What is Virtual Box? towards Virtualization

VirtualBox is open-source software for virtualizing the x86 computing architecture. It acts as a hypervisor, creating a VM (virtual machine) in which the user can run another OS (operating system). The operating system in which VirtualBox runs is called the "host" OS. The operating system running in the VM is called the "guest" OS. VirtualBox supports Windows, Linux, or macOS as its host OS. When configuring a virtual machine, the user can specify how many CPU cores, and how much RAM and disk space should be devoted to the VM. When the VM is running, it can be paused. System execution is frozen at that moment in time, and the user can resume using it later.

VirtualBox was first offered by Innotek GmbH from Weinstadt, Germany, under a proprietary software license, making one version of the product available at no cost for personal or evaluation use, subject to the VirtualBox Personal Use and Evaluation License (PUEL).In January 2007, based on counsel by LiSoG, Innotek GmbH released VirtualBox Open Source Edition (OSE) as free and open-source software, subject to the requirements of the GNU General Public License (GPL), version 2 Innotek GmbH 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 Windows Virtual PC and Microsoft Virtual Server, which enables various host-guest OS interactions like shared clipboards or dynamic viewport resizing. Sun Microsystems acquired Innotek in February 2008. Oracle Corporation acquired Sun in January 2010 and re-branded the product as "Oracle VM VirtualBox".In December 2019, VirtualBox started supporting only Hardware-based virtualization, dropping support for Software-based one.

Oracle VM VirtualBox (formerly Sun VirtualBox, Sun xVM VirtualBox, and Innotek VirtualBox) is a free and open-source hosted hypervisor for x86 virtualization, developed by Oracle Corporation. Created by Innotek, it was acquired by Sun Microsystems in 2008, which was in turn acquired by Oracle in 2010.

VirtualBox may be installed on Windows, macOS, Linux, Solaris, and OpenSolaris. There are also ports to FreeBSD and Genode. It supports the creation and management of guest virtual machines running Windows, Linux, BSD, OS/2, Solaris, Haiku, and OSx86, as well as limited virtualization of macOS guests on Apple hardware. For some guest operating systems, a "Guest Additions" package of device drivers and system applications is available, which typically improves performance, especially that of graphics.

Client virtualization software from Oracle for desktop computers. Oracle VM VirtualBox runs in Windows, Mac, Linux, and Solaris computers and is used to host these same operating systems and others as guests. VirtualBox is free for personal use. It is also available for enterprises with a minimum of 100 users as a paid product with tech support. Initially created by Innotek GmbH in 2007, VirtualBox was acquired by Sun and then Oracle in 2008. 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.

In computing, a virtual machine (VM) is an emulation of a computer system. Virtual machines are based on computer architectures and provide the functionality of a physical computer. Their implementations may involve specialized hardware, software, or a combination. System virtual machines (also termed full virtualization VMs) provide a substitute for a real machine. They provide the functionality needed to execute entire operating systems. A hypervisor uses native execution to share and manage hardware, allowing for multiple environments that are isolated from one another, yet exist on the same physical machine. Modern hypervisors use hardware-assisted virtualization, virtualization-specific hardware, primarily from the host CPUs.

Some virtual machines, such as QEMU, are designed to also emulate different architectures and allow execution of software applications and operating systems written for another CPU or architecture. Operating-system-level virtualization allows the resources of a computer to be partitioned via the kernel. The terms are not universally interchangeable.

The VirtualBox can be run from the menu Applications System Tools A kernel module is started when the host computer is booted, but nothing happens until you manually start a virtual machine. This can be automated by a script, but by default, if you reboot your host, your guest machines will not be running anymore.VirtualBox 2.0 and onwards provides straightforward networking allowing IP address assignment and internet access using NAT, the default network option. See VirtualBox/Networking for more sophisticated set-ups and information for older versions of Ubuntu and VirtualBox.

Virtualbox (by Sun) has some advantages and disadvantages. There is a free proprietary edition as well as a subscription-based enterprise edition. The free edition only allows usage of a 32-bit operating system (as the guest OS) whereas the subscription edition allows a 64-bit guest OS. (Both require registration.) There is also has a free open source edition, but this is not easy to install in Windows (unlike in Linux). Virtualbox is available for all operating system platforms, and therefore a virtual machine created in one operating system (Windows, Apple, Linux) can be used in another. Furthermore, it is possible to convert virtual machines created in Virtualbox to VMWare and vice versa.

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