Which Docker command allows you to define secrets for a container?

The command that allows you to define secrets for a container is indeed "docker secret create." This command is specifically designed to manage sensitive data, such as passwords, API keys, and other confidential information, within a Docker swarm environment.

When you use "docker secret create," you can securely store and manage secrets in a way that they can be accessed by services but are not directly exposed to the containers or the host system. This capability is crucial for maintaining security and compliance when running applications that require sensitive information.

Other commands listed serve different purposes. For example, creating a service with "docker service create" does not inherently create or manage secrets; instead, it allows you to deploy a service across the swarm. The "docker container start" command is used to start existing containers, while "docker build" is utilized to build images from a Dockerfile. These commands do not have the functionality to create or manage secrets, making "docker secret create" the appropriate choice for defining secrets associated with containers.