[CentOS] How to start a script to complete configuration

Hi,

We have a virtual environment based on XenServer. In this environment I
defined a template for CentOS 7 servers.

I would like to start a script a boot time to complete the configuration of
new VMs based on this template. How can I have a script started before any
login prompt to ask question to the user to complete the configuration such
as hostname, IP address, etc?

Thanks,
Bernard