How to save generated files in a container

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1

Hi @balena, My dockerfile is working very well and the processed images are saved into the ‘outputs’ folder in the container running on the Nvidia Jetson integrated with Balena cloud. However, I am not able to save these images outside of the container. The below is my docker-compose file. I used ‘volumes’ but it seems not working.

version: '2'

volumes:
  edge-data:

services:
  rapid_edge:
    restart: always
    build: .
    network_mode: host
    privileged: true
    environment:
      - UDEV=1
    devices: 
      - "/dev:/dev"
    volumes:
      - 'edge-data:/outputs'

More specifically, I am saving the processed images at the end of a python script in my app dockerized in the container. For this, I am using the below line having opencv library write function to save the processed images.

...
    cv2.imwrite('./outputs/frame_%d.jpg' % count, np_img, [cv2.IMWRITE_JPEG_QUALITY, 100])
    print('Saved image', count)
    count += 1
...

I am getting ‘Saved image …’ print output and the files are saved into ‘output’ folder in the container but not into the out of the container. I checked everywhere Host OS of the device including var/lib/docker/volumes but nothing was saved there.

Am I missing anything?

2

Hi,

on a quick check I’d say that the file path is pointing to the local path of the python execution context: ‘./outputs/frame_%d.jpg’.
In your docker-compose file you specify that the volume will be mounted to /output inside the running container (absolute path and without ‘s’)

Please try if changing to ‘/output/frame_%d.jpg’ fixes the issue.

For details I’m linking you the Balena documentation here: Communicate outside the container - Balena Documentation

Best Regards
Harald

3

Hi @fisehara, thanks a lot for a quick reply. I recognized that I miswrote ‘volumes’ part of docker-compose file in the forum. I fixed it on the post just now. Sorry for the confusion. Can you please look at it again to provide you with the accurate one?

I can say that there is no mismatch between the path in volume and the path in cv2.imwrite.

By the way, I saw the document you sent me before. For this, I can say that it seems my code follows it.

Do you have any else ideas?

4

@aktaseren the path is still wrong in your code, in your code you are using ./outputs, but you really want to write to /outputs (remove the .)

6

Guys thanks for the help. There was no issue with the paths in my python scripts. They are able to run without docker and now with docker. I made a silly mistake on docker-compose file that I recognized now. I should have coded mounting the volume in docker-compose as follows:

volumes:
      - 'edge-data:/app/outputs'

‘app’ is actually the main folder of my project that I containerize. In docker-compose file, I expected that I was already in the container and no need to add the main folder name at the start of the path. Now, adding ‘app’ solved this silly mistake.