How it Works · Cloud Native Buildpacks

From source code to a production-ready container image, without writing a Dockerfile. Scroll to follow a build from start to finish.
Point a platform such as pack at your app. There’s no Dockerfile to write or maintain: buildpacks work out what your app needs and how to package it.
A builder is an image that bundles an ordered set of buildpacks, a build-time base image to run them in, the lifecycle that orchestrates every phase, and a reference to the runtime base image your app will ship on.
After analyzing any previously built image, the lifecycle asks each buildpack, in order, whether it recognizes your app. A package.json lets the Node.js buildpack pass, a requirements.txt lets Python pass, and optional buildpacks with nothing to do simply opt out.
The lifecycle restores layers saved by earlier builds from the cache, so dependencies that haven’t changed don’t have to be downloaded or compiled again. Rebuilds stay fast.
The lifecycle runs each participating buildpack inside the build-time base image, and each one contributes its own layers: a language runtime, installed dependencies, your compiled app. Every layer is isolated, cacheable and can be described in a software bill of materials.
The lifecycle stacks those layers on top of the runtime base image and exports a standard OCI image, ready to push to any registry, with no build tools left inside.
When a vulnerability is fixed in the runtime base image, pack rebase swaps the base layers underneath your app without rebuilding it. Your app layers stay exactly as they were.
The result is a reproducible, well-structured container image that runs wherever containers do: on Kubernetes, on a cloud platform, or on your own machine.
Build an image from your app's source code with the pack CLI:
Start Tutorial Read the Docs
What a buildpack is and how it inspects and builds your app.
How buildpacks, base images and the lifecycle are packaged together.
Every phase the lifecycle runs, from analyze through export.
How app images get OS updates without a rebuild.
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