Most people know BuildKit as the thing that makes docker build fast. But BuildKit is a general-purpose build framework with a programmable architecture that can produce any artifact, not just container images. Here's how it works and how I used it to build Alpine APK packages.

Hacker News is a community-driven platform for sharing and discussing technology news, startups, and programming-related topics. Through user submissions and comments, Hacker News offers insights into emerging technology trends, industry developments, and entrepreneurial ventures. Readers can participate in discussions, share their insights, and stay informed about the latest advancements in technology and innovation.

Hacker News

BuildKit is far more than Docker's build engine — it's a general-purpose, pluggable build framework built around LLB (Low-Level Build definition), a protobuf-based DAG of filesystem operations. Its architecture separates frontends (which translate any build spec into LLB) from the solver (which executes the DAG with content-addressable caching and parallelism). The --output flag lets BuildKit produce tarballs, local directories, APK packages, or any artifact — not just container images. To demonstrate this, the author built a custom BuildKit frontend called apkbuild that reads a YAML spec and produces Alpine APK packages without any Dockerfile. Projects like Dagger and Earthly already use LLB as their execution backbone, making BuildKit a proven foundation for custom build tooling.

BuildKit: Docker's Hidden Gem That Can Build Almost Anything

Building APK packages with a custom frontend