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Mac OS X Tiger in a Nutshell by Jason McIntosh, Chuck Toporek, Chris Stone, Andy Lester

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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 superuser. 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).

Warning

Be careful changing the nvram utility, since incorrect settings can turn a G4 iMac into a $2,000 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.

-d variable

Deletes Open Firmware variable variable.

-p

Display all Open Firmware variables.

Table 2-5. 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 ...

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