Load environment variables with Docker Compose

Published: November 12, 2019 by Yi Zeng

• Categories:
• tutorials 26

• Tags:
• docker 4
• ruby on rails 10

Generally there are two ways to load environment variables with Docker Compose in docker-compose.yml.

Set directly

docker-compose.yml

web:
  depends_on:
    - 'db'
  build: .
  ports:
    - '3000:3000'
  environment:
    - RAILS_LOG_TO_STDOUT=enabled

Specify the env_file

For example, if the Rails project uses dotenv gem, then the .env file at the root of the project can be passed into Docker Compose like the following:

docker-compose.yml

version: '3'

services:
  db:
    image: 'postgres:10-alpine'
    volumes:
      - 'postgres:/var/lib/postgresql/data'
    ports:
      - '5432:5432'
    env_file:
      - '.env'

  web:
    depends_on:
      - 'db'
    build: .
    ports:
      - '3000:3000'
    volumes:
      - '.:/project'
    env_file:
      - '.env'

volumes:
  postgres:

.env

RAILS_LOG_TO_STDOUT=enabled