Unified Extensible Firmware Interface is a specification for the firmware architecture of a computing platform. When a computer is powered on, the UEFI-implementation is typically the first that runs, before starting the operating system. Examples include AMI Aptio, Phoenix SecureCore, TianoCore EDK II, InsydeH2O.
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.
The Quick Emulator (QEMU) is a free and open-source emulator that uses dynamic binary translation to emulate a computer's processor; that is, it translates the emulated binary codes to an equivalent binary format which is executed by the machine. It provides a variety of hardware and device models for the virtual machine, enabling it to run different guest operating systems. QEMU can be used with a Kernel-based Virtual Machine (KVM) to emulate hardware at near-native speeds. Additionally, it supports user-level processes, allowing applications compiled for one processor architecture to run on another.
Platform virtualization software, specifically emulators and hypervisors, are software packages that emulate the whole physical computer machine, often providing multiple virtual machines on one physical platform. The table below compares basic information about platform virtualization hypervisors.
OS-level virtualization is an operating system (OS) virtualization paradigm in which the kernel allows the existence of multiple isolated user space instances, including containers, zones, virtual private servers (OpenVZ), partitions, virtual environments (VEs), virtual kernels, and 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. Programs running inside a container can only see the container's contents and devices assigned to the container.
virt-manager is a desktop virtual machine monitor primarily developed by Red Hat.
FreeBSD is a free-software Unix-like operating system descended from the Berkeley Software Distribution (BSD). The first version was released in 1993 developed from 386BSD—the first fully functional and free Unix clone—and has since continuously been the most commonly used BSD-derived operating system.
Kernel-based Virtual Machine (KVM) is a free and open-source virtualization module in the Linux kernel that allows the kernel to function as a hypervisor. It was merged into the mainline Linux kernel in version 2.6.20, which was released on February 5, 2007. KVM requires a processor with hardware virtualization extensions, such as Intel VT or AMD-V. KVM has also been ported to other operating systems such as FreeBSD and illumos in the form of loadable kernel modules.
nouveau is a free and open-source graphics device driver for Nvidia video cards and the Tegra family of SoCs written by independent software engineers, with minor help from Nvidia employees.
oVirt is a free, open-source virtualization management platform. It was founded by Red Hat as a community project on which Red Hat Virtualization is based. It allows centralized management of virtual machines, compute, storage and networking resources, from an easy-to-use web-based front-end with platform independent access. KVM on x86-64, PowerPC64 and s390x architecture are the only hypervisors supported, but there is an ongoing effort to support ARM architecture in a future releases.
libvirt is an open-source API, daemon and management tool for managing platform virtualization. It can be used to manage KVM, Xen, VMware ESXi, QEMU and other virtualization technologies. These APIs are widely used in the orchestration layer of hypervisors in the development of a cloud-based solution.
libguestfs is a C library and a set of tools for accessing and modifying virtual disk images used in platform virtualization. The tools can be used for viewing and editing virtual machines (VMs) managed by libvirt and files inside VMs, scripting changes to VMs, creating VMs, and much else besides. It was created because of security issues, when virtual disk images are mounted directly on the host system.
SeaBIOS is an open-source implementation of an x86 BIOS, serving as a freely available firmware for x86 systems. Aiming for compatibility, it supports standard BIOS features and calling interfaces that are implemented by a typical proprietary x86 BIOS. SeaBIOS can either run on bare hardware as a coreboot payload, or can be used directly in emulators such as QEMU and Bochs.
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 (IaaS) 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.
Second Level Address Translation (SLAT), also known as nested paging, is a hardware-assisted virtualization technology which makes it possible to avoid the overhead associated with software-managed shadow page tables.
SmartOS is a free and open-source SVR4 hypervisor based on the UNIX operating system that combines OpenSolaris technology with bhyve and KVM virtualization. Its core kernel contributes to the illumos project. It features several technologies: Crossbow, DTrace, bhyve, KVM, ZFS, and Zones. Unlike other illumos distributions, SmartOS employs NetBSD pkgsrc package management. SmartOS is designed to be particularly suitable for building clouds and generating appliances. It was originally developed for and by Joyent, who announced in April 2022 that they had sold their business supporting and developing of Triton Datacenter and SmartOS to MNX Solutions. It is open-source and free for anyone to use.
mpv is free and open-source media player software based on MPlayer, mplayer2 and FFmpeg. It runs on several operating systems, including Unix-like operating systems and Microsoft Windows, along with having an Android port called mpv-android. It is cross-platform, running on ARM, MIPS, PowerPC, RISC-V, s390x, x86/IA-32, x86-64, and some other by 3rd party.
OpenZFS is an open-source implementation of the ZFS file system and volume manager initially developed by Sun Microsystems for the Solaris operating system, and is now maintained by the OpenZFS Project. Similar to the original ZFS, the implementation supports features like data compression, data deduplication, copy-on-write clones, snapshots, RAID-Z, and virtual devices that can create filesystems that span multiple disks.
GPU virtualization refers to technologies that allow the use of a GPU to accelerate graphics or GPGPU applications running on a virtual machine. GPU virtualization is used in various applications such as desktop virtualization, cloud gaming and computational science.
Windows Subsystem for Linux (WSL) is a feature of Microsoft Windows that allows for using a Linux environment without the need for a separate virtual machine or dual booting. WSL is installed by default in Windows 11. In Windows 10, it can be installed either by joining the Windows Insider program or manually via Microsoft Store or Winget.
