bootable usb-stick forPB G4 17" ?

[farinet at arcor.de]

Am 25.04.2014 22:20, schrieb lubuntu-users-request at lists.ubuntu.com:
> I boot from USB stick on a Titanium PowerBook G4.  Use dd to put the
> image onto the stick then do something like the following at the OF boot
> prompt:
> 
> 	boot usb1/@1:2,\\yaboot
> 
> It will be either usb1 or usb0 depending on the port used.

I did the following (on an amd machine):

---
dd if=~/Downloads/lubuntu-14.04-desktop-powerpc.iso bs=1M of=/dev/sdb
---

Apparently that worked well (the usb stick looks fine so far).

Then, at the yaboot prompt (on the PB - it was not used for a couple of
years - there is an old and totally messed up debian ppc installation) i
put in like you suggest (not so easy since i've a german keyboard layout
and the mac 3rd level chars are on unusual places ;) ):

---
boot usb1/@1:2,\\yaboot
---

But unfortunately that gives me an error:

---
Please wait, loading kernel ...
boot: Not a valid ELF image
---

I'm clueless at this point.

TIA for your patience!