PermissionError: [Errno 13] Permission denied: despite granting permission in Dockerfile – what could be the issue?

I have a Flask Python application which creates an application.log file in the /app folder. I have granted write permissions to that folder via my Dockerfile however I still see that error. I don’t see it when the file is created in the /opt/docker location. What could be the issue?

Here’s what my Dockerfile looks like:

FROM nexus.company.com/docker-private/company-base:1.4.0

LABEL team="Team"
LABEL maintainer=team@company.com

USER root

# Create directory for logs - kubernetes logging sidecar reads logs from this location
RUN mkdir -p /opt/docker/logs

# Grant write permission
RUN chown -R daemon:daemon /opt/docker

# Install required packages tools
RUN apt-get update -y && apt-get install -y python3-pip \
    # wget and zlib1g-dev to help with python3.6 installation
    &&  apt-get install -y wget && apt-get install -y zlib1g-dev \
    # The following line installs the ssl module required by pip3 to install requirements
    && apt-get install -y libssl-dev \
    # The following line installs the bz2 module required for pandas to install correctly
    && apt-get install -y libbz2-dev

WORKDIR /opt

# Download and install Python 3.6
RUN wget https://www.python.org/ftp/python/3.6.3/Python-3.6.3.tgz && tar -xvf Python-3.6.3.tgz
RUN cd Python-3.6.3 && ./configure && make && make install

# We copy just the requirements.txt first to leverage Docker cache
COPY ./requirements.txt /app/requirements.txt

# Permission for local application.log if running locally
RUN chown -R daemon:daemon /app

WORKDIR /app


RUN pip3 install --upgrade pip && pip3 install -r requirements.txt

# Copy all files to /app folder - we will run our application from here
COPY . /app

USER daemon

# Run flask app with uwsgi
ENTRYPOINT uwsgi --wsgi-file src/app.py --http-socket :9000 --callable app --ini app.ini

And here’s the error trace:

Traceback (most recent call last):
  File "src/app.py", line 9, in <module>
    app = create_app()
  File "./src/__init__.py", line 41, in create_app
    setup_logging(app)
  File "./src/__init__.py", line 51, in setup_logging
    handler = logging.FileHandler(app.container.config.get("app.LOG_FILE"))
  File "/usr/local/lib/python3.6/logging/__init__.py", line 1030, in __init__
    StreamHandler.__init__(self, self._open())
  File "/usr/local/lib/python3.6/logging/__init__.py", line 1059, in _open
    return open(self.baseFilename, self.mode, encoding=self.encoding)
PermissionError: [Errno 13] Permission denied: '/app/application.log'
unable to load app 0 (mountpoint='') (callable not found or import error)
*** no app loaded. GAME OVER ***

I have granted permissions with this line:

# Permission for local application.log if running locally
RUN chown -R daemon:daemon /app

Should I be doing something else?

>Solution :

You need to run chown after you copy the files into that directory. Alternatively, you can use the --chown flag to COPY. Otherwise they’ll be copied in as owned by the root user, leading to the permissions error.

COPY . /app
RUN chown daemon:daemon -R /app

Or using the --chown flag (linux only):

COPY --chown=daemon:daemon . /app