ESXi supports the detection and configuration of headless systems.
A headless system is a system that can be operated without a monitor, keyboard or mouse. Network Appliance boxes do not have VGA, the primary interface is a single serial port. You can leverage your existing headless systems to use ESXi. You can add ESXi appliances to a datacenter where virtual machines are managed with vSphere Virtual Center. All existing ESXi features can be used with a headless system that is configured with either embedded flash or minimal local storage. ESXi allows for dynamic switching between different serial modes, which is useful for diagnosing and debugging problems. You can switch between modes to view or modify system parameters.