Layout of Product and Package Directories

The Platform Source Tree contains a top-level directory called packages containing all the build packages for that layer. The present document describes the packages that are common to all of the layers. Each layer will introduce additional packages specific to that layer.

Directory map

In the diagram below, “pkg” refers to Fuchsia packages, the unit of installation in Fuchsia.

    default          # default build configuration for this layer
                     # by convention, default preinstalls development tools,
                     # and makes all prod packages available.
    <layer>          # all production pkg up to this layer
    buildbot         # all pkg declared at this layer; used by CQ/CI
    default          # monolith packages for daily development at this layer
    preinstall       # devtools for daily development at this layer
    kitchen_sink     # all pkg up to this layer
    all              # grab bag of every pkg in this layer
    prod/            # pkg that can be picked up in production
    tests/           # correctness tests (target & host)
    tools/           # dev tools not for prod (target & host)
    benchmarks/      # performance tests
    examples/        # pkg demonstrating features offered by this layer
  * experimental/    # pkg not quite ready for prod
  * config/          # config files for the system (e.g. what to boot into)
    sdk/             # SDK definitions
    ...              # each layer will also define additional packages

Cross-layer dependencies

  • <layer>(N) depends on <layer>(N-1) and adds all the production artifacts of (N)
    • this defines a pure production build
  • buildbot(N) depends on <layer>(N-1) and adds all artifacts of (N)
    • this defines a build suitable for verifying the integrity of (N)
  • kitchen_sink(N) depends on kitchen_sink(N-1) and adds all artifacts of (N)
    • this defines a build suitable for developing (N) as well as its dependencies

Inner-layer dependencies

Most directories in a packages directory contain a special all package which aggregates all packages in this directory. Every all package should roll up to the root all package, thereby creating a convenient shortcut to build “all packages in the layer”. Note that the directories that do not require aggregation are marked with * in the diagram above.

Disabling packages

Some packages might need to get (temporarily) disabled as refactorings occur in the Fuchsia codebase. In order to disable a package <layer>/<type>/foo, move it under <layer>/<type>/disabled/foo and remove it from <layer>/<type>/all. Note that this does not apply to packages in directories that do not require aggregation, as these packages are strictly opt-in already.


The //scripts/packages/verify_layer tool is used to verify that a layer‘s packages and products directory’s structure matches the description in the present document.

Note that only package files are allowed in such a directory, with the exception of files for documentation purposes.