Merge pull request #292034 from v-thepet/iot4

Freshness Edit: IoT-hub-device 4

Author: Jill Grant

articles/iot-hub-device-update/device-update-agent-overview.md

@@ -1,9 +1,9 @@
 ---
-title: Understand Device Update for Azure IoT Hub Agent
-description: Understand Device Update for Azure IoT Hub Agent.
+title: Azure Device Update for IoT Hub agent overview
+description: Understand the structure and functions of the Azure Device Update for IoT Hub agent.
 author: eshashah-msft
 ms.author: eshashah
-ms.date: 9/12/2022
+ms.date: 12/19/2024
 ms.topic: concept-article
 ms.service: azure-iot-hub
 ms.subservice: device-update
@@ -13,62 +13,58 @@ ms.subservice: device-update
 
 The Device Update agent consists of two conceptual layers:
 
-* The *interface layer* builds on top of [Azure IoT Plug and Play](../iot/overview-iot-plug-and-play.md), allowing for messaging to flow between the Device Update agent and Device Update service.
-* The *platform layer* is responsible for the high-level update actions of download, install, and apply that may be platform- or device-specific.
+- The *interface layer* builds on top of [Azure IoT Plug and Play](../iot/overview-iot-plug-and-play.md) (PnP) to allow messages to flow between the Device Update agent and the Device Update service.
+- The *platform layer* does the high-level update download, install, and apply actions, which can be platform- or device-specific.
 
-:::image type="content" source="media/understand-device-update/client-agent-reference-implementations.png" alt-text="Agent Implementations." lightbox="media/understand-device-update/client-agent-reference-implementations.png":::
+The following diagram lists Device Update agent capabilities and actions.
 
-## The interface layer
+:::image type="content" source="media/understand-device-update/client-agent-reference-implementations.png" alt-text="Diagram that shows agent implementations." border="false" lightbox="media/understand-device-update/client-agent-reference-implementations.png":::
 
-The interface layer is made up of the [Device Update core interface](https://github.com/Azure/iot-hub-device-update/tree/main/src/agent/adu_core_interface), [Device information interface](https://github.com/Azure/iot-hub-device-update/tree/main/src/agent/device_info_interface) and [Diagnostic information interface](https://github.com/Azure/iot-hub-device-update/tree/main/src/diagnostics_component/diagnostics_interface).
+## Interface layer
 
-These interfaces rely on a configuration file for the device specific values that need to be reported to the Device Update services. For more information, see [Device Update configuration file](device-update-configuration-file.md).
+The interface layer is made up of the following components:
+
+- [Device Update core interface](https://github.com/Azure/iot-hub-device-update/tree/main/src/agent/adu_core_interface)
+- [Device information interface](https://github.com/Azure/iot-hub-device-update/tree/main/src/agent/device_info_interface)
+- [Diagnostic information interface](https://github.com/Azure/iot-hub-device-update/tree/main/src/diagnostics_component/diagnostics_interface)
+
+These interfaces use a configuration file for the device specific values to report to Device Update services. For more information, see [Device Update configuration file](device-update-configuration-file.md).
 
 ### Device Update core interface
 
-The *Device Update interface* is the primary communication channel between the Device Update agent and services. For more information, see [Device Update core interface](https://github.com/Azure/iot-plugandplay-models/blob/main/dtmi/azure/iot/deviceupdate-1.json).
+The [Device Update core interface](https://github.com/Azure/iot-plugandplay-models/blob/main/dtmi/azure/iot/deviceupdate-1.json) is the primary communication channel between the Device Update agent and Device Update services.
 
 ### Device information interface
 
-The *device information interface* is used to implement the `Azure IoT PnP DeviceInformation` interface. For more information, see [Device information interface](https://github.com/Azure/iot-plugandplay-models/blob/main/dtmi/azure/devicemanagement/deviceinformation-1.json).
+The [device information interface](https://github.com/Azure/iot-plugandplay-models/blob/main/dtmi/azure/devicemanagement/deviceinformation-1.json) implements the Azure IoT PnP `DeviceInformation` interface.
 
 ### Diagnostic information interface
 
-The *diagnostic information interface* is used to enable [remote log collection](device-update-diagnostics.md#remote-log-collection) for diagnostics. For more information, see [Device information interface](https://github.com/Azure/iot-plugandplay-models/blob/main/dtmi/azure/devicemanagement/deviceinformation-1.json).
-
-## The platform Layer
+The [diagnostic information interface](https://github.com/Azure/iot-plugandplay-models/blob/main/dtmi/azure/iot/diagnosticinformation-1.json) enables [remote log collection](device-update-diagnostics.md#remote-log-collection) for diagnostics.
 
-The Linux *platform layer* integrates with [Delivery Optimization](https://github.com/microsoft/do-client) for downloads and is used in our Raspberry Pi reference image, and all clients that run on Linux systems.
+## Platform layer
 
-The Linux platform layer implementation can be found in the `src/platform_layers/linux_platform_layer` and it integrates with the [Delivery Optimization client](https://github.com/microsoft/do-client/releases) for downloads.
+All clients that run on Linux systems, such as the Device Update Raspberry Pi reference image, use the Linux platform layer. The Linux platform layer integrates with the [Delivery Optimization client](https://github.com/microsoft/do-client/releases) for downloads.
 
-This layer can integrate with different update handlers to implement the
-installers. For instance, the `SWUpdate` update handler, `Apt` update handler, and `Script` update handler.  
+The Linux platform layer implementation that integrates with [Delivery Optimization](https://github.com/microsoft/do-client) for downloads is in *src/platform_layers/linux_platform_layer*. This layer can integrate with update handlers such as `SWUpdate`, `Apt`, and `Script` to implement the installers.
 
-If you choose to implement with your own downloader in place of Delivery Optimization, be sure to review the [requirements for large file downloads](device-update-limits.md).
+If you choose to implement your own downloader instead of Delivery Optimization, be sure to review the [requirements for large file downloads](device-update-limits.md#requirements-for-large-file-downloads).
 
 ## Update handlers
 
-Update handlers are used to invoke installers or commands to do an over-the-air update. You can either use [existing update content handlers](https://github.com/Azure/iot-hub-device-update/blob/main/src/extensions/inc/aduc/content_handler.hpp) or [implement a custom content handler](https://github.com/Azure/iot-hub-device-update/tree/main/docs/agent-reference/how-to-implement-custom-update-handler.md) that can invoke any installer and execute the over-the-air update needed for your use case.
-
-## Changes to Device Update agent at GA release
-
-If you are using the Device Update agent versions, please migrate to the latest agent version 1.0.0 which is the GA version. See [GA agent for changes and how to upgrade](migration-public-preview-refresh-to-ga.md)
-
-You can check installed version of the Device Update agent and the Delivery Optimization agent in the Device Properties section of your [IoT device twin](../iot-hub/iot-hub-devguide-device-twins.md). [Learn more about device properties under ADU Core Interface](device-update-plug-and-play.md#device-properties).
-
-## Next Steps
-
-[Understand Device Update agent configuration file](device-update-configuration-file.md)
-
-You can use the following tutorials for a simple demonstration of Device Update for IoT Hub:
+Update handlers invoke installers or commands to do over-the-air updates. You can either use [existing update content handlers](https://github.com/Azure/iot-hub-device-update/blob/main/src/extensions/inc/aduc/content_handler.hpp), or implement a [custom content handler](https://github.com/Azure/iot-hub-device-update/tree/main/docs/agent-reference/how-to-implement-custom-update-handler.md) that can invoke any installer to execute the over-the-air updates you need for your use case.
 
-* [Image Update: Getting Started with Raspberry Pi 3 B+ Reference Yocto Image](device-update-raspberry-pi.md) extensible via open source to build your own images for other architecture as needed.
+## Check and upgrade agent version
 
-* [Package Update: Getting Started using Ubuntu Server 18.04 x64 Package agent](device-update-ubuntu-agent.md)
+You can check the installed versions of the Device Update agent and the Delivery Optimization agent in the [properties](device-update-plug-and-play.md#device-properties) section of your [IoT device twin](../iot-hub/iot-hub-devguide-device-twins.md).
 
-* [Proxy Update: Getting Started using Device Update binary agent for downstream devices](device-update-howto-proxy-updates.md)
+If you use the Device Update agent, make sure you're on the version 1.0.0 general availability (GA) version. For more information, see [Migrate devices and groups to the latest Device Update release](migration-public-preview-refresh-to-ga.md).
 
-* [Getting Started Using Ubuntu (18.04 x64) Simulator Reference Agent](device-update-simulator.md)
+## Related content
 
-* [Device Update for Azure IoT Hub tutorial for Azure-Real-Time-Operating-System](device-update-azure-real-time-operating-system.md)
+- [Device Update for IoT Hub configuration file](device-update-configuration-file.md)
+- [Azure Device Update for IoT Hub using a Raspberry Pi image](device-update-raspberry-pi.md)
+- [Azure Device Update for IoT Hub using the Ubuntu package agent](device-update-ubuntu-agent.md)
+- [Tutorial: Complete a proxy update by using Device Update for Azure IoT Hub](device-update-howto-proxy-updates.md)
+- [Azure Device Update for IoT Hub using a simulator agent](device-update-simulator.md)
+- [Device Update for Azure IoT Hub using Eclipse ThreadX](device-update-azure-real-time-operating-system.md)