How do I pass environment variables to Docker containers?

ghz 8months ago ⋅ 145 views

How can one access an external database from a container? Is the best way to hard code in the connection string?

Dockerfile

ENV DATABASE_URL amazon:rds/connection?string

Answers

Hardcoding the connection string in the Dockerfile is not recommended because it makes your application less flexible and harder to manage. A better approach is to use environment variables to pass sensitive information like database connection strings to your Docker containers.

Here's how you can use environment variables to manage database connection strings in Docker:

  1. Set Environment Variables: Define environment variables in your Docker container that store the database connection information. You can do this in your Dockerfile or through Docker Compose.

    ENV DATABASE_URL="amazon:rds/connection?string"

  2. Inject Environment Variables: When you run your Docker container, you can inject environment variables into the container using the -e flag.

    docker run -e DATABASE_URL="your_database_url_here" your_image_name

    Or if you're using Docker Compose:

    services:
  your_service_name:
    image: your_image_name
    environment:
      - DATABASE_URL=your_database_url_here

  3. Read Environment Variables: In your application code, read the database connection string from the environment variables. Most programming languages provide ways to access environment variables, such as process.env in Node.js or System.getenv() in Java.

    import os

db_url = os.getenv("DATABASE_URL")

  4. Handle Secrets Securely: If your database connection string contains sensitive information like passwords or access tokens, consider using a secret management tool like Docker Secrets (for Docker Swarm) or Docker Secrets Manager Plugin (for Docker Compose).

By using environment variables, you can keep your database connection strings separate from your application code, making it easier to manage different configurations for development, testing, and production environments. Additionally, it allows you to change the database connection string without modifying the Docker image or application code.

#docker