Pi-Hole on CentOS 7 installation

Here is how to install (a step by step guide) CentOS 7 minimal and then load Pi-Hole ad blocker. We run through the whole process on an old Atom D525 system with 2GB of memory and a 250GB HDD.
Pi-Hole is an ad blocker that stops malicious adverts from appearing when you’re browsing the Internet. It blocks adverts at a network level before every coming near your network.