“No such file or directory” when building Docker image

Question

I have an existing and working Dockerfile, that I want to update to have a better structure, and to allow me to volume-mount part of the application directory to enable persistence.

Folder structure is:

.git/
.gitignore
Dockerfile
README.md
Sorter.py
WebService.py
requirements.txt

The current working Dockerfile is:

FROM python:3.8-alpine
ADD . /
RUN pip install -r requirements.txt
EXPOSE 5000
CMD [ "python", "./WebService.py" ]

I now want to simply do this not in the root directory, so I do the following:

FROM python:3.8-alpine
WORKDIR /app
COPY . .
RUN pip install -r requirements.txt
EXPOSE 5000
ENTRYPOINT ["python"]
CMD ["WebService.py"]

I build the image "docker build -t, and run it using the same docker-compose file as for the first buildscript - and I get the error:

"python: can't open file '/app/WebService.py': [Errno 2] No such file or directory"

Answer 1

The problem is with this line WORKDIR /app , as you can see the Docker tries to run the file /app/WebService.py , but you do not have it. Your file is in . not in app folder. So either you should create the app folder and put your WebService.py in that folder, either just remove WORKDIR /app .

Answer 2

Here's the solution I found:

FROM python:3.8-alpine
RUN mkdir /app
ADD . /app
WORKDIR /app
RUN pip install -r requirements.txt
EXPOSE 5000
CMD [ "python", "./WebService.py" ]