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Xen 3.0 Virtualization User Guide
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B. Glossary of Terms

BVT
The BVT scheduler is used to give proportional fair shares of the CPU to domains.

Domain
A domain is the execution context that contains a running virtual machine. The relationship between virtual machines and domains on Xen is similar to that between programs and processes in an operating system: a virtual machine is a persistent entity that resides on disk (somewhat like a program). When it is loaded for execution, it runs in a domain. Each domain has a domain ID.

Domain 0
The first domain to be started on a Xen machine. Domain 0 is responsible for managing the system.

Domain ID
A unique identifier for a domain, analogous to a process ID in an operating system.

Full virtualization
An approach to virtualization which requires no modifications to the hosted operating system, providing the illusion of a complete system of real hardware devices.

Hypervisor
An alternative term for VMM, used because it means `beyond supervisor', since it is responsible for managing multiple `supervisor' kernels.

Live migration
A technique for moving a running virtual machine to another physical host, without stopping it or the services running on it.

Paravirtualization
An approach to virtualization which requires modifications to the operating system in order to run in a virtual machine. Xen uses paravirtualization but preserves binary compatibility for user space applications.

Shadow pagetables
A technique for hiding the layout of machine memory from a virtual machine's operating system. Used in some VMMs to provide the illusion of contiguous physical memory, in Xen this is used during live migration.

Virtual Block Device
Persistant storage available to a virtual machine, providing the abstraction of an actual block storage device. VBDs may be actual block devices, filesystem images, or remote/network storage.

Virtual Machine
The environment in which a hosted operating system runs, providing the abstraction of a dedicated machine. A virtual machine may be identical to the underlying hardware (as in full virtualization, or it may differ, as in paravirtualization).

VMM
Virtual Machine Monitor - the software that allows multiple virtual machines to be multiplexed on a single physical machine.

Xen
Xen is a paravirtualizing virtual machine monitor, developed primarily by the Systems Research Group at the University of Cambridge Computer Laboratory.

XenLinux
A name for the port of the Linux kernel that runs on Xen.



Footnotes

... 20031.1
http://www.cl.cam.ac.uk/netos/papers/2003-xensosp.pdf
... bridge-utils2.1
Available from http://bridge.sourceforge.net
... system2.2
Available from http://linux-hotplug.sourceforge.net/
... system2.3
See http://www.kernel.org/pub/linux/utils/kernel/hotplug/udev.html/
... kernel2.4
If you boot without first disabling TLS, you will get a warning message during the boot process. In this case, simply perform the rename after the machine is up and then run /sbin/ldconfig to make it take effect.


Xen Daemon 2006-01-11
Xen 3.0 Virtualization User Guide
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  Published under the terms of the GNU General Public License Design by Interspire