Mastering Docker ARG and ENV: Optimizing Configuration for Development and Production

Docker uses ARG for build-time variables and ENV for runtime variables, each serving distinct configuration purposes. ARG values are only available during the image build process and cannot be accessed in the application code. ENV variables are accessible both in the Dockerfile and within the running container's application code. You can set ENV variables in the Dockerfile, via the `docker run` command, or through a `.env` file, with runtime values overriding Dockerfile defaults. Storing sensitive data directly in the Dockerfile as environment variables is discouraged due to security risks as they get baked into the image. Instead, utilize separate environment files for sensitive information and exclude them from version control. ARG improves configuration flexibility by allowing the setting of default values at build time using the `--build-arg` flag. To optimize Docker builds, define ARG variables after dependency installations to avoid unnecessary reinstallation. Employing ARG and ENV appropriately contributes to building flexible, configurable, and secure Dockerized applications. Understanding the differences helps developers improve their workflows while maintaining security and efficiency.