When you downloaded Ubuntu for PowerPC, did you use Disk Utility to copy the image to the USB thumbdrive? You should not be selecting any compression schemes at all. Just use the "Restore" to restore the image to the USB thumbdrive.
Assuming, this is the only USB device you are using, go into open firmware and type the following:
devalias or dev /ls = What you will be looking for is anything that says "ud" in it. Lastly, once you find the "ud" type this:
boot ud:\\:tbxi - this should boot ubuntu, eliminating the need to type "boot usb1\disk@1:1;:/install/yaboot". Remember, you need to look for anything that says: ud,ud1, etc.. ud=ud0 which is the 1st USB device.
Let me know if this works for you.
P.S.: I have been booting USB on my PB G4 and PowerPC macs for almost 5 years now.. Its not hard at all.
I am getting exactly the same result as 123456789abcdefghi. I get the circle with the line through the middle. Please let me know if you have solved this problem. I think it could be the iso I am using, or the fact that I didn't use Disk Utility to copy the image to the usb thumb drive. I only have one machine that can run osx and that is my PowerBook G4, which currently has a broken hdd and broken optical drive. So I don't have access to Disk Utility. I am using Windows and have tried 'Rufus', 'UNetbootin' and 'ISO to USB'. None of them worked.
If you could point me to the iso you have used to create a working installer and whether you used Disk Utility or some other loader like the ones I have mentioned then I would be very greatful.
Let me know.
Has anybody any reference of this being possible? To boot Linux from USB on a PPC Mac? I haven't read about it, but that doesn't mean it isn't possible.
I know Linux doesn't boot as OSX from an external firewire CD or drive. But FreeBSD does, but I'm not far in my FreeBSD knowledge so I won't be able to help past the command line. But to there it's really very easy from CD. You may download an USB image specially made for PPC but I don't know if it will boot from USB. If somebody want to try.
If the PPC Mac is without internal drives I'd rather go for external firewire devices, smaller drives can be had second hand and even firewire CD drives. I got one really cheap and was surprised to find it capable of booting PPC Macs, it's a Dell SEM-Q10E CD drive. I also had another slim drive so I upgraded it to DVD/CDRW combi, but this won't do for all slim drives as I tried another one first which didn't boot.
In any case I would rather try Lubuntu with the less demanding LXDE desktop than plain Ubuntu. The Ubuntu-family installer requires 750-1000MB RAM depending on what you do, so installing a Linux in the Ubuntu-family requires a powerful computer. In use Lubuntu will be able to get going at 256MB RAM. Installing Debian is easier and less demanding on ressources, but then it's less easy to add software with Debian. To my knowledge for Linux you require an internal CD and/or hard drive, unless someone manages to boot from USB.