Which command starts the Vault server in development mode?

The command "vault server -dev" is used to start the Vault server in development mode. Development mode is a simplified mode intended for testing and experimentation, providing a quick way to run Vault without the complexities of a production setup. In this mode, Vault operates with a number of defaults that make it easier to get started, such as an in-memory storage backend and a predefined unseal key and root token. This allows users to access and perform operations on Vault without requiring extensive configuration.

Other commands listed do not correctly initiate the server in development mode. "vault init -dev" suggests a command for initialization, but Vault does not require an explicit initialization step in development mode, as it automatically generates necessary components. "vault start -dev" and "vault launch -dev" do not exist as valid commands within the Vault CLI reference, which governs the commands available for interacting with Vault. Thus, "vault server -dev" stands out as the correct choice.