My previous post went into why I think the days of the general purpose operating system (for servers) are numbered. But one interesting area I didn't comment on (but did talk about in the talk of the same name) was Unikernels.
It's All About Cost
One of the topics I didn't really touch on in discussing the end of the generally purpose operating system was cost. Historically, maintaining a general purpose operating system has been a costly endeavor, something only the largest companies or communities could sustain by themselves. Think Red Hat, Oracle, Microsoft, Sun, IBM, Debian, etc. The result of that is the assumption when building software that you should target one or more of a small number of operating systems. In doing so you're ceding some ground, and likely some revenue, to another vendor. You're also stuck with any underlying limitations of that OS as well as its release cadence. And invariably you're also stuck with the multiplying support cost of supporting your software on multiple versions of that OS over time.
I would posit that up until relatively recently, the cost of that support burden was hugely outweighed by the cost of maintaining an actual operating system. But that's now changing, as I outlined in the previous post. Now a small or medium sized software company (be it CoreOS, Rancher, Docker, Pivotal, etc.) can build and maintain it's own operating system as well. This is very much about the rising level of abstraction — all of the above leverage the huge efforts that go into the Linux kernel and into other projects like systemd (CoreOS) or Alpine (Docker's Moby) for instance.
But where do Unikernels fit into this narrative? I'd argue that they represent the fulfillment of this democratization. If building and maintaining a traditional OS is only possible for the largest of companies, and building and maintaining a more special-purpose OS (say for running containers, or a storage device) is cost-effective for medium sized software companies, then Unikernels will allow anyone to build their own single-purpose operating systems.
There are other technical reasons for (and against) Unikernels as an approach but most focus on the technical. I think the economic side is worth some consideration too. And not just the typical development and support costs, but the ability to own the end-to-end unit of software has lots of benefits, and Unikernels may make those benefits available to everyone, including small organizations and individuals.