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
https://copr.fedorainfracloud.org/coprs/jsynacek/systemd-backports-for-centos-7/
or
https://github.com/facebookincubator/rpm-backports

Up to date and legacy PHP versions
https://rpms.remirepo.net/
https://blog.remirepo.net/pages/Config-en

Current LTS or mainline kernel
http://elrepo.org/

More up to date qemu