We can use VMWare customization specification manager for customize our virutal machine, which we are deploying from the vm templates. As an example if we want to add virtual machine to the domain, we want to change the time zone or we want to use same local admin password for all the virtual machines. This is same as windows un-attendant installation files(Answer files).
First we need to create customization specification. We can use “Customization Specification Manager” option in Vcenter server. This features comes under management portion.