.. _overlays: Overlay step ============ The component parts of a rock are built in a sequence of five separate steps: pull, overlay, build, stage and prime. The overlay step is specific to rocks and is configured with overlay parameters. To learn more about pull, build, stage and prime see :doc:`/common/craft-parts/reference/part_properties` The overlay step provides the means to modify the base filesystem before the build step is applied. If ``overlay-packages`` is used, those packages will be installed first. ``overlay-script`` will run the provided script in this step. The location of the overlay is made available in the ${CRAFT_OVERLAY} environment variable. ``overlay`` can be used to specify which files will be migrated to the next steps, and when omitted its default value will be ``"*"``. .. Include a section about overlay parameters from the Craft Parts documentation. .. include:: /common/craft-parts/explanation/overlay_parameters.rst