.\" Copyright (c) 2017-2021 Netflix, Inc.
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.Dd April 7, 2021
.Dt EFIVAR 8
.Nd UEFI environment variable interaction
.Op Fl abdDHlLNpqRtuw
.Op Fl n Ar name
.Op Fl f Ar file
.Op Fl -append
.Op Fl -ascii
.Op Fl -attributes
.Op Fl -binary
.Op Fl -delete
.Op Fl -device-path
.Op Fl -fromfile Ar file
.Op Fl -guid
.Op Fl -hex
.Op Fl -list-guids
.Op Fl -list
.Op Fl -load-option
.Op Fl -name Ar name
.Op Fl -no-name
.Op Fl -print
.Op Fl -print-decimal
.Op Fl -quiet
.Op Fl -raw-guid
.Op Fl -utf8
.Op Fl -write
This program manages
.Dq Unified Extensible Firmware Interface
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
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:
.Bl -tag -width 20m
.It Fl n Ar name Fl -name Ar name
Specify the name of the variable to operate on.
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
for a complete list).
.It Fl f Ar file Fl -fromfile Ar file
When writing or appending to a variable, take the data for the
variable's value from
instead of from the command line.
This flag implies
flags are given.
This behavior is not well understood and is currently unimplemented
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
.It Fl a Fl -append
Append the specified value to the UEFI variable rather than replacing
.It Fl t Ar attr Fl -attributes Ar attr
Specify, in hexadecimal, the attributes for this
See section 7.2 (GetVariable subsection, Related Definitions) of the
UEFI Specification for hex values to use.
.It Fl A Fl -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.
.It Fl b Fl -binary
Display the variable data as binary data.
Usually will be used with the
Useful in scripts.
.It Fl D Fl -delete
Delete the specified variable.
May not be used with either the
may be specified.
.It Fl d Fl -device Fl -device-path
Interpret the variables printed as UEFI device paths and print the
UEFI standard string representation.
.It Fl g Fl -guid
Convert GUIDs to names if they are known
.Po and show them up in
.It Fl H Fl -hex
List variable data as a hex dump.
.It Fl L Fl -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
flag is specified.
.It Fl l Fl -list
List all the variables.
flag is also listed, their values will be displayed.
.It Fl -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.
.It Fl N Fl -no-name
Do not display the variable name.
.It Fl p Fl -print
Print the value of the variable.
.It Fl q Fl -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.
.It Fl R Fl -raw-guid
Do not substitute well known names for GUID numeric values in output.
.It Fl u Fl -utf8
Treat the value of the variable as UCS2 and convert it to UTF8 and
print the result.
.It Fl w Fl -write
Write (replace) the variable specified with the value specified from
No command line option to do this is available since UEFI variables
are binary structures rather than strings.
.Xr echo 1
can be used to specify simple strings.
.It Ar name
program is intended to be compatible (strict superset) with a program
of the same name included in the Red Hat libefivar package,
flags are not implemented and never will be.
flag is short for
.Fl -device-path .
.Sh SEE ALSO
Appendix A of the UEFI specification has the format for GUIDs.
.Dq Globally Unique Identifiers
have the format described in RFC 4122.
utility first appeared in
.Fx 11.1 .