xref: /freebsd/usr.sbin/efivar/efivar.8 (revision 2f2f5c6728faaff4697e5cb7342c7240d0b4aec2)

.\" Copyright (c) 2017 Netflix, Inc
.\" All rights reserved.
.\"
.\" 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.
.\"
.\" $FreeBSD$
.\"
.Dd March 4, 2017
.Dt EFIVAR 8
.Os
.Sh NAME
.Nm efivar
.Nd UEFI environemnt variable interaction
.Sh SYNOPSIS
.Nm
.Op Fl abdDHlLNpRtw
.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 -name Ar name
.Op Fl -no-name
.Op Fl -print
.Op Fl -print-decimal
.Op Fl -raw-guid
.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's 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 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
flag is given.
This is not well understood and currently unimplemented.
.It Fl a Fl -append
Append the specified value to the UEFI variable rather than replacing
it.p
.It Fl t Ar attr Fl -attributes Ar attr
Specify, in user hostile hexidecimal, 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 preceeded 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 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 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.
.Sh COMPATIBILITY
The
.Nm
program is intended to be compatible (strict superset) with a progam
of the same name included in the Red Hat libefivar package.
.Pp
Except the
.Fl d
and
.Fl -print-decimal
flags are not implmenented and never will be.
The
.Fl d
flag is a short-hand 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.
.El
.Pp
.Xr efivar 8
.Sh HISTORY
The
.Nm
utility first appeared in
.Fx 12.0 .