Virtual Machines in a Nutshell

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Many of you have probably heard the term “virtual machine“, but might not be familiar with what a VM is or does. Virtualization is a complicated topic, as there are many different kinds and it can be difficult for the novice to tell which is which. Today we’re going to talk specifically about OS virtualization and why you should care about this pretty fabulous piece of tech.

Let’s start with a physical computer. For the sake of having a consistent example, we’ll say it’s a Dell laptop running Windows 7. Dual booting is a popular method of installing an additional operating system onto a physical computer in order to have more options and flexibility with what programs you want to run. Lots of Mac users run Boot Camp so they can have both OS X and Windows side by side. While dual booting is a great choice for many, it has limitations. Installing an OS directly onto the hardware is expensive in terms of time and system resources, and doesn’t scale very well if you want to install LOTS of operating systems as a test. What if we want Mac, Windows, and a few flavors of Linux? Bringing more than two operating systems onto the hardware is asking for trouble. Dual booting is also overkill if you are just experimenting with an OS. If you are like me and you like to install things just to see if you like them and then throw them away when you are done, dual booting just takes too long.

Enter OS virtualization. Using virtualization software like VirtualBox, a user can have any number of operating systems running as virtual machines. Our trusty Dell laptop, henceforth referred to as the “host machine”, running Windows 7, henceforth referred to as the “host OS”, downloads a copy of VirtualBox for Windows and installs it just like any other program. Virtualization software is built to manage VMs (also known as a “guest OS”) just like Microsoft Word manages documents and iTunes manages music. VMs are just files that the virtualization software runs, making it far easier to download, install, backup and destroy any number of operating systems at will. It also allows the host machine to run several operating systems at once; Windows can be running VirtualBox which is running a Mac OS X guest OS and a Linux guest OS. As you could probably guess, having several VMs running at once can be a drain on memory, so just because you can run several at once doesn’t mean you should.

Now let’s talk about why you would want to virtualize operating systems. The first and most obvious reason is that it’s more convenient than installing a new OS straight onto the hardware. Many libraries are starting to leverage OS virtualization as part of their IT strategy. When you have hundreds of computers to manage, it’s a lot easier to install virtualization software on all of them and then deploy a single managed VM file (called an “image”) to all of them instead of installing the exact same set of programs on each one individually. It’s also a great way for regular users to experiment with new environments without fear of turning their computers into expensive paperweights. Since the host OS is never overwritten, there’s never any danger of accidentally deleting your entire system, and you can always go back to the OS you are familiar with when finished.

If you are a coder, VMs are mana from heaven for a many reasons. The first is that it allows you to download whatever you want without mucking up your host machine. I’m constantly downloading new tools and programs to test out, and I don’t keep 95% of them. Testing them out in a virtual machine means that I can just delete the entire VM when I’m done, taking all that junk leftover from the installation and any test files I created along with it. I can also play around with configurations in a VM without fear of doing irreparable damage.

Perhaps one of the most useful aspects of a VM for coders is the ability to mimic target environments. Here at FSU, all of our servers are running a specific kind of Linux called Red Hat v6.5. With OS virtualization, I can download a Red Hat v6.5 image and go hog wild installing, deleting and reconfiguring whatever I want without fear of accidentally trashing the server and taking down our website. If I do inadvertently break something in the VM, I just delete it and spin up another instance. This can be a great tool for teaching newbies how to work on your production server without actually letting them anywhere near your production server.

You can prepackage software on an image as well, which is handy when you and your team want a simple way to play around with some software that might be difficult to install. The Islandora project distributes a virtual machine containing all the necessary parts configured correctly to create a working Islandora instance. This has been a huge boon to the project because it lets newbies who don’t know what they are doing (such as myself) have access to a disposable Islandora to hack on without the pain of setting one up themselves. Catmandu, a bibliographic data processing toolkit, can also be downloaded as a VM for experimentation. Expect to see this trend of software being distributed in a virtual machine continue in the future.

Learning to leverage OS virtualization effectively has changed the way I work. I do almost all of my work inside of disposable VMs now just because it’s so much more clean and convenient; it’s like a quarantined area for when you are working on things that may or may not explode. Even if you aren’t a developer, there are plenty of convenient ways to use virtualization in your everyday work environment. Despite the complicated technology running under the hood, getting started with virtualization has never been easier. Give it a shot today and let me know what you think in the comments!

One thought on “Virtual Machines in a Nutshell

  1. Yes! Thanks for this post, Bryan. I’ve personally found it useful to have a Linux VM available on my personal Windows 7 laptop. Just being able to execute Unix commands alone makes the effort of installing a Linux VM worthwhile. I have to give a plug for !# (“CrunchBang”) as a lightweight distribution to try out.

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