I'm not sure what you mean by "flapping,"

Flapping, you know, when a person who cannot swim is drowning and just flailing and flapping their body, most notably arms, all over the place in an attempt to stay above water so that they do not drown.

but the technologies in your list do not all address the same problem space.

I don't know about you, but for me to get a fully configured, ready-to-serve system, I need both provisioning and configuration management. With that being the case, provisioning and configuration management fall under the same problem domain.

Vagrant allows you to create reproducible development environments using shell scripts (by default), so it should be right up your ally. Docker is used to containerize applications. runC is the container runtime used by Docker. Kubernetes orchestrates containerized applications across a fleet of CoreOS (a minimal "Docker host" Linux) machines. OpenStack orchestrates your data center. They are discrete solutions because they do different things. Each piece of the puzzle does one thing and (hopefully) does it well. That philosophy should sound familiar to you!

I'm familiar with all of those technologies, and yes it does indeed sound familiar to me!

But, what is unclear to me is, why I would use a discrete provisioning solution like Kubernetes instead of using, say, imgadm(1M) and vmadm(1M) through parallel SSH?

Why would I use a discrete, proprietary solution like Vagrant when I wrote my own, simple variable expansion function which uses eval(1), and that's all that's really needed for configuration management? I'm far, far better off with a simple shell function then using Salt or Ansible. Simplicity, the core of the UNIX principle. eval(1) is much simpler and easier to understand than an entire provisioning and/or configuration management engine! Or do you disagree?

Other than templated configuration excerpts and self-assembly, both easily implemented with a few simple lines of shell code in a small shell library which OS packages can source, what more do I need to configure systems? Why make things unnecessarily complex? In fact, that exact same approach is what Chef uses, conceptually, when one specifies the configuration management policy, except that with my solution, the system administrator need not learn a proprietary Ruby dialect and need not employ a client-server architecture; they can just dive in and leverage their existing shell programming knowledge, with a zero learning curve. And because it's all just shell and AWK, the system administrator has infinite possibilities to configure the systems and do anything they need to do, without being limited by the framework of whichever technology they are using (like YAML or Chef recipes).

So why bother??? Why flap?

Why would I need runC and Docker to provision systems, if I can just install OS packages which configure the system, and then make a ZFS image?

Or, in terms of Linux: why do I need say Docker and Kubernetes, if I have everything in OS packages, and I just use KickStart to PXE boot, automatically install and configure the target node with OS packages?

have you tried a configuration management tool?

You bet your ass I did! But that's not the point, the point is, why should I learn a discrete, proprietary systems, when I can just write a simple shell library which leverages the eval(1) command to do variable expansion, and BAM!!! I instantenously have a template expansion engine so all my configuration, even code, can be parametrized using the same varaible evaluation and expansion technology which the shell uses, and which the configuration packages can call?

With that:

- I don't have to use proprietary, discrete systems;

- I can leverage technology already built into the operating system;

- I don't need a client-server architecture like Chef or Puppet, ever (ssh-sshd is just fine, thank you!)

Why would anyone waste their time?