Virtual machines allow you to run an operating system in an application window on the desktop. They behave like a separate computer and you can use them to play different operating systems, run the software that your main operating system cannot, and test applications in a safe and isolated space.

There are several free applications of virtual machines (VMs) that make their configuration a simple and straightforward process. You can carry out a synapse search and then install a VM application and have access to the installation media for the operating system you want to install.

What Is A Virtual Machine?

A virtual machine application creates a virtualised environment, simply called a ‘virtual machine', which behaves like a separate computer system, with full virtual devices. The VM is executed as a process in a window of the current operating system. You can boot an operating system installation disk (or live CD) inside the virtual machine and the operating system will be ‘tricked' into believing it is running on a real computer. It will be installed and run as if it were on an actual physical machine. At any point in time, when you want to make use of the operating system, all you have to do is open the VM sequence and run it on a window on your PC.

In the world of virtual machines, the operating system that runs on your computer is called a ‘host', while any operating system that runs inside VM is called a ‘guest'. This helps to prevent things becoming too confusing.

In a virtual machine, the guest operating system is stored on a virtual hard disk - a large file of several gigabytes stored on your real hard disk. The VM application presents this file as a guest operating system on a real hard disk. This means that you won't have to lose partitions or other complex files within your actual hard drive.

Virtualisation adds an overload, so you shouldn't assume they'll be as quick had you installed the operating system on actual hardware. Heavy-data applications that entail serious visuals and CPU power may not perform well. Virtual machines aren't the perfect system to play PC games with Windows on Linux or Mac OS X; at least, unless those games are quite old or require less graphics. You can also run multiple virtual machines simultaneously, but you could be restricted by your system's resources. Each VM consumes CPU, RAM and other resources.

Virtual machines also allow you to experiment with another operating system without having to install it on the physical hardware. For example, they're a great way to try Linux (or with a new Linux distribution) and see if it's of any benefit. When you finish playing with an operating system, you can simply delete the virtual machine.

Virtual machines also provide a way to run other operating system software. For example, as a Linux or Mac user, you can install Windows on a virtual machine to run Windows applications that you don't otherwise have access to. Another advantage offered by virtual machines is that they are ‘isolated' from the rest of the system. Software within a VM cannot escape from the VM to manipulate the rest of its system. This makes virtual machines a safe place to test applications or websites (that you don't trust) and see what they do.

Sandboxing also allows you to run unsafe operating systems more securely. If you still need Windows XP for previous applications, you can run it on a VM that mitigates any damage resulting from running an old, incompatible operating system.

Applications of the Virtual Machine

The following are VM programs you can choose from:

• Virtual Box: (Windows, Mac OS X, Linux): Virtual Box is very common, due to its completely and open-source nature. There is no paid version of Virtual Box, so you don't have to deal with additional purchases and the usual ‘upgrade to get more features' issues. Virtual Box works very well - especially in Windows and Linux, where there is less competition - so it's a good starting point for virtual machines.
• VMware Player: (Windows, Linux): VMware has its own line of programs for virtual machines. You can use VMware Player on Windows or Linux as a basic and free virtual machine tool. The more advanced features (many of which are free on Virtual Box) require an upgrade to the premium VMware Workstation package. My recommendation is that you start with Virtual Box; however, if that doesn't work properly, you may want to try the VMware player.
• VMware Synthesis: (Mac OS X): Mac users need to purchase VMware Fusion to use a VMware product, because the free VMware player is not available on Mac. However, VMware Fusion is more polished.
• Parallels Desktop: (Mac OS X): Macs also have free to access Desktop twins. Both VMware Fusion and Parallels Desktop for Mac are more refined than virtual machine programs on other platforms, as they are marketed for average Mac users who want to run Windows software.

Configuring a Virtual Machine

After choosing an application and installing it, setting up a virtual machine is simple enough. We're going to perform the basic process in Virtual Box, but most applications manage creating a virtual machine in the same way.

1. Open the VM application and click on the button to create a new virtual machine.

2. The wizard will guide you through the process and first ask you which operating system you want to install. If you type the name of the operating system in the ‘Name' box, the application will automatically select the type and version for the operating system. If you don't do this or guess correctly, select these items yourself from the drop-down menus. When finished, click ‘Next'.

3. Depending on the operating system you intend to install, the wizard will select certain default settings for the user beforehand, but you can change them on the following screens.

4. The wizard will also create the virtual hard disk file that the VM will use. As you have the hard disk file already, simply select the option to create a new one.

5. You will be asked if you want to create a fixed size disk dynamically. With a dynamically assigned disk, you can set a maximum disk size, but the file will grow at that level only if necessary. With a fixed size disk, it also sets a size, but the created file will be larger, as it has been created.

6. It's recommended to create fixed-size disks, because although they consume a little more disk space, they work even better, making the VM a little more receptive. In addition, you'll be alerted to the disk space you've used and there will be no surprises when VM files start increasing.

7. You can then set the size of the virtual disk. You can choose the default configuration or change the size according to your needs. After clicking on ‘Create', the virtual hard disk will be created.

8. After that, return to the main window of the VM application, where the new VM should appear. Ensure the required installation media is available for the machine; generally, this implies to indicate an ISO file or a real disk through the virtual machine configuration. You can run the new VM by selecting it and pressing ‘Start'.

Of course, we've just dealt with the basics of using virtual machines here, but you can glean more information from the advanced guidelines in subsequent articles.

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