Docker Toolbox error "can't open file"

Question

I've been struggling to get a Docker image up and running on Windows 10 Home, using Docker Toolbox. Here is the error that I see in Kitematic:

python: can't open file 'src/__main__.py': [Errno 2]   
No such file or directory

This Python command that is failing is the entry point for the 'notes' Docker container.

After Docker/up.sh the process finishes without any errors.

Successfully built f59c275721cf
Successfully tagged docker_mysql:latest
Creating mysql ... done
Creating notes ... done

Additionally, this is a group project in which other users on Macs aren't able to duplicate this error. After updating Dockerfile to below and running:

Successfully built 42a95cd419f2
Successfully tagged docker_mysql:latest
Creating mysql ... done
Creating notes ... done

User@DESKTOP-EBUI9GE MINGW64 /c/users/user/Desktop/6440/Procedure-Notes-Application (master)
$ docker ps
CONTAINER ID        IMAGE               COMMAND                  CREATED             STATUS              PORTS                     NAMES
68f60fdba6f5        docker_mysql        "docker-entrypoint.s…"   15 seconds ago      Up 9 seconds        0.0.0.0:23306->3306/tcp   mysql

User@DESKTOP-EBUI9GE MINGW64 /c/users/user/Desktop/6440/Procedure-Notes-Application (master)
$ docker ps -a
CONTAINER ID        IMAGE               COMMAND                  CREATED             STATUS                      PORTS                     NAMES
e7fbd5b73189        docker_notes        "python /app/src/__m…"   23 seconds ago      Exited (2) 17 seconds ago                             notes
68f60fdba6f5        docker_mysql        "docker-entrypoint.s…"   23 seconds ago      Up 17 seconds               0.0.0.0:23306->3306/tcp   mysql

Updated Dockerfile:

### Use an official Python runtime as a parent image 
FROM python:2.7-slim

### set working directory to the code location
WORKDIR /app

### copy the code base over (redone by the compose file)
COPY . .

### Install any needed packages specified in requirements.txt
RUN pip install --trusted-host pypi.python.org -r requirements.txt

### Make port available to the world outside this container
EXPOSE 5000

### start the application
CMD ["python", "/app/src/__main__.py"]

I am now getting another error:

 * Serving Flask app "__main__" (lazy loading)
 * Environment: production
   WARNING: Do not use the development server in a production environment.
   Use a production WSGI server instead.
 * Debug mode: on
 * Running on http://0.0.0.0:5000/ (Press CTRL+C to quit)
 * Restarting with stat
Traceback (most recent call last):
  File "/app/src/__main__.py", line 57, in <module>
    app.run(debug=True, host='0.0.0.0')
  File "/usr/local/lib/python2.7/site-packages/flask/app.py", line 943, in run
    run_simple(host, port, self, **options)
  File "/usr/local/lib/python2.7/site-packages/werkzeug/serving.py", line 988, in run_simple
    run_with_reloader(inner, extra_files, reloader_interval, reloader_type)
  File "/usr/local/lib/python2.7/site-packages/werkzeug/_reloader.py", line 332, in run_with_reloader
    sys.exit(reloader.restart_with_reloader())
  File "/usr/local/lib/python2.7/site-packages/werkzeug/_reloader.py", line 176, in restart_with_reloader
    exit_code = subprocess.call(args, env=new_environ, close_fds=False)
  File "/usr/local/lib/python2.7/subprocess.py", line 172, in call
    return Popen(*popenargs, **kwargs).wait()
  File "/usr/local/lib/python2.7/subprocess.py", line 394, in __init__
    errread, errwrite)
  File "/usr/local/lib/python2.7/subprocess.py", line 1047, in _execute_child
    raise child_exception
OSError: [Errno 8] Exec format error

Answer 1

My first remark, that let the process start was:

You don't need mkdir, as WORKDIR will create it. It's also better to use absolute references, such as WORKDIR /app and CMD ["python", "/app/src/__main__.py"].

The Python script now starts and stops the error:

  File "/usr/local/lib/python2.7/subprocess.py", line 1047, in _execute_child
    raise child_exception

This is typically an error in the Python script. One possibility is described in the post python subprocess.call() not working as expected:

By default subprocess.call doesn't use a shell to run our commands you so can't shell commands like cd.

To use a shell to run your commands use shell=True as parameter. In that case it is recommended to pass your commands as a single string rather than as a list. And as it's run by a shell you can use ~/ in your path, too:

subprocess.call("(cd ~/catkin_ws/src && catkin_make)", shell=True)