What do “rolling release” and “stable” mean in the context of operating systems?

In a recent post on his blog, Chris Siebenmann wrote about his experience with Fedora upgrades and how, because of some of the non-standard things he does, upgrades are painful for him. At the end, he said “What I really want is a rolling release of ‘stable’ Fedora, with no big bangs of major releases, but this will probably never exist.”

I’m sympathetic to that position. Despite the fact that developers have worked to improve the ease of upgrades over the years, they are inherently risky. But what would a stable rolling release look like?

“Arch!” you say. That’s not wrong, but it also misses the point. What people generally want is new stuff so long as it doesn’t cause surprise. Rolling releases don’t prevent that, they spread it out. With Fedora’s policy, for example, major changes (should) happen as the release is being developed. Once it’s out, you get bugfixes and minor enhancements, but no big changes. You get the stability.

On the other hand, you can run Fedora Rawhide, which gets you the new stuff as soon as it’s available, but you don’t know when the big changes will come. And sometimes, the changes (big and little) are broken. It can be nice because you get the newness quickly. And the major changes (in theory) don’t all come at once.

Rate of change versus total change

For some people, it’s the distribution of change, not the total amount of change that makes rolling releases compelling. And in most cases, the changes aren’t that dramatic. When updates are loosely-coupled or totally independent, the timing doesn’t matter. The average user won’t even notice the vast majority of them.

But what happens when a really monumental change comes in? Switching the init system, for example, is kind of a big deal. In this case, you generally want the integration that most distributions provide. It’s not just that you get an assortment of packages from your distribution, it’s that you get a set of packages that work together. This is a fundamental feature for a Linux distribution (excepting those where do-it-yourself is the point).

Applying it to Fedora

An alternate phrasing of what I understand Chris to want is “release-quality packages made available when they’re ready, not on the release schedule.” That’s perfectly reasonable. And in general, that’s what Fedora wants Rawhide to be. It’s something we’re working on, particularly with the ability to gate Rawhide updates.

But part of why we have defined releases is to ensure the desired stability. The QA team and other testers put a lot of effort into automated and manual tests of releases. It’s hard to test against the release criteria when the target keeps shifting. It’s hard to make the distribution a cohesive whole instead of a collection of packages.

What Chris asks for isn’t wrong or unreasonable. But it’s also a difficult task to undertake and sustain. This is one area where ostree-based variants like Fedora CoreOS (for servers/cloud), Silverblue (for desktops), and IoT (for edge devices) bring a lot benefit. The big changes can be easily rolled back if there are problems.