How to use environment variables (.env) in docker compose file

Introduction

This guide demonstrates how to use environment variables (.env) in docker compose file

If you want to use different credentials on different servers, environment variables work great with Docker Compose.

Below is an example docker-compose.yml (based on a Redis + redis-commander recipe) demonstrating how to consume variables from a .env file and provide defaults.

version: "3.7"

services:

  redis:
    image: redis:latest
    ports:
      - 6379:6379
    command: ["redis-server", "--appendonly", "yes"]
    volumes:
      - redis-data:/data

  redis-commander:
    image: rediscommander/redis-commander:latest
    environment:
      - REDIS_HOSTS=local:redis:6379
      - HTTP_USER=${REDIS_USER:-admin}
      - HTTP_PASSWORD=${REDIS_PASSWORD:-qwerty}
    ports:
      - 8081:8081
    depends_on:
      - redis

volumes:
  redis-data:

Notes

• HTTP_USER=${REDIS_USER:-admin} — this uses the ${VAR:-default} syntax: use the REDIS_USER variable from the .env file; if it's missing, use admin as the default.
• Docker Compose automatically picks up a .env file located next to the compose file when you run docker-compose up -d. You don't need to pass it explicitly.

If you run the compose file without a .env file, the credentials for redis-commander will be admin / qwerty.

Create a .env file next to your docker-compose.yml with the following contents to override the defaults (example):

# .env
REDIS_USER=test
REDIS_PASSWORD=1234

With the above .env, redis-commander credentials will be test / 1234.