We may simply be using different terminology. systemd has had bugs (a lot of them), many of which impacted the system at a high level (being the init and everything else), sometimes due to ineractions with the kernel, sometimes due to interactions with other parts of the system. Perhaps others wouldn't call that "userspace", I dunno. I figure if it affects users trying to run software it's "userspace".

But, I'm happy to take the "broke userspace" assertion back if you don't like the term. Let's just say systemd has had a lot of bugs, sometimes stupid ones, and sometimes stubbornly held on to despite kernel devs or other devs asking for changes. I would hope we're not arguing about whether systemd has had an exciting number of bugs and compatibility issues (I think we can all agree on that, even if we like systemd).

I inferred a bunch from my recollection of how the LKML has talked about systemd in the past. I assumed Linus was talking about systemd and that when he says he doesn't trust it, it was about systemd being sloppy and stubborn about compatibility and fixing bugs. I could be wrong about that.

Linus is generally very specific when he talks about things breaking userspace - changes to the kernel should not make things that work in userspace stop working.

systemd doesn't really have the power to completely break userspace in the manner Linus refers to, though it certainly has the power to break a system.

(One of my favorites was when a systemd update shut down dhclient but did not restart it, so once dhcp leases expired, servers lost connectivity. It was fun seeing several thousand machines go offline all at once. "Fun.")

You're right. I should be more careful about language. When talking about kernel developers, they do usually mean the ABI.

But Linus wasn't the one who wrote about breaking userspace here, so Linus' use of that term is irrelevant.

It's a term of art -- one defined by Linus and the kernel team over the past 25+ years. People who have been involved in one way or another with kernel development know what it means, and it makes little sense to redefine it here.

English is defined by usage, and whether or not it make "little sense" to you, if people use it differently and makes it clear they mean it differently, it makes even less sense to try to belabour the point based on a different definition.

Your point is taken that English is indeed an evolving language, but there's a strong benefit to consistency that is illustrated here.

If definitions are inconsistent in the minds of people participating in a conversation, it can muddy an issue and make people needlessly argue because they aren't communicating effectively about what they mean. It also makes it more difficult for a reader to understand the debate.

Specifically, in this discussion, when I said "breaks userspace," I and others were referring to the term of art as developed over the past 25 years, and I expected (this being HN) that others would also understand it as such and discuss accordingly. Instead, this thread has turned into a morass of misunderstanding and confusion, because still others believe the term means something else, and are arguing a tangential point as a result.