Things I wish I knew before using CentOS (7)

This is an ongoing, updated post of things I wish I knew beforehand.
CentOS is a solid base for any server, as it requires minimum maintenance and is very conservative when it comes to updated versions.
This post will be a mess at first, but continue to grow and evolve.

Current systemd for CentOS7

Up to date and legacy PHP versions

Current LTS or mainline kernel

More up to date qemu