Write buildpacks

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To write a buildpack, we follow the Buildpack Specification, which defines the contract between buildpacks and the lifecycle.

Use the build plan

The Build Plan is a document that buildpacks can use to pass information between the detect and build phases, and between each other. The build plan is passed (by the lifecycle) as a parameter to the detect and build binaries of each buildpack.

Create dependency layers

Each directory created by the buildpack under the CNB_LAYERS_DIR can be used as a layer in the final app image or build cache.

Specify process types

One of the benefits of buildpacks is that they are multi-process - an image can have multiple entrypoints for each operational mode.

Provide a Software Bill-of-Materials

Buildpacks can provide a Software Bill-of-Materials (SBOM) to describe the dependencies that they provide.

Add labels to the application image

Clear the buildpack environment

Create slice layers

Re-use dependency layers

Specify the environment

Use exec.d binaries to configure the application at runtime