How do I pass environment variables to Docker containers?

Question

I\'m new to Docker, and it\'s unclear how to access an external database from a container. Is the best way to hard-code in the connection string?

# Dockerfil         


        

Answer 1

If you are using 'docker-compose' as the method to spin up your container(s), there is actually a useful way to pass an environment variable defined on your server to the Docker container.

In your docker-compose.yml file, let's say you are spinning up a basic hapi-js container and the code looks like:

hapi_server:
  container_name: hapi_server
  image: node_image
  expose:
    - "3000"

Let's say that the local server that your docker project is on has an environment variable named 'NODE_DB_CONNECT' that you want to pass to your hapi-js container, and you want its new name to be 'HAPI_DB_CONNECT'. Then in the docker-compose.yml file, you would pass the local environment variable to the container and rename it like so:

hapi_server:
  container_name: hapi_server
  image: node_image
  environment:
    - HAPI_DB_CONNECT=${NODE_DB_CONNECT}
  expose:
    - "3000"

I hope this helps you to avoid hard-coding a database connect string in any file in your container!