will be allocated for the second VM (which may not
even be able to start if that memory is not available). On the
other hand, you should specify as much as your guest OS (and
your applications) will require to run properly.</
para>
<
para>A Windows XP guest will require at least a few hundred MB RAM
to run properly, and Windows Vista will even refuse to install with
less than 512 MB. Of course, if you want to run graphics-intensive
applications in your VM, you may require even more RAM.</
para>
<
para>So, as a rule of thumb, if you have 1 GB of RAM or more in
your host computer, it is usually safe to allocate 512 MB to each
VM. But, in any case, make sure you always have at least 256 to 512
MB of RAM left on your host operating system. Otherwise you may
cause your host OS to excessively swap out memory to your hard disk,
effectively bringing your host system to a standstill.</
para>
<
para>VirtualBox restricts the amount of guest RAM to 1500 MB on
32-bit Windows hosts and to 2560 MB on 32-bit Linux and Solaris
hosts due to address-space limitations. These restrictions do
not apply to 64-bit hosts.</
para>
<
para>As with the other settings, you can change this setting later,
after you have created the VM.</
para>
<
para>Next, you must specify a <
emphasis role="bold">virtual hard
disk</
emphasis> for your VM.</
para>
<
para>There are many and potentially complicated ways in which
VirtualBox can provide hard disk space to a VM (see <
xref linkend="storage" /> for details), but the most common way is to use
a large image file on your "real" hard disk, whose contents
VirtualBox presents to your VM as if it were a complete hard
<
para>The wizard shows you the following window:</
para>
<
para>The wizard allows you to create an image file or use an
existing one. Note also that the disk images can be separated from a
particular VM, so even if you delete a VM, you can keep the image,
or copy it to another host and create a new VM for it there.</
para>
<
para>In the wizard, you have the following options:</
para>
<
para>If you have previously created any virtual hard disks
which have not been attached to other virtual machines, you
can select those from the drop-down list in the wizard
<
para>Otherwise, to create a new virtual hard disk, press the
<
emphasis role="bold">"New"</
emphasis> button.</
para>
<
para>Finally, for more complicated operations with virtual
disks, the <
emphasis role="bold">"Existing..."</
emphasis>
button will bring up the Virtual Media Manager, which is
described in more detail in <
xref linkend="vdis" />.</
para>
</
itemizedlist>Most probably, if you are using VirtualBox for the
first time, you will want to create a new disk image. Hence, press
<
para>This brings up another window, the <
emphasis role="bold">"Create New Virtual Disk Wizard".</
emphasis></
para>
<
para>VirtualBox supports two types of image files:<
itemizedlist>
<
para>A <
emphasis role="bold">dynamically expanding
file</
emphasis> will only grow in size when the guest actually
stores data on its virtual hard disk. It will therefore
initially be small on the host hard drive and only later grow
to the size specified as it is filled with data.</
para>
<
para>A <
emphasis role="bold">fixed-size file</
emphasis> will
immediately occupy the file specified, even if only a fraction
of the virtual hard disk space is actually in use. While
occupying much more space, a fixed-size file incurs less
overhead and is therefore slightly faster than a dynamically
<
para>For details about the differences, please refer to <
xref linkend="vdidetails" />.</
para>
<
para>To prevent your physical hard disk from running full,
VirtualBox limits the size of the image file. Still, it needs to be
large enough to hold the contents of your operating system and the
applications you want to install -- for a modern Windows or Linux
guest, you will probably need several gigabytes for any serious
<
para>After having selected or created your image file, again press
<
emphasis role="bold">"Next"</
emphasis> to go to the next
<
para>After clicking on <
emphasis role="bold">"Finish"</
emphasis>,
your new virtual machine will be created. You will then see it in
the list on the left side of the main window, with the name you have
<
title>Running your virtual machine</
title>
<
para>You will now see your new virtual machine in the list of virtual
machines, at the left of the VirtualBox main window. To start the virtual
machine, simply double-click on it, or select it and press the "Start"
button at the top.</
para>
<
para>This opens up a new window, and the virtual machine which you
selected will boot up. Everything which would normally be seen on the
virtual system's monitor is shown in the window, as can be seen with the
image in <
xref linkend="virtintro" />.</
para>
<
para>Since this is the first time you are running this VM, another wizard
will show up to help you select an installation medium. Since the VM is
created empty, it would otherwise behave just like a real computer with no
operating system installed: it will do nothing and display an error
message that it cannot boot an operating system.</
para>
<
para>For this reason, the "First Start Wizard" helps you select an
operating system medium to install an operating system from. In most
cases, this will either be a real CD or DVD (VirtualBox can then configure
the virtual machine to use your host's drive), or you might have an ISO
image of a CD or DVD handy, which VirtualBox can then present to the
<
para>In both cases, after making the choices in the wizard, you will be
able to install your operating system.</
para>
<
para>In general, you can use the virtual machine much like you would use
a real computer. There are couple of points worth mentioning
<
title>Keyboard and mouse support in virtual machines</
title>
<
title id="keyb_mouse_normal">Capturing and releasing keyboard and
<
para>As of version 3.2, VirtualBox provides a virtual USB tablet
device to new virtual machines through which mouse events are
communicated to the guest operating system. As a result, if you are
running a fairly recent guest operating system that can handle such
devices, mouse support may work out of the box without the mouse being
"captured" as described below; see <
xref linkend="settings-motherboard" /> for more information.</
para>
<
para>Otherwise, if the virtual machine only sees standard PS/2 mouse
and keyboard devices, since the operating system in the virtual
machine does not "know" that it is not running on a real computer, it
expects to have exclusive control over your keyboard and mouse. This
is, however, not the case since, unless you are running the VM in
full-screen mode, your VM needs to share keyboard and mouse with other
applications and possibly other VMs on your host.</
para>
<
para>As a result, initially after installing a guest operating system
and before you install the Guest Additions (we will explain this in a
minute), only one of the two -- your VM or the rest of your computer
-- can "own" the keyboard and the mouse. You will see a
<
emphasis>second</
emphasis> mouse pointer which will always be
confined to the limits of the VM window. Basically, you activate the
VM by clicking inside it.</
para>
<
para>To return ownership of keyboard and mouse to your host operating
system, VirtualBox reserves a special key on your keyboard for itself:
the <
emphasis role="bold">"host key".</
emphasis> By default, this is
the <
emphasis>right Control key</
emphasis> on your keyboard; on a Mac
host, the default host key is the left Command key. You can change
this default in the VirtualBox Global Settings. In any case, the
current setting for the host key is always displayed <
emphasis>at the
bottom right of your VM window,</
emphasis> should you have forgotten
</
mediaobject>In detail, all this translates into the
<
para>Your <
emphasis role="bold">keyboard</
emphasis> is owned by
the VM if the VM window on your host desktop has the keyboard
focus (and then, if you have many windows open in your guest
operating system as well, the window that has the focus in your
VM). This means that if you want to type within your VM, click
on the title bar of your VM window first.</
para>
<
para>To release keyboard ownership, press the Host key (as
explained above, typically the right Control key).</
para>
<
para>Note that while the VM owns the keyboard, some key
sequences (like Alt-Tab for example) will no longer be seen by
the host, but will go to the guest instead. After you press the
host key to re-enable the host keyboard, all key presses will go
through the host again, so that sequences like Alt-Tab will no
longer reach the guest.</
para>
<
para>Your <
emphasis role="bold">mouse</
emphasis> is owned by
the VM only after you have clicked in the VM window. The host
mouse pointer will disappear, and your mouse will drive the
guest's pointer instead of your normal mouse pointer.</
para>
<
para>Note that mouse ownership is independent of that of the
keyboard: even after you have clicked on a titlebar to be able
to type into the VM window, your mouse is not necessarily owned
<
para>To release ownership of your mouse by the VM, also press
<
para>As this behavior can be inconvenient, VirtualBox provides a set
of tools and device drivers for guest systems called the "VirtualBox
Guest Additions" which make VM keyboard and mouse operation a lot more
seamless. Most importantly, the Additions will get rid of the second
"guest" mouse pointer and make your host mouse pointer work directly
<
para>This will be described later in <
xref linkend="guestadditions" />.</
para>
<
title>Typing special characters</
title>
<
para>Operating systems expect certain key combinations to initiate
certain procedures. Some of these key combinations may be difficult to
enter into a virtual machine, as there are three candidates as to who
receives keyboard input: the host operating system, VirtualBox, or the
guest operating system. Who of these three receives keypresses depends
on a number of factors, including the key itself.</
para>
<
para>Host operating systems reserve certain key combinations for
themselves. For example, it is impossible to enter the <
emphasis role="bold">Ctrl+Alt+Delete</
emphasis> combination if you want to
reboot the guest operating system in your virtual machine, because
this key combination is usually hard-wired into the host OS (both
Windows and Linux intercept this), and pressing this key
combination will therefore reboot your
<
emphasis>host</
emphasis>.</
para>
<
para>Also, on Linux and Solairs hosts, which use the X Window
System, the key combination <
emphasis role="bold">Ctrl+Alt+Backspace</
emphasis> normally resets the X
server (to restart the entire graphical user interface in case it
got stuck). As the X server intercepts this combination, pressing
it will usually restart your <
emphasis>host</
emphasis> graphical
user interface (and kill all running programs, including
VirtualBox, in the process).</
para>
<
para>Third, on Linux hosts supporting virtual terminals, the key
combination <
emphasis role="bold">Ctrl+Alt+Fx</
emphasis> (where Fx
is one of the function keys from F1 to F12) normally allows to
switch between virtual terminals. As with Ctrl+Alt+Delete, these
combinations are intercepted by the host operating system and
therefore always switch terminals on the
<
emphasis>host</
emphasis>.</
para>
<
para>If, instead, you want to send these key combinations to the
<
emphasis>guest</
emphasis> operating system in the virtual
machine, you will need to use one of the following methods:</
para>
<
para>Use the items in the "Machine" menu of the virtual
machine window. There you will find "Insert Ctrl+Alt+Delete"
and "Ctrl+Alt+Backspace"; the latter will only have an effect
with Linux or Solaris guests, however.</
para>
<
para>Press special key combinations with the Host key
(normally the right Control key), which VirtualBox will then
translate for the virtual machine:<
itemizedlist>
<
para><
emphasis role="bold">Host key + Del</
emphasis> to
send Ctrl+Alt+Del (to reboot the guest);</
para>
<
para><
emphasis role="bold">Host key +
Backspace</
emphasis> to send Ctrl+Alt+Backspace (to
restart the graphical user interface of a Linux or
<
para><
emphasis role="bold">Host key + F1</
emphasis> (or
other function keys) to simulate Ctrl+Alt+F1 (or other
function keys,
i.e. to switch between virtual terminals
in a Linux guest).</
para>
<
para>For some other keyboard combinations such as <
emphasis role="bold">Alt-Tab</
emphasis> (to switch between open windows),
VirtualBox allows you to configure whether these combinations will
affect the host or the guest, if a virtual machine currently has
the focus. This is a global setting for all virtual machines and
can be found under "File" -> "Preferences" -> "Input" ->
"Auto-capture keyboard".</
para>
<
title>Changing removable media</
title>
<
para>While a virtual machine is running, you can change removable media
in the "Devices" menu of the VM's window. Here you can select in detail
what VirtualBox presents to your VM as a CD, DVD, or floppy.</
para>
<
para>The settings are the same as would be available for the VM in the
"Settings" dialog of the VirtualBox main window, but since that dialog
is disabled while the VM is in the "running" or "saved" state, this
extra menu saves you from having to shut down and restart the VM every
time you want to change media.</
para>
<
para>Hence, in the "Devices" menu, VirtualBox allows you to attach the
host drive to the guest or select a floppy or DVD image using the Disk
Image Manager, all as described in <
xref linkend="configbasics" />.</
para>
<
title>Saving the state of the machine</
title>
<
para>When you click on the "Close" button of your virtual machine
window (at the top right of the window, just like you would close any
other window on your system) (or press the Host key together with "Q"),
VirtualBox asks you whether you want to "save" or "power off" the
</
mediaobject>The difference between these three options is crucial.
<
para><
emphasis role="bold">Save the machine state:</
emphasis> With
this option, VirtualBox "freezes" the virtual machine by completely
saving its state to your local disk. When you later resume the VM
(by again clicking the "Start" button in the VirtualBox main
window), you will find that the VM continues exactly where it was
left off. All your programs will still be open, and your computer
resumes operation.</
para>
<
para>Saving the state of a virtual machine is thus in some ways
similar to suspending a laptop computer (
e.g. by closing its
<
para><
emphasis role="bold">Send the shutdown signal.</
emphasis>
This will send an ACPI shutdown signal to the virtual machine, which
has the same effect as if you had pressed the power button on a real
computer. So long as a fairly modern operating system is installed
and running in the VM, this should trigger a proper shutdown
mechanism in the VM.</
para>
<
para><
emphasis role="bold">Power off the machine:</
emphasis> With
this option, VirtualBox also stops running the virtual machine, but
<
emphasis>without</
emphasis> saving its state.</
para>
<
para>This is equivalent to pulling the power plug on a real
computer without shutting it down properly. If you start the machine
again after powering it off, your operating system will have to
reboot completely and may begin a lengthy check of its (virtual)
<
para>As a result, this should not normally be done, since it can
potentially cause data loss or an inconsistent state of the guest
<
para>As an exception, if your virtual machine has any snapshots
(see the next chapter), you can use this option to quickly <
emphasis role="bold">restore the current snapshot</
emphasis> of the virtual
machine. Only in that case, powering off the machine is not
<
para>The <
emphasis role="bold">"Discard"</
emphasis> button in the main
VirtualBox window discards a virtual machine's saved state. This has the
same effect as powering it off, and the same warnings apply.</
para>
<
para>With snapshots, you can save a particular state of a virtual machine
for later use. At any later time, you can revert to that state, even
though you may have changed the VM considerably since then.</
para>
<
para>You can see the snapshots of a virtual machine by first selecting a
machine from the list on the left of the VirtualBox main window and then
selecting the "Snapshots" tab on the right. Initially, until you take a
snapshot of the machine, that list is empty except for the "Current state"
item, which represents the "Now" point in the lifetime of the virtual
<
para>There are three operations related to snapshots:<
orderedlist>
<
para>You can <
emphasis role="bold">take a
snapshot</
emphasis>.<
itemizedlist>
<
para>If your VM is currently running, select "Take snapshot"
from the "Machine" pull-down menu of the VM window.</
para>
<
para>If your VM is currently in either the "saved" or the
"powered off" state (as displayed next to the VM in the
VirtualBox main window), click on the "Snapshots" tab on the
top right of the main window, and then<
itemizedlist>
<
para>either on the small camera icon (for "Take
<
para>right-click on the "Current State" item in the
list and select "Take snapshot" from the menu.</
para>
<
para>In any case, a window will pop up and ask you for a snapshot
name. This name is purely for reference purposes to help you
remember the state of the snapshot. For example, a useful name would
be "Fresh installation from scratch, no external drivers". You can
also add a longer text in the "Description" field if you
<
para>Your new snapshot will then appear in the list of snapshots
under the "Snapshots" tab. Underneath, you will see an item called
"Current state", signifying that the current state of your VM is a
variation based on the snapshot you took earlier. If you later take
another snapshot, you will see that they will be displayed in
sequence, and each subsequent snapshot is a derivation of the
earlier one:<
mediaobject>
<
para>VirtualBox allows you to take an unlimited number of snapshots
-- the only limitation is the size of your disks. Keep in mind that
each snapshot stores the state of the virtual machine and thus takes
<
para>You can <
emphasis role="bold">restore a snapshot</
emphasis> by
right-clicking on any snapshot you have taken in the list of
snapshots. By restoring a snapshot, you go back (or forward) in
time: the current state of the machine is lost, and the machine is
restored to exactly the same state as it was when then snapshot was
<
para>Both the terminology and the functionality of restoring
snapshots has changed with VirtualBox 3.1. Before that version,
it was only possible to go back to the very last snapshot taken
-- not earlier ones, and the operation was called "Discard
current state" instead of "Restore last snapshot". The
limitation has been lifted with version 3.1. It is now possible
to restore <
emphasis>any</
emphasis> snapshot, going backward and
<
para>Restoring a snapshot will affect the virtual hard drives
that are connected to your VM, as the entire state of the virtual
hard drive will be reverted as well. This means also that all
files that have been created since the snapshot and all other file
changes <
emphasis>will be lost. </
emphasis>In order to prevent
such data loss while still making use of the snapshot feature, it
is possible to add a second hard drive in "write-through" mode
using the <
computeroutput>VBoxManage</
computeroutput> interface
and use it to store your data. As write-through hard drives are
<
emphasis>not</
emphasis> included in snapshots, they remain
unaltered when a machine is reverted. See <
xref linkend="hdimagewrites" os="" /> for details.</
para>
<
para>By restoring an earlier snapshot and taking more snapshots
from there, it is even possible to create a kind of alternate
reality and to switch between these different histories of the
virtual machine. This can result in a whole tree of virtual machine
snapshots, as shown in the screenshot above.</
para>
<
para>You can also <
emphasis role="bold">delete a
snapshot</
emphasis>, which will not affect the state of the virtual
machine, but only release the files on disk that VirtualBox used to
store the snapshot data, thus freeing disk space. To delete a
snapshot, right-click on it in the snapshots tree and select
"Delete". As of VirtualBox 3.2, snapshots can be deleted even while
a machine is running.<
note>
<
para>Whereas taking and restoring snapshots are fairly quick
operations, deleting a snapshot can take a considerable amount
of time since large amounts of data may need to be copied
between several disk image files. Temporary disk files may also
need large amounts of disk space while the operation is in
<
para>There are some situations which cannot be handled while a VM
is running, and you will get an appropriate message that you need to
perform this snapshot deletion when the VM is shut down.</
para>
<
para>Think of a snapshot as a point in time that you have preserved. More
formally, a snapshot consists of three things:<
itemizedlist>
<
para>It contains a complete copy of the VM settings, so that when
you restore a snapshot, the VM settings are restored as well. (For
example, if you changed the hard disk configuration, that change is
undone when you restore the snapshot.)</
para>
<
para>The state of all the virtual disks attached to the machine is
preserved. Going back to a snapshot means that all changes, bit by
bit, that had been made to the machine's disks will be undone as
<
para>(Strictly speaking, this is only true for virtual hard disks
in "normal" mode. As mentioned above, you can configure disks to
behave differently with snapshots; see <
xref linkend="hdimagewrites" />. Even more formally and technically
correct, it is not the virtual disk itself that is restored when a
snapshot is restored. Instead, when a snapshot is taken, VirtualBox
creates differencing images which contain only the changes since the
snapshot were taken, and when the snapshot is restored, VirtualBox
throws away that differencing image, thus going back to the previous
state. This is both faster and uses less disk space. For the
details, which can be complex, please see <
xref linkend="diffimages" />.)</
para>
<
para>Finally, if you took a snapshot while the machine was running,
the memory state of the machine is also saved in the snapshot (the
same way the memory can be saved when you close the VM window) so
that when you restore the snapshot, execution resumes at exactly the
point when the snapshot was taken.</
para>
<
title id="configbasics">Virtual machine configuration</
title>
<
para>When you select a virtual machine from the list in the main
VirtualBox window, you will see a summary of that machine's settings on
the right of the window, under the "Details" tab.</
para>
<
para>Clicking on the "Settings" button in the toolbar at the top of
VirtualBox main window brings up a detailed window where you can configure
many of the properties of the VM that is currently selected. But be
careful: even though it is possible to change all VM settings after
installing a guest operating system, certain changes might prevent a guest
operating system from functioning correctly if done after
<
para>The "Settings" button is disabled while a VM is either in the
"running" or "saved" state. This is simply because the settings dialog
allows you to change fundamental characteristics of the virtual computer
that is created for your guest operating system, and this operating
system may not take it well when, for example, half of its memory is
taken away from under its feet. As a result, if the "Settings" button is
disabled, shut down the current VM first.</
para>
<
para>VirtualBox provides a plethora of parameters that can be changed for
a virtual machine. The various settings that can be changed in the
"Settings" window are described in detail in <
xref linkend="BasicConcepts" />. Even more parameters are available with the
command line interface; see <
xref linkend="vboxmanage" />.</
para>
<
para>For now, if you have just created an empty VM, you will probably be
most interested in the settings presented by the "
CD/
DVD-ROM" section if
you want to make a CD or a DVD available the first time you start it, in
order to install your guest operating system.</
para>
<
para>For this, you have two options:</
para>
<
para>If you have actual CD or DVD media from which you want to
install your guest operating system (
e.g. in the case of a Windows
installation CD or DVD), put the media into your host's CD or DVD
<
para>Then, in the settings dialog, go to the "
CD/
DVD-ROM" section and
select "Host drive" with the correct drive letter (or, in the case of
a Linux host, device file).</
para>
<
para>This will allow your VM to access the media in your host drive,
and you can proceed to install from there.</
para>
<
para>If you have downloaded installation media from the Internet in
the form of an ISO image file (most probably in the case of a Linux
distribution), you would normally burn this file to an empty CD or DVD
and proceed as just described. With VirtualBox however, you can skip
this step and mount the ISO file directly. VirtualBox will then
present this file as a CD or DVD-ROM drive to the virtual machine,
much like it does with virtual hard disk images.</
para>
<
para>In this case, in the settings dialog, go to the "
CD/
DVD-ROM"
section and select "ISO image file". This brings up the Virtual Media
Manager, where you perform the following steps:</
para>
<
para>Press the "Add" button to add your ISO file to the list of
registered images. This will present an ordinary file dialog
that allows you to find your ISO file on your host
<
para>Back to the manager window, select the ISO file that you
just added and press the "Select" button. This selects the ISO
<
para>The Virtual Media Manager is described in detail in <
xref linkend="vdis" />.</
para>
<
title>Deleting virtual machines</
title>
<
para>To remove a virtual machine which you no longer need, right-click on
it in the list of virtual machines in the main window and select "Delete"
from the context menu that comes up. All settings for that machine will be
<
para>The "Delete" menu item is disabled while a machine is in "Saved"
state. To delete such a machine, discard the saved state first by pressing
on the "Discard" button.</
para>
<
para>However, any hard disk images attached to the machine will be kept;
you can delete those separately using the Virtual Media Manager; see <
xref linkend="vdis" />.</
para>
<
para>You cannot delete a machine which has snapshots or is in a saved
state, so you must discard these first.</
para>
<
title>Importing and exporting virtual machines</
title>
<
para>Starting with version 2.2, VirtualBox can import and export virtual
machines in the industry-standard Open Virtualization Format (OVF).</
para>
<
para>OVF is a cross-platform standard supported by many virtualization
products which allows for creating ready-made virtual machines that can
then be imported into a virtualizer such as VirtualBox. As opposed to
other virtualization products, VirtualBox now supports OVF with an
easy-to-use graphical user interface as well as using the command line.
This allows for packaging so-called <
emphasis role="bold">virtual
appliances</
emphasis>: disk images together with configuration settings
that can be distributed easily. This way one can offer complete
ready-to-use software packages (operating systems with applications) that
need no configuration or installation except for importing into
<
para>The OVF standard is complex, and support in VirtualBox is an
ongoing process. In particular, no guarantee is made that VirtualBox
supports all appliances created by other virtualization software. For
a list of know limitations, please see <
xref linkend="KnownIssues" />.</
para>
<
para>An appliance in OVF format will typically consist of several
<
para>one or several disk images, typically in the widely-used VMDK
format (see <
xref linkend="vdidetails" />) and</
para>
<
para>a textual description file in an XML dialect with an
<
computeroutput>.ovf</
computeroutput> extension.</
para>
<
para>These files must reside in the same directory for VirtualBox to be
able to import them.</
para>
<
para>A future version of VirtualBox will also support packages that
include the OVF XML file and the disk images packed together in a single
<
para>To <
emphasis role="bold">import</
emphasis> an appliance in OVF
format, select "File" -> "Import appliance" from the main window of the
VirtualBox graphical user interface. Then open the file dialog and
navigate to the OVF text file with the
<
computeroutput>.ovf</
computeroutput> file extension.</
para>
<
para>If VirtualBox can handle the file, a dialog similar to the following
</
mediaobject>This presents the virtual machines described in the OVF
file and allows you to change the virtual machine settings by
double-clicking on the description items. Once you click on <
emphasis role="bold">"Import"</
emphasis>, VirtualBox will copy the disk images and
create local virtual machines with the settings described in the dialog.
These will then show up in the list of virtual machines.</
para>
<
para>Note that since disk images tend to be big, and VMDK images that
come with virtual appliances are typically shipped in a special compressed
format that is unsuitable for being used by virtual machines directly, the
images will need to be unpacked and copied first, which can take a few
<
para>For how to import an image at the command line, please see <
xref linkend="vboxmanage-import" />.</
para>
<
para>Conversely, to <
emphasis role="bold">export</
emphasis> virtual
machines that you already have in VirtualBox, select the machines and
"File" -> "Export appliance". A different dialog window shows up that
allows you to combine several virtual machines into an OVF appliance.
Then, you select the target location where the OVF and VMDK files should
be stored, and the conversion process begins. This can again take a
<
para>For how to export an image at the command line, please see <
xref linkend="vboxmanage-export" />.<
note>
<
para>OVF cannot describe snapshots that were taken for a virtual
machine. As a result, when you export a virtual machine that has
snapshots, only the current state of the machine will be exported, and
the disk images in the export will have a "flattened" state identical
to the current state of the virtual machine.</
para>
<
title>Alternative front-ends</
title>
<
para>As briefly mentioned in <
xref linkend="features-overview" />,
VirtualBox has a very flexible internal design that allows you to use
different front-ends to control the same virtual machines. To illustrate,
you can, for example, start a virtual machine with VirtualBox's
easy-to-use graphical user interface and then stop it from the command
line. With VirtualBox's support for the Remote Desktop Protocol (VRDP),
you can even run virtual machines remotely on a headless server and have
all the graphical output redirected over the network.</
para>
<
para>In detail, the following front-ends are shipped in the standard
VirtualBox package:</
para>
<
para><
computeroutput>VirtualBox</
computeroutput> is our graphical
user interface (GUI), which most of this User Manual is dedicated to
describing, especially in <
xref linkend="BasicConcepts" />. While
this is the easiest-to-use of our interfaces, it does not (yet)
cover all the features that VirtualBox provides. Still, this is the
best way to get to know VirtualBox initially.</
para>
<
para><
computeroutput>VBoxManage</
computeroutput> is our
command-line interface for automated and very detailed control of
every aspect of VirtualBox. It is described in <
xref linkend="vboxmanage" />.</
para>
<
para><
computeroutput>VBoxSDL</
computeroutput> is an alternative,
simple graphical front-end with an intentionally limited feature
set, designed to only display virtual machines that are controlled
in detail with <
computeroutput>VBoxManage</
computeroutput>. This is
interesting for business environments where displaying all the bells
and whistles of the full GUI is not feasible.
<
computeroutput>VBoxSDL</
computeroutput> is described in <
xref linkend="vboxsdl" />.</
para>
<
para>Finally, <
computeroutput>VBoxHeadless</
computeroutput> is yet
another front-end that produces no visible output on the host at
all, but merely acts as a VRDP server. Now, even though the other
graphical front-ends (VirtualBox and VBoxSDL) also have VRDP support
built-in and can act as a VRDP server, this particular front-end
requires no graphics support. This is useful, for example, if you
want to host your virtual machines on a headless Linux server that
has no X Window system installed. For details, see <
xref linkend="vboxheadless" />.</
para>
</
orderedlist>If the above front-ends still do not satisfy your
particular needs, it is relatively painless to create yet another
front-end to the complex virtualization engine that is the core of
VirtualBox, as the VirtualBox core neatly exposes all of its features in a
clean API; please refer to <
xref linkend="VirtualBoxAPI" />.</
para>
