One Button Booting from Classic to MacOS X by Michael Coyle

Currently, if you have Classic MacOS and MacOS X on the same partition, switching from one to the other requires a trip to the Startup Disk control panel. The following tutorial, adapted from a YABOOT script for PPC/Linux, allows you to boot into MacOS X by holding the Space Bar at the beginning of a reboot.

Let me start by saying that nothing this edit does not harm your computer. It's possible that a typo can cause the computer to hang at boot time, but zapping the PRAM will cure the problem and return the computer to its original state.

Normally when the computer is started it looks for the location of the System Folder. With a simple text file and a few lines typed into Open Firmware, we can tell the computer to look at a text file for instructions first.

First, boot into MacOS X and launch the Terminal. Become the root super-user by typing "su" and then your password. We need to get the partition number where the System Folder (Classic) and System (MacOS X) reside.

The program that provides this information is pdisk. Below is the output of pdisk for my hard disk.

[localhost:~] coyle% su
Password: ********
[localhost:/Users/coyle] root# pdisk 
Top level command (? for help): L
/dev/rdisk0  map block size=512
   #:                 type name                 length   base     ( size )
   1:  Apple_partition_map Apple                    63 @ 1       
   2:       Apple_Driver43*Macintosh                54 @ 64      
   3:       Apple_Driver43*Macintosh                74 @ 118     
   4:     Apple_Driver_ATA*Macintosh                54 @ 192     
   5:     Apple_Driver_ATA*Macintosh                74 @ 246     
   6:       Apple_FWDriver Macintosh               200 @ 320     
   7:   Apple_Driver_IOKit Macintosh               512 @ 520    
   8:        Apple_Patches Patch Partition         512 @ 1032
   9:            Apple_HFS untitled           38057984 @ 1544     ( 18.1G)
  10:            Apple_HFS untitled 2          8192000 @ 38059528 (  3.9G)

Partition 9 contains my operating systems. Yours may be different, but the majority of Apple hard drives come from the factory with partioin 9 as the first bootable partition. Jot this number down so you don't forget it, then restart the computer into MacOS 9.

Open Simpletext and paste in the following:

If your boot partition was a number other than 9, be sure to change it in the text above. Save this file as bootinfo.txt and place it loose in your MacOS 9 System Folder.

The file bootinfo.txt tells the computer to see if the Space Key is being held down, if it is, boot the MacOS X system folder, otherwise boot Classic MacOS.

Maybe you have heard of the mysterious Open Firmware command on Apple computers. By holding the Option-Command-O-F keys at startup, you will see a screen of text that resembles the terminal in MacOS X. Below is the OF screen from my Powerbook:

Boot into Open Firmware and at the prompt, type the following three lines of text and hit return after each. (Change the partition number if yours is not 9!)

We just told the computer to look for the file bootinfo.txt and get its instructions from there.

After typing the three lines of text, type shut-down. Restart the computer and do not touch any keys. It should boot into MacOS 9. If it does, restart and hold the Space Key. It should now boot into MacOS X. If it does, send me a dollar for being a swell guy. :-)

If upon the first restart you get the Open Firmware prompt and an error message, restart the computer by holding the Control-Apple-Power keys and then immediately hold the Option-Apple-P-R keys until you hear the startup chime cycle twice. (This resets the PRAM). These are tricky keyboard maneuvers, so if you don't make it the first time, try again.

Look for errors in the bootinfo.txt file or the three lines you typed into Open Firmware. I have used this trick to boot into Linux and MacOS X on a variety of machines for several years, but it's possible there is a version of Open Firmware that this will not work under. Remember, if you get stuck, just reset the PRAM.

Be sure to read Part II for advanced techniques.