Intel Extensible Firmware Interface, Specification

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Boot Manager
Version 1.02 12/12/00 323
17.2 Globally-Defined Variables
This section defines a set of variables that have architecturally defined meanings. In addition to the
defined data content, each such variable has an architecturally defined attribute that indicates when
the data variable may be accessed. The variables with an attribute of NV are non-volatile. This
means that their values are persistent across resets and power cycles. The value of any environment
variable that does not have this attribute will be lost when power is removed from the system and
the state of firmware reserved memory is not otherwise preserved. The variables with an attribute of
BS are only available before
ExitBootServices()
is called. This means that these
environment variables can only be retrieved or modified in the pre-boot environment. They are not
visible to an operating system. Environment variables with an attribute of RT are available before
and after
ExitBootServices()
is called. Environment variables of this type can be retrieved
and modified in the pre-boot environment, and from an operating system. All architecturally
defined variables use the
EFI_GLOBAL_VARIABLE VendorGuid
:
#define EFI_GLOBAL_VARIABLE \
{8BE4DF61-93CA-11d2-AA0D-00E098032B8C}
To prevent name collisions with possible future globally defined variables, other internal firmware
data variables that are not defined here must be saved with a unique
VendorGuid
other than
EFI_GLOBAL_VARIABLE
. Table 17-1 lists the global variables.
Table 17-1 Global Variables
Variable Name Attribute Description
LangCodes BS, RT The language codes that the firmware supports.
Lang NV, BS, RT The language code that the system is configured for.
Timeout NV, BS, RT The firmware’s boot managers timeout, in seconds,
before initiating the default boot selection.
ConIn NV, BS, RT The device path of the default input console.
ConOut NV, BS, RT The device path of the default output console.
ErrOut NV, BS, RT The device path of the default error output device.
ConInDev BS, RT The device path of all possible console input devices.
ConOutDev BS, RT The device path of all possible console output devices.
ErrOutDev BS, RT The device path of all possible error output devices.
Boot#### NV, BS, RT A boot load option. #### is a printed hex value. No 0x
or h is included in the hex value.
BootOrder NV, BS, RT The ordered boot option load list.
BootNext NV, BS, RT The boot option for the next boot only.
BootCurrent BS, RT The boot option that was selected for the current boot.
Driver#### NV, BS, RT A driver load option. #### is a printed hex value.
DriverOrder NV, BS, RT The ordered driver load option list.