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Manual Pages  — EFIVAR

NAME

efivar – UEFI environment variable interaction

CONTENTS

SYNOPSIS


efivar [-abdDHlLNpRtuw] [-n name] [-f file] [--append] [--ascii] [--attributes] [--binary] [--delete] [--device-path] [--fromfile file] [--guid] [--hex] [--list-guids] [--list] [--name name] [--no-name] [--print] [--print-decimal] [--raw-guid] [--utf8] [--write]

DESCRIPTION

This program manages "Unified Extensible Firmware Interface" (UEFI) environment variables. UEFI variables have three part: A namespace, a name and a value. The namespace is a GUID that is self assigned by the group defining the variables. The name is a Unicode name for the variable. The value is binary data. All Unicode data is presented to the user as UTF-8.

The following options are available:
-n name --name name
  Specify the name of the variable to operate on. The name argument is the GUID of the variable, followed by a dash, followed by the UEFI variable name. The GUID may be in numeric format, or may be one of the well known symbolic name (see --list-guids for a complete list).
-f file --fromfile file
  When writing or appending to a variable, take the data for the variable's value from file instead of from the command line. This flag implies --write unless the --append flag is given. This behavior is not well understood and is currently unimplemented.
-a --append
  Append the specified value to the UEFI variable rather than replacing it.
-t attr --attributes attr
  Specify, in hexadecimal, the attributes for this variable. See section 7.2 (GetVariable subsection, Related Definitions) of the UEFI Specification for hex values to use.
-A --ascii
  Display the variable data as modified ascii: All printable characters are printed, while unprintable characters are rendered as a two-digit hexadecimal number preceded by a % character.
-b --binary
  Display the variable data as binary data. Usually will be used with the -N or --no-name flag. Useful in scripts.
-D --delete
  Delete the specified variable. May not be used with either the --write or the --append flags. No value may be specified.
-d --device --device-path
  Interpret the variables printed as UEFI device paths and print the UEFI standard string representation.
-g --guid
  flag is specified, guids are converted to names if they are known (and show up in --list-guids -).
-H --hex
  List variable data as a hex dump.
-L --list-guids
  Lists the well known GUIDs. The names listed here may be used in place of the numeric GUID values. These names will replace the numeric GUID values unless --raw-guid flag is specified.
-l --list
  List all the variables. If the --print flag is also listed, their values will be displayed.
-N --no-name
  Do not display the variable name.
-p --print
  Print the value of the variable.
-R --raw-guid
  Do not substitute well known names for GUID numeric values in output.
-u --utf8
  Treat the value of the variable as UCS2 and convert it to UTF8 and print the result.
-w --write
  Write (replace) the variable specified with the value specified from standard input. No command line option to do this is available since UEFI variables are binary structures rather than strings. echo(1) -n can be used to specify simple strings.
name Display the name environment variable.

COMPATIBILITY

The efivar program is intended to be compatible (strict superset) with a program of the same name included in the Red Hat libefivar package, but the -d and --print-decimal flags are not implemented and never will be.

The -d flag is short for --device-path.

SEE ALSO

Appendix A of the UEFI specification has the format for GUIDs. All GUIDs "Globally Unique Identifiers" have the format described in RFC 4122.

HISTORY

The efivar utility first appeared in FreeBSD 11.1 .

EFIVAR (8) May 22, 2017

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Please direct any comments about this manual page service to Ben Bullock.

Ken Thompson was once asked by a reporter what he would have changed about Unix if he had it all to do over again. His answer: “I would spell creat with an ‘e.'”