In order to perform this procedure, you will need an external FireWire hard drive, as well as copies of Mac OS X for both Intel-based and PowerPC-based Macs. You will also need access to both an Intel-based and a PowerPC-based Mac.
The normal disk formatting scheme you would use for booting an Intel-based Mac is GUID. For a proper dual-boot device, however, we cannot use this format. The reason is that there is no way to boot from a GUID partition on most PowerPC-based Macs (aside from the very newest G4 and G5 systems).
So the partition scheme we'll use is APS (Apple Partition Scheme).
Just as there is only one table of contents in a book, there is only one partition table on a hard drive. There is no way to hybridize the table so that it is legal in both GUID and APS, so you have to pick one or the other. Since we know that you cannot boot from a GUID drive on most of the PowerPC macs, APS is the format of choice.
Step 1: Format your drive with APS
Attach your external FireWire drive to a host system running Mac OS X. Now open Disk Utility (located in Applications/Utilities) and click on your FireWire drive in the left-hand pane.
Next click the "Partition" tab, and then click the "Options" button in the lower portion of the Window. Select "Apple Partition Map" from the list, then click "OK."
Step 2: Partition the drive Now you will need to set up your hard drive with the various partitions you will need. Your partition list should look something like this, with approximate sizes you should use in parentheses.
- Service PPC (~10GB)
- Service Intel (~20 GB)
- Service Classic (~2 GB) [optional]
- Users (~2 GB)
- Data partition (rest of space)
Click the partition button, and wait for the process to complete, then eject the drive and disconnect it from the host system.
Note that while the title of this article mentions a dual-boot drive, you actually have the option to create a triple-boot drive that is also capable of booting Mac OS 9 systems. If you do not intend to boot Mac OS 9 systems, do not create the "Service Classic" partition and skip the following paragraph.
Step 3: Install Mac OS 9 (optional) To populate the Classic partition, simply connect the drive to a Mac OS 9 system, then drag and drop the System Folder and Applications directories to the "Service Classic" partition. If you are installing from a Mac OS 9 restore CD, follow the instructions listed in the tutorial "Installing Classic over a current Mac OS X installation.". While the FireWire disk is still attached to the Mac OS 9 Mac, open the "Startup Disk" control panel and select the "Service Classic" partition as your startup drive. This "blesses" the classic installation and will make it be able to appear in the boot-picker when you hold the option key at startup. Again, this requires a machine that can boot OS 9.
Step 4: Install Mac OS X for PowerPC This is the easiest part of this process -- simply connect your drive to a PowerPC-based Mac OS X system, then insert the Mac OS X PowerPC installer disk, restart, and install Mac OS X on the Service PPC partition. Boot from this partition and apply the appropriate updates.
Step 5: Install Mac OS X for Intel This step is a bit more tricky, because the Mac OS X for Intel installer will not allow direct installation on an Apple Partition Scheme drive.
If you attempt to run the installer, it will say "you cannot install Mac OS on this volume. You cannot start up from this hard drive". This is not true, but installation will be prevented nonetheless.
What you will need to do is the following:
- Install a bare-bones copy of Mac OS X for Intel on a GUID-formatted drive. Avoid installing any extra languages, print drivers, etc.
- Connect your external FireWire drive to the Intel-based Mac with the bare-bones copy of Mac OS X for Intel.
- Open Disk Utility and select the bare-bones Mac OS X for Intel installation partition (where you just installed Mac OS X for Intel) in the left-hand pane.
- Go to the "File" menu, and select "New > Disk Image from disk0..."
- Save the disk image.
- Now select the "Service Intel" partition on your FireWire hard disk, and click the "Restore" tab.
- Next to the "Source:" field, press the "Image..." button, then select the disk image you just created.
- Go to the "Startup Disk" pane of System Preferences, and select the Mac OS X for Intel installation on your FireWire hard disk in order to bless it and make it accessible from the boot-picker.
- When you startup from the Mac OS X for Intel installation on your FireWire disk, use the same username as on your Mac OS X for PowerPC installation.
You should now be able to boot from the hard drive on all three volumes, on the architecture-appropriate Macs. Test them all, and repeat the steps above if one or more doesn't work.
Step 6: Create a shared Users folder This process will create a shared user folder so that you can have a single account to manage all of your booting partitions. This way, no matter which architecture (PowerPC or Intel) you boot, you will have access to the same settings and information.
- First, boot from the FireWire hard disk on a PowerPC-based Mac. Create a new folder inside the "Users" partition, and name it "Users".
- Now drag and drop your home folder into the new "Users" folder.
- Next, open "NetInfo Manager" (located in Applications/Utilities). Click the lock at the bottom of the screen and enter your administrator password to authenticate.
- Click on "users" in the middle pane, and find the username you setup on your PowerPC partition, e.g.: /Users/(name of user)
- In the Property field at the bottom of the window, look for the "home" property. Double-click the value "/Users/(name of user)" and change it to "/Volumes/Users/Users/(name of user)" (without quotation marks).
- Next go to the "Management" menu at the top of the screen and select "Restart local netinfo domains."
- Log out and back in. Your home icon should now be in the Users folder you made.
Now boot from the FireWire hard disk on an Intel-based Mac and repeat the above steps (except for copying the user folder). This time when you log out and back in again, you will see the exact same home folder you had on the other platform. The two are now sharing the one home folder. Changes made on one architecture will occur for the other as well.
You now have a triple booting service drive with shared home folder. You may have to adjust permissions and other settings folders at the root of the users folder you copied, since just being dragged they didn't maintain the special permissions of the files at the root of your users folder.
[Thanks to Virtual1 for contributing to this article]
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