Technical Q&A HW45

Invoking the Open Firmware user interface

Q: How is the Open Firmware user interface invoked?

A: There are two ways to invoke the interface; either one will accomplish the same behavior from Open firmware. The first method is to hold down the Command-Option-O-F keys while starting your Macintosh. This key sequence will stop the boot sequence at the Open Firmware user interface.

The second method is more complicated, but will stop the boot sequence at the Open Firmware user interface every time the computer is started from a cold or warm restart. Use the first method (Command-Option-O-F) to get into the interface. Type "printenv" to list the configuration variables. Note the variable called "auto-boot?" which has a default value of True. Changing this value to False will invoke the user interface every time the computer is started until the value is returned to true. Here is how to change that variable using the Forth word setenv:

    setenv auto-boot? false

There are two ways to return the variable to default. As you might guess:

    setenv auto-boot? true

The other method will reset all configuration variables, however. With the computer turned off, start the computer with the Command-Option-P-R keys depressed. Wait until the second peep before releasing the keys.