Software distribution is taking an interesting turn with virtual appliances, which combine an application and underlying operating system.

If you have ever had the experience of trying out a new application, it can be daunting: hours of tweaking operating system settings and downloading libraries (dependency hell) to get to the point of even starting up the application. For demo or evaluation software it can be the kiss of death - no matter how good the installer, it is always challenging to tame a general-purpose operating system to get a smoothly running application.

Virtual appliances give vendors the ability to pre-tune and configure the operating system with the minimal set of components needed to run the application. The end result: a more secure, smaller and better tuned operating system and an application installation experience that is as smooth as possible.

Now many people have issues with appliances in general. Will the vendor keep the patches up to date? What is the support model? For many users, appliances (whether hardware or software) make things more difficult because they cannot be customized “just so.” Instead you have to rely on the vendor to maintain the appliance for you.

For other users, that is precisely the point. Who needs customization? Just spare us the hassle of maintenance and patching. If you dislike appliances in general, then virtual appliances won’t change your mind. But if you are open to using hardware appliances, then virtual appliances will add many benefits that will make your life easier.

VMware recently announced its Virtual Appliance Marketplace and certification program. With more than 300 virtual appliances to choose from, the “marketplace” is a single point of sourcing for a variety of applications. The value of the certification program will of course have to be judged over time, based on how strictly VMware controls the quality of virtual appliances. Xensource is also fueling this trend with the ability to minimize the overhead of the virtualization layer. Egenera recently added Xen to its blade system, allowing the deployment of vBlades (another form of virtual appliance).

IT executives who have embraced the virtualization strategy will find virtual appliances a convenient mechanism for software distribution and deployment. They can stop worrying about hardening, configuring and tuning the operating system and focus instead on infrastructure and application management. Of course, the virtual appliance technology will have a serious impact on operating system vendors: the operating system is far less important, as it is completely hidden from view.