Docker: ./entrypoint.sh not found - docker

Question

I am trying to setup a django project and dockerize it.
I'm having trouble running the container.
As far as I know, it's successfully abe to build it, but fails to run.
This is the error I get:
ERROR: for web Cannot start service web: OCI runtime create failed: container_linux.go:349: starting container process caused "exec: \"./entrpoint.sh\": stat ./entrpoint.sh: no such file or directory": unknown
ERROR: Encountered errors while bringing up the project.
This is the dockerfile:
FROM python:3.6
RUN mkdir /backend
WORKDIR /backend
ADD . /backend/
RUN pip install -r requirements.txt
RUN apt-get update \
&& apt-get install -yyq netcat
RUN chmod 755 entrypoint.sh
ENTRYPOINT ["./entrpoint.sh"]
This is the compose file:
version: '3.7'
services:
db:
image: postgres:12.0-alpine
volumes:
- postgres_data:/var/lib/postgresql/data/
environment:
- POSTGRES_USER=django
- POSTGRES_PASSWORD=password
- POSTGRES_DB=database
web:
restart: on-failure
build: .
container_name:backend
volumes:
- .:/backend
env_file:
- ./api/.env
command: python manage.py runserver 0.0.0.0:8000
ports:
- "8000:8000"
hostname: web
depends_on:
- db
volumes:
postgres_data:
And there is an entrypoint file which runs automatic migrations, if any:
Here is the script:
#!/bin/sh
if [ "$DATABASE" = "postgres" ]
then
echo "Waiting for postgres..."
while ! nc -z $SQL_HOST $SQL_PORT; do
sleep 0.1
done
echo "PostgreSQL started"
fi
python manage.py migrate
exec "$#"
Where am I going wrong?

Answer 1

The problem is that you it's not the entrypoint.sh missing but the nc command.
To solve this you have to install the netcat package.
Since python:3.6 is based on debian buster, you can simply add the following command after the FROM directive:
RUN apt-get update \
&& apt-get install -yyq netcat
EDIT for further improvements:
copy only the requirements.txt, install the packages then copy the rest. This will improve the cache usage and every build (after the first) will be faster (unless you touch the requirements.txt)
replace the ADD with COPY unless you're exploding a tarball
The result should look like this:
FROM python:3.6
RUN apt-get update \
&& apt-get install -yyq netcat
RUN mkdir /backend
WORKDIR /backend
COPY requirements.txt /backend/
RUN pip install -r requirements.txt
COPY . /backend/
ENTRYPOINT ["./entrypoint.sh"]