Rumor has it that:
Open Firmware is a bootup scheme that initializes the hardware in your 
machine right after you turn it on. If you have Open Firmware you can 
set it to boot either the macos or Linux. Under the Macos there is a 
program called boot variables that you can use to modify the OF 
variables. Under Linux the program is called setnvram
jcarr@linuxppc.org

Ehh... make that command under linux 'nvsetenv'.

Also note that access to /dev/nvram was (and still is, but there are patches) broken in 2.3.x kernels.

Michel Lanners <mlan@cpu.lu>