Michael Eng

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How to set up a multi-boot menu in Open Firmware

This page describes a number of Open Firmware commands on modern Apple Macintoshes. These commands permit the use of a boot menu, allowing the user to easily switch between Mac OS 9, Mac OS X, Linux, multiple boot devices, and so on.

HEALTH WARNING: It is possible to stop your computer from booting, leaving you with a dead Mac, or at worst to damage your hardware by inadvertent modification of hardware parameters in Open Firmware. In addition, Apple Support may refuse to support your Mac with such modifications in place. It is normally possible to reset Open Firmware variables to default settings by holding down Command-Option-P-R simultaneously whilst switching on the machine.

You should note that the management will not be responsible for any damage or distress caused by the correct or incorrect use of the software or commands specified on this page. So there.

Introduction

Open Firmware is a inbuilt FORTH interpreter on the Mac which allows specification of boot variables and modification of system parameters, amongst other things. For readers familiar with Sun equipment, Open Firmware is very similar in design and use to Sun OpenBoot, as they conform to the same specification. In fact, many of the commands are compatible.

One of the principal differences between Open Firmware and OpenBoot is that Open Firmware is not designed for use by end-users. For this reason, there is relatively little help and documentation available. Primarily, documentation is provided in three Apple Developer TechNotes (see REFERENCES for details).

Getting Started

On 'new-world' Macs (from the iMac onwards), it is possible to get into Open Firmware by holding down Command-Option-O-F during power on (before the 'Happy Mac' or Apple logo appears on the display).

The following commands can then be typed at the prompt. The command reset-all will reboot the machine, writing any changes.

Boot Menu

Download bootstrap to the root of your boot hard disk. Note that this is a plain-text file with Mac line breaks, not Unix line breaks. SimpleText on OS 9 can be used to edit such a file.

A Unix text version of bootstrap can be downloaded here. It is highly recommended that you examine the file carefully before installing it in your system!

Now enter the following commands in OF to load the bootstrap:

setenv boot-command boot
setenv boot-device hd:\bootstrap
reset-all

Other useful tricks

Boot OS X with console enabled

This allows you to see the boot messages on the console as the system comes up and down. It is similar to holding down V at boot time.

setenv boot-args -v
reset-all

Dual-display on iBook

This is the well known modification which allows dual-head operation on some models of iBooks and iMacs.

nvedit
" /" select-dev
00000008 " graphic-options" get-my-property 2drop !
unselect

[press control-c to leave nvedit]

nvstore
setenv use-nvramrc? true
reset-all

Enabling boot-time password protection

password
setenv security-mode full
reset-all

To switch off password protection:

setenv security-mode none
reset-all

References

Apple Technotes TN1044 TN1061 TN1052 and TN2001 are relevant.

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Michael Eng

my e-mail address is meng ! daydream . org . uk, but replace the ! with @ and remove the spaces