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Table Of Contents
About Headless Systems 15
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 set up your
existing headless systems to use ESXi. You can add ESXi appliances to a data center 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.
This chapter includes the following topics:
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Detecting a Headless System
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About Serial Mode Dynamic Switching
Detecting a Headless System
ESXi automatically detects headless systems.
ESXi automatically redirects the DCUI over a serial port connection to improve headless detection. When
ESXi automatically detects a headless system, ESXi will set up the serial port as COM1, 115200 baud,
and redirects the DCUI over this serial port. The specific settings of com port and baud rate are read from
the SPCR (Serial Port Console Redirection) table, if it exists. This behavior can be disabled using new
boot parameters if the default settings are not acceptable. You can set the headless flag in the ACPI
FADT table to mark a system as headless.
About Serial Mode Dynamic Switching
ESXi supports dynamic switching between four different serial port modes.
ESXi supports serial mode dynamic switching to provide maximum platform flexibility, and to allow
debugging and supportability in the text box. ESXi examines the input characters for any serial port mode
and switches the modes based on the input key sequence. DCUI, Shell, GDB, and Logging modes are
supported. If you have two serial ports, only one of the four modes is allowed on each port. Two serial
ports cannot be in the same mode. If you attempt a dynamic switch to a mode in use by the other serial
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