Env file is not read when I use docker-compose -f in a different directory

Question

I have a problem with my Docker .env file. When I'm in my Docker folder (where I have the docker-compose.yml and .env file), the environment variables are read from .env fine. However, when I run docker-compose -f ./docker/docker-compose.yml up --build -d in a higher-level directory I get warnings like:

The MYSQL_ROOT_PASSWORD variable is not set. Defaulting to a blank string. 

Has anyone encountered this problem? I tried setting the env_file property in docker-compose.yml and using other file encodings (I found this solution in Google) and still nothing.

This is my config:

version: '2'

services:
    mysql:
        container_name: mysql
        image: mysql
        volumes:
            - "./.data/db:/var/lib/mysql"
        environment:
            MYSQL_ROOT_PASSWORD: ${MYSQL_ROOT_PASSWORD}
            MYSQL_DATABASE: ${MYSQL_DATABASE}
            MYSQL_USER: ${MYSQL_USER}
            MYSQL_PASSWORD: ${MYSQL_PASSWORD}

.env file:

# MySQL
MYSQL_ROOT_PASSWORD=test
MYSQL_DATABASE=test
MYSQL_USER=test
MYSQL_PASSWORD=test

Answer 1

As Tagc says, this is the documented behavior of docker-compose with a .env file, it must be in the directory where you are running docker-compose. You cannot use env_file for this because that's setting a different environment. The .env file sets the environment used by docker-compose to parse the yml file (and therefore could not be set from within the file, that would be a circular dependency), while the env_file injects environment variables into the running containers.

If you cannot cd into the folder or move your .env file for some reason, you can manually source the file with something like:

env $(cat docker/.env | grep -v ^# | xargs) \
  docker-compose -f docker/docker-compose.yml up --build -d