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4 .\" Please also read the file DISCLAIMER which is included in this software
7 .\" This program is free software; you can redistribute it and/or modify it
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16 .TH NVRAMTOOL 8 "September 2008"
18 nvramtool \- read/write coreboot-related information
20 .B "nvramtool [OPTS] [-n] -r NAME"
22 .B "nvramtool [OPTS] -e NAME"
24 .B "nvramtool [OPTS] -a"
26 .B "nvramtool [OPTS] -w NAME=VALUE"
28 .B "nvramtool [OPTS] -p INPUT_FILE"
30 .B "nvramtool [OPTS] -i"
32 .B "nvramtool [OPTS] -c [VALUE]"
34 .B "nvramtool [OPTS] -l [ARG]"
36 .B "nvramtool [OPTS] -d"
38 .B "nvramtool [OPTS] -Y"
40 .B "nvramtool [OPTS] -b OUTPUT_FILE"
42 .B "nvramtool [OPTS] -B INPUT_FILE"
44 .B "nvramtool [OPTS] -x"
46 .B "nvramtool [OPTS] -X DUMPFILE"
48 .B "nvramtool [OPTS] -v"
50 .B "nvramtool [OPTS] -h"
53 is a utility for reading/writing coreboot parameters and displaying
54 information from the coreboot table.
56 The coreboot table resides in low physical memory. It is created at boot
57 time by coreboot, and contains various system information such as the type
58 of mainboard in use. It specifies locations in the CMOS (nonvolatile RAM)
59 where the coreboot parameters are stored.
61 This program is intended for (x86-based) systems that use coreboot. For
62 information about coreboot, see
64 https://www.coreboot.org/.
68 Show the value of the coreboot parameter given by
72 is specified, show only the value. Otherwise show both parameter name and
76 Show all possible values for parameter given by
80 Show the names and values for all coreboot parameters.
85 to coreboot parameter given by
89 Assign values to coreboot parameters according to the contents of
91 The format of this file is described below.
94 This is similar to the
96 option, except that the contents of the input file are taken from standard
102 is present then set the CMOS checksum for the coreboot parameters to
104 Otherwise, show the checksum value.
109 is present then show information from the coreboot table as specified by
111 Otherwise show all possible values for
115 Do a low-level dump of the coreboot table.
118 Write CMOS layout information to standard output. If redirected to a file,
119 the layout information may be used as input for the
120 .B "'-y LAYOUT_FILE'"
124 Write the contents of CMOS memory to the binary file
126 The first 14 bytes of
128 do not contain actual CMOS data, and are always written as zeros. This is
129 because the first 14 bytes of the CMOS area do not contain CMOS memory. These
130 bytes are involved with the functioning of the real time clock.
133 Read binary data from
135 and write the data to CMOS memory. The first 14 bytes of
137 are skipped and data is written to CMOS starting at the 15th byte of the CMOS
138 area. This is because the first 14 bytes of the CMOS area do not contain CMOS
139 memory. These bytes are involved with the functioning of the real time clock.
142 Show a hex dump of all CMOS data. The first 14 bytes of the dump do not
143 contain actual CMOS data, and are always shown as zeros. This is because the
144 first 14 bytes of the CMOS area do not contain CMOS memory. These bytes are
145 involved with the functioning of the real time clock.
148 Read binary data from
150 (presumably a CMOS dumpfile created using the
152 option) and show a hex dump of the data.
155 Show version information for this program.
158 Show a help message for this program.
162 evaluates to the following:
164 .B " [-y LAYOUT_FILE | -t]"
167 .B "'-y LAYOUT_FILE'"
168 option tells nvramtool to obtain CMOS layout information from the contents of
172 option tells nvramtool to obtain CMOS layout information from the CMOS option
173 table (contained within the coreboot table). If neither option is
174 specified, the CMOS option table is used by default.
176 follows the format of the
178 files provided by coreboot.
180 If the coreboot installed on your system was built without specifying
181 .B "CONFIG_HAVE_OPTION_TABLE,"
182 then the coreboot table will not contain a CMOS option table. In this case,
184 .B "'-y LAYOUT_FILE'"
187 These two options are silently ignored when used in combination with other
190 for instance) for which they are not applicable.
196 must consist of a sequence of lines such that each line is either a blank
197 line, a comment, or an assignment. A blank line consists only of zero or
198 more whitespace characters (spaces and tabs). A comment is constructed as
205 indicates optional whitespace characters and
207 indicates optional text. Blank lines and comments are both ignored. An
208 assignment is constructed as follows:
210 .B " [ws]NAME[ws]=[ws]VALUE[ws]"
214 is the name of a coreboot parameter and
216 is the value that will be assigned to
219 is allowed to contain whitespace characters, but it must begin and end with
220 nonwhitespace characters. Note that each comment must appear on a line by
221 itself. If you attempt to add a comment to the end of an assignment, then the
222 comment will be interpreted as part of
224 It is useful to observe that the output produced by both the
230 specified) adheres to this file format.
232 This program does not implement any type of synchronization to ensure that
233 different processes don't stomp on each other when trying to access the
234 nonvolatile RAM simultaneously. Therefore, corruption of the BIOS parameter
235 values may occur if multiple instances of this program are executed
238 David S. Peterson <dsp@llnl.gov> <dave_peterson@pobox.com>
240 Stefan Reinauer <stepan@coresystems.de>