1.3. Features overview

Portability. VirtualBox runs on a large number of 32-bit and 64-bit host operating systems (again, see Section 1.4, “Supported host operating systems” for details).

VirtualBox is a so-called "hosted" hypervisor (sometimes referred to as a "type 2" hypervisor). Whereas a "bare-metal" or "type 1" hypervisor would run directly on the hardware, VirtualBox requires an existing operating system to be installed. It can thus run alongside existing applications on that host.

To a very large degree, VirtualBox is functionally identical on all of the host platforms, and the same file and image formats are used. This allows you to run virtual machines created on one host on another host with a different host operating system; for example, you can create a virtual machine on Windows and then run it under Linux.

In addition, virtual machines can easily be imported and exported using the Open Virtualization Format (OVF, see Section 1.14, “Importing and exporting virtual machines”), an industry standard created for this purpose. You can even import OVFs that were created with a different virtualization software.

No hardware virtualization required. For many scenarios, VirtualBox does not require the processor features built into newer hardware like Intel VT-x or AMD-V. As opposed to many other virtualization solutions, you can therefore use VirtualBox even on older hardware where these features are not present. The technical details are explained in Section 10.3, “Hardware vs. software virtualization”.

Guest Additions: shared folders, seamless windows, 3D virtualization. The VirtualBox Guest Additions are software packages which can be installed inside of supported guest systems to improve their performance and to provide additional integration and communication with the host system. After installing the Guest Additions, a virtual machine will support automatic adjustment of video resolutions, seamless windows, accelerated 3D graphics and more. The Guest Additions are described in detail in Chapter 4, Guest Additions.

In particular, Guest Additions provide for "shared folders", which let you access files from the host system from within a guest machine. Shared folders are described in Section 4.3, “Shared folders”.

Great hardware support. Among others, VirtualBox supports:

Multigeneration branched snapshots. 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 Section 1.10, “Snapshots”. You can create and delete snapshots while the virtual machine is running.

VM groups. VirtualBox provides a groups feature that enables the user to organize and control virtual machines collectively, as well as individually. In addition to basic groups, it is also possible for any VM to be in more than one group, and for groups to be nested in a hierarchy -- i.e. groups of groups. In general, the operations that can be performed on groups are the same as those that can be applied to individual VMs i.e. Start, Pause, Reset, Close (Save state, Send Shutdown, Poweroff), Discard Saved State, Show in fileSystem, Sort.

Clean architecture; unprecedented modularity. 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 Section 1.16, “Alternative front-ends” for details.

Due to its modular architecture, VirtualBox can also expose its full functionality and configurability through a comprehensive software development kit (SDK), which allows for integrating every aspect of VirtualBox with other software systems. Please see Chapter 11, VirtualBox programming interfaces for details.

Remote machine display. The VirtualBox Remote Desktop Extension (VRDE) allows for high-performance remote access to any running virtual machine. This extension supports the Remote Desktop Protocol (RDP) originally built into Microsoft Windows, with special additions for full client USB support.

The VRDE does not rely on the RDP server that is built into Microsoft Windows; instead, it is plugged directly into the virtualization layer. As a result, it works with guest operating systems other than Windows (even in text mode) and does not require application support in the virtual machine either. The VRDE is described in detail in Section 7.1, “Remote display (VRDP support)”.

On top of this special capacity, VirtualBox offers you more unique features: