Docker - lesson 6 | HackIndia Skills

Docker - lesson 6 | HackIndia Skills | HackIndia

Example

Compose wiring

Compose can read variables from a .env file in the project directory. It can then pass them into each service container.

Inside the app container, the database host is db because that is the Compose service name.

services:
  app:
    build: .
    ports:
      - "127.0.0.1:${APP_PORT}:3000"
    environment:
      DATABASE_URL: ${DATABASE_URL}
    depends_on:
      - db

  db:
    image: postgres:16
    environment:
      POSTGRES_USER: ${POSTGRES_USER}
      POSTGRES_PASSWORD: ${POSTGRES_PASSWORD}
      POSTGRES_DB: ${POSTGRES_DB}
    volumes:
      - db_data:/var/lib/postgresql/data

volumes:
  db_data:

Your to-do

Use it safely

Do each one yourself, then tap it to tick it off. The ticks are only a checklist for you: they are not marked or scored.

Create .env by copying .env.example.
Change secrets in .env if the project will be used beyond local testing.
Read env variables in your app code, not from hard-coded strings.
Run the app with the modern docker compose command.
Open the app and test one feature that touches the database.

0 of 5 done

cp .env.example .env
docker compose up --build

Common mistake

Common leak

Beginners put DATABASE_URL or API keys in the Dockerfile with ENV. That makes the value part of the image metadata.

Another common issue is committing .env by mistake. Check git status before pushing your repo.

git status

Handle Environment Variables Safely

One rule

Two env files

File setup

Compose wiring

Use it safely

Common leak

Check AI output

Do this now

Quick check