xen

Xen Virtualization: Hypervisor (aka VMM aka Microkernel)

Xen is a virtual machine monitor for x86 that supports execution of multiple guest operating systems with unprecedented levels of performance and resource isolation. This package contains the Xen Hypervisor. (tm) Modern computers are sufficiently powerful to use virtualization to present the illusion of many smaller virtual machines (VMs), each running a separate operating system instance. Successful partitioning of a machine to support the concurrent execution of multiple operating systems poses several challenges. Firstly, virtual machines must be isolated from one another: It is not acceptable for the execution of one to adversely affect the performance of another. This is particularly true when virtual machines are owned by mutually untrusting users. Secondly, it is necessary to support a variety of different operating systems to accommodate the heterogeneity of popular applications. Thirdly, the performance overhead introduced by virtualization should be small. Xen uses a technique called paravirtualization: The guest OS is modified, mainly to enhance performance. The Xen hypervisor (microkernel) does not provide device drivers for your hardware (except for CPU and memory). This job is left to the kernel that's running in domain 0. Thus the domain 0 kernel is privileged; it has full hardware access. It's started immediately after Xen starts up. Other domains have no access to the hardware; instead they use virtual interfaces that are provided by Xen (with the help of the domain 0 kernel). In addition to this package you need to install the kernel-xen, xen-libs and xen-tools packages to use Xen. Xen version 3 and newer also supports running unmodified guests using full virtualization, if appropriate hardware is present. [Hypervisor is a trademark of IBM]