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documentation/source/contributing/services/overview.rst
Lucy Cifferello 1f5d7be961 building proper
2021-02-08 08:32:12 -07:00

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.. _service_package_overview:
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Service Package Overview
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Let's start at a high level. What actually is a service, in a technical sense, on the Embassy?
Each service is an image. An image is a snapshot of a linux environment in which an application runs. All service application data is stored in a volume directory. This volume is persisted across updates. The image is immutable: when the service is updated, the image is replaced with the complete new image containing the updated features.
The volume directory (for seeding data into the volume) is typically: ``/root/volumes/<serviceId>``.
.. important::
Any files that are in the image at the volume path will be overwritten when a backup restore occurs.
A service is mounted to the EmbassyOS image. Each service application gets a volume allocated to it by EmbassyOS. Within the Docker container that encompasses the service image, a path is specified as to where it should mount on EmbassyOS. This path is specified in the :ref:`manifest <service_manifest>`.
The config spec, config rules, and manifest get bundled into the ``.s9pk`` package, `built using appmgr <https://github.com/Start9Labs/appmgr>`_. Each new version release should include the updated version of these files re-bundled into a new binary.
.. note::
Due to tech debt, code in appmgr may reference ``app-id`` instead of ``service-id``.
Environment Setup
=================
At minimum, docker, docker-builx, and appmgr are required to package a service for EmbassyOS.
Recommended Dependencies
------------------------
`docker <https://docs.docker.com/get-docker>`_
`docker-buildx <https://docs.docker.com/buildx/working-with-buildx/>`_
`appmgr <https://github.com/Start9Labs/embassy-os/tree/master/appmgr>`_
`cargo <https://doc.rust-lang.org/cargo/>`_
`yq (version 4) <https://mikefarah.gitbook.io/yq>`_
`make <https://www.gnu.org/software/make/>`_
`musl <https://github.com/Start9Labs/rust-musl-cross>`_