After you create a virtual machine, you can clone it to a template. Templates are primary copies of virtual machines that let you create ready-for-use virtual machines. You can make changes to the template, such as installing additional software in the guest operating system, while preserving the original virtual machine.
You cannot modify templates after you create them. To alter an existing template, you must convert it to a virtual machine, make the required changes, and convert the virtual machine back to a template. To preserve the original state of a template, clone the template to a template.
If a load generator is running in the virtual machine, stop it before you perform the clone operation.
Verify that you have the following privileges:
Virtual machine .Provisioning.Create template from virtual machine on the source virtual machine.
Virtual machine .Inventory.Create from existing on virtual machine folder where the template is created.
Resource.Assign virtual machine to resource pool on the destination host, cluster, or resource pool.
Datastore.Allocate space on all datastores where the template is created.