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CentOS - the one we'll mostly be using

The other part of the traditional server-space war, CentOS features its own soldiers and martyrs. It is still widely used, and has a reputation for stability and boredom that rivals Debian's.

The Community Enterprise Operating System (CentOS) is a freely available and compiled version of the Red Hat Enterprise Linux distribution, which aims to offer functional compatibility, generally replacing the Red Hat logo with the CentOS logo to avoid trademark infringement. (In January of 2014 it was announced that Red Hat was joining forces with CentOS, to help drive and invest in CentOS development.)

Because of its nature, a lot of systems administrators have installed CentOS to better understand the Red Hat world, because (as mentioned previously) Red Hat has a good reputation in Enterprise companies, so it would make sense to install something so strikingly similar.

This installation trend goes both ways. I have seen companies who started out by installing CentOS because it was readily available and allowed them to design their infrastructure easily, utilizing publicly available and free repos, before moving to a RHEL deployment for the finished product.

Repos is a short form way of saying repositories, which are the common location from which software is installed on a Linux system. Where Windows usually has downloads from websites, and macOS has the App Store, Linux has used software repositories for most of its life, and they have the advantage of being easily searchable with a few keystrokes on the command line.

I have also seen companies who deployed RHEL everywhere, only to realise that they were spending a lot of money, and never invoking the support they'd bought because their operations team was just that good! They would then gradually phase out their Red Hat deployments and move to CentOS, changing very little in the process.

Releases come about every few years, with version 7 being released in 2014, and getting consistent updates since then. However, it should be noted that version 6, which was released in 2011, will be getting maintenance updates until 2020.

CentOS can be downloaded from https://centos.org. We will go through this in the installation section.