Open Source Summit India 2026

Docker popularized containers as the solution to the classic “it works on my machine” problem by packaging applications with their environments. Ironically, while containers make runtime environments reproducible, images builds often are not. Docker builds tend to have unrestricted network access, depend on unpinned packages, and may produce different results over time—leading to inconsistent environments, fragile CI/CD pipelines, and difficult-to-reproduce failures.

Deterministic software builds are a well-understood problem in the broader build systems world. From a build perspective, container images are simply artifacts—no different from compiled binaries—and follow the same principles of
reproducibility.

The Nix build system was designed to produce hermetic, reproducible builds. By using Nix to construct OCI images, we can eliminate many sources of non-determinism while enabling the same environment definitions to be reused across development, CI, and containers.

In this talk, we’ll explore common sources of non-determinism in Docker builds and show how Nix can produce deterministic OCI images, from augmenting existing Docker workflows to building images entirely with Nix.