How do you specify environment variables in a Docker container?

Specifying environment variables in a Docker container using the -e flag in the docker run command is correct because this option allows users to directly set environment variables for the container at runtime. When executing the docker run command, the -e flag is followed by the variable name and value, allowing you to configure the environment of the container without modifying the image itself or relying on predefined settings.

This functionality is crucial for situations where applications need configuration settings that vary between environments, such as development, testing, and production. By using the -e flag, you can easily pass in different values without needing to rebuild the Docker image.

While the --env flag is synonymous with -e and could also be used to achieve the same outcome, the question asks specifically for the method involving the docker run command, and the -e flag is the commonly used shorthand for this operation. The other options, such as specifying variables only in the Dockerfile or setting them in the Docker daemon settings, don't provide flexibility during runtime and are not applicable in all scenarios.