But you said specifically "...and systemd has broken userspace a lot."
What did you mean by this? It seems like a complete nonsense statement in the context of user space breakage of the form the kernel is responsible for.
The main clash between the kernel maintainers and the systemd maintainers was over systemd reading the kernel argv in an error prone way to trigger debug information. Other than that the interactions seem completely minimal. Linus Torvalds uses systemd at work and at home.
"What did you mean by this? It seems like a complete nonsense statement in the context of user space breakage of the form the kernel is responsible for."
Does it? systemd is the init, the service manager, the interface to D-bus (and kernel devs had a bit of a tussle with the systemd devs about kdbus), the logging interface of most services (possibly including kernel logs), etc. systemd interacts with both the kernel directly (as the system init, as one interface to cgroups and namespaces, etc.) and with users (as everything else it does). I like it, but I understand the Borg accusations.
"The main clash between the kernel maintainers and the systemd maintainers was over systemd reading the kernel argv in an error prone way to trigger debug information."
Searching the LKML for systemd seems to indicate otherwise. It seems like there have been a few scuffles over the years. I don't subscribe to the LKML or read it religiously and haven't for many years, so I'm mostly guessing based on context, but the context seems clear to me.
Again, I ask, if not systemd, then which init is Linus talking about?
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.")
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.
Userspace programs that others frequently depend on the behavior of can easily break userspace. Look how many things break when you change ps or ls out with another tool.
What did you mean by this? It seems like a complete nonsense statement in the context of user space breakage of the form the kernel is responsible for.
The main clash between the kernel maintainers and the systemd maintainers was over systemd reading the kernel argv in an error prone way to trigger debug information. Other than that the interactions seem completely minimal. Linus Torvalds uses systemd at work and at home.