In computing, a virtual machine (VM) is the
virtualization
In computing, virtualization or virtualisation (sometimes abbreviated v12n, a numeronym) is the act of creating a virtual (rather than actual) version of something at the same abstraction level, including virtual computer hardware platforms, st ...
/
emulation of a
computer system
A computer is a machine that can be programmed to carry out sequences of arithmetic or logical operations ( computation) automatically. Modern digital electronic computers can perform generic sets of operations known as programs. These prog ...
. Virtual machines are based on
computer architecture
In computer engineering, computer architecture is a description of the structure of a computer system made from component parts. It can sometimes be a high-level description that ignores details of the implementation. At a more detailed level, the ...
s and provide functionality of a physical computer. Their implementations may involve specialized hardware, software, or a combination.
Virtual machines differ and are organized by their function, shown here:
* ''
System virtual machines'' (also termed
full virtualization
In computer science, virtualization is a modern technique developed in late 1990s and is different from simulation and emulation. Virtualization employs techniques used to create instances of an environment, as opposed to simulation, which mode ...
VMs) provide a substitute for a real machine. They provide functionality needed to execute entire
operating system
An operating system (OS) is system software that manages computer hardware, software resources, and provides common daemon (computing), services for computer programs.
Time-sharing operating systems scheduler (computing), schedule tasks for ef ...
s. A
hypervisor
A hypervisor (also known as a virtual machine monitor, VMM, or virtualizer) is a type of computer software, firmware or hardware that creates and runs virtual machines. A computer on which a hypervisor runs one or more virtual machines is called ...
uses
native execution to share and manage hardware, allowing for multiple environments which are isolated from one another, yet exist on the same physical machine. Modern hypervisors use
hardware-assisted virtualization
In computing, hardware-assisted virtualization is a platform virtualization approach that enables efficient full virtualization using help from hardware capabilities, primarily from the host processors. A full virtualization is used to emulate a c ...
, virtualization-specific hardware, primarily from the host CPUs.
* Process virtual machines are designed to execute computer programs in a platform-independent environment.
Some virtual machine emulators, such as
QEMU
QEMU is a free and open-source emulator (Quick EMUlator). It emulates the machine's processor through dynamic binary translation and provides a set of different hardware and device models for the machine, enabling it to run a variety of g ...
and
video game console emulator
A video game console emulator is a type of emulator that allows a computing device to emulate a video game console's hardware and play its games on the emulating platform. More often than not, emulators carry additional features that surpass ...
s, are designed to also emulate (or "virtually imitate") different system architectures thus allowing execution of software applications and operating systems written for another
CPU
A central processing unit (CPU), also called a central processor, main processor or just processor, is the electronic circuitry that executes instructions comprising a computer program. The CPU performs basic arithmetic, logic, controlling, an ...
or architecture.
Operating-system-level virtualization
OS-level virtualization is an operating system (OS) paradigm in which the kernel allows the existence of multiple isolated user space instances, called ''containers'' (LXC, Solaris containers, Docker, Podman), ''zones'' (Solaris containers), '' ...
allows the resources of a computer to be partitioned via the
kernel
Kernel may refer to:
Computing
* Kernel (operating system), the central component of most operating systems
* Kernel (image processing), a matrix used for image convolution
* Compute kernel, in GPGPU programming
* Kernel method, in machine lea ...
. The terms are not universally interchangeable.
Definitions
System virtual machines
A "virtual machine" was originally defined by
Popek and Goldberg as "an efficient, isolated duplicate of a real computer machine."
[ Current use includes virtual machines that have no direct correspondence to any real hardware.][
The physical, "real-world" hardware running the VM is generally referred to as the 'host', and the virtual machine emulated on that machine is generally referred to as the 'guest'. A host can emulate several guests, each of which can emulate different operating systems and hardware platforms.
The desire to run multiple operating systems was the initial motive for virtual machines, so as to allow time-sharing among several single-tasking operating systems. In some respects, a system virtual machine can be considered a generalization of the concept of ]virtual memory
In computing, virtual memory, or virtual storage is a memory management technique that provides an "idealized abstraction of the storage resources that are actually available on a given machine" which "creates the illusion to users of a very ...
that historically preceded it. IBM's CP/CMS
CP/CMS (Control Program/Cambridge Monitor System) is a discontinued time-sharing operating system of the late 1960s and early 1970s, known for its excellent performance and advanced features. It had three distinct versions:
* CP-40/CMS, an im ...
, the first systems to allow full virtualization
In computer science, virtualization is a modern technique developed in late 1990s and is different from simulation and emulation. Virtualization employs techniques used to create instances of an environment, as opposed to simulation, which mode ...
, implemented time sharing
In computing, time-sharing is the sharing of a computing resource among many users at the same time by means of multiprogramming and multi-tasking.DEC Timesharing (1965), by Peter Clark, The DEC Professional, Volume 1, Number 1
Its emergence ...
by providing each user with a single-user operating system, the Conversational Monitor System
The Conversational Monitor System (CMS – originally: "Cambridge Monitor System") is a simple interactive single-user operating system. CMS was originally developed as part of IBM's CP/CMS operating system, which went into production use ...
(CMS). Unlike virtual memory, a system virtual machine entitled the user to write privileged instructions in their code. This approach had certain advantages, such as adding input/output devices not allowed by the standard system.[
As technology evolves virtual memory for purposes of virtualization, new systems of memory overcommitment may be applied to manage memory sharing among multiple virtual machines on one computer operating system. It may be possible to share ''memory pages'' that have identical contents among multiple virtual machines that run on the same physical machine, what may result in mapping them to the same physical page by a technique termed ]kernel same-page merging
In computing, kernel same-page merging (KSM), also known as kernel shared memory, memory merging, memory deduplication, and page deduplication is a kernel feature that makes it possible for a hypervisor system to share memory pages that have ...
(KSM). This is especially useful for read-only pages, such as those holding code segments, which is the case for multiple virtual machines running the same or similar software, software libraries, web servers, middleware components, etc. The guest operating systems do not need to be compliant with the host hardware, thus making it possible to run different operating systems on the same computer (e.g., Windows
Windows is a group of several proprietary graphical operating system families developed and marketed by Microsoft. Each family caters to a certain sector of the computing industry. For example, Windows NT for consumers, Windows Server for ...
, Linux
Linux ( or ) is a family of open-source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically packaged as a Linux distribution, which i ...
, or prior versions of an operating system) to support future software.[
The use of virtual machines to support separate guest operating systems is popular in regard to ]embedded system
An embedded system is a computer system—a combination of a computer processor, computer memory, and input/output peripheral devices—that has a dedicated function within a larger mechanical or electronic system. It is ''embedded'' ...
s. A typical use would be to run a real-time operating system
A real-time operating system (RTOS) is an operating system (OS) for real-time applications that processes data and events that have critically defined time constraints. An RTOS is distinct from a time-sharing operating system, such as Unix, which ...
simultaneously with a preferred complex operating system, such as Linux or Windows. Another use would be for novel and unproven software still in the developmental stage, so it runs inside a sandbox. Virtual machines have other advantages for operating system development and may include improved debugging access and faster reboots.[
Multiple VMs running their own guest operating system are frequently engaged for server consolidation.][
]
Process virtual machines
A process VM, sometimes called an ''application virtual machine'', or ''Managed Runtime Environment'' (MRE), runs as a normal application inside a host OS and supports a single process. It is created when that process is started and destroyed when it exits. Its purpose is to provide a platform
Platform may refer to:
Technology
* Computing platform, a framework on which applications may be run
* Platform game, a genre of video games
* Car platform, a set of components shared by several vehicle models
* Weapons platform, a system ...
-independent programming environment that abstracts away details of the underlying hardware or operating system and allows a program to execute in the same way on any platform.
A process VM provides a high-level abstraction that of a high-level programming language
In computer science, a high-level programming language is a programming language with strong abstraction from the details of the computer. In contrast to low-level programming languages, it may use natural language ''elements'', be easier to ...
(compared to the low-level ISA abstraction of the system VM). Process VMs are implemented using an interpreter; performance comparable to compiled programming languages can be achieved by the use of just-in-time compilation
In computing, just-in-time (JIT) compilation (also dynamic translation or run-time compilations) is a way of executing computer code that involves compiler, compilation during execution of a program (at run time (program lifecycle phase), run tim ...
.
This type of VM has become popular with the Java programming language
Java is a high-level, class-based, object-oriented programming language that is designed to have as few implementation dependencies as possible. It is a general-purpose programming language intended to let programmers ''write once, run an ...
, which is implemented using the Java virtual machine
A Java virtual machine (JVM) is a virtual machine that enables a computer to run Java programs as well as programs written in other languages that are also compiled to Java bytecode. The JVM is detailed by a specification that formally describ ...
. Other examples include the Parrot virtual machine
Parrot was a register-based process virtual machine designed to run dynamic languages efficiently. It is possible to compile Parrot assembly language and Parrot intermediate representation (PIR, an intermediate language) to Parrot bytecode ...
and the .NET Framework
The .NET Framework (pronounced as "''dot net"'') is a proprietary software framework developed by Microsoft that runs primarily on Microsoft Windows. It was the predominant implementation of the Common Language Infrastructure (CLI) until bein ...
, which runs on a VM called the Common Language Runtime
The Common Language Runtime (CLR), the virtual machine component of Microsoft .NET Framework, manages the execution of .NET programs. Just-in-time compilation converts the managed code (compiled intermediate language code) into machine instruc ...
. All of them can serve as an abstraction layer
In computing, an abstraction layer or abstraction level is a way of hiding the working details of a subsystem. Examples of software models that use layers of abstraction include the OSI model for network protocols, OpenGL, and other graphics libra ...
for any computer language.
A special case of process VMs are systems that abstract over the communication mechanisms of a (potentially heterogeneous) computer cluster
A computer cluster is a set of computers that work together so that they can be viewed as a single system. Unlike grid computers, computer clusters have each node set to perform the same task, controlled and scheduled by software.
The comp ...
. Such a VM does not consist of a single process, but one process per physical machine in the cluster. They are designed to ease the task of programming concurrent applications by letting the programmer focus on algorithms rather than the communication mechanisms provided by the interconnect and the OS. They do not hide the fact that communication takes place, and as such do not attempt to present the cluster as a single machine.
Unlike other process VMs, these systems do not provide a specific programming language, but are embedded in an existing language; typically such a system provides bindings for several languages (e.g., C and Fortran). Examples are Parallel Virtual Machine
Parallel Virtual Machine (PVM) is a software tool for parallel networking of computers. It is designed to allow a network of heterogeneous Unix and/or Windows machines to be used as a single distributed parallel processor. Thus large computati ...
(PVM) and Message Passing Interface (MPI). They are not strictly virtual machines because the applications running on top still have access to all OS services and are therefore not confined to the system model.
History
Both system virtual machines and process virtual machines date to the 1960s and continue to be areas of active development.
''System virtual machines'' grew out of time-sharing
In computing, time-sharing is the sharing of a computing resource among many users at the same time by means of multiprogramming and multi-tasking.DEC Timesharing (1965), by Peter Clark, The DEC Professional, Volume 1, Number 1
Its emergence ...
, as notably implemented in the Compatible Time-Sharing System
The Compatible Time-Sharing System (CTSS) was the first general purpose time-sharing operating system. Compatible Time Sharing referred to time sharing which was compatible with batch processing; it could offer both time sharing and batch proce ...
(CTSS). Time-sharing allowed multiple users to use a computer concurrently: each program appeared to have full access to the machine, but only one program was executed at the time, with the system switching between programs in time slices, saving and restoring state each time. This evolved into virtual machines, notably via IBM's research systems: the M44/44X, which used partial virtualization, and the CP-40
CP-40 was a research precursor to CP-67, which in turn was part of IBM's then-revolutionary CP 67CMS – a virtual machine/virtual memory time-sharing operating system for the IBM System/360 Model 67, and the parent of IBM's VM family. CP-40 ran ...
and SIMMON
SIMMON (SIMulation MONitor) was a proprietary software testing system developed in the late 1960s in the IBM Product Test Laboratory, then at Poughkeepsie, N.Y. It was designed for the then-new line of System/360 computers as a vehicle for testi ...
, which used full virtualization
In computer science, virtualization is a modern technique developed in late 1990s and is different from simulation and emulation. Virtualization employs techniques used to create instances of an environment, as opposed to simulation, which mode ...
, and were early examples of hypervisor
A hypervisor (also known as a virtual machine monitor, VMM, or virtualizer) is a type of computer software, firmware or hardware that creates and runs virtual machines. A computer on which a hypervisor runs one or more virtual machines is called ...
s. The first widely available virtual machine architecture was the CP-67
CP-67 was the ''control program'' portion of CP/CMS, a virtual machine operating system developed for the IBM System/360-67 by IBM's Cambridge Scientific Center. It was a reimplementation of their earlier research system CP-40, which ran on ...
/CMS (see History of CP/CMS for details). An important distinction was between using multiple virtual machines on one host system for time-sharing, as in M44/44X and CP-40, and using one virtual machine on a host system for prototyping, as in SIMMON. Emulator
In computing, an emulator is hardware or software that enables one computer system (called the ''host'') to behave like another computer system (called the ''guest''). An emulator typically enables the host system to run software or use peri ...
s, with hardware emulation of earlier systems for compatibility, date back to the IBM System/360
The IBM System/360 (S/360) is a family of mainframe computer systems that was announced by IBM on April 7, 1964, and delivered between 1965 and 1978. It was the first family of computers designed to cover both commercial and scientific applic ...
in 1963,[ while the software emulation (then-called "simulation") predates it.
''Process virtual machines'' arose originally as abstract platforms for an ]intermediate language
An intermediate representation (IR) is the data structure or code used internally by a compiler or virtual machine to represent source code. An IR is designed to be conducive to further processing, such as optimization and translation. A "good" ...
used as the intermediate representation
An intermediate representation (IR) is the data structure or code used internally by a compiler or virtual machine to represent source code. An IR is designed to be conducive to further processing, such as optimization and translation. A "good ...
of a program by a compiler
In computing, a compiler is a computer program that translates computer code written in one programming language (the ''source'' language) into another language (the ''target'' language). The name "compiler" is primarily used for programs that ...
; early examples date to around 1966. An early 1966 example was the O-code machine
BCPL ("Basic Combined Programming Language") is a procedural programming, procedural, imperative programming, imperative, and structured programming, structured programming language. Originally intended for writing compilers for other langua ...
, a virtual machine that executes O-code (object code) emitted by the front end of the BCPL
BCPL ("Basic Combined Programming Language") is a procedural, imperative, and structured programming language. Originally intended for writing compilers for other languages, BCPL is no longer in common use. However, its influence is still ...
compiler. This abstraction allowed the compiler to be easily ported to a new architecture by implementing a new back end that took the existing O-code and compiled it to machine code for the underlying physical machine. The Euler
Leonhard Euler ( , ; 15 April 170718 September 1783) was a Swiss mathematician, physicist, astronomer, geographer, logician and engineer who founded the studies of graph theory and topology and made pioneering and influential discoveries in ma ...
language used a similar design, with the intermediate language named ''P'' (portable).[ This was popularized around 1970 by Pascal, notably in the Pascal-P system (1973) and Pascal-S compiler (1975), in which it was termed ]p-code
Bytecode (also called portable code or p-code) is a form of instruction set designed for efficient execution by a software interpreter. Unlike human-readable source code, bytecodes are compact numeric codes, constants, and references (normal ...
and the resulting machine as a p-code machine. This has been influential, and virtual machines in this sense have been often generally called p-code machines. In addition to being an intermediate language, Pascal p-code was also executed directly by an interpreter implementing the virtual machine, notably in UCSD Pascal
UCSD Pascal is a Pascal programming language system that runs on the UCSD p-System, a portable, highly machine-independent operating system. UCSD Pascal was first released in 1977. It was developed at the University of California, San Diego (UC ...
(1978); this influenced later interpreters, notably the Java virtual machine
A Java virtual machine (JVM) is a virtual machine that enables a computer to run Java programs as well as programs written in other languages that are also compiled to Java bytecode. The JVM is detailed by a specification that formally describ ...
(JVM). Another early example was SNOBOL4
SNOBOL ("StriNg Oriented and symBOlic Language") is a series of programming languages developed between 1962 and 1967 at AT&T Bell Laboratories by David J. Farber, Ralph E. Griswold and Ivan P. Polonsky, culminating in SNOBOL4. It was one of ...
(1967), which was written in the SNOBOL Implementation Language (SIL), an assembly language for a virtual machine, which was then targeted to physical machines by transpiling to their native assembler via a macro assembler
Macro (or MACRO) may refer to:
Science and technology
* Macroscopic, subjects visible to the eye
* Macro photography, a type of close-up photography
* Image macro, a picture with text superimposed
* Monopole, Astrophysics and Cosmic Ray Observa ...
.[ Macros have since fallen out of favor, however, so this approach has been less influential. Process virtual machines were a popular approach to implementing early microcomputer software, including ]Tiny BASIC
Tiny BASIC is a family of dialects of the BASIC programming language that can fit into 4 or fewer KBs of memory. Tiny BASIC was designed in response to the open letter published by Bill Gates complaining about users pirating Altair BASIC, which ...
and adventure games, from one-off implementations such as Pyramid 2000 to a general-purpose engine like Infocom
Infocom was an American software company based in Cambridge, Massachusetts, that produced numerous works of interactive fiction. They also produced a business application, a relational database called ''Cornerstone''.
Infocom was founded on ...
's z-machine
The Z-machine is a virtual machine that was developed by Joel Berez and Marc Blank in 1979 and used by Infocom for its text adventure games. Infocom compiled game code to files containing Z-machine instructions (called story files or Z-code ...
, which Graham Nelson
Graham A. Nelson (born 1968) is a British mathematician, poet, and the creator of the Inform design system for creating interactive fiction (IF) games. He has authored several IF games, including '' Curses'' (1993) and '' Jigsaw'' (1995).
Educa ...
argues is "possibly the most portable virtual machine ever created".[
Significant advances occurred in the implementation of ]Smalltalk
Smalltalk is an object-oriented, dynamically typed reflective programming language. It was designed and created in part for educational use, specifically for constructionist learning, at the Learning Research Group (LRG) of Xerox PARC by ...
-80,[
particularly the Deutsch/Schiffmann implementation][
which pushed just-in-time (JIT) compilation forward as an implementation approach that uses process virtual machine.][
Later notable Smalltalk VMs were ]VisualWorks
VisualWorks is a cross-platform implementation of the Smalltalk language. It is implemented as a development system based on "images", which are dynamic collections of software objects, each contained in a system image.
The lineage of VisualWorks ...
, the Squeak Virtual Machine,[
and Strongtalk.][
A related language that produced a lot of virtual machine innovation was the ]Self
The self is an individual as the object of that individual’s own reflective consciousness. Since the ''self'' is a reference by a subject to the same subject, this reference is necessarily subjective. The sense of having a self—or ''selfhood ...
programming language,[ which pioneered adaptive optimization][ and generational garbage collection. These techniques proved commercially successful in 1999 in the ]HotSpot
Hotspot, Hot Spot or Hot spot may refer to:
Places
* Hot Spot, Kentucky, a community in the United States
Arts, entertainment, and media Fictional entities
* Hot Spot (comics), a name for the DC Comics character Isaiah Crockett
* Hot Spot (Tra ...
Java virtual machine.[
Other innovations include having a register-based virtual machine, to better match the underlying hardware, rather than a stack-based virtual machine, which is a closer match for the programming language; in 1995, this was pioneered by the Dis virtual machine for the ]Limbo
In Catholic theology, Limbo (Latin ''limbus'', edge or boundary, referring to the edge of Hell) is the afterlife condition of those who die in original sin without being assigned to the Hell of the Damned. Medieval theologians of Western Europ ...
language. OpenJ9 is an alternative for HotSpot JVM in OpenJDK and is an open source eclipse project claiming better startup and less resource consumption compared to HotSpot.
Full virtualization
In full virtualization, the virtual machine simulates enough hardware to allow an unmodified "guest" OS (one designed for the same instruction set
In computer science, an instruction set architecture (ISA), also called computer architecture, is an abstract model of a computer. A device that executes instructions described by that ISA, such as a central processing unit (CPU), is called a ...
) to be run in isolation. This approach was pioneered in 1966 with the IBM CP-40
CP-40 was a research precursor to CP-67, which in turn was part of IBM's then-revolutionary CP 67CMS – a virtual machine/virtual memory time-sharing operating system for the IBM System/360 Model 67, and the parent of IBM's VM family. CP-40 ran ...
and CP-67
CP-67 was the ''control program'' portion of CP/CMS, a virtual machine operating system developed for the IBM System/360-67 by IBM's Cambridge Scientific Center. It was a reimplementation of their earlier research system CP-40, which ran on ...
, predecessors of the VM family.
Examples outside the mainframe field include Parallels Workstation
Parallels Workstation is the first commercial software product released by Parallels, Inc., a developer of desktop and server virtualization software. The Workstation software consists of a virtual machine suite for Intel x86-compatible computers ...
, Parallels Desktop for Mac, VirtualBox
Oracle VM VirtualBox (formerly Sun VirtualBox, Sun xVM VirtualBox and Innotek VirtualBox) is a type-2 hypervisor for x86 virtualization developed by Oracle Corporation.
VirtualBox was originally created by Innotek GmbH, which was acquired by ...
, Virtual Iron, Oracle VM
An oracle is a person or agency considered to provide wise and insightful counsel or prophetic predictions, most notably including precognition of the future, inspired by deities. As such, it is a form of divination.
Description
The word '' ...
, Virtual PC, Virtual Server, Hyper-V
Microsoft Hyper-V, codenamed Viridian, and briefly known before its release as Windows Server Virtualization, is a native hypervisor; it can create virtual machines on x86-64 systems running Windows. Starting with Windows 8, Hyper-V superseded Wi ...
, VMware Workstation, VMware Server (discontinued, formerly called GSX Server), VMware ESXi
VMware ESXi (formerly ESX) is an enterprise-class, type-1 hypervisor developed by VMware for deploying and serving virtual computers. As a type-1 hypervisor, ESXi is not a software application that is installed on an operating system (OS); ...
, QEMU
QEMU is a free and open-source emulator (Quick EMUlator). It emulates the machine's processor through dynamic binary translation and provides a set of different hardware and device models for the machine, enabling it to run a variety of g ...
, Adeos, Mac-on-Linux, Win4BSD, Win4Lin Pro, and Egenera vBlade technology.
Hardware-assisted virtualization
In hardware-assisted virtualization, the hardware provides architectural support that facilitates building a virtual machine monitor and allows guest OSes to be run in isolation.[
Hardware-assisted virtualization was first introduced on the IBM System/370 in 1972, for use with VM/370, the first virtual machine operating system offered by IBM as an official product.][Randal, A. (2019). The Ideal Versus the Real: Revisiting the History of Virtual Machines and Containers.]
In 2005 and 2006, Intel
Intel Corporation is an American multinational corporation and technology company headquartered in Santa Clara, California, Santa Clara, California. It is the world's largest semiconductor chip manufacturer by revenue, and is one of the devel ...
and AMD provided additional hardware to support virtualization. Sun Microsystems (now Oracle Corporation
Oracle Corporation is an American multinational computer technology corporation headquartered in Austin, Texas. In 2020, Oracle was the third-largest software company in the world by revenue and market capitalization. The company sells da ...
) added similar features in their UltraSPARC T-Series processors in 2005. Examples of virtualization platforms adapted to such hardware include KVM, VMware Workstation, VMware Fusion, Hyper-V
Microsoft Hyper-V, codenamed Viridian, and briefly known before its release as Windows Server Virtualization, is a native hypervisor; it can create virtual machines on x86-64 systems running Windows. Starting with Windows 8, Hyper-V superseded Wi ...
, Windows Virtual PC, Xen, Parallels Desktop for Mac, Oracle VM Server for SPARC, VirtualBox
Oracle VM VirtualBox (formerly Sun VirtualBox, Sun xVM VirtualBox and Innotek VirtualBox) is a type-2 hypervisor for x86 virtualization developed by Oracle Corporation.
VirtualBox was originally created by Innotek GmbH, which was acquired by ...
and Parallels Workstation
Parallels Workstation is the first commercial software product released by Parallels, Inc., a developer of desktop and server virtualization software. The Workstation software consists of a virtual machine suite for Intel x86-compatible computers ...
.
In 2006, first-generation 32- and 64-bit x86 hardware support was found to rarely offer performance advantages over software virtualization.[
]
Operating-system-level virtualization
In operating-system-level virtualization, a physical server is virtualized at the operating system level, enabling multiple isolated and secure virtualized servers to run on a single physical server. The "guest" operating system environments share the same running instance of the operating system as the host system. Thus, the same operating system kernel
The kernel is a computer program at the core of a computer's operating system and generally has complete control over everything in the system. It is the portion of the operating system code that is always resident in memory and facilitates in ...
is also used to implement the "guest" environments, and applications running in a given "guest" environment view it as a stand-alone system. The pioneer implementation was FreeBSD jails; other examples include Docker, Solaris Containers
Solaris Containers (including Solaris Zones) is an implementation of operating system-level virtualization technology for x86 and SPARC systems, first released publicly in February 2004 in build 51 beta of Solaris 10, and subsequently in the ...
, OpenVZ, Linux-VServer, LXC
Linux Containers (LXC) is an operating-system-level virtualization method for running multiple isolated Linux systems (containers) on a control host using a single Linux kernel.
The Linux kernel provides the cgroups functionality that allows li ...
, AIX Workload Partitions, Parallels Virtuozzo Containers, and iCore Virtual Accounts.
See also
* Amazon Machine Image
* Desktop virtualization
Desktop virtualization is a software technology that separates the desktop environment and associated application software from the physical client device that is used to access it.
Desktop virtualization can be used in conjunction with applicati ...
* Linux containers
* Native development kit
* Paravirtualization
In computing, paravirtualization or para-virtualization is a virtualization technique that presents a software interface to the virtual machines which is similar, yet not identical, to the underlying hardware–software interface.
The intent o ...
* Storage hypervisor
* Universal Turing machine
In computer science, a universal Turing machine (UTM) is a Turing machine that can simulate an arbitrary Turing machine on arbitrary input. The universal machine essentially achieves this by reading both the description of the machine to be simu ...
* Virtual appliance
A virtual appliance is a pre-configured virtual machine image, ready to run on a hypervisor; virtual appliances are a subset of the broader class of software appliances. Installation of a software appliance on a virtual machine and packaging that ...
* Virtual backup appliance
* Virtual disk image
* Virtual DOS machine
Virtual DOS machines (VDM) refer to a technology that allows running 16-bit/32-bit DOS and 16-bit Windows programs when there is already another operating system running and controlling the hardware.
Overview
Virtual DOS machines can operate ei ...
(VDM)
* Virtual machine escape
References
Further reading
* James E. Smith, Ravi Nair, ''Virtual Machines: Versatile Platforms For Systems And Processes'', Morgan Kaufmann, May 2005, , 656 pages (covers both process and system virtual machines)
* Craig, Iain D. ''Virtual Machines''. Springer
Springer or springers may refer to:
Publishers
* Springer Science+Business Media, aka Springer International Publishing, a worldwide publishing group founded in 1842 in Germany formerly known as Springer-Verlag.
** Springer Nature, a multinationa ...
, 2006, , 269 pages (covers only process virtual machines)
External links
*
Sandia National Laboratories Runs 1 Million Linux Kernels as Virtual Machines
The design of the Inferno virtual machine by Phil Winterbottom and Rob Pike
{{DEFAULTSORT:Virtual Machine
Operating system technology
Programming language implementation