LinuxKit and NanoServer: Building Minimal OS Images for the Cloud Era

Another year of DockerCon; since 2014 I've followed Docker, and each DockerCon brings many surprising things; this year's new toys are LinuxKit and Moby.

I quickly played with it today; packaging a brand‑new Linux server image directly from a YAML file is extremely simple, reminiscent of LEGO bricks; DockerCon highlighted this LEGO‑like approach, even the background music felt like an arcade.

The cloud‑era OS shape is a question many cloud vendors are exploring. Most vendors simply stash common OSes in template libraries, but the problem is that traditional host‑OSes are multipurpose, whereas cloud OSes are single‑purpose. Historically we packed many apps onto one host to save resources, requiring a heavyweight, feature‑rich OS. With virtualization and cloud, we aim to run a single application per host to improve deployment speed, responsiveness, and agility, making the bloated general‑purpose OS less suitable.

In recent years DevOps has surged, creating many buzzwords, but the core goal remains efficiency.

Improving efficiency boils down to two ideas: 1) Reduce granularity – simplify complex problems and lower management overhead; 2) Decouple – give systems and teams freedom to work at their own pace, reducing friction and turning resources into productivity.

These ideas relate closely to LinuxKit/NanoServer. Docker’s approach is a dimensionality‑reduction strategy. Docker orchestrates technology stacks; after optimizing the application layer, the next step is to tackle the OS layer. LinuxKit lets users describe OS components in a YAML file, dynamically creating custom OS images, giving fundamental control over the tech stack, reducing dependencies, simplifying problems, and lowering coupling.

NanoServer, introduced in Windows Server 2016, is a lightweight OS edition that also lets users select needed components and generate a dedicated OS version. Below is the Nano Server Image Builder UI for component selection:

Below is a linuxkit.yml file used to assemble an OS:

With such tools we can create very small, fast‑booting OS images, e.g., Windows Server can be reduced to 400 MB and boot in 40 seconds:

LinuxKit can produce images around 60 MB:

This is the proper way to use an OS in the cloud era; Microsoft and Docker have teamed up. Remember, we don’t need the OS itself, we need the applications on top; building the building then removing the foundation is a capability unique to the software industry.