Docker bind and volume mount

Question

Hi,
I am trying to store a csv file inside a docker container and use binds to store it locally. The problem I'm facing is if i use just the file name to write to csv it is getting saved in /app directory. If I use any other path say /mydata/output.csv it's not getting stored.

If I use mount to store the file in local directory the container is failing with message "Error ./main.py is not a file or directory".

local_file_name="output.csv"
local_path = "/mydata/output"
os.mkdir(local_path)
upload_file_path = os.path.join(local_path, local_file_name)

with open(upload_file_path, 'a') as csvfile:
    print("opened csv file")
    csvwriter = csv.writer(csvfile)                   
    csvwriter.writerow(metalist)

Deployment manifest

"HostConfig": {
                    "Binds": [
                        "/opt/localstorage/output:/app"
                    ]
                }

Answer 1

Hello @ambharesh venkatraman ,

To be able to read and write files located on the host file system, there are a couple of things to check:

• the code which access the file system
• The bindingof the container
• Access to the file system folders

You can investigate the folder access inside the module with

sudo docker exec -i -t [the name of your azure iot edge module] /bin/bash

Please check out this blog post where a comparable situation is investigated.