A+ Core 2 (220-1102) Cram Notes

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1. Operating System

1.9 Explain the basics of client-side visualization

Virtualization has become very popular because of its main two advantages the performance and cost saving. Virtualization can be implemented through open source like Xen and VirtualBox as well as proprietary solutions like VMware. It allows you to make one physical device appear as a number of standalone entities to users. A virtual desktop is often referred as VDI(Virtual Desktop Interface) it refers to software and hardware needed to create virtual environment. Microsoft Virtual PC 2007 is available for Windows XP and Vista and Windows Virtual PC is available for Windows 7.

Purpose of Virtual Machines

A workstation can have multiple operating systems installed on it but can run only one OS at a time but by running virtualization software same workstation can run Windows server along with windows 7 and Linux or any other operating system at the same time. This will allow a developer to test a code on various environments at the same time and he can also move code from one operating system to another with basic copy paste.

Each virtual desktop will typically need full network access. Configuring permissions for each virtual desktop can be tricky for administrator. Remote administration often uses virtual desktop to work on a workstation without knowledge of user sitting on the workstation.

Resource requirements

The hardware on the machine must have enough memory, hard drive space and processor capability to support virtualization. Also software is needed to make virtualization possible these requirements are based on the type of environment you are creating.

Emulator requirements

Window XP has a free emulator from Microsoft that you can download and use as a virtual emulator. In most cases, the motherboard and associated BIOS settings need no alteration to provide service to these virtual machines. Some of the newer virtualization products like Microsoft’s Hyper-V and Windows 7 Virtual PC require that the motherboard support hardware-assisted virtualization. The advantage of using hardware-assisted virtualization is it allows the Hypervisor (the virtualization product) to dynamically allocate memory and CPU to virtual machines as required.

Security Requirements

Security for virtualization is important because if somebody gains access to the host, they effectively would gain access to at least parts of all those different operating systems. And if you have a failure of the hardware of that host, then of course all of those other operating systems are not going to work either.

Main security threat in virtualization is to the hypervisor. The VM escaping is a new type of security concern. Because if you can gain access to those virtual machines and then even gain access from one virtual machine to the other through the hypervisor, that’s a significant security hole. The bad guys are trying to create malware and find ways to get around and move around that operating system or multiple operating systems much easier than what they can do today. If they can take advantage of the hypervisor, that gives them a very, very useful channel. Both physical and digital security methods are used to ensure security in virtualization

Network Requirements

While it is possible to do desktop virtualization on a computer without an internet connection there are several reasons for which having internet connection is an advantage. First hypervisors can be obtained from internet, and updates to hypervisors, host operating system, guest operating system are easily available on internet. Furthermore, if you create a virtual machine to test an operating system or other software for use in a normal environment, then you certainly should include testing how it works on a network. Therefore, the hypervisors we use simulate a network card within each virtual machine, as well as a network on the host, so that multiple virtual machines can communicate with each other and the underlying host. Then, through a virtual connection to the host computer’s physical network adapter, each VM has access to an external network, and through that to the Internet, if available. Of course, you can turn off these and other features for a VM, if you desire.


To do desktop or server virtualization, you first need a hypervisor. A hypervisor, also called a virtual machine monitor (VMM), is the software that creates a virtual machine, providing access to the necessary hardware on the host machine in isolation from other virtual machines and the host operating system, if present. This allows multiple operating systems to run simultaneously on a single physical computer, such as a network server or desktop computer. A hypervisor must create a virtual CPU compatible with that of the underlying machine—mainly either an Intel or an AMD CPU. This means that the installed OS must be capable of installing directly on the underlying computer. Also, today’s hypervisors require, or at least work best on, computers with Hardware-Assisted Virtualization (HAV) features, either Intel Virtualization Technology for x86 (Intel VT-x) or AMD Virtualization (AMD-V). HAV supports and improves the performance of virtual machines on the host. Both Intel and AMD CPUs have supported HAV since 2006.

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