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In order for a virtual machine to run, users need to have a virtual server in place, explained Gary Chen, enterprise research, SME IT infrastructure and applications senior analyst at the Yankee Group. He is author of the new Yankee Group report, "Virtually Possible: Virtual Appliances Ready to Shake Up Application Delivery."
Enterprises may use virtual servers from Xen, VMware and even Microsoft's new Hyper-V. All of them support a standard called OVF (Open Virtual Machine Format), Chen said.
In a world of virtual machine-delivered software, open source OSes, such as Linux, may gain greater use, because of the integration advantages for ISVs.
Microsoft and other OS vendors have definite reasons to worry. When you get into the "Virtual Appliance" mindset, you just think of the app, you don't even want to (or must I say have to) touch the OS. There is a big chance that Linux will gain popularity with its simpler, thinner images BUT be warned Microsoft too is going strong with its console based OS.