NAME
efivar – UEFI environment variable interaction
SYNOPSIS
efivar [-abdDHlLNpqRtuw] [-n name] [-f file] [--append] [--ascii] [--attributes] [--binary] [--delete] [--device-path] [--fromfile file] [--guid] [--hex] [--list-guids] [--list] [--load-option] [--name name] [--no-name] [--print] [--print-decimal] [--quiet] [--raw-guid] [--utf8] [--write]
DESCRIPTION
This program manages “Unified Extensible Firmware Interface” (UEFI) environment variables. UEFI variables have three parts: 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 names (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 or --print flags are given. This behavior is not well understood and is currently unimplemented for writes. When --print is specified, the contents of the file are used as the value to print using any other specified flags. This is used primarily for testing purposes for more complicated variable decoding.
- -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
-
Convert GUIDs to names if they are known (and show them 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 the --raw-guid flag is specified.
- -l --list
-
List all the variables. If the --print flag is also listed, their values will be displayed.
- --load-option
-
Decode the variable as if it were a UEFI Boot Option, including information about what device and/or paths the UEFI DevicePaths decode to.
- -N --no-name
-
Do not display the variable name.
- -p --print
-
Print the value of the variable.
- -q --quiet
-
When an error occurs, exit with a non-zero value without outputting any error messages. Otherwise, produce the normal output and exit with a zero status.
- -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.