together for a desired task. One neat trick is to run a set of servers locally and
then add compute resources from a cloud computing pool such as Amazon’s
EC2, Ubuntu Enterprise Cloud (using Eucalyptus), Ubuntu Cloud
Infrastructure (using OpenStack), or OpenStack to start up VMs on their
network, as needed, using them while paying for the time they are running
and then deleting them (see Chapter 31, “Ubuntu in the Cloud”). This saves a
lot of time and money.
What if you run only one machine, and it is your desktop or laptop?
Virtualization might be useful to you, as well. Have you ever wanted to test a
different operating system than the one you are using? Perhaps you found that
you have a need to run a specific program that runs only on Windows, but you
have Ubuntu installed on your system. Maybe you want to run the latest
development version of Ubuntu to help with testing, but you don’t want to use
it as your main system operating system. You might want to try out another
distribution of Linux or even BSD. In the past, doing these things typically
involved partitioning your hard drive and installing both operating systems
side by side. That worked, but you couldn’t easily move data from one
partition to the other, and you couldn’t run both operating systems at the same
time. Wouldn’t it be great if you could run another operating system as a
guest on your same machine? You can with virtualization.
There is a trade-off with virtualization, depending on the software used. Some
virtualization software runs as an additional layer on top of another operating
system. This is great if you want to test something while running on your
local desktop machine, but it can add some unwanted and sometimes
unacceptable delays when creating a new server. Other virtualization software
runs on or near “bare metal,” meaning the virtualization software is either a
part of the operating system kernel or runs as the operating system, and there
are no other software layers between it and the physical resources being
used/managed. This method is faster but not as convenient on the desktop, at
least for users who are not as technically advanced.
Virtualization is not new. For example, IBM had useful virtualization running
on its mainframes in the 1960s. What has created the recent buzz is that the
technology has become available to perform the task on much less-expensive
x86 hardware.
In November 2005, Intel released its first processors that supported an
extension called VT-x, which allows virtualization software access to the
processor and other hardware. Before that, virtualization on any x86 platform
was slow because it required difficult software workarounds and massaging to
get it working. VT-x is available on many of Intel’s processors but not
necessarily all of them as it is one of the ways that Intel differentiates the