6.5.1

Table Of Contents
About Headless Systems 13
ESXi supports the detection and conguration 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
congured with either embedded ash or minimal local storage. ESXi allows for dynamic switching
between dierent 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:
n
“Detecting a Headless System,” on page 171
n
About Serial Mode Dynamic Switching,” on page 171
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 specic seings 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 seings are not acceptable. You can set the headless ag in the ACPI FADT table to
mark a system as headless.
About Serial Mode Dynamic Switching
ESXi supports dynamic switching between four dierent serial port modes.
ESXi supports serial mode dynamic switching to provide maximum platform exibility, 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 aempt a dynamic switch to a mode in use by the other serial port, the
request is ignored. Dynamic switching eliminates the need to interrupt the boot process manually or to
create a custom image to redirect to a serial port. It also addresses supportability issues regarding headless
systems that only have one serial port, by making it possible to switch the serial port between dierent
modes of operation.
VMware, Inc.
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