How to read .env file while building an image with Dockerfile? - docker

Question

Here is my Docker file that is using by docker-compose build command:
FROM python:3.5
ENV PYTHONUNBUFFERED 1
RUN apt-get update \
&& apt-get install -y --no-install-recommends libnewlib-arm-none-eabi avr-libc git \
&& rm -rf /var/lib/apt/lists/* \
&& pip install cryptography
RUN mkdir /code
COPY . /code/
WORKDIR /code
RUN pip install -r /code/misc/requirements.txt
RUN mkdir /static
RUN python /code/manage.py migrate
RUN python /code/manage.py collectstatic --noinput
Here is the service in docker-compose.yml that uses this Dockerfile:
version: "3.5"
services:
...
django:
build:
context: .
command: bash -c "/code/run/gunicorn.sh"
volumes:
- ./static:/data/django/static
- ./media:/data/django/media
depends_on:
- db
env_file:
- misc/envs/.env
So, when I try to build this compose with docker-compose build --no-cache command it says that this environment variable is still undefined even if I try to explicityly add RUN set -a && source /code/misc/envs/.env && set +a step into Dockerfile
UPD
As a result my code running on last Dockerfile step
from django.core.exceptions import ImproperlyConfigured
import os
def get_env_setting(setting, default=None):
try:
return os.environ[setting]
except KeyError:
if default is not None:
return default
error_msg = "Set the %s env variable" % setting
raise ImproperlyConfigured(error_msg)
SECRET_KEY = get_env_setting('SECRET_KEY')
gives me an error:
File "/code/project/settings.py", line 34, in <module>
SECRET_KEY = get_env_setting('SECRET_KEY')
File "/code/project/settings.py", line 22, in get_env_setting
raise ImproperlyConfigured(error_msg)
django.core.exceptions.ImproperlyConfigured: Set the SECRET_KEY env variable