In computing, a virtual machine (VM) is the virtualization or emulation of a computer system. Virtual machines are based on computer architectures and provide the functionality of a physical computer. Their implementations may involve specialized hardware, software, or a combination of the two. Virtual machines differ and are organized by their function, shown here:
A web hosting service is a type of Internet hosting service that hosts websites for clients, i.e. it offers the facilities required for them to create and maintain a site and makes it accessible on the World Wide Web. Companies providing web hosting services are sometimes called web hosts.
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 a host machine, and each virtual machine is called a guest machine. The hypervisor presents the guest operating systems with a virtual operating platform and manages the execution of the guest operating systems. Unlike an emulator, the guest executes most instructions on the native hardware. Multiple instances of a variety of operating systems may share the virtualized hardware resources: for example, Linux, Windows, and macOS instances can all run on a single physical x86 machine. This contrasts with operating-system–level virtualization, where all instances must share a single kernel, though the guest operating systems can differ in user space, such as different Linux distributions with the same kernel.
A dedicated hosting service, dedicated server, or managed hosting service is a type of Internet hosting in which the client leases an entire server not shared with anyone else. This is more flexible than shared hosting, as organizations have full control over the server(s), including choice of operating system, hardware, etc.
A logical partition (LPAR) is a subset of a computer's hardware resources, virtualized as a separate computer. In effect, a physical machine can be partitioned into multiple logical partitions, each hosting a separate instance of an operating system.
OS-level virtualization is an operating system (OS) virtualization paradigm in which the kernel allows the existence of multiple isolated user space instances, called containers, zones, virtual private servers (OpenVZ), partitions, virtual environments (VEs), virtual kernels, or jails. Such instances may look like real computers from the point of view of programs running in them. A computer program running on an ordinary operating system can see all resources of that computer. However, programs running inside of a container can only see the container's contents and devices assigned to the container.
IBM Z is a family name used by IBM for all of its z/Architecture mainframe computers. In July 2017, with another generation of products, the official family was changed to IBM Z from IBM z Systems; the IBM Z family now includes the newest model, the IBM z16, as well as the z15, the z14, and the z13, the IBM zEnterprise models, the IBM System z10 models, the IBM System z9 models and IBM eServer zSeries models.
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.
VMware ESXi is an enterprise-class, type-1 hypervisor developed by VMware, a subsidiary of Broadcom, 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); instead, it includes and integrates vital OS components, such as a kernel.
In computer science, full virtualization (fv) is a modern virtualization technique developed in late 1990s. It is different from simulation and emulation. Virtualization employs techniques that can create instances of a virtual environment, as opposed to simulation, which models the environment; and emulation, which replicates the target environment with certain kinds of virtual environments called emulation environments for virtual machines. Full virtualization requires that every salient feature of the hardware be reflected into one of several virtual machines – including the full instruction set, input/output operations, interrupts, memory access, and whatever other elements are used by the software that runs on the bare machine, and that is intended to run in a virtual machine. In such an environment, any software capable of execution on the raw hardware can be run in the virtual machine and, in particular, any operating systems. The obvious test of full virtualization is whether an operating system intended for stand-alone use can successfully run inside a virtual machine.
Hardware virtualization is the virtualization of computers as complete hardware platforms, certain logical abstractions of their componentry, or only the functionality required to run various operating systems. Virtualization hides the physical characteristics of a computing platform from the users, presenting instead an abstract computing platform. At its origins, the software that controlled virtualization was called a "control program", but the terms "hypervisor" or "virtual machine monitor" became preferred over time.
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 Windows Virtual PC as the hardware virtualization component of the client editions of Windows NT. A server computer running Hyper-V can be configured to expose individual virtual machines to one or more networks. Hyper-V was first released with Windows Server 2008, and has been available without additional charge since Windows Server 2012 and Windows 8. A standalone Windows Hyper-V Server is free, but has a command-line interface only. The last version of free Hyper-V Server is Hyper-V Server 2019, which is based on Windows Server 2019.
Infrastructure as a service (IaaS) is a cloud computing service model by means of which computing resources are supplied by a cloud services provider. The IaaS vendor provides the storage, network, servers, and virtualization. This service enables users to free themselves from maintaining an on-premises data center. The IaaS provider is hosting these resources in either the public cloud, the private cloud, or the hybrid cloud.
A virtual security appliance is a computer appliance that runs inside virtual environments. It is called an appliance because it is pre-packaged with a hardened operating system and a security application and runs on a virtualized hardware. The hardware is virtualized using hypervisor technology delivered by companies such as VMware, Citrix and Microsoft. The security application may vary depending on the particular network security vendor. Some vendors such as Reflex Systems have chosen to deliver Intrusion Prevention technology as a Virtualized Appliance, or as a multifunctional server vulnerability shield delivered by Blue Lane. The type of security technology is irrelevant when it comes to the definition of a Virtual Security Appliance and is more relevant when it comes to the performance levels achieved when deploying various types of security as a virtual security appliance. Other issues include visibility into the hypervisor and the virtual network that runs inside.
In computing, virtualization or virtualisation in British English is the act of creating a virtual version of something at the same abstraction level, including virtual computer hardware platforms, storage devices, and computer network resources.
An embedded hypervisor is a hypervisor that supports the requirements of embedded systems.
OpenNebula is an open source cloud computing platform for managing heterogeneous data center, public cloud and edge computing infrastructure resources. OpenNebula manages on-premises and remote virtual infrastructure to build private, public, or hybrid implementations of Infrastructure as a Service and multi-tenant Kubernetes deployments. The two primary uses of the OpenNebula platform are data center virtualization and cloud deployments based on the KVM hypervisor, LXD/LXC system containers, and AWS Firecracker microVMs. The platform is also capable of offering the cloud infrastructure necessary to operate a cloud on top of existing VMware infrastructure. In early June 2020, OpenNebula announced the release of a new Enterprise Edition for corporate users, along with a Community Edition. OpenNebula CE is free and open-source software, released under the Apache License version 2. OpenNebula CE comes with free access to patch releases containing critical bug fixes but with no access to the regular EE maintenance releases. Upgrades to the latest minor/major version is only available for CE users with non-commercial deployments or with significant open source contributions to the OpenNebula Community. OpenNebula EE is distributed under a closed-source license and requires a commercial Subscription.
Google Compute Engine (GCE) is the Infrastructure as a Service (IaaS) component of Google Cloud Platform which is built on the global infrastructure that runs Google's search engine, Gmail, YouTube and other services. Google Compute Engine enables users to launch virtual machines (VMs) on demand. VMs can be launched from the standard images or custom images created by users. GCE users must authenticate based on OAuth 2.0 before launching the VMs. Google Compute Engine can be accessed via the Developer Console, RESTful API or command-line interface (CLI).
In computing, a system virtual machine is a virtual machine (VM) that provides a complete system platform and supports the execution of a complete operating system (OS). These usually emulate an existing architecture, and are built with the purpose of either providing a platform to run programs where the real hardware is not available for use, or of having multiple instances of virtual machines leading to more efficient use of computing resources, both in terms of energy consumption and cost effectiveness, or both. A VM was originally defined by Popek and Goldberg as "an efficient, isolated duplicate of a real machine".
In computer networking, a bare-metal server is a physical computer server that is used by one consumer, or tenant, only. Each server offered for rental is a distinct physical piece of hardware that is a functional server on its own. They are not virtual servers running in multiple pieces of shared hardware.
