What is the purpose of the --link flag in Docker?

The purpose of the --link flag in Docker is to connect one container to another for communication. This flag allows you to define relationships between containers, enabling one container to access the resources and network of another. When two containers are linked, Docker automatically sets up environment variables in the linked container that provide information about the source container, such as its IP address and exposed ports. This simplifies inter-container communication, allowing services running in different containers to interact seamlessly.

While the other options might be relevant to container operations, they do not accurately describe the role of the --link flag. It does not pertain to storage volume management, port exposure, or setting environment variables explicitly, which can occur independently of linking containers. The linking feature primarily focuses on enabling direct communication between containers, making it a vital tool for applications that require interaction among different microservices or services running in separate containers.