NVRAMTOOL(8) | System Manager's Manual | NVRAMTOOL(8) |
nvramtool - read/write coreboot-related information
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
nvramtool is a utility for reading/writing coreboot parameters and displaying 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 (nonvolatile RAM) where the coreboot parameters are stored.
This program is intended for (x86-based) systems that use
coreboot. For information about coreboot, see
https://www.coreboot.org/.
In all cases above, [OPTS] evaluates to the following:
[-y LAYOUT_FILE | -t]
The '-y LAYOUT_FILE' option tells nvramtool to obtain CMOS layout information 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 follows 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 applicable.
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] indicates 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 specified) adheres to this file format.
This program does not implement any type of synchronization to ensure that different processes don't stomp on each other when trying to access the nonvolatile RAM simultaneously. Therefore, corruption of the BIOS parameter values may occur if multiple instances of this program are executed concurrently.
David S. Peterson <dsp@llnl.gov>
<dave_peterson@pobox.com>
Stefan Reinauer <stepan@coresystems.de>
September 2008 |