#RaspberryPi – Putting all together to display device temperature using #AzureIoT and #docker. Privilege permissions and other lessons learned


Today challenge was based on an easy one

How do I get a Raspberry Pi temperature using Python?

The lines to do this are quite simple, with the following lines we can get the absolute value for the device temperature, in Celsius (of course!)

Easy! My next step was to add a new [Device Property] to my [Device Template] in Azure IoT. I’ll store this as a temp string, so this is fine.

azure iot device template for raspberry pi with the temperature as device property

The lines to send the temperature as a device property are part of the following code sample. I also track the temperature as telemetry so I can work with the history of the device temp

So far, so good!

Now it was time to package all this in a docker image and run it from a container. I got an ugly surprise when I realize that I got an exception trying to get the device temperature

VCHI Initialization failed

Time to read and learn more about docker and containers on Raspberry Pi.

In the official documentation of [Docker Run, see references] I found a couple of options which may help me. There are 2 options to allow me access to the device temperature

  • Run the container with the specific path to the device I want to grant privileged access for my container
  • Run the container with the [–privileged] argument to enable access to all devices on the host

Of course, the 2nd one is easier, but much more dangerous

When the operator executes docker run –privileged, Docker will enable access to all devices on the host as well as set some configuration in AppArmor or SELinux to allow the container nearly all the same access to the host as processes running outside containers on the host. Additional information about running with –privileged is available on the Docker Blog.

I didn’t think twice and run my image with the [–privileged] argument.

sudo docker run --privileged -p 80:80 <Image ID>

And now I can get an amazing history and track of information using docker, containers and Azure IoT with a Raspberry Pi

azure iot dashboard displaying temperature history as a telemetry

Happy coding!



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