Para-Virtualization by Xen

An open-source project developed by the ‘University of Cambridge Computer Laboratory' in coordination with the ‘Open Source Development Labs' and several Linux distributors and currently managed by Xen.source.
It requires the user to boot up a Xen Linux Kernel package, server tools and documentation and then launch para-virtualized guest OS systems.
The kernel package incorporates support for running Xen in domain 0 (xen0) as a server and for unprivileged (xenU) user access. The virtual machines are called domains. When the Xen Kernel starts up, it creates a primary domain, domain0, which manages the system and set up virtual machines for other operating systems.
xend server: Manages virtual machines
/var/log/xend.log: places the xend messages
xend-config: for configuring Xen xend server
The guest OS is modified and configured to access the Xen interface.
HVM Abstraction Layer: It provides support for the Hardware Virtual Machine (HVM). The configuration file for HVM is in the /etc/xen directory and has the extension .hvm

Increased Efficiency for Enterprise-level systems: Virtual machines have nearly the same efficiency as the native kernel
It has full native device drive access support for graphics.
Setup a separate test system: Xen isolates servers in virtual machines on the system, which lets the virtual machine access the hardware support provided by the native kernel.

Constraint: Only UNIX and LINUX OS configured to be Xen compatible.

It provides a desktop interface to manage Xen domains (starting, stopping, or rebooting) or virtual machines, adding new ones, or deleting old ones.
It can be used on most distributions, which include Debian, SUSE, and Ubuntu.
The dashboard lets users check statistics like CPU and memory usage.
Allows to save the snapshot of a machine and restore to the point
xenman command to start XenMan from a terminal window
xenman.conf: XenMan configuration file. Global definitions held in the /etc/xenman/xenman.conf file. The file defines virtual block devices, snapshots location, provides an environment, specific configurations, and client configuration like GNOME support, use of images collected into an image store.
Each user has .xenman directory.