What should be used to directly control a server that has no network connectivity?

Using KVM (Keyboard, Video, Mouse) is the most suitable choice for directly controlling a server that lacks network connectivity because it allows for direct physical access to the server's interface. KVM setups enable an administrator to connect a keyboard, monitor, and mouse directly to the server, facilitating management tasks without the need for a network connection.

The other options are primarily designed for remote management or control. SSH (Secure Shell) and RDP (Remote Desktop Protocol) are both remote management tools that require network connectivity to access the server's operating system and interfaces from a different machine. They cannot be utilized if the server is not connected to a network. Similarly, iLO (Integrated Lights-Out) and iDRAC (Integrated Dell Remote Access Controller) are management interfaces that provide remote access and management capabilities over a network, making them unsuitable for situations where direct control is necessary and network access is unavailable. Thus, KVM is the only option that directly addresses the need for managing a server without any network connectivity.