systemd clicked for me when I started realizing that a lot of its decisions mapped directly to Red Hat business decisions in cloud computing and containers, like their backing of Project Atomic. nspawn, the "stateless" system features through dynamic configuration population, GPT partition discovery deprecating fstab(5), having a big centralized blob journal, the embedded network management (which is mostly useful for container deployments rather than desktops) and NSS extensions, the GNOME system upgrade logic and so on.
It's theoretically meant to be general-purpose, but it really shines at virtualized deployments and some desktops because of the multi-seat integration (though logind these days has some power management features that is just as relevant for servers).
I don't think Red Hat was the driving force behind systemd's container and VM integration.
systemd-nspawn was created to provide rapid testing of systemd, and it was (and, for now, still is) marked as an experimental utility that isn't for production purposes.
If you look at many of the early blog posts mentioning systemd and containers/VMs, you'll actually see my work and my company (Pantheon) mentioned more than Red Hat. In more recent posts, you'll see lots of CoreOS influence. Project Atomic isn't working with systemd in any direct, significant way; you won't see much coordination other than in some shared philosophy about a stateless base OS, and even that is more attributable to CoreOS's influence than Red Hat's.
I think the influence of Red Hat on systemd is overstated. Of the two perspectives: (1) Red Hat driving everything and (2) Lennart answering mostly to himself, the latter is way more accurate, for better or worse (depending on your opinion of him).
Well, Red Hat were quick to adopt CoreOS' appc, before a lot of companies ultimately united under the Open Container Project banner.
As for:
and it was (and, for now, still is) marked as an experimental utility that isn't for production purposes.
rkt used nspawn for a while, and it's still systemd-based.
The fact that Lennart was giving out presentations about nspawn specifically makes me believe it's very much intended to be used in production, as a "chroot on steroids".
> The fact that Lennart was giving out presentations about nspawn specifically makes me believe it's very much intended to be used in production, as a "chroot on steroids".
This is a recent development -- and why I put the caveat "for now." systemd-nspawn is probably going to be marked production-ready quite soon, especially because it's the foundation for the CoreOS Rocket container tool.
Of course. Systemd is Red Hat's "embrace, extend, extinguish" strategy. Just as Microsoft were once the plucky upstart who became their rival IBM, so Red Hat are becoming Microsoft.
It's theoretically meant to be general-purpose, but it really shines at virtualized deployments and some desktops because of the multi-seat integration (though logind these days has some power management features that is just as relevant for servers).