This how to shows how grub2 can be used to boot a PowerPC live/desktop iso file stored on a USB flash drive. It is an alternative to using the dd command or extracting the contents of the iso file.
This method is so easy my dog could do it!
I've tested this on a fat32 flash drive using an MS-DOS partition table. You'll have to do some adjustments if the flash drive is formatted with an Apple Partition Map (becuase the map takes up partition 1).
Copy the live/desktop iso file to the first partition of your USB flash drive.
Copy the attached files (grub.cfg, grub.img and ofboot.b) to the first partition of your USB flash drive.
Boot into openfirmware
Check you have fat support:
and look for the listing "/fat-files".
Find your usb partition using the dir command (this command lists files). Your partition will probably be usb0/disk@1:1 , usb1/disk@1:1 or ud:1
Then boot the ofboot.b file. For example:
You'll get some error message about prefix not being set. Just ignore it.
Choose your ubuntu derivative and machine from the menu. The menu entries are setup for 12.04, so if you've downloaded a different version you'll have to edit the menu entry by pressing 'e'. Change the isofile value to the name of the iso.
Your live system should now boot!
The gub.img was created with this command
If you want to re-run the command you need to install the grub-ieee1275 package.
sudo grub-mkimage --prefix="(grubdevice,1)" -o grub.img -O powerpc-ieee1275 -v part_apple part_msdos hfs hfsplus ext2 fat iso9660 loopback linux configfile