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cmos

Introduction

LinuxBIOS supports a number of configuration options in CMOS. After booting, LinuxBIOS leaves a table in RAM which details the available option values. The table, and the current cmos settings are accessed by cmos_util.

cmos_util [-d | -u] [-s] [–image filename]

-d dumps current settings to stdout

-u reads desired settings form stdin

Because cmos_util must access system memory and can change the operation of the system, it must be run as root.

The configuration format is human readable ASCII text consisting of options seperated by #####

Within each group will be a series of <option> = <value> statements representing all of the possible values for the option. All but one will be commented out by a '#' at the beginning of the line.

so:

cmos_util -d >cmos.config

Would yield a file containing (amongst other options):

#####

baud_rate = 115200 # baud_rate = 57600 # baud_rate = 38400 # baud_rate = 19200 # baud_rate = 9600 # baud_rate = 4800 # baud_rate = 2400 # baud_rate = 1200

#####

hyper_threading = Enable # hyper_threading = Disable

In the preceeding example, the serial console is to run at 115200 baud, and hyperthreading is to be enabled.

To disable hyperthreading, edit the file to look like:

#####

baud_rate = 115200 # baud_rate = 57600 # baud_rate = 38400 # baud_rate = 19200 # baud_rate = 9600 # baud_rate = 4800 # baud_rate = 2400 # baud_rate = 1200

#####

# hyper_threading = Enable hyper_threading = Disable

Then:

cmos_util -u <cmos.config

cmos.txt · Last modified: 2010/04/15 21:18 (external edit)