When you customize your guest OS you can set up a virtual machine with the operating system that you want.
vCloud Director can customize the network settings of the guest operating system of a virtual machine created from a vApp template. When you customize your guest operating system, you can create and deploy multiple unique virtual machines based on the same vApp template without machine name or network conflicts.
When you configure a vApp template with the prerequisites for guest customization and add a virtual machine to a vApp based on that template, vCloud Director creates a package with guest customization tools. When you deploy and power on the virtual machine for the first time, vCloud Director copies the package, runs the tools, and deletes the package from the virtual machine.