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-What: /sys/firmware/efi/vars
-Date: April 2004
-Contact: Matt Domsch <>
- This directory exposes interfaces for interactive with
- EFI variables. For more information on EFI variables,
- see 'Variable Services' in the UEFI specification
- (section 7.2 in specification version 2.3 Errata D).
- In summary, EFI variables are named, and are classified
- into separate namespaces through the use of a vendor
- GUID. They also have an arbitrary binary value
- associated with them.
- The efivars module enumerates these variables and
- creates a separate directory for each one found. Each
- directory has a name of the form "<key>-<vendor guid>"
- and contains the following files:
- attributes: A read-only text file enumerating the
- EFI variable flags. Potential values
- include:
- See the EFI documentation for an
- explanation of each of these variables.
- data: A read-only binary file that can be read
- to attain the value of the EFI variable
- guid: The vendor GUID of the variable. This
- should always match the GUID in the
- variable's name.
- raw_var: A binary file that can be read to obtain
- a structure that contains everything
- there is to know about the variable.
- For structure definition see "struct
- efi_variable" in the kernel sources.
- This file can also be written to in
- order to update the value of a variable.
- For this to work however, all fields of
- the "struct efi_variable" passed must
- match byte for byte with the structure
- read out of the file, save for the value
- portion.
- **Note** the efi_variable structure
- read/written with this file contains a
- 'long' type that may change widths
- depending on your underlying
- architecture.
- size: As ASCII representation of the size of
- the variable's value.
- In addition, two other magic binary files are provided
- in the top-level directory and are used for adding and
- removing variables:
- new_var: Takes a "struct efi_variable" and
- instructs the EFI firmware to create a
- new variable.
- del_var: Takes a "struct efi_variable" and
- instructs the EFI firmware to remove any
- variable that has a matching vendor GUID
- and variable key name.