When you customize a clone using Sysprep, you need to provide a customization specification.
Sysprep is available for View Composer linked-clone desktop pools and automated full-clone desktop pools, but not instant-clone desktop pools. You create customization specifications by using the Customization Specification wizard in vSphere. See the vSphere Virtual Machine Administration document for information on using the Customization Specification wizard.
It is recommended that you test a customization specification in vSphere before you use it to create a desktop pool. When you use a Sysprep customization specification to join a Windows desktop to a domain, you must use the fully qualified domain name (FQDN) of the Active Directory domain. You cannot use the NetBIOS name.