Oracle VM VirtualBox (formerly Sun VirtualBox, Sun xVM VirtualBox and Innotek VirtualBox) is a free and open-source hostedhypervisor for x86 computers currently being developed by Oracle Corporation. Developed initially by Innotek GmbH, it was acquired by Sun Microsystems in 2008 which was in turn acquired by Oracle in 2010.
The core package is, since version 4 in December 2010, free software under GNU General Public License version 2 (GPLv2). The separate "VirtualBox Oracle VM VirtualBox extension pack" providing support for USB 2.0 and 3.0 devices, Remote Desktop Protocol (RDP), disk encryption, NVMe and Preboot Execution Environment (PXE) boot is under a proprietary license, called Personal Use and Evaluation License (PUEL), which permits use of the software for personal use, educational use, or evaluation, free of charge. Oracle defines personal use as the installation of the software on a single host computer for non-commercial purposes.
Prior to version 4, there were two different packages of the VirtualBox software. The full package was offered free under the PUEL, with licenses for other commercial deployment purchasable from Oracle. A second package called the VirtualBox Open Source Edition (OSE) was released under GPLv2. This removed the same proprietary components not available under GPLv2.
Although VirtualBox has experimental support for Mac OS X guests, the end user license agreement of does not permit the operating system to run on non-Apple hardware, and this is enforced within the operating system by calls to the Apple System Management Controller (SMC) in all Apple machines, which verifies the authenticity of the hardware.
Users of VirtualBox can load multiple guest OSs under a single host operating-system (host OS). Each guest can be started, paused and stopped independently within its own virtual machine (VM). The user can independently configure each VM and run it under a choice of software-based virtualization or hardware assisted virtualization if the underlying host hardware supports this. The host OS and guest OSs and applications can communicate with each other through a number of mechanisms including a common clipboard and a virtualized network facility. Guest VMs can also directly communicate with each other if configured to do so.
In the absence of hardware-assisted virtualization, VirtualBox adopts a standard software-based virtualization approach. This mode supports 32-bit guest OSs which run in rings 0 and 3 of the Intel ring architecture.
The system reconfigures the guest OS code, which would normally run in ring 0, to execute in ring 1 on the host hardware. Because this code contains many privileged instructions which cannot run natively in ring 1, VirtualBox employs a Code Scanning and Analysis Manager (CSAM) to scan the ring 0 code recursively before its first execution to identify problematic instructions and then calls the Patch Manager (PATM) to perform in-situ patching. This replaces the instruction with a jump to a VM-safe equivalent compiled code fragment in hypervisor memory.
The guest user-mode code, running in ring 3, generally runs directly on the host hardware in ring 3.
In both cases, VirtualBox uses CSAM and PATM to inspect and patch the offending instructions whenever a fault occurs. VirtualBox also contains a dynamic recompiler, based on QEMU to recompile any real mode or protected mode code entirely (e.g. BIOS code, a DOS guest, or any operating system startup).
Using these techniques, VirtualBox can achieve a performance comparable to that of VMware.
VirtualBox supports both Intel's VT-x and AMD's AMD-V hardware-virtualization. Making use of these facilities, VirtualBox can run each guest VM in its own separate address-space; the guest OS ring 0 code runs on the host at ring 0 in VMX non-root mode rather than in ring 1.
A VirtualBox virtual machine can, therefore, use disks previously created in VMware or Microsoft Virtual PC, as well as its own native format. VirtualBox can also connect to iSCSI targets and to raw partitions on the host, using either as virtual hard disks. VirtualBox emulates IDE (PIIX4 and ICH6 controllers), SCSI, SATA (ICH8M controller) and SAS controllers to which hard drives can be attached.
Both ISO images and host-connected physical devices can be mounted as CD/DVD drives. For example, the DVD image of a Linux distribution can be downloaded and used directly by VirtualBox.
By default VirtualBox provides graphics support through a custom virtual graphics-card that is VESA compatible. The Guest Additions for Windows, Linux, Solaris, OpenSolaris, or OS/2 guests include a special video-driver that increases video performance and includes additional features, such as automatically adjusting the guest resolution when resizing the VM window
or desktop composition via virtualized WDDM drivers .
The emulated network cards allow most guest OSs to run without the need to find and install drivers for networking hardware as they are shipped as part of the guest OS. A special paravirtualized network adapter is also available, which improves network performance by eliminating the need to match a specific hardware interface, but requires special driver support in the guest. (Many distributions of Linux ship with this driver included.) By default, VirtualBox uses NAT through which Internet software for end-users such as Firefox or ssh can operate. Bridged networking via a host network adapter or virtual networks between guests can also be configured. Up to 36 network adapters can be attached simultaneously, but only four are configurable through the graphical interface.
For a sound card, VirtualBox virtualizes Intel HD Audio, Intel ICH AC'97 and SoundBlaster 16 devices.
A USB 1.1 controller is emulated so that any USB devices attached to the host can be seen in the guest. The proprietary extension pack adds a USB 2.0 or USB 3.0 controllers and, 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, although only if the client supports this VirtualBox-specific extension (Oracle provides clients for Solaris, Linux and Sun Ray thin clients that can do this, and have promised support for other platforms in future versions).
Run and control guest applications from the host – for automated software deployments
Since version 4.0
The PUEL/OSE separation was given up in favor of an open source base product and a closed source extension pack that can be installed on top of the base product. As part of this change, additional components of VirtualBox were made open source (installers, documentation, device drivers)
Paravirtualization support for Windows and Linux guests to improve time-keeping accuracy and performance
USB3 controller based on Intel's hardware implementation. It's supported by any Windows version starting from Windows 7, any Linux kernel starting from 2.6.31 and Mac OS X starting from version 10.7.4.
Bidirectional drag and drop support for Windows, Linux and Solaris guests
While Guest Additions are installed within each suitable guest virtual machine, the Extension Pack is installed on the host running VirtualBox.
Host OS support
Since version 5 (July 2015), VirtualBox has stated that they are dropping support for Windows XP host, thus leaving its users with Windows XP hosts vulnerable to flaws of earlier releases. VirtualBox can also be run under GNU/Linux, macOS, Sun Solaris and FreeBSD.
^"Oracle VM VirtualBox 4.3 Now Available" (Press release). Oracle Corporation. 2013-10-15. Retrieved . Generally available today, Oracle VM VirtualBox 4.3 delivers the latest enhancements to the world's most popular, free and open-source, cross-platform virtualization software.
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