How to provide an environment variable to a composed container?

General
1

The mysql image requires a MYSQL_ROOT PASSWORD. With docker run, this is simple:

docker run -d -e 'MYSQL_ROOT_PASSWORD=whatever' mysql

However, I am creating the mysql container with a docker-compose.yml file. That said, I still want to enable the user to specify their MYSQL_ROOT_PASSWORD when they run:

docker-compose up

e.g., some equivalent of this (which doesn’t work):

docker-compose up -e 'MYSQL_ROOT_PASSWORD=whatever'

Anybody know how to do this?

2

The way I like to do it is this:

echo 'MYSQL_ROOT_PASSWORD=whatever' > .env

and then in the docker-compose.yml:

mysql:
    image: mysql
    env_file: .env
1 Like
3

I was thinking about using the env_file functionality, but using it in combination with echo is a lot better than what I had in mind :slight_smile: I think this might be a suitable solution, even if it does result in the MySQL root password being housed in a plaintext file on the docker host.

4

The dirty secret about secrets is that if they have to be readable somewhere. You could always remove the .env file immediately after calling the docker-compose command.

5

Seems like that’d be an issue for future recreation of the containers with docker-compose up, though. You’d have to remember to make that .env file every time before you run it, or the mysql run would fail.