In unmanaged VPS hosting, the user enjoys full freedom to control the web server. The user gets access to the remote web server and they get the administrative power of the server. Unmanaged VPS hosting thus give you complete administrative functions of the web server and the user gets the freedom to select the administrator who can control the server technically.
Both single-machine and cloud-based VPSes are managed using a software program called a hypervisor. The machine that runs the hypervisor is called the host machine and the individual virtual private servers are called guest machines or guest instances. The hypervisor can start and stop the virtual machines and allocates system resources, such as CPU, memory, and disk storage to each VPS.
Partitioning a single server to appear as multiple servers has been increasingly common on microcomputers since the launch of VMware ESX Server in 2001. The physical server typically runs a hypervisor which is tasked with creating, releasing, and managing the resources of "guest" operating systems, or virtual machines. These guest operating systems are allocated a share of resources of the physical server, typically in a manner in which the guest is not aware of any other physical resources save for those allocated to it by the hypervisor. As a VPS runs its own copy of its operating system, customers have superuser-level access to that operating system instance, and can install almost any software that runs on the OS; however, due to the number of virtualization clients typically running on a single machine, a VPS generally has limited processor time, RAM, and disk space.