What does the ENV command do in a Dockerfile?

The ENV command in a Dockerfile is used to set environment variables within the Docker container. By defining environment variables, you can configure settings or parameters that your application or processes running in the container can use. These variables are set at build time and will persist in the resulting image, making them accessible during the container's runtime.

Setting environment variables can be particularly useful for providing configuration data without hardcoding values into your application. This allows for more flexible and secure handling of configuration settings, such as database connection strings, API tokens, or other runtime parameters.

Using the ENV command properly helps ensure that your environment is correctly set up, thereby promoting better portability and maintainability of your Dockerized applications.