nvram — non-volatile RAM
Contents
Description
The nvram driver provides access to BIOS configuration NVRAM on i386 and amd64 systems.
PC motherboard uses a small non-volatile memory to store BIOS settings which is usually part of its clock
chip and sometimes referred as “CMOS SRAM”. This driver exposes bytes 14 through 128 of the NVRAM, or a
total of 114 bytes, at offset zero of the device file /dev/nvram.
This driver is useful for cloning machines that shares the same hardware configuration and need same BIOS
setting tweaks.
Examples
Backup existing BIOS NVRAM to nvram.bin:
ddif=/dev/nvramof=nvram.bin
Restore BIOS NVRAM from nvram.bin:
ddif=nvram.binof=/dev/nvramHistory
The nvram device driver first appeared in FreeBSD 6.4.
Implementation Notes
The BIOS NVRAM's bytes 16 through 31 are checksummed at byte 32. This driver doesnot take care for
these checksums.
Name
nvram — non-volatile RAM
See Also
dd(1)
Synopsis
To compile this driver into the kernel, place the following line in your kernel configuration file:
devicenvram
Alternatively, to load the driver as a module at boot time, place the following line in loader.conf(5):
nvram_load="YES"
