A Guest Operating System (Guest OS) is an operating system installed and running inside a virtual machine (VM), which operates on top of a hypervisor or host OS. Unlike the host operating system, the guest OS does not directly interact with physical hardware but accesses virtualized resources — CPU, RAM, storage, and network interfaces — provided by the hypervisor.
The guest OS can be any standard OS, such as Windows, Linux, BSD, Solaris, and others. This flexibility allows multiple different operating systems to run simultaneously on a single physical machine, each within its isolated virtual environment.
Role of the Guest OS in Virtualization
The guest OS gives users access to applications, services, and the system interface inside an isolated virtual machine. It operates like a standard OS, with support for updates, drivers, antivirus, user management, and services — all confined within the VM environment. This isolation helps improve system stability, security, and resource control.
Key Features of Guest Operating Systems
- Isolation – Each VM runs independently from others and from the host.
- Cross-platform compatibility – Multiple OS types (e.g., Linux, Windows) can run on the same physical server.
- Flexibility – Guest OS instances can be easily cloned, snapshotted, migrated, or restored.
- Hardware abstraction – The guest interacts with virtual hardware through the hypervisor.
- Integration tools support – Tools like VMware Tools, Hyper-V Integration Services, and VirtualBox Guest Additions enhance performance and communication between host and guest.
Supported Platforms and Hypervisors
Guest OSes are supported across major virtualization platforms, including:
- VMware ESXi, Workstation, Fusion
- Microsoft Hyper-V
- KVM, Proxmox, QEMU
- Oracle VirtualBox
- XenServer, Nutanix AHV
Modern hypervisors allow the deployment of dozens of different Windows and Linux versions, including custom enterprise distributions.