path: root/usr.sbin/efivar/efivar.8

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.Dd March 6, 2019
.Dt EFIVAR 8
.Os
.Sh NAME
.Nm efivar
.Nd UEFI environment variable interaction
.Sh SYNOPSIS
.Nm
.Op Fl abdDHlLNpRtuw
.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 -raw-guid
.Op Fl -utf8
.Op Fl -write
.Sh DESCRIPTION
This program manages
.Dq Unified Extensible Firmware Interface
.Pq 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.
.Pp
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.
The
.Ar 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
.Fl -list-guids
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
.Ar file
instead of from the command line.
This flag implies
.Fl -write
unless the
.Fl -append
or
.Fl -print
flags are given.
This behavior is not well understood and is currently unimplemented
for writes.
When
.Fl -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.
.It Fl a Fl -append
Append the specified value to the UEFI variable rather than replacing
it.
.It Fl t Ar attr Fl -attributes Ar 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.
.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
.Fl N
or
.Fl -no-name
flag.
Useful in scripts.
.It Fl D Fl -delete
Delete the specified variable.
May not be used with either the
.Fl -write
or the
.Fl -append
flags.
No
.Ar value
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
flag is specified, guids are converted to names if they are known (and
show up in
.Fl -list-guids ).
.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
.Fl -raw-guid
flag is specified.
.It Fl l Fl -list
List all the variables.
If the
.Fl -print
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 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
standard input.
No command line option to do this is available since UEFI variables
are binary structures rather than strings.
.Xr echo 1
.Fl n
can be used to specify simple strings.
.It Ar name
Display the
.Ar name
environment variable.
.El
.Sh COMPATIBILITY
The
.Nm
program is intended to be compatible (strict superset) with a program
of the same name included in the Red Hat libefivar package,
but the
.Fl d
and
.Fl -print-decimal
flags are not implemented and never will be.
.Pp
The
.Fl d
flag is short for
.Fl -device-path .
.Sh SEE ALSO
Appendix A of the UEFI specification has the format for GUIDs.
All GUIDs
.Dq Globally Unique Identifiers
have the format described in RFC 4122.
.Sh HISTORY
The
.Nm
utility first appeared in
.Fx 11.1 .