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NVRAMTOOL(8)		    System Manager's Manual		  NVRAMTOOL(8)

NAME
       nvramtool - read/write coreboot-related information

SYNOPSIS
       nvramtool [OPTS]	[-n] -r	NAME
       nvramtool [OPTS]	-e NAME
       nvramtool [OPTS]	-a
       nvramtool [OPTS]	-w NAME=VALUE
       nvramtool [OPTS]	-p INPUT_FILE
       nvramtool [OPTS]	-i
       nvramtool [OPTS]	-c [VALUE]
       nvramtool [OPTS]	-l [ARG]
       nvramtool [OPTS]	-d
       nvramtool [OPTS]	-Y
       nvramtool [OPTS]	-b OUTPUT_FILE
       nvramtool [OPTS]	-B INPUT_FILE
       nvramtool [OPTS]	-x
       nvramtool [OPTS]	-X DUMPFILE
       nvramtool [OPTS]	-v
       nvramtool [OPTS]	-h

DESCRIPTION
       nvramtool is a utility for reading/writing coreboot parameters and dis-
       playing information from	the coreboot table.

       The coreboot table resides in low physical memory.  It  is  created  at
       boot  time by coreboot, and contains various system information such as
       the type	of mainboard in	use.  It specifies locations in	the CMOS (non-
       volatile	RAM) where the coreboot	parameters are stored.

       This  program  is  intended  for	(x86-based) systems that use coreboot.
       For information about coreboot, see
       http://www.coreboot.org/.

PARAMETERS
       [-n] -r NAME
	      Show the value of	the coreboot parameter given by	NAME.	If  -n
	      is  specified, show only the value.  Otherwise show both parame-
	      ter name and value.

       -e NAME
	      Show all possible	values for parameter given by NAME.

       -a     Show the names and values	for all	coreboot parameters.

       -w NAME=VALUE
	      Assign VALUE to coreboot parameter given by NAME.

       -p INPUT_FILE
	      Assign values to coreboot	parameters according to	 the  contents
	      of INPUT_FILE.  The format of this file is described below.

       -i     This  is	similar	 to the	-p option, except that the contents of
	      the input	file are taken from standard input.

       -c [VALUE]
	      If VALUE is present then set the CMOS checksum for the  coreboot
	      parameters to VALUE.  Otherwise, show the	checksum value.

       -l [ARG]
	      If  ARG is present then show information from the	coreboot table
	      as specified by ARG.  Otherwise show  all	 possible  values  for
	      ARG.

       -d     Do a low-level dump of the coreboot table.

       -Y     Write CMOS layout	information to standard	output.	 If redirected
	      to a file, the layout information	may be used as input  for  the
	      '-y LAYOUT_FILE' option (see below).

       -b OUTPUT_FILE
	      Write  the  contents  of	CMOS  memory  to  the binary file OUT-
	      PUT_FILE.	 The first 14 bytes of OUTPUT_FILE do not contain  ac-
	      tual  CMOS  data,	 and are always	written	as zeros.  This	is be-
	      cause the	first 14 bytes of the CMOS area	do  not	 contain  CMOS
	      memory.	These  bytes  are involved with	the functioning	of the
	      real time	clock.

       -B INPUT_FILE
	      Read binary data from INPUT_FILE and write the data to CMOS mem-
	      ory.   The  first	14 bytes of INPUT_FILE are skipped and data is
	      written to CMOS starting at the 15th  byte  of  the  CMOS	 area.
	      This  is because the first 14 bytes of the CMOS area do not con-
	      tain CMOS	memory.	 These bytes are involved with the functioning
	      of the real time clock.

       -x     Show  a  hex  dump  of all CMOS data.  The first 14 bytes	of the
	      dump do not contain actual CMOS data, and	are  always  shown  as
	      zeros.   This  is	because	the first 14 bytes of the CMOS area do
	      not contain CMOS memory.	These  bytes  are  involved  with  the
	      functioning of the real time clock.

       -X DUMPFILE
	      Read  binary data	from DUMPFILE (presumably a CMOS dumpfile cre-
	      ated using the -b	OUTPUT_FILE option) and	show a hex dump	of the
	      data.

       -v     Show version information for this	program.

       -h     Show a help message for this program.

OPTIONS
       In all cases above, [OPTS] evaluates to the following:

	   [-y LAYOUT_FILE | -t]

       The  '-y	 LAYOUT_FILE' option tells nvramtool to	obtain CMOS layout in-
       formation from the contents of LAYOUT_FILE.  Likewise, the '-t'	option
       tells  nvramtool	to obtain CMOS layout information from the CMOS	option
       table (contained	within the coreboot  table).   If  neither  option  is
       specified,  the CMOS option table is used by default.  LAYOUT_FILE fol-
       lows the	format of the cmos.layout files	provided by coreboot.

       If the coreboot installed on your system	was built  without  specifying
       CONFIG_HAVE_OPTION_TABLE,  then	the  coreboot table will not contain a
       CMOS option table.  In this case, the '-y LAYOUT_FILE' option  must  be
       used.

       These  two  options  are	silently ignored when used in combination with
       other options (such as -h, for instance)	for which they are not	appli-
       cable.

FILE FORMAT
       For  the	-p option, INPUT_FILE must consist of a	sequence of lines such
       that each line is either	a blank	line, a	comment, or an assignment.   A
       blank  line consists only of zero or more whitespace characters (spaces
       and tabs).  A comment is	constructed as follows:

	   [ws]#[text]

       Here, [ws] indicates optional whitespace	characters  and	 [text]	 indi-
       cates  optional	text.	Blank lines and	comments are both ignored.  An
       assignment is constructed as follows:

	   [ws]NAME[ws]=[ws]VALUE[ws]

       Here, NAME is the name of a coreboot parameter and VALUE	is  the	 value
       that  will be assigned to NAME.	VALUE is allowed to contain whitespace
       characters, but it must begin and end  with  nonwhitespace  characters.
       Note that each comment must appear on a line by itself.	If you attempt
       to add a	comment	to the end of an assignment, then the comment will  be
       interpreted  as part of VALUE.  It is useful to observe that the	output
       produced	by both	the -a and the '[-n] NAME' options (without -n	speci-
       fied) adheres to	this file format.

BUGS
       This  program  does not implement any type of synchronization to	ensure
       that different processes	don't stomp on each other when trying  to  ac-
       cess  the nonvolatile RAM simultaneously.  Therefore, corruption	of the
       BIOS parameter values may occur if multiple instances of	 this  program
       are executed concurrently.

AUTHORS
       David S.	Peterson <dsp@llnl.gov>	<dave_peterson@pobox.com>
       Stefan Reinauer <stepan@coresystems.de>

				September 2008			  NVRAMTOOL(8)

NAME | SYNOPSIS | DESCRIPTION | PARAMETERS | OPTIONS | FILE FORMAT | BUGS | AUTHORS

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