How do I make my 1.5 GHz PowerBook G4 boot from a USB stick?

I have done this many times since I posted this question.

1. Create usb stick like this:

   sudo dd if=/<path to iso file>/<name of iso file> of=/<path to usb stick> bs=32768 conv=notrunc,noerror,sync
   

2. Put the USB stick into your Mac and press the power button while holding down Command ⌘+Option+O+F

3. At the prompt, type the following:

   boot usb1/disk@1:,\\yaboot
   

Note: If you are booting linux then use ,\\yaboot, but if you are booting a Mac OS use ,\\tbxi.

Note 2: If your stick is in the right side of the machine, then you need to do this:

boot usb0/disk@1:,\\yaboot

Note 3: If these commands don't work, then there is most likely a problem with your media or iso file.

I have found that Ubuntu, Debian, and openSUSE work great. I cannot get Fedora or Gentoo to boot this way yet. My optical drive does not work anymore, so this is how I install OS X on my machine. I made a live USB stick of the OS X install disc this way.

boot usb1/disk@1:,\\yaboot

OR

boot usb1/disk@1:,\\tbxi

is not a complete command. You need to list a partition number after the ":"

for example, if you are trying to install on a Mac, you will need to enter something like this

boot usb1/disk@1:10,\\tbxi

(where "10" is the partition number of the usb drive, disk@1 in this example).

To find out the partition number where OSX is located on your USB, use Disk Utility, Click on the partition you set up with OS X and then R-click or Ctrl-L click and select "Information".

You will get something to the effect of: disk1s10

s10 is the partition number. Refer to the example above.

This thread is old, but i want to add some information that may be useful:

On a Powerbook G4 A1138 (1,67 Ghz 15" late 2005) the above instructions didn't work out of the box. I used the finnix ppc rescue ISO, dumped with dd to the usb key.

1.) OF creates the devalias ud for the usb key in the left port. This ud alias maps to /pci@f2000000/usb@15/disk@1

2.) You can call yaboot with boot ud:2,\\yaboot - but then the kernel will panic because it still searches his initrd + rootfs somewhere at cd:2,/ ... (the cd alias is hardcoded inside files like ofboot.b, yaboot.conf ... on the ISO)

3.) Quick and dirty workaround: overwrite the cd alias in OF with the path to your USB Key (copy the path from the ud alias): devalias cd /pci@f2000000/usb@15/disk@1

4.) Now boot with boot cd:2,\\yaboot

5.) No problem anymore with hardcoded cd alias - it's now poiting to your USB Key. You can just choose a default kernel entry - *finnix in my case - and it will boot properly.

The alias will be resetted to default at the next cold boot and thus you will have to repeat the procedure for every USB-boot.