nvram(4) non-volatile RAM


To compile this driver into the kernel, place the following line in your kernel configuration file:
device nvram

Alternatively, to load the driver as a module at boot time, place the following line in loader.conf5:



The 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.


The BIOS NVRAM's bytes 16 through 31 are checksummed at byte 32. This driver does not take care for these checksums.


Backup existing BIOS NVRAM to nvram.bin

dd if=/dev/nvram of=nvram.bin

Restore BIOS NVRAM from nvram.bin

dd if=nvram.bin of=/dev/nvram


The device driver first appeared in Fx 6.4 .


An -nosplit The device driver was written by An Peter Wemm . This manual page was written by An Xin LI .