How can you specify environment variables when running a container?

Specifying environment variables when running a container is commonly done using the '-e' flag in the 'docker run' command. This approach allows you to define environment variables directly in the command line when initiating a container, providing flexibility for dynamically setting configurations that the application inside the container might need at runtime.

For instance, the command docker run -e ENV_VAR_NAME=value image_name sets the environment variable ENV_VAR_NAME to value within the container. This is particularly useful for sensitive data like API keys or configuration settings that should not be hard-coded into the image or source code.

While there are other methods to set environment variables, such as using the '--env' flag in the 'docker create' command, these are less common for standard runtime practices. Editing the Dockerfile or modifying the .dockerignore file does not facilitate the direct runtime specification of environment variables; they serve completely different purposes in the Docker workflow. The Dockerfile determines the configuration of the Docker image itself, while the .dockerignore file excludes files from being sent to the Docker daemon during the image build process. Therefore, using the '-e' flag in the 'docker run' command is the standard, most straightforward method for setting environment variables while running a container