Environment FIle

While docker compose does allow us to define variables within the docker-compose.yml file, this is not a secure or effective way to store sensitive information, as the docker-compose file should be committed and tracked in your version control, without concern of sharing passwords, usernames, etc.

To simplify management of sensitive information between docker-compose configuration files, and allow for re-usability of variables, docker-compose recognizes .env files that live alongside the compose file.

In the below example, we will define how to use .env files, version control them, and share the variables in docker-compose:

Environment File Example

While our actual .env file should never be committed or left in unsecured areas, it is very helpful to include an example of the actual file, showing what variables are required in an actual .env.

Create a .env.example file and fill in your variable names, but not the values:

MYSQL_ROOT_PASSWORD=
MYSQL_DATABASE=
MYSQL_USER=
MYSQL_PASSWORD=

Live Environment File

MYSQL_ROOT_PASSWORD=root_pwd
MYSQL_DATABASE=app_db
MYSQL_USER=db_admin
MYSQL_PASSWORD=dn_admin_pwd

Use Env Variables in docker-compose

Once we've defined our actual environment file, we can now call on them from our docker-compose files by using ${variable_name}.

Example:

services:
  node_db:
    container_name: node_db
    image: mysql:latest
    restart: unless-stopped
    environment:
      MYSQL_ROOT_PASSWORD: ${MYSQL_ROOT_PASSWORD}
      MYSQL_DATABASE: ${MYSQL_DATABASE}
      MYSQL_USER: ${MYSQL_USER}
      MYSQL_PASSWORD: ${MYSQL_PASSWORD}