What is CentOS? | Fedora Podcast 059

A couple of episodes back, Carl George came on to talk about EPEL, and about half that conversation ended up being about a neighboring project called CentOS. The questions kept coming in afterward, so we did the obvious thing and made a whole episode out of it. What is CentOS? Where does it sit relative to Fedora and RHEL? And why does the answer depend so much on which year you last looked?

This turned into the biggest panel we have ever had on the show. Amy Marrich chairs the CentOS Board and does technical marketing for OpenStack at Red Hat. Troy Dawson leads the CentOS Stream team, sits on the board, works in the ISA and Alternative Images SIGs building CentOS Stream for RISC-V, and sews his own penguin shirts. And Shaun McCance, the CentOS Community Architect, joined us at the last minute, which turned out to be lucky, because a couple of weeks ago he also became the Fedora Community Architect.

A few things worth carrying away from this one:

• CentOS Linux and CentOS Stream are not the same thing, and one of them no longer exists. As Troy put it, CentOS Linux was ten years of support and downstream of RHEL. CentOS Stream is five years of support and upstream of it. If the CentOS in your head is a rebuild that trails RHEL, that project retired around the RHEL 9 timeframe.
• The pipeline is Fedora, then ELN, then Stream, then RHEL. Fedora ELN is the subset of Rawhide packages that would go into RHEL, rebuilt with RHEL’s flags and tags. Btrfs is the example everyone reaches for: Fedora has it, RHEL does not, and the flag is off in ELN. Every three years CentOS Stream takes a cut from ELN, and that cut becomes the next major RHEL.
• Stream and RHEL are now built from the same commit. This was the part I did not fully appreciate. A RHEL engineer changes glibc or vim in the CentOS Stream GitLab repo, and that exact code builds and tests on both at once. Stream ships it on a one-week cadence, RHEL on a six-month one. So you can watch RHEL being built in public instead of waiting for a beta.
• That is a real advantage if you build on RHEL. When RHEL 9 launched, partners who had been building against CentOS Stream 9 for months shipped their products on day one. Amy made the same case for hardware drivers and for the feedback loop that lets the project fix things before they land in a product.
• The board is community governed, and only one seat speaks for Red Hat. Amy walked through it: one liaison to the business unit, everyone else speaking for the community even if Red Hat signs their paycheck, and members from Fermilab, Meta, and Microsoft. Nothing in the governance caps how many people come from one company, and being a Red Hatter does not get you elected.
• You do not have to write code to contribute. Amy’s advice was to start with the docs, because being new is exactly what makes you good at spotting the step everyone else skips, and because working through them is manual QA that earns you trust. That thread produced my favorite exchange of the episode, when Noah asked whether the people least confident in their technical chops might be the best documentation writers.

We also got into the SIGs and the newer SIG Council, why Hyperscale can ship Btrfs when RHEL will not, where to actually file a bug (spoiler: file it against RHEL, not at Troy), and the fact that Shaun made a tablecloth that is half Fedora and half CentOS for shared conference booths.

If you want to meet these folks in person, CentOS Connect runs alongside FOSDEM in Brussels, and the crew will be at DevConf US in Boston, All Things Open in Raleigh, SCaLE, and Texas Linux Fest the first weekend of November. I will be at Texas Linux Fest too, so come say hello.

Next episode we are talking about Project Hummingbird with Jorge Castro and Scott McCarty. And a couple of episodes after that, Shaun is back alongside Justin Wheeler to talk about the Fedora Community Architect handoff.