Read and Write to a file using iot edge custom Module

Question

Hi,

I have a requirement to read json data from a file in Iot edge custom module and after doing some processing I want to overwrite that file with new data.

I am using C# modules for custom modules and iot edge Runtime is installed in RHEL 8.

Locally I am able to run the module and it is working as expected, but after build and push it is throwing error -

Unhandled exception. System.AggregateException: One or more errors occurred. (Could not find file '/app/data.json'.)

Is there something that I am missing?

Answer 1

Hello @Satyam Chauhan ,

As seen in the link @chbeier provided, you have to both add a binding to the container create options and provide filesystem access to the host folder.

The module is sandboxed. It only sees a local folder structure (inside the module). You need to add a folder to the module which maps to a folder on the host filesystem.

Check out the filesystem folders inside the container with:

sudo docker exec -i -t echo /bin/bash

See also this blob post with an example.

Answer 2

Hi @Satyam Chauhan ,

Have you checked the documentation on how to provide your module access to the device local storage for persistence? how-to-access-host-storage-from-module