Virtualization Lab: Part 2 – Concepts and Terminology

Virtualization Lab: Part 2 – Concepts and Terminology

Welcome to part two of my Virtualization Lab series. If you haven’t read part one, I would recommend reading it first.

In this post I want to go over the concepts and terms that are used so frequently. Understanding the gist of virtualization will help lay a steady foundation upon which advanced topics seem more natural and intuitive.

Commonly used terms:
Host – This term is used to describe the operating system and physical computer that exists and runs virtual software/hardware.

Guest – This term is used when referring to a virtual computer or operating system which is running on a host system.

VM – a Virtual Machine is the same thing as a guest and is used much more frequently.

Hypervisor: A hypervisor is a lower level operating system that exists somewhere between the physical hardware and the VM’s. A hypervisor usually takes the place of your user system and is essentially a small highly optimized operating system for running virtual machines.

P2V: This acronym stands for Physical to Virtual. P2V conversions are great when they work and help convert current systems into a VM.

There are many other terms and acronyms out there, but these are the most common.

Where to start:
For the absolute beginner and most others, I recommend installing VirtualBox which can be downloaded here. Go ahead and get VirtualBox installed since we will be going over it in more detail in part three of this series. You will also need to download a .iso file for next weeks post. I will be installing Ubuntu 9.04 Jaunty Jackalope 32bit which can be downloaded from here.


VirtualBox and cloning virtual hard disk drives

After breaking my VMWare Workstation install by upgrading to the latest kernel, I decided to give VirtualBox a try. VirtualBox comes in two flavors, the full version and the open source edition (OSE). I have had a great time creating virtual machines in VirtualBox, the application really is quite solid. I am seeing performance similar to what I am use to with VMWare.

I primarily use virtual machines for testing production type systems in an environment that I can experiment with. Something about trying out new products and ideas seems to worry my clients and end users, no surprise there. With that being said, I have created a Windows 2008 Standard addition VM, a Windows XP Professional VM, and a Windows Vista Business VM. That is about where I would like the creation to stop, I want to simulate multiple client machines, but I do not want to manually load all of the client systems. In VMWare it is quite straight forward, you simply shut the VM down, highlight it and click on Clone. Well VirtualBox is almost that straight forward, but you have to do the cloning from the command line, and more importantly, you must use absolute paths.

The command is documented in many places across the web, but most if not all of them that I found were something like this:

VBoxManage clonevdi yourvirtualhdd.vdi yourclonedvirtualhdd.vdi

The problem with this is that the above command uses relative paths which is kind of standard for most apps, not VirtualBox. So in my case the command would actually look like this:

VBoxManage clonevdi /home/himuraken/VM/VirtualBox/BaseInstalls/yourvirtualdd.vdi /home/himuraken/VM/VirtualBox/BaseInstalls/yourclonedvirtualhdd.vdi

This may appear complex or difficult to understand for some but just understand it this way, you need to provide the full path to the image you want to clone and the full path to the location you want to store the cloned VDI to.