Docker compose change the default environment variables file

Question

In docker-compose.yml I'm trying to change the file which contains the environment variables to .env.local file but nothing works. The values are still thoses from .env file. I'm following this doc: https://docs.docker.com/compose/environment-variables/#the-env_file-configuration-option here is my docker-compose.yml file:

version: '3'

services:
    mysqldb:
        image: mysql:5.7
        container_name: project_mysql
        volumes:
          - mysql:/var/lib/mysql
        env_file:
          - .env.local
        environment:
          MYSQL_DATABASE: ${MYSQL_DATABASE}
          MYSQL_ROOT_PASSWORD: ${MYSQL_ROOT_PASSWORD}
          TZ: "Europe/Berlin"
        ports:
            - "3306:3306/tcp"

I also tried to change the name from the file to .env.local.env, .local.env or .variables.env but nothing new happened. I also clear the caches with

docker kill $(docker ps -q)
docker_clean_ps
docker rmi $(docker images -a -q)

but the problem is still here. And there is no error message or code

I have no idea about what's going wrong. Can anybody help me ?

Mickael B. · Accepted Answer · 2020-05-03 16:17:11Z

3

TL; DR: You have a problem of precedence. Don't redefine variables from .env.local with the environment key.

The documentation on env_file says:

Environment variables declared in the environment section override these values – this holds true even if those values are empty or undefined.

The priority for precedence with the .env is

Compose file

Shell environment variables

Environment file

Dockerfile

Variable is not defined

env_file:
  - .env.local
environment:
  MYSQL_DATABASE: ${MYSQL_DATABASE} # Takes precedence over .env.local
  MYSQL_ROOT_PASSWORD: ${MYSQL_ROOT_PASSWORD} # Takes precedence over .env.local
  TZ: "Europe/Berlin" # Takes precedence over .env.local

Note that using the env_file key will set all the variables from that file, whereas with the environment key you have more control on what variable you want to set.

edited May 3, 2020 at 16:17

answered May 3, 2020 at 15:17

Mickael B.

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2 Comments

Entourloupe Over a year ago

If I understood correcly, I should define those variables in the compose file ? since those files are versionned isn't it a security issue ?

Mickael B. Over a year ago

No, you can let them in the .env.local but you can't redifine them in your compose-file using the environment key since it takes precedence over the .env.local file and file override the values.

Slacky · Accepted Answer · 2020-05-03 18:19:08Z

1

Based on the answer provided by @Michael B. I am providing the adapted compose file of the inquiry:

version: '3'

services:
    mysqldb:
        image: mysql:5.7
        container_name: project_mysql
        volumes:
          - mysql:/var/lib/mysql
        env_file:
          - ./local.env
        environment:
          TZ: "Europe/Berlin"
        ports:
            - "3306:3306/tcp"

Note the removal of the MYSQL_DATABASE and MYSQL_ROOT_PASSWORD entries from the environment dictionary due to the fact that based on documentation these would take precedence over the entries defined in the custom env_file.

edited May 3, 2020 at 18:19

answered May 3, 2020 at 15:11

Slacky

1478 bronze badges

4 Comments

Entourloupe Over a year ago

I also tried .env.local.env. But I don't have any error

Slacky Over a year ago

What I mean is to drop the .env prefix. Use just local.env, without .env in front. Also try using relative path using ./ in front: ./local.env

Entourloupe Over a year ago

I updated my question. I tried your suggestion but the problem is still here

Slacky Over a year ago

I updated my suggestion based on @MickaelB 's answer. As he said you should not define them at all under environment.

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