Sure. What I think is unclear that I intend to highlight is that systemd (and yes, upstart) have intentionally and unnecessarily created this technical conflict.
well, I wouldn't call the technical conflict unnecessary - if there wasn't a need for a more featureful init system, then there wouldn't have been a motive to write a new one. As for the social conflict, that's just what you get with social groups experiencing change.
Your assertion is strictly false. All features of this new process invocation system could be implemented without making a "new init system." That's my primary point in commenting here. It is a false dichotomy.
> All features of this new process invocation system could be implemented without making a "new init system."
Er, no. A major feature of systemd is that it is declarative. You have hooks for running custom commands, but a unit file is declarative and easy to parse.
If you want to acquire more intelligence about an init script, you have to resort to disgusting hacks like parsing comments in order to get a dependency system working. And socket-based activation? Sysvinit is a dead end. It's the counter to "keep it simple, stupid": when you fail to capture enough information in your "simple" model, you are going to end up with more issues than if you had created a slightly more complex system.
We already do. I think most people in this discussion aren't realizing that the current sysV init system is an extremely small pid 1 /sbin/init, and most of the logic in external rc scripts. Moving rc scripts to systemd declarative syntax is fine.
The important part with respect to software architecture is less complexity in pid 1. Subprocesses of init can be safely updated and restarted. More code in init is a real problem -- that's why systemd as pid 1 is controversial.
I'm not sure this was the point of parent, but anyway, why would you want something like that? It's not like sysvinit has any redeeming feature, and you would still want to have systemd .service files. I could understand an argument like "/bin/systemd does too many things and ought to be split up more", but the rationale for having bad old sysvinit launch /etc/init.d/systemd.sh escapes me. Not to mention that you definitely don't want both systemd and sysvinit to attempt to launch scripts in /etc/init.d, when they don't have a .service...
But if systemd was pid 1 and something killed it, you would have a kernel panic. How is that better than a system with a bunch of unmonitored processes? At least with the latter you can safely bring down the system, instead of having a hard crash.