How do I pass environment variables to Docker containers when running them?

General Discussions
1

I want to access an external database from within a Docker container. Is hardcoding the connection string in the Dockerfile the best approach? How can I pass environment variables like the database connection string to a container during docker run to keep it flexible and secure?

2

I’ve been through the frustration of having connection strings hardcoded in Dockerfiles, it’s just not the best practice when it comes to flexibility and security. Over the years, I always make sure to pass environment variables when running containers with the -e flag. For instance:

docker run -e DB_CONN="your_connection_string" your_image

This approach lets you adjust connection details without having to rebuild the image. Plus, it helps keep secrets out of your Dockerfile. It’s a simple yet powerful way to ensure your apps are more portable and secure, especially when you’re managing multiple environments.

3

Exactly! I’ve been in situations where flexibility was key, and using environment variables in Docker containers is the best way to go. Instead of hardcoding sensitive info, I pass environment variables during the docker run using the --env or -e flag, like so:

docker run --env DB_CONN="db_connection_string" myapp

This way, you don’t have to reconfigure your Dockerfile. And if you’ve got several variables to handle, it’s even better to use an env file with --env-file. That method keeps everything neat and secure by managing sensitive information outside the image itself.

4

I can’t stress enough how risky hardcoding sensitive data like DB credentials in your Dockerfile is. In my experience, it’s always safer to pass environment variables when launching a container. Here’s a quick example:

docker run -e DATABASE_URL="your_db_url" mycontainer

Alternatively, you can group all your variables into an .env file and load them with --env-file. This not only keeps your secrets secure but also makes it easy to switch configurations across different environments without modifying the code. Keeping it flexible, secure, and maintainable is the key here.