What command is used to initialize a new Swarm cluster?

To initialize a new Swarm cluster, the command used is "docker swarm init." This command sets up the current Docker host as a manager node in a new Swarm cluster, allowing it to manage other nodes and orchestrate container deployments across them.

When executed, "docker swarm init" configures the Docker daemon on the current host to start operating in Swarm mode, making it ready to accept other nodes to join the cluster. It will also provide instructions for adding worker nodes to the Swarm, displaying a join token necessary for that process.

In the context of the other provided options, "docker swarm create," "docker swarm start," and "docker swarm run" do not represent valid commands in the context of initializing a Swarm cluster. Instead, their phrasing or purpose either does not match the intended operation of setting up a Swarm or does not exist as a recognized Docker command. Thus, "docker swarm init" is the correct and necessary command for this specific task.