Coming your way: Unikernels

At Artirix, our DevOps team is constantly working on improving our infrastructure. I admit, we are selfish human beings - we want to do less firefighting, never wake up to 4am PagerDuty incidents again, and stop doing repetitive work. Luckily, though, all this comes with the added benefit of increased customer value.

We are currently running a somewhat traditional setup in AWS (pictured above). While we agree that containers is the next logical step to take, we’ve had increasing interest in looking one step ahead: unikernels. We see this as a way to further simplify our infrastructure while making it more resilient.

Unikernels are operating systems that are custom-built to run a single application directly on the hypervisor.

So, what are unikernels anyway? Start by thinking about your typical server in the cloud. It's running your application, along with a plethora of supporting services enabled by default. Everything is stacked on top of an operating system that is designed to support a wide variety of platforms, devices and software. Therefore, by design, the operating system contains a lot of components that make absolutely no sense in the cloud. When was the last time you needed a mouse (or a floppy) driver module loaded into your kernel?

In a sense, the rise of containerisation only makes this worse. Consider the following stack for running a containerised application in AWS:

It may seem overly complex - probably because it is. When deploying a carelessly built container, you are effectively installing another operating system on top of an operating system. Now, consider the same application running as a unikernel:

The beauty of unikernels is simplicity. Only the things your application needs are baked into the operating system. There are no floppy or mouse drivers, unless you explicitly decided to build them in. Your application has only the necessary components to fulfil its function and run as a virtual machine directly on the hypervisor.

A unikernel contains the least amount of moving parts needed to do the job.

Needless to say, this has serious security implications as well. The attack surface of a unikernel is typically only a fraction of what a containerised application running on, say, Ubuntu Linux would have. By requiring you to explicitly build in functionality, unikernels provide exceptional visibility to what your stack is actually running.

There are several promising projects around unikernels. We’ve experimented mainly with OSv and rumprun. Take a look at MirageOSLINGHaLVM and Clive as well.

While unikernels are certainly interesting, there are many obstacles to work around before they reach the maturity required for widespread usage. However, with the recent purchase of Unikernel Systems by Docker, we might see quick developments in unikernel monitoring, debugging and deployment - which are all needed to efficiently utilise the technology.

We’ve started a Meetup group in London for people interested in Unikernels. Become a member and check out the next meetup at