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Use the related files feature to reference multiple update files

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Use the related files feature when you need to express relationships between different update files in a single update.

When importing an update to Device Update for IoT Hub, an import manifest containing metadata about the update payload is required. The file-level metadata in the import manifest can be a flat list of update payload files in the simplest case. However, for more advanced scenarios, the related files feature provides a way for you to specify relationships between multiple update files.

When creating an import manifest using the related files feature, you can add a collection of related files to one or more of your primary payload files. An example of this concept is the Device Update delta update feature, which uses related files to specify a delta update that is associated with a full image file. In the delta scenario, the related files feature allows the full image and delta update to both be imported as a single update action, and then either one can be deployed to a device. However, the related files feature isn't limited to delta updates, since it's designed to be extensible by our customers depending on their own unique scenarios.

The related files feature is available for import manifests that are version 5 or later.

When you add related files to an import manifest, include the following information:

  • File details

    Define the related files by providing the filename, size, and hash.

  • A download handler

    Specify how to process these related files to produce the target file. You specify the processing approach by including a downloadHandler property in your import manifest. Including downloadHandler is required if you specify a non-empty collection of relatedFiles in a file element. You can specify a downloadHandler using a simple id property. The Download handler id has a limit of 64 ASCII characters.

  • Related files properties

    You can provide extra metadata for the update handler on your device to know how to interpret and properly use the files that you've specified as related files. This metadata is added as part of a properties property bag to the file and relatedFile objects.

For more information about the import schema for related files, see relatedFiles object.

The following sample import manifest demonstrates how the related files feature is used to import a delta update. In this example, you can see that in the files section, there's a full image specified (full-image-file-name) with a properties item. The properties item in turn has an associated relatedFiles item below it. Within the relatedFiles section, you can see another properties section for the delta update file (delta-from-v1-file-name), and also a downloadHandler item with the appropriate id listed (microsoft/delta:1).

Note

This example uses delta updates to demonstrate how to reference related files. If you want to use delta updates as a feature, learn more in the delta update documentation.

    {
      "updateId": {
        // provider, name, version
      },
      "compatibility": [
        {
          // manufacturer, model, etc.
        }
      ],
      "instructions": {
        "steps": [
          // Inline steps...
        ]
      },
      "files": [
        {  
          // standard file properties
          "fileName": "full-image-file-name",
          "sizeInBytes": 12345,
          "hashes": {
            "SHA256": "full-image-file-hash"
          },
          "mimeType": "application/octet-stream",
          // new properties
          "properties  ": {},
          "relatedFiles": [
            {
              // delta from version 1.0.0.0
              // standard file properties
              "fileName": "delta-from-v1-file-name",
              "sizeInBytes": 1234,
              "hashes": {
                "SHA256": "delta-from-v1-file-hash"
              },
              "mimeType": "application/octet-stream",
              // new properties
              "properties": {
                "microsoft.sourceFileHash": "delta-source-file-hash",
                "microsoft.sourceFileHashAlgorithm": "sha256"
              }
            }  
          ],
          // handler to download/process our related files
      "downloadHandler": {
        "id": "microsoft/delta:1"
      }
    }
  ],
  "createdDateTime": "2021-12-01T01:12:21Z",
  "manifestVersion": "5.0"
    }

The az iot du init v5 command for creating an import manifest supports an optional --related-file parameter.

The --related-file parameter takes a path and properties key:

--related-file path=<replace with path(s) to your delta file(s), including the full file name> properties='{"microsoft.sourceFileHashAlgorithm": "sha256", "microsoft.sourceFileHash": "<replace with the source SWU image file hash>"}'

For example:

az iot du update init v5 \
--update-provider Microsoft --update-name myBundled --update-version 2.0 \
--compat manufacturer=Contoso model=SpaceStation \
--step handler=microsoft/script:1 properties='{"arguments": "--pre"}' description="Pre-install script" \
--file path=/my/update/scripts/preinstall.sh downloadHandler=microsoft/delta:1 \
--related-file path=/my/update/scripts/related_preinstall.json properties='{"microsoft.sourceFileHashAlgorithm": "sha256"}' \
--step updateId.provider=Microsoft updateId.name=SwUpdate updateId.version=1.1 \
--step handler=microsoft/script:1 properties='{"arguments": "--post"}' description="Post-install script" \
--file path=/my/update/scripts/postinstall.sh

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