Virtual machine
Encyclopedia
A virtual machine is a "completely isolated guest operating system installation within a normal host operating system". Modern virtual machines are implemented with either software emulation or hardware virtualization or (in the most cases) both together.
(OS). In contrast, a process virtual machine is designed to run a single program
, which means that it supports a single process
. An essential characteristic of a virtual machine is that the software running inside is limited to the resources and abstractions provided by the virtual machine—it cannot break out of its virtual world.
A virtual machine was originally defined by Popek and Goldberg
as "an efficient, isolated duplicate of a real machine". Current use includes virtual machines which have no direct correspondence to any real hardware.
The main disadvantages of VMs are:
Multiple VMs each running their own operating system (called guest operating system) are frequently used in server consolidation, where different services that used to run on individual machines to avoid interference are instead run in separate VMs on the same physical machine.
The desire to run multiple operating systems was the original motivation for virtual machines, as it allowed time-sharing a single computer between several single-tasking Operation Systems. In some respects, a system virtual machine can be considered a generalization of the concept of virtual memory
that historically preceded it. IBM's CP/CMS
, the first systems to allow full virtualization
, implemented time sharing by providing each user with a single-user operating system, the CMS
. Unlike virtual memory, a system virtual machine allowed the user to use privileged instructions in their code. This approach had certain advantages, for instance it allowed users to add input/output devices not allowed by the standard system.
The guest OSes do not have to be compliant with the hardware making it possible to run different OSes on the same computer (e.g., Microsoft Windows
and Linux
, or older versions of an OS to support software that has not yet been ported to the latest version). The use of virtual machines to support different guest OSes is becoming popular in embedded systems; a typical use is to support a real-time operating system
at the same time as a high-level OS such as Linux or Windows.
Another use is to sandbox
an OS that is not trusted, possibly because it is a system under development. Virtual machines have other advantages for OS development, including better debugging access and faster reboots.
A process VM provides a high-level abstraction — that of a high-level programming language
(compared to the low-level ISA abstraction of the system VM). Process VMs are implemented using an interpreter
; performance comparable to compiled programming languages is achieved by the use of just-in-time compilation
.
This type of VM has become popular with the Java programming language
, which is implemented using the Java virtual machine
. Other examples include the Parrot virtual machine
, which serves as an abstraction layer
for several interpreted languages, and the .NET Framework
, which runs on a VM called the Common Language Runtime
.
A special case of process VMs are systems that abstract over the communication mechanisms of a (potentially heterogeneous) computer cluster. 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 parallel 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 parallel 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 PVM (Parallel Virtual Machine
) and MPI (Message Passing Interface
). They are not strictly virtual machines, as the applications running on top still have access to all OS services, and are therefore not confined to the system model provided by the "VM".
of the hardware, and can be implemented using a Type 1 or Type 2 hypervisor
. (A Type 1 hypervisor runs directly on the hardware; a Type 2 hypervisor runs on another operating system, such as Linux
). Each virtual machine can run any operating system supported by the underlying hardware. Users can thus run two or more different "guest" operating systems simultaneously, in separate "private" virtual computers.
The pioneer system using this concept was IBM's CP-40
, the first (1967) version of IBM's CP/CMS
(1967–1972) and the precursor to IBM's VM family
(1972–present). With the VM architecture, most users run a relatively simple interactive computing
single-user operating system, CMS
, as a "guest" on top of the VM control program (VM-CP
). This approach kept the CMS design simple, as if it were running alone; the control program quietly provides multitasking and resource management services "behind the scenes". In addition to CMS, VM users can run any of the other IBM operating systems, such as MVS
or z/OS
. z/VM
is the current version of VM, and is used to support hundreds or thousands of virtual machines on a given mainframe. Some installations use Linux for zSeries to run Web server
s, where Linux
runs as the operating system within many virtual machines.
Full virtualization is particularly helpful in operating system development, when experimental new code can be run at the same time as older, more stable, versions, each in a separate virtual machine. The process can even be recursive: IBM
debugged new versions of its virtual machine operating system, VM
, in a virtual machine running under an older version of VM, and even used this technique to simulate new hardware.
The standard x86 processor architecture as used in the modern PCs does not actually meet the Popek and Goldberg virtualization requirements
. Notably, there is no execution mode where all sensitive machine instructions always trap, which would allow per-instruction virtualization.
Despite these limitations, several software packages have managed to provide virtualization on the x86 architecture
, even though dynamic recompilation
of privileged code, as first implemented by VMware
, incurs some performance overhead as compared to a VM running on a natively virtualizable architecture such as the IBM System/370 or Motorola MC68020
. By now, several other software packages such as Virtual PC, VirtualBox
, Parallels Workstation
and Virtual Iron
manage to implement virtualization on x86 hardware.
Intel and AMD have introduced features to their x86 processors to enable virtualization in hardware.
As well as virtualization of the resources of a single machine, multiple independent nodes in a cluster can be combined and accessed as a single virtual NUMA
machine .
, allowing software applications and operating systems written for another computer processor architecture to be run.
Some virtual machines emulate hardware that only exists as a detailed specification. For example:
This technique allows diverse computers to run any software written to that specification; only the virtual machine software itself must be written separately for each type of computer on which it runs.
is a server virtualization technology which virtualizes server
s on an operating system
(kernel) layer. It can be thought of as partitioning: a single physical server is sliced into multiple small partitions (otherwise called virtual environments (VE), virtual private server
s (VPS), guests, zones, etc.); each such partition looks and feels like a real server, from the point of view of its users.
For example, Solaris Zones supports multiple guest OSes running under the same OS (such as Solaris 10). All guest OSes have to use the same kernel level and cannot run as different OS versions. Solaris native Zones also requires that the host OS be a version of Solaris; other OSes from other manufacturers are not supported.,however you need to use Solaris Branded zones to use another OSes as zones.
Another example is System Workload Partitions (WPARs), introduced in the IBM AIX 6.1 operating system. System WPARs are software partitions running under one instance of the global AIX OS environment.
The operating system level architecture has low overhead that helps to maximize efficient use of server resources. The virtualization introduces only a negligible overhead and allows running hundreds of virtual private server
s on a single physical server. In contrast, approaches such as full virtualization
(like VMware
) and paravirtualization
(like Xen
or UML
) cannot achieve such level of density, due to overhead of running multiple kernels. From the other side, operating system-level virtualization does not allow running different operating systems (i.e. different kernels), although different libraries, distributions etc. are possible.
System (hardware) virtual machine software
Operating system level virtualization software
VM Definitions
A virtual machine (VM) is a software implementation of a machine (i.e. a computer) that executes programs like a physical machine. Virtual machines are separated into two major categories, based on their use and degree of correspondence to any real machine. A system virtual machine provides a complete system platform which supports the execution of a complete operating systemOperating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...
(OS). In contrast, a process virtual machine is designed to run a single program
Computer program
A computer program is a sequence of instructions written to perform a specified task with a computer. A computer requires programs to function, typically executing the program's instructions in a central processor. The program has an executable form that the computer can use directly to execute...
, which means that it supports a single process
Process (computing)
In computing, a process is an instance of a computer program that is being executed. It contains the program code and its current activity. Depending on the operating system , a process may be made up of multiple threads of execution that execute instructions concurrently.A computer program is a...
. An essential characteristic of a virtual machine is that the software running inside is limited to the resources and abstractions provided by the virtual machine—it cannot break out of its virtual world.
A virtual machine was originally defined by Popek and Goldberg
Popek and Goldberg virtualization requirements
The Popek and Goldberg virtualization requirements are a set of conditions sufficient for a computer architecture to support system virtualization efficiently. They were introduced by Gerald J. Popek and Robert P. Goldberg in their 1974 article "Formal Requirements for Virtualizable Third...
as "an efficient, isolated duplicate of a real machine". Current use includes virtual machines which have no direct correspondence to any real hardware.
System virtual machines
System virtual machines- multiple OS environments can co-exist on the same computer, in strong isolation from each other
- the virtual machine can provide an instruction setInstruction setAn instruction set, or instruction set architecture , is the part of the computer architecture related to programming, including the native data types, instructions, registers, addressing modes, memory architecture, interrupt and exception handling, and external I/O...
architecture (ISA) that is somewhat different from that of the real machine - application provisioning, maintenance, high availability and disaster recovery
The main disadvantages of VMs are:
- a virtual machine is less efficient than a real machine when it accesses the hardware indirectly
- when multiple VMs are concurrently running on the same physical host, each VM may exhibit a varying and unstable performance (Speed of Execution, and not results), which highly depends on the workload imposed on the system by other VMs, unless proper techniques are used for temporal isolation among virtual machinesTemporal isolation among virtual machinesTemporal isolation or performance isolation among virtual machine refers to the capability of isolating the temporal behavior of multiple VMs among each other, despite them running on the same physical host and sharing a set of physical resources such as processors, memory, and...
.
Multiple VMs each running their own operating system (called guest operating system) are frequently used in server consolidation, where different services that used to run on individual machines to avoid interference are instead run in separate VMs on the same physical machine.
The desire to run multiple operating systems was the original motivation for virtual machines, as it allowed time-sharing a single computer between several single-tasking Operation Systems. In some respects, a system virtual machine can be considered a generalization of the concept of virtual memory
Virtual memory
In computing, virtual memory is a memory management technique developed for multitasking kernels. This technique virtualizes a computer architecture's various forms of computer data storage , allowing a program to be designed as though there is only one kind of memory, "virtual" memory, which...
that historically preceded it. IBM's CP/CMS
CP/CMS
CP/CMS was a time-sharing operating system of the late 60s and early 70s, known for its excellent performance and advanced features...
, the first systems to allow full virtualization
Full virtualization
In computer science, full virtualization is a virtualization technique used to provide a certain kind of virtual machine environment, namely, one that is a complete simulation of the underlying hardware...
, implemented time sharing by providing each user with a single-user operating system, the CMS
Conversational Monitor System
The Conversational Monitor System is a relatively simple interactive computing single-user operating system.* CMS is part of IBM's VM family, which runs on IBM mainframe computers...
. Unlike virtual memory, a system virtual machine allowed the user to use privileged instructions in their code. This approach had certain advantages, for instance it allowed users to add input/output devices not allowed by the standard system.
The guest OSes do not have to be compliant with the hardware making it possible to run different OSes on the same computer (e.g., Microsoft Windows
Microsoft Windows
Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
and Linux
Linux
Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...
, or older versions of an OS to support software that has not yet been ported to the latest version). The use of virtual machines to support different guest OSes is becoming popular in embedded systems; a typical use is to support a real-time operating system
Real-time operating system
A real-time operating system is an operating system intended to serve real-time application requests.A key characteristic of a RTOS is the level of its consistency concerning the amount of time it takes to accept and complete an application's task; the variability is jitter...
at the same time as a high-level OS such as Linux or Windows.
Another use is to sandbox
Sandbox (software development)
A sandbox is a testing environment that isolates untested code changes and outright experimentation from the production environment or repository, in the context of software development including Web development and revision control...
an OS that is not trusted, possibly because it is a system under development. Virtual machines have other advantages for OS development, including better debugging access and faster reboots.
Process virtual machines
A process VM, sometimes called an application virtual machine, 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-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
High-level programming language
A high-level programming language is a programming language with strong abstraction from the details of the computer. In comparison to low-level programming languages, it may use natural language elements, be easier to use, or be from the specification of the program, making the process of...
(compared to the low-level ISA abstraction of the system VM). Process VMs are implemented using an interpreter
Interpreter (computing)
In computer science, an interpreter normally means a computer program that executes, i.e. performs, instructions written in a programming language...
; performance comparable to compiled programming languages is achieved by the use of just-in-time compilation
Just-in-time compilation
In computing, just-in-time compilation , also known as dynamic translation, is a method to improve the runtime performance of computer programs. Historically, computer programs had two modes of runtime operation, either interpreted or static compilation...
.
This type of VM has become popular with the Java programming language
Java (programming language)
Java is a programming language originally developed by James Gosling at Sun Microsystems and released in 1995 as a core component of Sun Microsystems' Java platform. The language derives much of its syntax from C and C++ but has a simpler object model and fewer low-level facilities...
, which is implemented using the Java virtual machine
Java Virtual Machine
A Java virtual machine is a virtual machine capable of executing Java bytecode. It is the code execution component of the Java software platform. Sun Microsystems stated that there are over 4.5 billion JVM-enabled devices.-Overview:...
. Other examples include the Parrot virtual machine
Parrot virtual machine
Parrot is a register-based process virtual machine designed to run dynamic languages efficiently. It uses just-in-time compilation for speed to reduce the interpretation overhead. It is currently possible to compile Parrot assembly language and PIR to Parrot bytecode and execute it...
, which serves as an abstraction layer
Abstraction layer
An abstraction layer is a way of hiding the implementation details of a particular set of functionality...
for several interpreted languages, and the .NET Framework
.NET Framework
The .NET Framework is a software framework that runs primarily on Microsoft Windows. It includes a large library and supports several programming languages which allows language interoperability...
, which runs on a VM called the Common Language Runtime
Common Language Runtime
The Common Language Runtime is the virtual machine component of Microsoft's .NET framework and is responsible for managing the execution of .NET programs. In a process known as just-in-time compilation, the CLR compiles the intermediate language code known as CIL into the machine instructions...
.
A special case of process VMs are systems that abstract over the communication mechanisms of a (potentially heterogeneous) computer cluster. 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 parallel 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 parallel 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
C (programming language)
C is a general-purpose computer programming language developed between 1969 and 1973 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system....
and FORTRAN
Fortran
Fortran is a general-purpose, procedural, imperative programming language that is especially suited to numeric computation and scientific computing...
). Examples are PVM (Parallel Virtual Machine
Parallel Virtual Machine
The Parallel Virtual Machine 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 computational problems can be solved more cost effectively by...
) and MPI (Message Passing Interface
Message Passing Interface
Message Passing Interface is a standardized and portable message-passing system designed by a group of researchers from academia and industry to function on a wide variety of parallel computers...
). They are not strictly virtual machines, as the applications running on top still have access to all OS services, and are therefore not confined to the system model provided by the "VM".
Emulation of the underlying raw hardware (native execution)
This approach is described as full virtualizationFull virtualization
In computer science, full virtualization is a virtualization technique used to provide a certain kind of virtual machine environment, namely, one that is a complete simulation of the underlying hardware...
of the hardware, and can be implemented using a Type 1 or Type 2 hypervisor
Hypervisor
In computing, a hypervisor, also called virtual machine manager , is one of many hardware virtualization techniques that allow multiple operating systems, termed guests, to run concurrently on a host computer. It is so named because it is conceptually one level higher than a supervisory program...
. (A Type 1 hypervisor runs directly on the hardware; a Type 2 hypervisor runs on another operating system, such as Linux
Linux
Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...
). Each virtual machine can run any operating system supported by the underlying hardware. Users can thus run two or more different "guest" operating systems simultaneously, in separate "private" virtual computers.
The pioneer system using this concept was IBM's CP-40
IBM CP-40
CP-40 was a research precursor to CP-67, which in turn was part of IBM's then-revolutionary CP[-67]/CMS – a virtual machine/virtual memory time-sharing operating system for the IBM System/360-67, and the parent of IBM's VM family. CP-40 ran multiple instances of client operating systems...
, the first (1967) version of IBM's CP/CMS
CP/CMS
CP/CMS was a time-sharing operating system of the late 60s and early 70s, known for its excellent performance and advanced features...
(1967–1972) and the precursor to IBM's VM family
VM (operating system)
VM refers to a family of IBM virtual machine operating systems used on IBM mainframes System/370, System/390, zSeries, System z and compatible systems, including the Hercules emulator for personal computers. The first version, released in 1972, was VM/370, or officially Virtual Machine Facility/370...
(1972–present). With the VM architecture, most users run a relatively simple interactive computing
Interactive computing
In computer science, interactive computing refers to software which accepts input from humans — for example, data or commands. Interactive software includes most popular programs, such as word processors or spreadsheet applications. By comparison, noninteractive programs operate without human...
single-user operating system, CMS
Conversational Monitor System
The Conversational Monitor System is a relatively simple interactive computing single-user operating system.* CMS is part of IBM's VM family, which runs on IBM mainframe computers...
, as a "guest" on top of the VM control program (VM-CP
VM-CP
VM-CP was the official name of the control program portion of VM/370, a re-implementation of CP/CMS for the IBM System/370. It was originally called CP-370. VM/370 was announced in 1972, when virtual memory was added to the System/370 series. A successor of this software is found in today's z/VM....
). This approach kept the CMS design simple, as if it were running alone; the control program quietly provides multitasking and resource management services "behind the scenes". In addition to CMS, VM users can run any of the other IBM operating systems, such as MVS
MVS
Multiple Virtual Storage, more commonly called MVS, was the most commonly used operating system on the System/370 and System/390 IBM mainframe computers...
or z/OS
Z/OS
z/OS is a 64-bit operating system for mainframe computers, produced by IBM. It derives from and is the successor to OS/390, which in turn followed a string of MVS versions.Starting with earliest:*OS/VS2 Release 2 through Release 3.8...
. z/VM
Z/VM
z/VM is the current version in IBM's VM family of virtual machine operating systems. z/VM was first released in October 2000 and remains in active use and development . It is directly based on technology and concepts dating back to the 1960s, with IBM's CP/CMS on the IBM System/360-67...
is the current version of VM, and is used to support hundreds or thousands of virtual machines on a given mainframe. Some installations use Linux for zSeries to run Web server
Web server
Web server can refer to either the hardware or the software that helps to deliver content that can be accessed through the Internet....
s, where Linux
Linux
Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...
runs as the operating system within many virtual machines.
Full virtualization is particularly helpful in operating system development, when experimental new code can be run at the same time as older, more stable, versions, each in a separate virtual machine. The process can even be recursive: IBM
IBM
International Business Machines Corporation or IBM is an American multinational technology and consulting corporation headquartered in Armonk, New York, United States. IBM manufactures and sells computer hardware and software, and it offers infrastructure, hosting and consulting services in areas...
debugged new versions of its virtual machine operating system, VM
VM (operating system)
VM refers to a family of IBM virtual machine operating systems used on IBM mainframes System/370, System/390, zSeries, System z and compatible systems, including the Hercules emulator for personal computers. The first version, released in 1972, was VM/370, or officially Virtual Machine Facility/370...
, in a virtual machine running under an older version of VM, and even used this technique to simulate new hardware.
The standard x86 processor architecture as used in the modern PCs does not actually meet the Popek and Goldberg virtualization requirements
Popek and Goldberg virtualization requirements
The Popek and Goldberg virtualization requirements are a set of conditions sufficient for a computer architecture to support system virtualization efficiently. They were introduced by Gerald J. Popek and Robert P. Goldberg in their 1974 article "Formal Requirements for Virtualizable Third...
. Notably, there is no execution mode where all sensitive machine instructions always trap, which would allow per-instruction virtualization.
Despite these limitations, several software packages have managed to provide virtualization on the x86 architecture
X86 virtualization
In computing, x86 virtualization is the facility that allows multiple operating systems to simultaneously share x86 processor resources in a safe and efficient manner, a facility generically known as hardware virtualization...
, even though dynamic recompilation
Dynamic recompilation
In computer science, dynamic recompilation is a feature of some emulators and virtual machines, where the system may recompile some part of a program during execution...
of privileged code, as first implemented by VMware
VMware
VMware, Inc. is a company providing virtualization software founded in 1998 and based in Palo Alto, California, USA. The company was acquired by EMC Corporation in 2004, and operates as a separate software subsidiary ....
, incurs some performance overhead as compared to a VM running on a natively virtualizable architecture such as the IBM System/370 or Motorola MC68020
Motorola 68020
The Motorola 68020 is a 32-bit microprocessor from Motorola, released in 1984. It is the successor to the Motorola 68010 and is succeeded by the Motorola 68030...
. By now, several other software packages such as Virtual PC, VirtualBox
VirtualBox
Oracle VM VirtualBox is an x86 virtualization software package, originally created by software company Innotek GmbH, purchased by Sun Microsystems, and now developed by Oracle Corporation as part of its family of virtualization products...
, Parallels Workstation
Parallels Workstation
Parallels Workstation is the first commercial software product released by Parallels, Inc., a developer of desktop and server virtualization software...
and Virtual Iron
Virtual Iron
Virtual Iron Software, was located in Lowell, Massachusetts, sold proprietary software for virtualization and management of a virtual infrastructure...
manage to implement virtualization on x86 hardware.
Intel and AMD have introduced features to their x86 processors to enable virtualization in hardware.
As well as virtualization of the resources of a single machine, multiple independent nodes in a cluster can be combined and accessed as a single virtual NUMA
Non-Uniform Memory Access
Non-Uniform Memory Access is a computer memory design used in Multiprocessing, where the memory access time depends on the memory location relative to a processor...
machine .
Emulation of a non-native system
Virtual machines can also perform the role of an emulatorEmulator
In computing, an emulator is hardware or software or both that duplicates the functions of a first computer system in a different second computer system, so that the behavior of the second system closely resembles the behavior of the first system...
, allowing software applications and operating systems written for another computer processor architecture to be run.
Some virtual machines emulate hardware that only exists as a detailed specification. For example:
- One of the first was the p-code machineP-Code machineIn computer programming, a p-code machine, or portable code machine is a virtual machine designed to execute p-code...
specification, which allowed programmers to write Pascal programsComputer programA computer program is a sequence of instructions written to perform a specified task with a computer. A computer requires programs to function, typically executing the program's instructions in a central processor. The program has an executable form that the computer can use directly to execute...
that would run on any computer running virtual machine software that correctly implemented the specification. - The specification of the Java virtual machineJava Virtual MachineA Java virtual machine is a virtual machine capable of executing Java bytecode. It is the code execution component of the Java software platform. Sun Microsystems stated that there are over 4.5 billion JVM-enabled devices.-Overview:...
. - The Common Language InfrastructureCommon Language InfrastructureThe Common Language Infrastructure is an open specification developed by Microsoft and standardized by ISO and ECMA that describes the executable code and runtime environment that form the core of the Microsoft .NET Framework and the free and open source implementations Mono and Portable.NET...
virtual machine at the heart of the Microsoft .NET.NET FrameworkThe .NET Framework is a software framework that runs primarily on Microsoft Windows. It includes a large library and supports several programming languages which allows language interoperability...
initiative. - Open FirmwareOpen FirmwareOpen Firmware, or OpenBoot in Sun Microsystems parlance, is a standard defining the interfaces of a computer firmware system, formerly endorsed by the Institute of Electrical and Electronics Engineers . It originated at Sun, and has been used by Sun, Apple, IBM, and most other non-x86 PCI chipset...
allows plug-in hardware to include boot-time diagnostics, configuration code, and device drivers that will run on any kind of CPU.
This technique allows diverse computers to run any software written to that specification; only the virtual machine software itself must be written separately for each type of computer on which it runs.
Operating system-level virtualization
Operating system-level virtualizationOperating system-level virtualization
Operating system-level virtualization is a server virtualization method where the kernel of an operating system allows for multiple isolated user-space instances, instead of just one. Such instances may look and feel like a real server, from the point of view of its owner...
is a server virtualization technology which virtualizes server
Server (computing)
In the context of client-server architecture, a server is a computer program running to serve the requests of other programs, the "clients". Thus, the "server" performs some computational task on behalf of "clients"...
s on an operating system
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...
(kernel) layer. It can be thought of as partitioning: a single physical server is sliced into multiple small partitions (otherwise called virtual environments (VE), virtual private server
Virtual private server
Virtual private server is a term used by internet hosting services to refer to a virtual machine. The term is used for emphasizing that the virtual machine, although running in software on the same physical computer as other customers' virtual machines, is functionally equivalent to a separate...
s (VPS), guests, zones, etc.); each such partition looks and feels like a real server, from the point of view of its users.
For example, Solaris Zones supports multiple guest OSes running under the same OS (such as Solaris 10). All guest OSes have to use the same kernel level and cannot run as different OS versions. Solaris native Zones also requires that the host OS be a version of Solaris; other OSes from other manufacturers are not supported.,however you need to use Solaris Branded zones to use another OSes as zones.
Another example is System Workload Partitions (WPARs), introduced in the IBM AIX 6.1 operating system. System WPARs are software partitions running under one instance of the global AIX OS environment.
The operating system level architecture has low overhead that helps to maximize efficient use of server resources. The virtualization introduces only a negligible overhead and allows running hundreds of virtual private server
Virtual private server
Virtual private server is a term used by internet hosting services to refer to a virtual machine. The term is used for emphasizing that the virtual machine, although running in software on the same physical computer as other customers' virtual machines, is functionally equivalent to a separate...
s on a single physical server. In contrast, approaches such as full virtualization
Full virtualization
In computer science, full virtualization is a virtualization technique used to provide a certain kind of virtual machine environment, namely, one that is a complete simulation of the underlying hardware...
(like VMware
VMware
VMware, Inc. is a company providing virtualization software founded in 1998 and based in Palo Alto, California, USA. The company was acquired by EMC Corporation in 2004, and operates as a separate software subsidiary ....
) and paravirtualization
Paravirtualization
In computing, paravirtualization is a virtualization technique that presents a software interface to virtual machines that is similar but not identical to that of the underlying hardware....
(like Xen
Xen
Xen is a virtual-machine monitor providing services that allow multiple computer operating systems to execute on the same computer hardware concurrently....
or UML
User-mode Linux
User-mode Linux enables multiple virtual Linux systems to run as an application within a normal Linux system...
) cannot achieve such level of density, due to overhead of running multiple kernels. From the other side, operating system-level virtualization does not allow running different operating systems (i.e. different kernels), although different libraries, distributions etc. are possible.
List of hardware with virtual machine support
- Alcatel-LucentAlcatel-LucentAlcatel-Lucent is a global telecommunications corporation, headquartered in the 7th arrondissement of Paris, France. It provides telecommunications solutions to service providers, enterprises, and governments around the world, enabling these customers to deliver voice, data, and video services...
3B20D/3B21D emulated on commercial off-the-shelfCommercial off-the-shelfIn the United States, Commercially available Off-The-Shelf is a Federal Acquisition Regulation term defining a nondevelopmental item of supply that is both commercial and sold in substantial quantities in the commercial marketplace, and that can be procured or utilized under government contract...
computers with 3B2OE or 3B21E system - AMD-V (formerly code-named Pacifica)
- ARM TrustZoneARM architectureARM is a 32-bit reduced instruction set computer instruction set architecture developed by ARM Holdings. It was named the Advanced RISC Machine, and before that, the Acorn RISC Machine. The ARM architecture is the most widely used 32-bit ISA in numbers produced...
- Boston Circuits gCore (grid-on-chip) with 16 ARCARC InternationalARC International plc was a developer of configurable microprocessor technology and is now owned by Synopsys. ARC developed synthesisable IP and licensed it to semiconductor companies....
750D cores and Time-machine hardware virtualization module. - Freescale PowerPCPowerPCPowerPC is a RISC architecture created by the 1991 Apple–IBM–Motorola alliance, known as AIM...
MPC8572 and MPC8641D - IBMIBMInternational Business Machines Corporation or IBM is an American multinational technology and consulting corporation headquartered in Armonk, New York, United States. IBM manufactures and sells computer hardware and software, and it offers infrastructure, hosting and consulting services in areas...
System/370System/370The IBM System/370 was a model range of IBM mainframes announced on June 30, 1970 as the successors to the System/360 family. The series maintained backward compatibility with the S/360, allowing an easy migration path for customers; this, plus improved performance, were the dominant themes of the...
, System/390, and zSeriesZSeriesIBM System z, or earlier IBM eServer zSeries, is a brand name designated by IBM to all its mainframe computers.In 2000, IBM rebranded the existing System/390 to IBM eServer zSeries with the e depicted in IBM's red trademarked symbol, but because no specific machine names were changed for...
mainframes - IBM Power SystemsIBM Power SystemsPower Systems is the name of IBM's Power Architecture-based server line.Before the Power Systems line was announced on April 2, 2008, IBM had two distinct Power-based lines: the System i running IBM i - and the System p series running AIX or Linux.- History :IBM had two discrete Power Architecture...
- Intel VT-x (formerly code-named Vanderpool)
- Sun MicrosystemsSun MicrosystemsSun Microsystems, Inc. was a company that sold :computers, computer components, :computer software, and :information technology services. Sun was founded on February 24, 1982...
sun4v (UltraSPARC T1UltraSPARC T1|right|262px|UltraSPARC T1 processorSun Microsystems' UltraSPARC T1 microprocessor, known until its 14 November 2005 announcement by its development codename "Niagara", is a multithreading, multicore CPU...
and T2UltraSPARC T2Sun Microsystems' UltraSPARC T2 microprocessor is a multithreading, multi-core CPU. It is a member of the SPARC family, and the successor to the UltraSPARC T1. The chip is sometimes referred to by its codename, Niagara 2...
) – utilized by Logical DomainsLogical DomainsLogical Domains is the server virtualization and partitioning technology from Sun Microsystems released in April 2007. It has been re-branded as Oracle VM Server for SPARC since Oracle Corporation completed the acquisition of Sun in January 2010. Each domain is a full virtual machine with a...
- HP vPAR and cell based nPARHP nPar (Hard Partitioning)nPar partitions are electrically isolated from other nPar partitions within the same chassis. Cells make up nPar partitions. Being electrically isolated means that if a nPar partition were to fail due to hardware failure, then the other nPar partitions would continue to work...
- GEGêGê are the people who spoke Ge languages of the northern South American Caribbean coast and Brazil. In Brazil the Gê were found in Rio de Janeiro, Minas Gerais, Bahia, Piaui, Mato Grosso, Goias, Tocantins, Maranhão, and as far south as Paraguay....
Project MAC then - HoneywellHoneywellHoneywell International, Inc. is a major conglomerate company that produces a variety of consumer products, engineering services, and aerospace systems for a wide variety of customers, from private consumers to major corporations and governments....
Multics systems - HoneywellHoneywellHoneywell International, Inc. is a major conglomerate company that produces a variety of consumer products, engineering services, and aerospace systems for a wide variety of customers, from private consumers to major corporations and governments....
200/2000 systems Liberator replacing IBM 14xx systems, Level 62/64/66 GCOS - IBMIBMInternational Business Machines Corporation or IBM is an American multinational technology and consulting corporation headquartered in Armonk, New York, United States. IBM manufactures and sells computer hardware and software, and it offers infrastructure, hosting and consulting services in areas...
System/360 Model 145 Hardware emulator for Honeywell 200/2000 systems - RCARCARCA Corporation, founded as the Radio Corporation of America, was an American electronics company in existence from 1919 to 1986. The RCA trademark is currently owned by the French conglomerate Technicolor SA through RCA Trademark Management S.A., a company owned by Technicolor...
Spectra/70 Series emulated IBM System/360 - NASNasNasir bin Olu Dara Jones, who performs under the name Nas , formerly Nasty Nas, is an American rapper and actor. He is regarded as one of the most important figures in hip hop and one of the most skilled and influential rappers of all-time...
CPUs emulated IBM and Amdahl machines - HoneywellHoneywellHoneywell International, Inc. is a major conglomerate company that produces a variety of consumer products, engineering services, and aerospace systems for a wide variety of customers, from private consumers to major corporations and governments....
Level 6 minicomputers emulated predecessor 316/516/716 minis - XeroxXeroxXerox Corporation is an American multinational document management corporation that produced and sells a range of color and black-and-white printers, multifunction systems, photo copiers, digital production printing presses, and related consulting services and supplies...
Sigma 6 CPUs were modified to emulate GE/Honeywell 600/6000 systems
List of virtual machine software
Process (application) virtual machine software- BaanBaanBaan was a vendor of enterprise resource planning software that is now owned by Infor Global Solutions.Baan or Baan ERP was also the name of the ERP product created by this company.-History:...
Bshell Virtual Machine, Baan 4GL - Common Language InfrastructureCommon Language InfrastructureThe Common Language Infrastructure is an open specification developed by Microsoft and standardized by ISO and ECMA that describes the executable code and runtime environment that form the core of the Microsoft .NET Framework and the free and open source implementations Mono and Portable.NET...
, C#, Visual Basic .NETVisual Basic .NETVisual Basic .NET , is an object-oriented computer programming language that can be viewed as an evolution of the classic Visual Basic , which is implemented on the .NET Framework...
, J#J SharpVisual J# |sharp]]') programming language is a discontinued transitional language for programmers of Java and Visual J++ languages, so they may use their existing knowledge and applications on .NET Framework....
, C++/CLIC++/CLIC++/CLI is Microsoft's language specification intended to supersede Managed Extensions for C++. It is a complete revision that aims to simplify the older Managed C++ syntax . C++/CLI is standardized by Ecma as ECMA-372...
(formerly Managed C++Managed Extensions for C++Managed Extensions for C++ or just Managed C++ is a now deprecated Microsoft set of deviations from C++, including grammatical and syntactic extensions, keywords and attributes, to bring the C++ syntax and language to the .NET Framework...
) - Dalvik virtual machineDalvik virtual machineDalvik is the process virtual machine in Google's Android operating system. It is the software that runs the apps on Android phones. Dalvik is thus an integral part of Android, which is typically used on mobile devices such as mobile phones, tablet computers and netbooks. Programs are commonly...
, part of Android operating systems - Dis, InfernoInferno (operating system)Inferno is a distributed operating system started at Bell Labs, but is now developed and maintained by Vita Nuova Holdings as free software. Inferno was based on the experience gained with Plan 9 from Bell Labs, and the further research of Bell Labs into operating systems, languages, on-the-fly...
operating system and its Limbo language - DOSBoxDOSBoxDOSBox is emulator software that emulates an IBM PC compatible computer running MS-DOS. It is intended especially for use with old PC games. DOSBox is free software....
- EiffelStudioEiffelStudioEiffelStudio is a development environment for the Eiffel programming language developed and distributed by Eiffel Software.EiffelStudio includes a combination of tools integrated under a single user interface: compiler, interpreter, debugger, browser, metrics tool, profiler, diagram tool...
for the EiffelEiffel (programming language)Eiffel is an ISO-standardized, object-oriented programming language designed by Bertrand Meyer and Eiffel Software. The design of the language is closely connected with the Eiffel programming method...
language - Erlang language
- Forth virtual machine, Forth
- GlulxGlulxGlulx is a 32-bit portable virtual machine intended for writing and playing interactive fiction. It was designed by Andrew Plotkin to relieve some of the restrictions in the venerable Z-machine format...
, GlulxGlulxGlulx is a 32-bit portable virtual machine intended for writing and playing interactive fiction. It was designed by Andrew Plotkin to relieve some of the restrictions in the venerable Z-machine format...
, Z-codeZ-machineThe 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 , and could therefore port all its text adventures to a new platform simply by writing a... - Hec, Hasm AssemblerBytecodeBytecode, also known as p-code , is a term which has been used to denote various forms of instruction sets designed for efficient execution by a software interpreter as well as being suitable for further compilation into machine code...
- Java Virtual MachineJava Virtual MachineA Java virtual machine is a virtual machine capable of executing Java bytecode. It is the code execution component of the Java software platform. Sun Microsystems stated that there are over 4.5 billion JVM-enabled devices.-Overview:...
, JavaJava (programming language)Java is a programming language originally developed by James Gosling at Sun Microsystems and released in 1995 as a core component of Sun Microsystems' Java platform. The language derives much of its syntax from C and C++ but has a simpler object model and fewer low-level facilities...
, Nice, NetRexxNetRexxNetRexx is an open source, originally IBM's, variant of the REXX programming language to run on the Java virtual machine. It supports a classic REXX syntax, with no reserved keywords, along with considerable additions to support object-oriented programming in a manner compatible with Java's object...
, Scala, Groovy, ClojureClojureClojure |closure]]") is a recent dialect of the Lisp programming language created by Rich Hickey. It is a general-purpose language supporting interactive development that encourages a functional programming style, and simplifies multithreaded programming....
, JRubyJRubyJRuby is a Java implementation of the Ruby programming language, being developed by the JRuby team. It is free software released under a three-way CPL/GPL/LGPL license... - Low Level Virtual MachineLow Level Virtual MachineThe Low Level Virtual Machine is a compiler infrastructure written in C++ that is designed for compile-time, link-time, run-time, and "idle-time" optimization of programs written in arbitrary programming languages...
(LLVM), currently CC (programming language)C is a general-purpose computer programming language developed between 1969 and 1973 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system....
, C++C++C++ is a statically typed, free-form, multi-paradigm, compiled, general-purpose programming language. It is regarded as an intermediate-level language, as it comprises a combination of both high-level and low-level language features. It was developed by Bjarne Stroustrup starting in 1979 at Bell...
, Stacker - Lua
- Macromedia Flash Player, SWFSWFSWF is an Adobe Flash file format used for multimedia, vector graphics and ActionScript. Originating with FutureWave Software, then transferred to Macromedia, and then coming under the control of Adobe, SWF files can contain animations or applets of varying degrees of interactivity and function.,...
- Memory Array Redcode Simulator (MARS), virtual machine that executes Corewars programs
- MMIXMMIXMMIX is a 64-bit RISC instruction set architecture designed by Donald Knuth, with significant contributions by John L. Hennessy and Richard L. Sites...
, MMIXAL - Neko virtual machine, currently NekoNeko (programming language)Neko is a high-level dynamically typed programming language developed by Nicolas Cannasse as part of R&D efforts at Motion-Twin.-Concept:Neko has a compiler and a virtual machine with garbage collection. The compiler converts a source .neko file into a bytecode .n file that can be executed with the...
and haXeHaXehaXe is a versatile open-source high-level multiplatform programming language described on its website as a "universal language".It can produce:* Flash applications and games* Multi-platform client-side web applications* Apache CGI web applications... - O-code machineO-code machineThe O-code machine is a virtual machine that was developed by Martin Richards in the late 1960s to give machine independence to BCPL, the low-level forerunner to C and C++. The concept behind the O-Code machine was to create O-code output through the BCPL compiler. The O-code was then either...
, BCPLBCPLBCPL is a procedural, imperative, and structured computer programming language designed by Martin Richards of the University of Cambridge in 1966.- Design :... - p-code machineP-Code machineIn computer programming, a p-code machine, or portable code machine is a virtual machine designed to execute p-code...
, PascalPascal (programming language)Pascal is an influential imperative and procedural programming language, designed in 1968/9 and published in 1970 by Niklaus Wirth as a small and efficient language intended to encourage good programming practices using structured programming and data structuring.A derivative known as Object Pascal... - ParrotParrot virtual machineParrot is a register-based process virtual machine designed to run dynamic languages efficiently. It uses just-in-time compilation for speed to reduce the interpretation overhead. It is currently possible to compile Parrot assembly language and PIR to Parrot bytecode and execute it...
, Perl 6Perl 6Perl 6 is a major revision to the Perl programming language. It is still in development, as a specification from which several interpreter and compiler implementations are being written. It is introducing elements of many modern and historical languages. Perl 6 is intended to have many... - PerlPerlPerl is a high-level, general-purpose, interpreted, dynamic programming language. Perl was originally developed by Larry Wall in 1987 as a general-purpose Unix scripting language to make report processing easier. Since then, it has undergone many changes and revisions and become widely popular...
virtual machine, Perl - CPythonCPythonCPython is the default, most-widely used implementation of the Python programming language. It is written in C. In addition to CPython, there are two other production-quality Python implementations: Jython, written in Java, and IronPython, which is written for the Common Language Runtime. There...
, PythonPython (programming language)Python is a general-purpose, high-level programming language whose design philosophy emphasizes code readability. Python claims to "[combine] remarkable power with very clear syntax", and its standard library is large and comprehensive... - YARVYARVYARV is a bytecode interpreter that was developed for the Ruby programming language by Koichi Sasada. The goal of the project was to greatly reduce the execution time of Ruby programs....
, Ruby MRIRuby MRIMatz's Ruby Interpreter or Ruby MRI is the reference implementation of the Ruby programming language. As there is currently no specification of the Ruby language, the MRI implementation is considered the de facto reference. The RubySpec project has created a large test suite that captures... - RubiniusRubiniusRubinius is an alternative Ruby programming language implementation created by Evan Phoenix. Based loosely on the Smalltalk-80 Blue Book design, Rubinius seeks to"provide a rich, high-performance environment for running Ruby code."-Goals:...
, RubyRuby (programming language)Ruby is a dynamic, reflective, general-purpose object-oriented programming language that combines syntax inspired by Perl with Smalltalk-like features. Ruby originated in Japan during the mid-1990s and was first developed and designed by Yukihiro "Matz" Matsumoto... - ScummVMScummVMScummVM is a collection of game engine recreations. Originally designed to play LucasArts adventure games that use the SCUMM system , it now also supports a variety of non-SCUMM games by companies like Revolution Software and Adventure Soft. It was originally written by Ludvig Strigeus...
, ScummSCUMMScript Creation Utility for Maniac Mansion is a scripting language developed at LucasArts to ease development of the graphical adventure game Maniac Mansion.... - SECD machineSECD machineThe SECD machine is a highly influential virtual machine and abstract machine intended as a target for functional programming language compilers. The letters stand for Stack, Environment, Code, Dump, the internal registers of the machine...
, ISWIMISWIMISWIM is an abstract computer programming language devised by Peter J. Landin and first described in his article, The Next 700 Programming Languages, published in the Communications of the ACM in 1966...
, Lispkit LispLispkit LispLispkit Lisp is a lexically scoped, purely functional subset of Lisp developed as a testbed for functional programming concepts. It was first used for early experimentation with lazy evaluation. An SECD machine-based implementation written in an ALGOL variant was published by the developer Peter... - SedSedsed is a Unix utility that parses text and implements a programming language which can apply transformations to such text. It reads input line by line , applying the operation which has been specified via the command line , and then outputs the line. It was developed from 1973 to 1974 as a Unix...
the stream-editor can also be seen as a VM with 2 storage spaces - SmalltalkSmalltalkSmalltalk is an object-oriented, dynamically typed, reflective programming language. Smalltalk was created as the language to underpin the "new world" of computing exemplified by "human–computer symbiosis." It was designed and created in part for educational use, more so for constructionist...
virtual machine, Smalltalk language- SqueakSqueakThe Squeak programming language is a Smalltalk implementation. It is object-oriented, class-based and reflective.It was derived directly from Smalltalk-80 by a group at Apple Computer that included some of the original Smalltalk-80 developers...
virtual machine, Squeak language
- Squeak
- SQLiteSQLiteSQLite is an ACID-compliant embedded relational database management system contained in a relatively small C programming library. The source code for SQLite is in the public domain and implements most of the SQL standard...
virtual machine, SQLite opcodes - SWEET16SWEET16SWEET16 is an interpreted "byte-code" language invented by Steve Wozniak and implemented as part of the Integer BASIC ROM in the Apple II series of computers...
- Tamarin (JavaScript engine)Tamarin (JavaScript engine)Tamarin is a free virtual machine with just-in-time compilation support intended to implement the fourth edition of the ECMAScript standard....
, ActionScript VM in Flash 9 - TrueTypeTrueTypeTrueType is an outline font standard originally developed by Apple Computer in the late 1980s as a competitor to Adobe's Type 1 fonts used in PostScript...
virtual machine, TrueType - V8 (JavaScript engine)V8 (JavaScript engine)The Google V8 JavaScript Engine is an open source JavaScript engine developed by Google and ships with the Google Chrome web browser. Lars Bak is the head programmer....
, JavaScript VM - ValgrindValgrindValgrind is a GPL licensed programming tool for memory debugging, memory leak detection, and profiling. The name valgrind comes from the main entrance to Valhalla in Norse mythology....
, checking of memory accesses and leaks in x86/x86-64X86-64x86-64 is an extension of the x86 instruction set. It supports vastly larger virtual and physical address spaces than are possible on x86, thereby allowing programmers to conveniently work with much larger data sets. x86-64 also provides 64-bit general purpose registers and numerous other...
code under LinuxLinuxLinux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds... - Virtual ProcessorVirtual processorTao Virtual Processor is a virtual machine from Tao Group.The first version, VP1, was the basis of its parallel processing multimedia OS and platform, TAOS...
(VP) from Tao Groumadarchodp (UKUnited KingdomThe United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
). - VX32VX32The Vx32 virtual extension environment is an application-level virtual machine implemented as an ordinary user-mode library and designed to run native x86 code...
virtual machine, application-level virtualization for native code - Waba, virtual machine for small devices, similar to Java
- Warren Abstract MachineWarren abstract machineIn 1983, David H. D. Warren designed an abstract machine for the execution of Prolog consisting of a memory architecture and an instruction set. This design became known as the Warren Abstract Machine and has become the de facto standard target for Prolog compilers.-Purpose:The purpose of...
, PrologPrologProlog is a general purpose logic programming language associated with artificial intelligence and computational linguistics.Prolog has its roots in first-order logic, a formal logic, and unlike many other programming languages, Prolog is declarative: the program logic is expressed in terms of...
, CSCComputer Sciences CorporationComputer Sciences Corporation is an American information technology and business services company headquartered in Falls Church, Virginia, USA...
GraphTalk - Z-machineZ-machineThe 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 , and could therefore port all its text adventures to a new platform simply by writing a...
, Z-CodeZ-machineThe 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 , and could therefore port all its text adventures to a new platform simply by writing a... - Zend EngineZend engineThe Zend Engine is an open source scripting engine , commonly known for the important role it plays in the web automation language PHP. It was originally developed by Andi Gutmans and Zeev Suraski while they were students at the Technion - Israel Institute of Technology. They later founded a...
, PHPPHPPHP is a general-purpose server-side scripting language originally designed for web development to produce dynamic web pages. For this purpose, PHP code is embedded into the HTML source document and interpreted by a web server with a PHP processor module, which generates the web page document... - libJIT Just-In-Time compilation library, libJIT bytecode
System (hardware) virtual machine software
- ATLAS Transformation LanguageATLAS Transformation LanguageATL is a model transformation language and toolkit developed and maintained by OBEO and AtlanMod. It was initiated by the team...
(ATL), a MTLModel Transformation LanguageA model transformation language in systems and software engineering is a language for model transformation.- Overview :The notion of model transformation is of central importance to information technology. A software system may be seen as a set of information transformations...
virtual machine - BochsBochsBochs is a portable x86 and x86-64 IBM PC compatible emulator and debugger mostly written in C++ and distributed as free software under GNU Lesser General Public License...
, portable open source x86 and AMD64 PCs emulator - CHARON-AXP, virtualizes AlphaServerAlphaServerAlphaServer was the name given to a series of server computers, produced from 1994 onwards by Digital Equipment Corporation, and latterly by Compaq and HP. As the name suggests, the AlphaServers were based on the DEC Alpha 64-bit microprocessor...
to migrate OpenVMS or Tru64 applications to x86 hardware - CHARON-VAX, virtualizes PDP-11PDP-11The PDP-11 was a series of 16-bit minicomputers sold by Digital Equipment Corporation from 1970 into the 1990s, one of a succession of products in the PDP series. The PDP-11 replaced the PDP-8 in many real-time applications, although both product lines lived in parallel for more than 10 years...
or VAXVAXVAX was an instruction set architecture developed by Digital Equipment Corporation in the mid-1970s. A 32-bit complex instruction set computer ISA, it was designed to extend or replace DEC's various Programmed Data Processor ISAs...
hardware to migrate OpenVMS or Tru64 applications to x86 or HP integrity hardware - CoLinux Open Source Linux inside Windows
- CoWareCowareCoWare, now part of Synopsys, was a supplier of platform-driven electronic system level design software and services.CoWare was headquartered in San Jose, California, and had offices around the world, major R&D offices in Belgium, Germany and India....
Virtual Platform - DenaliDenali (operating system)The Denali operating system is "an IA-32 virtual machine monitor, that allows for untrusted services to be run in isolated domains."...
, uses paravirtualization of x86 for running para-virtualized PC operating systems. - Hercules emulatorHercules emulatorHercules is a computer emulator which allows software designed for IBM mainframe computers and for plug-compatible mainframes to run on other types of computer hardware: notably on low-cost personal computers...
, free System/370, ESA/390, z/Mainframe - KVMKernel-based Virtual MachineKernel-based Virtual Machine is a virtualization infrastructure for the Linux kernel. KVM supports native virtualization on processors with hardware virtualization extensions....
- Logical DomainsLogical DomainsLogical Domains is the server virtualization and partitioning technology from Sun Microsystems released in April 2007. It has been re-branded as Oracle VM Server for SPARC since Oracle Corporation completed the acquisition of Sun in January 2010. Each domain is a full virtual machine with a...
- LynxSecureLynxSecureLynxSecure is a Type 1 Embedded Hypervisor and separation kernel from LynuxWorks which utilizes system virtual machines to provide hardware virtualization for embedded systems built on multicore x86 architecture....
uses the MILS architectureMultiple Independent Levels of SecurityMultiple Independent Levels of Security/Safety is a high-assurance security architecture based on the concepts of separation and controlled information flow; implemented by separation mechanisms that support both untrusted and trustworthy components; ensuring that the total security solution is...
to provide high assurance for embedded systems on x86 - Windows Virtual PCWindows Virtual PCWindows Virtual PC is a virtualization program for Microsoft Windows. In July 2006 Microsoft released the Windows-hosted version as a free product...
(formerly Microsoft Virtual PC) and Microsoft Virtual ServerMicrosoft Virtual ServerMicrosoft Virtual Server is a virtualization solution that facilitates the creation of virtual machines on the Windows XP, Windows Vista and Windows Server 2003 operating systems. Originally developed by Connectix, it was acquired by Microsoft prior to release... - Oracle VMOracle VMOracle VM is the server virtualization offering from Oracle Corporation. Oracle VM is based on the open-source Xen hypervisor technology, supports Windows, Linux, and Oracle Solaris guests and includes an integrated Web based management console. Oracle VM features fully tested and certified Oracle...
- OVPsimOVPsimOVPsim is a multiprocessor platform emulator that uses dynamic binary translation technology to achieve high simulation speeds. It has public APIs allowing users to create their own processor, peripheral and platform models. Various models are available as source . OVPsim is a key component of the...
is a freely available virtual platform simulator designed to simulate complex multiprocessor systems at very high speeds - PalaciosPalacios- People :* Miguel Asin Y Palacios, a Spanish scholar and Roman Catholic priest who published Islam and the Divine Comedy in 1919* Alfredo Palacios, an Argentine politician* Antonio Palacios, a Spanish architect* Odón Betanzos Palacios, Spanish writer...
is an OS independent embeddable VMM, it is an open source virtual machine monitor for modern architectures - Parallels WorkstationParallels WorkstationParallels Workstation is the first commercial software product released by Parallels, Inc., a developer of desktop and server virtualization software...
, virtualizes x86 to run unmodified PC operating systems - Parallels Desktop for MacParallels Desktop for MacParallels Desktop for Mac by Parallels, Inc., is software providing hardware virtualization for Macintosh computers with Intel processors.-Overview:Parallels, Inc...
, virtualizes x86 to run virtual machines on Mac OS X - QEMUQEMUQEMU is a processor emulator that relies on dynamic binary translation to achieve a reasonable speed while being easy to port on new host CPU architectures....
, is a simulator based on a virtual machine - SheepShaverSheepShaverSheepShaver is an open source PowerPC Apple Macintosh emulator originally designed for BeOS and Linux. The name is a play on ShapeShifter, a Macintosh II emulator for AmigaOS , which is in turn not to be confused with a third-party preference pane for Mac OS X with the same name...
- SimicsSimicsSimics is a full-system simulator used to run unchanged production binaries of the target hardware at high-performance speeds. Simics was originally developed by the Swedish Institute of Computer Science , and then spun off to Virtutech for commercial development in 1998...
- Sun xVMSun xVMSun xVM is a product group from Sun Microsystems that addresses virtualization technology on x86 platforms.-History:Sun originally announced the xVM product family in October 2007 as a broader product line...
- SVISTASVISTASVISTA is a former commercial virtual machine software product marketed by Serenity Systems International. Windows, OS/2, Linux and FreeBSD hosted versions were available.This product is no longer available nor supported....
- twoOStwoTwoOStwotwoOStwo was a commercial software product developed by Parallels Software Studio . The workstation software consisted of a virtual machine suite for Intel x86-compatible computers which allowed the creation and execution of multiple x86 virtual computers simultaneously...
- User-mode LinuxUser-mode LinuxUser-mode Linux enables multiple virtual Linux systems to run as an application within a normal Linux system...
- VirtualBoxVirtualBoxOracle VM VirtualBox is an x86 virtualization software package, originally created by software company Innotek GmbH, purchased by Sun Microsystems, and now developed by Oracle Corporation as part of its family of virtualization products...
- Virtual IronVirtual IronVirtual Iron Software, was located in Lowell, Massachusetts, sold proprietary software for virtualization and management of a virtual infrastructure...
(Virtual Iron 3.1) - VMVM (operating system)VM refers to a family of IBM virtual machine operating systems used on IBM mainframes System/370, System/390, zSeries, System z and compatible systems, including the Hercules emulator for personal computers. The first version, released in 1972, was VM/370, or officially Virtual Machine Facility/370...
from IBM - VMLite
- VMwareVMwareVMware, Inc. is a company providing virtualization software founded in 1998 and based in Palo Alto, California, USA. The company was acquired by EMC Corporation in 2004, and operates as a separate software subsidiary ....
(ESX Server, Fusion, Virtual Server, Workstation, Player and ACE) - XenXenXen is a virtual-machine monitor providing services that allow multiple computer operating systems to execute on the same computer hardware concurrently....
(Opensource) - IBM POWER systems
Operating system level virtualization software
- Microsoft Hyper-V
- OpenVZOpenVZOpenVZ is an operating system-level virtualization technology based on the Linux kernel and operating system. OpenVZ allows a physical server to run multiple isolated operating system instances, known as containers, Virtual Private Servers , or Virtual Environments...
- FreeVPS
- Linux-VServerLinux-VServerLinux-VServer is a virtual private server implementation that was created by adding operating system-level virtualization capabilities to the Linux kernel. It is developed and distributed as open source software.The project was started by Jacques Gélinas...
- FreeBSD JailFreeBSD JailThe FreeBSD jail mechanism is an implementation of operating system-level virtualization that allows administrators to partition a FreeBSD-based computer system into several independent mini-systems called jails....
s - Solaris ContainersSolaris ContainersSolaris Containers 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 first full release of Solaris 10, 2005.It is present in newer OpenSolaris based...
- AIX Workload PartitionsWorkload PartitionsAIX Workload partitions are a software implementation of operating system-level virtualization technology introduced in the IBM's AIX 6.1 operating system that provides application environment isolation and resource control....
- LXCLXCLXC is an operating system-level virtualization method for running multiple isolated Linux systems on a single control host...
Extended descriptions of selected virtualization software
The following software products can virtualize hardware so that several operating systems can share it.- Windows 2008 R2 Hyper-V provides x64 type 1 virtualization.
- AdeosAdeosAdeos is a nanokernel hardware abstraction layer or a hypervisor that operates between computer hardware and the operating system that runs on it. It is distinct from other nanokernels, in that it is not just a low level layer for an outer kernel...
is a hardware abstraction layer that can be loaded as a Kernel Module in LinuxLinuxLinux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...
. It allows the loading of a real-time kernel as a module, at the same time as Linux but with higher priority. - DenaliDenali (operating system)The Denali operating system is "an IA-32 virtual machine monitor, that allows for untrusted services to be run in isolated domains."...
uses paravirtualisation to provide high-performance virtual machines on x86 computers. Denali's virtual machines support specialised minimal OSs for Internet services. The system can scale to thousands of virtual machines. Denali does not preserve the application binary interface (ABI), and so applications must be recompiled to run within a library operating system; in this sense it is similar to the ExokernelExokernelExokernel is an operating system kernel developed by the MIT Parallel and Distributed Operating Systems group, and also a class of similar operating systems....
. - OKL4 from Open Kernel LabsOpen Kernel LabsOpen Kernel Labs is a privately owned company that develops microkernel-based hypervisors and operating systems for embedded systems. The company was founded in 2006 by Steve Subar and Gernot Heiser as a spinout from NICTA...
is designed for use in embedded systems and is primarily deployed in mobile phoneMobile phoneA mobile phone is a device which can make and receive telephone calls over a radio link whilst moving around a wide geographic area. It does so by connecting to a cellular network provided by a mobile network operator...
s. It is the only commercial hypervisor employing capability-based securityCapability-based securityCapability-based security is a concept in the design of secure computing systems, one of the existing security models. A capability is a communicable, unforgeable token of authority. It refers to a value that references an object along with an associated set of access rights...
. - OpenVZOpenVZOpenVZ is an operating system-level virtualization technology based on the Linux kernel and operating system. OpenVZ allows a physical server to run multiple isolated operating system instances, known as containers, Virtual Private Servers , or Virtual Environments...
provides operating system level server virtualization, built on Linux. - ParallelsParallels, Inc.Parallels, Inc. is a privately held virtualization technology company with offices in the USA, Germany, UK, France, Japan, China, Russia and Ukraine. Parallels' US offices are in Renton, WA.The company has more than 700 employees as of 2010....
virtualizes x86 to run unmodified PC operating systems, and uses a lightweight hypervisor technology to improve security and to increase the efficiency. Parallels has become popular for its ability to run Windows as a guest under Mac OS XMac OS XMac OS X is a series of Unix-based operating systems and graphical user interfaces developed, marketed, and sold by Apple Inc. Since 2002, has been included with all new Macintosh computer systems...
on the Apple–Intel architecture. - QEMUQEMUQEMU is a processor emulator that relies on dynamic binary translation to achieve a reasonable speed while being easy to port on new host CPU architectures....
is a simulator based on a virtual machine, which gives it the ability to emulate a variety of guest CPU architectures on many different host platforms. - Returnil Virtual SystemReturnil Virtual SystemReturnil Virtual System is a sandbox application for Microsoft Windows. Its goal is to prevent malware and potentially unwanted programs from permanently infecting or modifying a system.-How it works:...
can virtualize Windows based systems, needs only a restart to rebuild the virtual machine. - VirtualBoxVirtualBoxOracle VM VirtualBox is an x86 virtualization software package, originally created by software company Innotek GmbH, purchased by Sun Microsystems, and now developed by Oracle Corporation as part of its family of virtualization products...
is an open source (GPLGNU General Public LicenseThe GNU General Public License is the most widely used free software license, originally written by Richard Stallman for the GNU Project....
)/proprietaryProprietary softwareProprietary software is computer software licensed under exclusive legal right of the copyright holder. The licensee is given the right to use the software under certain conditions, while restricted from other uses, such as modification, further distribution, or reverse engineering.Complementary...
virtual machine developed by Sun MicrosystemsSun MicrosystemsSun Microsystems, Inc. was a company that sold :computers, computer components, :computer software, and :information technology services. Sun was founded on February 24, 1982...
(originally developed by Innotek GmbH and now owned by Oracle CorporationOracle CorporationOracle Corporation is an American multinational computer technology corporation that specializes in developing and marketing hardware systems and enterprise software products – particularly database management systems...
). It allows virtualization of x86 and supports various host operating systems including WindowsMicrosoft WindowsMicrosoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
, LinuxLinuxLinux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...
, BSDBerkeley Software DistributionBerkeley Software Distribution is a Unix operating system derivative developed and distributed by the Computer Systems Research Group of the University of California, Berkeley, from 1977 to 1995...
and Solaris. It also supports VMwareVMwareVMware, Inc. is a company providing virtualization software founded in 1998 and based in Palo Alto, California, USA. The company was acquired by EMC Corporation in 2004, and operates as a separate software subsidiary ....
, ParallelsParallelsParallels may refer to:* Circle of latitude , imaginary east-west circles connecting all locations that share a given latitude* "Parallels", the third track from the 1977 Yes album Going for the One...
and MicrosoftMicrosoftMicrosoft Corporation is an American public multinational corporation headquartered in Redmond, Washington, USA that develops, manufactures, licenses, and supports a wide range of products and services predominantly related to computing through its various product divisions...
Virtual Machine Disk Formats. - Virtual IronVirtual IronVirtual Iron Software, was located in Lowell, Massachusetts, sold proprietary software for virtualization and management of a virtual infrastructure...
provides virtual machines for x86 that run unmodified operating systems, such as Windows, Red Hat and SUSE; open source, implements native virtualizationNative virtualizationIn computing, hardware-assisted virtualization is a platform virtualization approach that enables efficient full virtualization using help from hardware capabilities, primarily from the host processors...
, which delivers near-native performance for x86 operating systems. Virtual Iron provides full OS compatibility for existing or new OSes with near-native performance without the performance trade-offs between paravirualization and binary translation.
- VMwareVMwareVMware, Inc. is a company providing virtualization software founded in 1998 and based in Palo Alto, California, USA. The company was acquired by EMC Corporation in 2004, and operates as a separate software subsidiary ....
provides virtual machines for x86 that can run unmodified PC operating systems. The technology involved in doing this is complex and also incurs (sometimes significant) performance overheads with hosted VMware products (VM Server and Workstation). ESX server provides near-native performance and a fully virtualized option (along with para-virtualization of some hardware components). - XenXenXen is a virtual-machine monitor providing services that allow multiple computer operating systems to execute on the same computer hardware concurrently....
trades running of existing operating systems for running modified (paravirtualized) operating systems with improved performance. Xen Virtualization system's motivation differs from that of Denali in that it is intended to run a moderate number of full-featured operating systems, rather than a large number of specialised, lightweight ones. - KVMKernel-based Virtual MachineKernel-based Virtual Machine is a virtualization infrastructure for the Linux kernel. KVM supports native virtualization on processors with hardware virtualization extensions....
is a Linux kernelLinux kernelThe Linux kernel is an operating system kernel used by the Linux family of Unix-like operating systems. It is one of the most prominent examples of free and open source software....
module that enables a modified QEMU program to use hardware virtualization. - libJIT Just-In-Time Compilation library is a library for development of advanced Just-in-time compilationJust-in-time compilationIn computing, just-in-time compilation , also known as dynamic translation, is a method to improve the runtime performance of computer programs. Historically, computer programs had two modes of runtime operation, either interpreted or static compilation...
(JIT) in Virtual MachineVirtual machineA virtual machine is a "completely isolated guest operating system installation within a normal host operating system". Modern virtual machines are implemented with either software emulation or hardware virtualization or both together.-VM Definitions:A virtual machine is a software...
implementations, Dynamic programming languageDynamic programming languageDynamic programming language is a term used broadly in computer science to describe a class of high-level programming languages that execute at runtime many common behaviors that other languages might perform during compilation, if at all...
s, and Scripting languages. Currently it is used for Common Intermediate LanguageCommon Intermediate LanguageCommon Intermediate Language is the lowest-level human-readable programming language defined by the Common Language Infrastructure specification and is used by the .NET Framework and Mono...
, RubyRuby (programming language)Ruby is a dynamic, reflective, general-purpose object-oriented programming language that combines syntax inspired by Perl with Smalltalk-like features. Ruby originated in Japan during the mid-1990s and was first developed and designed by Yukihiro "Matz" Matsumoto...
, JavaJava bytecodeJava bytecode is the form of instructions that the Java virtual machine executes. Each bytecode opcode is one byte in length, although some require parameters, resulting in some multi-byte instructions. Not all of the possible 256 opcodes are used. 51 are reserved for future use...
, Domain-specific programming languages.
See also
- Comparison of platform virtual machines
- Comparison of application virtual machinesComparison of Application Virtual MachinesThis article lists some software virtual machines that are typically used for allowing application bytecode to be portably run on many different computer architectures and operating systems. The application is usually run on the computer using an interpreter or just-in-time compilation...
- Virtual applianceVirtual applianceA virtual appliance is a virtual machine image designed to run on a virtualization platform ....
- HypervisorHypervisorIn computing, a hypervisor, also called virtual machine manager , is one of many hardware virtualization techniques that allow multiple operating systems, termed guests, to run concurrently on a host computer. It is so named because it is conceptually one level higher than a supervisory program...
- Storage hypervisorStorage hypervisorIn computing, a storage hypervisor is a portable software program that runs on a physical hardware platform, on a virtual machine, inside a hypervisor OS or in all three places. It may co-reside with virtual machine supervisors or have exclusive control of its platform...
- Native development kitNative development kitA native development kit is a software development kit based on a native application programming interface which allows computer software to be developed directly on a computing platform, rather than via a virtual machine....
- ICL's VME operating system
- Amazon Machine ImageAmazon Machine ImageAn Amazon Machine Image is a special type of virtual appliance which is used to instantiate a virtual machine within the Amazon Elastic Compute Cloud...
- Virtual backup applianceVirtual Backup Appliance-Definition:A Virtual Backup Appliance is a small virtual machine that backs up and restores other virtual machines.Unlike some backup solutions that require a dedicated host to act as a proxy server for the backups, virtual backup appliances use the virtual infrastructure platform itself for the...
- Virtual disk imageVirtual disk imageA virtual disk image is a file on a physical disk, which has a well-defined, published or proprietary, format and is interpreted by a Virtual Machine Monitor as a hard disk. IT administrators and software developers administer them through offline operations using built-in or third-party tools...
Further reading
- James E. Smith, Ravi Nair, Virtual Machines: Versatile Platforms For Systems And Processes, Morgan Kaufmann, May 2005, ISBN 1-55860-910-5, 656 pages (covers both process and system virtual machines)
- Craig, Iain D. Virtual Machines. Springer, 2006, ISBN 1-85233-969-1, 269 pages (covers only process virtual machines)
External links
- The Reincarnation of Virtual Machines, Article on ACM Queue by Mendel Rosenblum, Co-Founder, VMware
- Sandia National Laboratories Runs 1 Million Linux Kernels as Virtual Machines
- The design of the Inferno virtual machine by Phil Winterbottom and Rob Pike
- Software Portability by Virtual Machine Emulation by Stefan Vorkoetter