Kickstart

One method of automating the deployment of boxes are kickstart files, which are frequently used in large deployments to automatically answer the questions that the installer asks the user.

If you take a look in the /root/ folder of a CentOS VM, there's a good chance you'll find a file called anaconda-ks.cfg, which is effectively the kickstart file for the manual steps you took when installing the machine (anaconda being the name of the installer).

These files are tweaked, or written from scratch, and then hosted on a web server, on an installation network, ready to be picked up by an unconfigured machine.