Recently I wrote a detailed article on using VMware Fusion and Parallels Desktop on the Mac. These two programs are virtualization solutions--they allow one "host" operating system (Mac OS X) to run any number of other "guest" operating systems (Windows, Linux, DOS, etc.) within the host operating system. As described in the article, the primary reason many individuals do this is to run some version of Windows on their Macs to gain access to programs that aren't available on the Mac. But there's something else you can do with virtualization software--virtualize the same operating system that you're currently running.
For instance, if you're running Windows XP, you could install a Windows virtualization application (there are a number of such products, including VirtualPC from Microsoft), and then install Windows XP as a virtual installation. You must, of course, then have two licenses for Windows XP, as you'll occasionally be using two copies of the OS at once. So why might you want to do this?
For one thing, by running a virtual copy of your core OS, you can safely experiment with new software packages. Before you install some complex new app, create a snapshot of your virtual machine, then install the program and test. If things go poorly, you can revert to the saved snapshot in a matter of a few mouse clicks. Or perhaps you've read about some Windows registry tweak that will improve performance, and you want to test it before you apply it to your "real" machine. Another possible use, especially in a world filled with 'drive by' malware infestations on poorly-protetected Windows machines, would be to do your casual browsing on a browser running in a virtual machine. If the virtual machine becomes infected, your main OS will not--and you can then revert the virtual machine, or if it's beyond salvation, just throw it away and start over. Finally, virtual copies of your real OS are great "playgrounds" to help learn about the OS without fear of breaking things badly if you make a really bad mistake.
With Windows XP, Microsoft allowed (or more specifically, didn't disallow) virtualization of the OS. (They also allow it with their Windows server products.) When Windows Vista shipped, however, things changed. The new Vista license only allowed the Ultimate and Business versions of the OS to be installed as guest operating systems within a virtualization program. The Home Basic and Home Premium licenses explicitly forbid their use in virtualization programs. This change was not greeted well by consumers.
It was received so poorly, in fact, that Microsoft changed the rules in January, allowing Home Basic and Premium to be used in virtualization applications. So now, regardless of whether you have Windows XP or Vista, Server or Client, in any version, you can use it in a virtualization program.
If only the same were true of OS X.
Until recently, in fact, OS X wasn't legally usable in any virtualization application. That changed for OS X Server with the release of OS X 10.5--its license allows for multiple installs on the same Mac. Again, you'll need to have a license for each installation, but this is great news for those who run multiple server installations. In many cases, you may be running servers that have relatively light loads, and don't merit a full hardware box of their own. As of OS X 10.5 Server, you can install such servers alongside other licensed copies of OS X Server on the same piece of hardware, assuming you have a virtualization solution to do just that.
Enter VMware and Parallels. Both companies have products in the works that will allow for multiple installations of OS X Server on any Mac that's capable of running their products. Soon you'll be able to install OS X Server on a virtual machine running on anything from an Intel-powered mini up to the latest Xserves. While this is wonderful news for those who use OS X Server, it still leaves Apple trailing Microsoft in one key area: virtualizing non-server versions of the OS.
As I described above, being able to run a virtual machine version of your desktop OS is a very useful capability. Unfortunately, for those of us who use non-server versions of OS X, we won't be able to do this (unless we're willing to pay for OS X Server, of course). Unlike the server license, there was no change in the OS X client license with the release of 10.5. As such, neither Parallels or VMware will allow the installation of OS X client on their upcoming products, respecting the terms in Apple's license agreement.
As a consumer, this is a frustrating situation. There are many valid reasons to install a virtual copy of OS X, but between the company's license terms and the installation limits in VMware and Parallels' upcoming products, it just can't be done. It's not very often I find myself saying this, but this is one time I really hope Apple copies Microsoft. Apple, please change your license agreement and allow consumers to legally install OS X 10.5 client on virtual machines. You've seen the light with Server, but understand that consumers will also benefit greatly from a similar change in the license agreement for non-server versions of OS X.
This story, "OS X Virtualization Options Limited for Desktop Users" was originally published by Macworld.