VirtualBox is an x86 virtualization software package, originally created by German software company innotek, now developed by Sun Microsystems as part of its Sun xVM virtualization platform. It is installed on an existing host operating system; within this application, additional operating systems, each known as a Guest OS, can be loaded and run, each with its own virtual environment.
Supported host operating systems include Linux, Mac OS X, OS/2 Warp, Windows XP or Vista, and Solaris, while supported guest operating systems include DragonFlyBSD, FreeBSD, Linux, OpenBSD, OS/2 Warp, Windows and Solaris. The latest version also supports Windows 7 beta and release candidate 1.
According to a 2007 survey by DesktopLinux.com, VirtualBox was the third most popular software package for running Windows programs on Linux desktops.History
The application was initially offered under a proprietary software license. One version of the product was available at no cost for personal or evaluation use, subject to the VirtualBox Personal Use and Evaluation License (PUEL). In January 2007, VirtualBox OSE (Open Source Edition) was released as free software, subject to the requirements of the GNU General Public License (GPL), version 2.
The original developer, innotek, also contributed to the development of OS/2 and Linux support in virtualization and OS/2 ports of products from Connectix which were later acquired by Microsoft. Specifically, innotek developed the “additions” code in both Microsoft Virtual PC and Microsoft Virtual Server, which greatly improves host-guest OS interactions. OS/2 has been notoriously difficult to run virtualized in the past due to extensive ring 2 execution.[citation needed]
Sun Microsystems acquired Innotek in February 2008.
Emulated environment
Several guest operating systems can be loaded. Each can be started, paused and stopped independently. The host operating system and guest operating systems can communicate with each other, using the network facility provided, as can guest operating systems if more than one is running.
Hardware emulation
VirtualBox supports both Intel's hardware virtualization VT-x and AMD's AMD-V.
Hard disks are emulated in a special container format called "Virtual Disk Images", which is, at present, incompatible with the formats used by other virtualization solutions. These are normally stored as system files on the host operating system (with a .vdi suffix). Alternatively, VirtualBox has a unique feature in that it can connect to iSCSI targets and use them as virtual hard disks as well. VirtualBox can also read and write disk images in VMware Virtual Machine Disk Format (VMDK) and Microsoft Virtual PC VHD format. This means that a VirtualBox virtual machine can be set up using disks that were created in VMware or Microsoft Virtual PC.
ISO images can be mounted as CD/DVD drives. For example the DVD image of a Linux distribution can be downloaded and used directly by VirtualBox. While there's no need to burn a disk, it is also possible to mount physical disks directly to a virtual machine.
By default VirtualBox provides graphics support through a custom virtual graphics card which is VESA compatible. With the Guest Additions for Windows, Linux, Solaris or OS/2 guests comes a special video driver that allows for better performance and features such as dynamically adjusting the guest resolution when the VM window is resized.
For an Ethernet network adapter, VirtualBox virtualizes these Network Interface Cards: AMD PCnet PCI II (Am79C970A), AMD PCnet-Fast III (Am79C973), Intel Pro/1000 MT Desktop (82540EM), Intel Pro/1000 MT Server (82545EM), and Intel Pro/1000 T Server (82543GC). Such a broad range of the emulated network cards allows running many operating systems without finding and installing drivers. By default, VirtualBox sets the network up with NAT through which user programs like Firefox or ssh can operate. For hosts other than Windows Vista, other options exist, such as virtual networks between guests. Up to four network adapters can be attached simultaneously.
For a sound card, VirtualBox virtualizes an Intel ICH AC'97 device or a SoundBlaster 16 card.
In the "full release" (not in the open-source edition), a USB controller is emulated (both USB 1.1 and USB 2.0) so that any USB devices attached to the host can be seen in the guest. If VirtualBox acts as an RDP server, it can also use USB devices on the remote RDP client as if they were connected to the host.
VirtualBox attempts to run as much guest code natively (that is, directly on the host processor) as possible. This works well for user-mode code running in the guest's ring 3 of the Intel ring architecture. However, the guest's ring-0 code, which will usually contain many privileged instructions, will need to be intercepted. VirtualBox has a rather novel approach to fix this conflict: It tricks the guest operating system to actually execute its ring-0 code in ring 1, which is normally unused on the Intel architecture.
If problems arise, VirtualBox has a built-in dynamic recompiler, like other virtualizers do. VirtualBox's recompiler is based on the free and open-source QEMU. In addition, however, VirtualBox automatically disassembles and, in many situations, patches the guest code to avoid future recompilations, as these are relatively expensive. As a result, both the guest's ring-3 and ring-0 code can run natively most of the time, and with this combination of "traditional" recompiling and actual code patching, VirtualBox achieves a performance that is comparable to that of VMware.
Feature set
- 64-bit guests (64 bit hosts with CPU virtualisation extensions or experimentally on 64bit capable 32bit host operating systems)
- NCQ support for SATA raw disks and partitions
- Snapshots
- Seamless mode
- Clipboard
- Shared folders
- Special drivers and utilities to facilitate switching between systems
- Experimental OpenGL drivers for win32 and Linux to render on Host hardware
- Command line interaction (in addition to the GUI)
- Public API (Java, Python, SOAP, XPCOM) to control VM configuration and execution [16]
- Remote display (useful for headless host machines)
- Nested paging for AMD-V and Intel Intel Core i7
- Raw hard disk access - allows a guest operating system to access its virtual hard disk without going through the host OS file system
- VMware Virtual Machine Disk Format (VMDK) support - allows VirtualBox to use a disk image created in VMware
- Microsoft VHD support
Only available in the full version:
- Remote Desktop Protocol (RDP) control of VM
- USB support, with remote devices over RDP
- iSCSI support
- Open Virtualization Format (OVF) support (import/export)
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