Ask Different is a question and answer site for power users of Apple hardware and software. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I have an old iBook (2003, G4) with a burnt-out harddrive. Being a poor academic, I don't want to bother with replacing the drive. I'd like to use an external USB drive in place of the harddrive. I managed to get a copy of MacOSX (it was Tiger at the time of the burnout) onto a USB before the harddrive completely gave out (it seemed to be a problem with overheating so I took it into the coldest part of the house and copied it there). But all my experiments in the open firmware came to naught: it seems that my iBook is too old to be able to boot directly from a USB.

Under Linux, this is not a problem. I can put the kernel and boot stuff onto a CD. The iBook will happily boot from a CD. Then I can tell the kernel to find its root device from the USB stick (via a UUID). This works well, and is my current system.

But I miss Mac OSX ... a little. More so now that I have an iPad and don't want to have to use Windows to sync stuff with it. Plus, I hate the fact that I got so close and yet couldn't quite get it to work.

So ... is it possible to specify a different root device to a MacOSX kernel than the device it is booted from?

share|improve this question
Have you tried booting with the instal CD for 10.4 and using Disk Utility to format your USB drive as APM / HFS+ and seeing if the installer will instal the OS onto a USB drive? Although not "advertised" most of the iBooks I remember would boot from USB drives. Maybe we cloned them / created them from FireWire interface - it's been a while... – bmike Oct 25 '11 at 19:18
@bmike: I'm pretty sure I've tried that (admittedly it's been a while since I last tried this) but Tiger wouldn't install onto a USB stick. – Loop Space Oct 26 '11 at 19:18

If your USB drive is partitioned with Apple Partition Map and the volume with Mac OS X is HFS+ formatted it will probably boot iBook G4 by simply holding Alt/Optn at startup and choosing said disk.

This may not work on occasion of USB chipset in external box is not compatible.

It will probably not work if you just copied content of your hard drive and not restored it through Disk Utility (or cloned by other means).

If you cloned it properly and it still not booting try this Open Firmware trick.

P.S. Here is a link on how to change HDD if you will decide to go that route. I've done it few times. I've been putting this drive inside. But now I would definitely buy IDE 2.5 32GB SSD from ebay for the same money but better speed. Still I'm not sure if it worth it if you have one of the slowest of iBook G4 models.

share|improve this answer
The "copying" was via dd, is that good or bad? That blog post brought back memories - when I was originally trying this I'd have nightmares about pci@f200000 stuff! – Loop Space Oct 25 '11 at 20:31
I believe dd is fine for the purpose, still I can't attest since I'm not a terminal guy. I will update the answer with the link on how to change that iBook HDD just in case. – iskra Oct 26 '11 at 19:14

First, boot into Open Firmware shell. Then execute

dev / ls

and look for your USB drive. There should be something like

ff98ab00:    /usb@01
ff9a4f80:      /disk@1

then type


and look up the alias name of your USB drive. Then you can issue the boot command


where is the <devalias> you gathered in the second step (something like usb3), <device> the id of the actual drive which you can see from the first step in the line after your usb device (in this example they are /usb@01 and disk@1) and <partition> the partition number of OS X root partition, most likely 1.

If that starts to you boot, but then panics, try setting the root device explicitly and redo the procedure. Back in the OF shell:

nvram rd=disk<num>s<partition>

where <partition> is the same as above and <num> is a best guess of the devices path of your usb device. It's most likely 1 or 2. Then repeat the steps above.


share|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.