Azure IoT Edge – exec user process caused “exec format error”

If running Edge on a Raspberry Pi  and an Edge container’s logs show  ‘exec user process caused “exec format error”‘ as an error then most likely you are running a non Raspberry Pi container on the Raspberry Pi. If the docker file used to build the container starts with:

  • FROM microsoft/dotnet:2.0.0-runtime

or

  • FROM microsoft/dotnet:2.0.0-runtime-nanoserver-1709

then the line above should be changed to one of the following:

  • FROM microsoft/dotnet:2.0.5-runtime-stretch-arm32v7
  • FROM microsoft/dotnet:2.0-runtime-stretch-arm32v7
  • FROM microsoft/dotnet:2.0.5-runtime-deps-stretch-arm32v7
  • FROM microsoft/dotnet:2.0-runtime-deps-stretch-arm32v7
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Azure IoT Edge stuck restarting

If your Azure IoT Edge runtime is giving the status of:

IoT Edge Status: RESTARTING
ERROR: Runtime is restarting. Please retry later.

and is not allowing for any of the other commands and you have waited an appropriated amount of time, then try the following:

First stop the edgeAgent container in docker:

sudo docker stop edgeAgent

Then, run the setup script for the iotedgectl again:

sudo iotedgectl setup --connection-string "{device connection string}" --auto-cert-gen-force-no-passwords (make sure to use your parameters)

The edge run-time should restart appropriately.

Create Azure Function to process IoT Hub file upload

 

On the Wren Solutions project, there was need to sync a large data set from a device and merge data from it into an existing data set in Microsoft Azure. To accomplish this we decided to use the following workflow:

Upload the file using Azure IoT Hub

If you haven’t, first you have to create an Azure IoT Hub.

Associate an Azure Storage account to IoT Hub

When you associate an Azure Storage account with an IoT hub, the IoT hub generates a SAS URI. A device can use this SAS URI to securely upload a file to a blob container. The IoT Hub service and the device SDKs coordinate the process that generates the SAS URI and makes it available to a device to use to upload a file.

Make sure that a blob container is associated with your IoT hub and that file notifications are enabled.

To use the file upload functionality in IoT Hub, you must first associate an Azure Storage account with your hub. Select File upload to display a list of file upload properties for the IoT hub that is being modified.

file-upload-settings

Storage container: Use the Azure portal to select a blob container in an Azure Storage account in your current Azure subscription to associate with your IoT Hub. If necessary, you can create an Azure Storage account on the Storage accounts blade and blob container on the Containersblade. IoT Hub automatically generates SAS URIs with write permissions to this blob container for devices to use when they upload files.

file-upload-settings

enable-file-notifications

Use Azure IoT SDK to upload blob

Use the Azure IoT Hub C# SDK to upload the file. Below is a Gist of a code sample showing how to upload using the SDK. The code showcases how to utilize UploadToBlobAsync method on the Device Client. To use the sample replace the DeviceConnectionString and the FilePath variable.

Trigger a function on the Azure Blob creation

A Blob storage trigger starts an Azure Function when a new or updated blob is detected. The blob contents are provided as input to the function. Setup the blob trigger to use the container we linked to the Azure IoT Hub previously. First lets configure and manage your function apps in the Azure portal.

To begin, go to the Azure portal and sign in to your Azure account. In the search bar at the top of the portal, type the name of your function app and select it from the list. After selecting your function app, you see the following page:

azure-function-app-main

Go to the Platform Features tab by clicking the tab of the same name.

azure-function-app-features-tab

Function apps run in, and are maintained, by the Azure App Service platform. As such, your function apps have access to most of the features of Azure’s core web hosting platform. The Platform features tab is where you access the many features of the App Service platform that you can use in your function apps.

configure-function-app-settings

Add a connection string from the blob storage account as an app setting. For the sack of this demo lets name it MyStorageAccountAppSetting. Reference that in your JSON  for you Blob Trigger. Then use that blob name as a reference to that blob in your function.

 

 

Your app is currently in read-only mode because you have published a generated function.json

If you published your Azure function from Visual Studio and are seeing the message:

Your app is currently in read-only mode because you have published a generated function.json

Then do the following steps:

From the functions page click Platform Features.

Click platform features

After you go to the platform features page, click on App Service Editor

platform featuresAfter that, find your function in the list of functions. In the image below the function name is “IoTUploadProcessingFunction”. Expand the files underneath it and select the function.json file. Delete the line “generatedBy”: “Microsoft.NET.Sdk.Functions-1.0.0.0”.

Delete this line

After that your function should be running. If not go back to the functions screen in Azure and start it.