Docker mount only works in interactive mode

Question

I'm new to Docker and I am trying to use the mount options of the run command, but they're not working in my linux environemnt.

I have an executable called transformer, whose purpose is taking a txt file from a directory called txts, transform it into a python file and save such file into another directory called dict. On top of these 2 folders, I have a third one (lib) containing the libraries required to launch transformer.

So the structure of my project folder is as such:

* folder txts
 |
 |__ myfile.txt
* folder dict
* folder lib <contains some cpp libraries>
* executable transformer
* Dockerfile
Path to this directory: /home/ec2-user/MyDockerTests/transformerproject/

Running transformer requires launching the following command:

./transformer -d <path to the txt file> -o <path where you want to save the newly created python file>

With this, I tried running the process inside a Docker container.

Dockerfile:

FROM alpine
FROM gcc

COPY . /usr/project/

ENV LD_LIBRARY_PATH=/usr/project/lib

WORKDIR /usr/project/

CMD ./transformer -d txts/myfile.txt -o dict/mytransformedfile.py

And with this I built the image calling it transformercontainer

docker build --tag transformercontainer .

However, obviously, the container runs, does its thing, immediately stops afterwards and I'm left without my python file, so the next step would be linking the dict folder of the container to the dict folder of the host machine. And here's where I keep failing.

I launch the following command:

docker run -v /home/ec2-user/MyDockerTests/transformerproject/dict/:/usr/project/dict/ transformercontainer

And the python file doesn't appear inside my host machine dict folder.

What I did then was trying to manually launch the transformer executable inside the container by running it in interactive mode

docker run -it -v /home/ec2-user/MyDockerTests/transformerproject/dict/:/usr/project/dict/ transformercontainer

At this point I ran the same exact command I wrote in the CMD portion of the Dockerfile directly, and now not only I can clearly see that, inside the container, the dict folder is now populated with a new python file, but when I close the container I can also find that same python file inside my host machine's dict folder, so the directory mount worked just fine.

Clearly I'm doing something wrong but after countless attempts I'm at my last straw.

Answer 1

Everything seems ok apart from the quote in CMD "./transformer -d txts/myfile.txt -o dict/mytransformedfile.py

Please try: CMD ./transformer -d txts/myfile.txt -o dict/mytransformedfile.py