Mac OS X Panther in a Nutshell, 2nd Edition

Name

nvram

Synopsis

nvram [ -p] [-f filename] [name ] [= value ] ...
                  

Modifies Open Firmware variables, which control the boot- time behavior of your Macintosh. To list all Open Firmware variables, use nvram -p. The Apple Open Firmware page is http://bananajr6000.apple.com.

To change a variable, you must run nvram as root or as the super_user. To set a variable, use variable=value. For example, to configure Mac OS X to boot verbosely, use nvram boot-args=-v. (Booting into Mac OS 9 or earlier resets this.) The table in this section lists Open Firmware variables. Some variables use the Open Firmware Device Tree notation (see the TechNotes available at the Apple Open Firmware page).

Tip

Be careful changing the nvram utility, since incorrect settings can turn a G4 iMac into a $2000 doorstop. If you render your computer unbootable, you can reset Open Firmware by zapping the PRAM. To zap the PRAM, hold down Option--P-R as you start the computer, and then release the keys when you hear a second startup chime.

Options

-f filename

Read the variables to be set from filename, a text file of name=value statements.

-p

Display all Open Firmware variables.

Variable	Description
auto-boot?	The automatic boot settings. If true (the default), Open Firmware automatically boots an operating system. If false, the process stops at the Open Firmware prompt. Be careful using this with Old World (unsupported) ...