I've not had any success booting from a CD or DVD with various PPC versions of Ubuntu using any of the suggested keys such as "C". The only thing that has worked consistently for me is booting into open firmware. The problem I am now running into is that when I tell OF to boot from the CD it can't find the \install\yaboot file. I think this is because the CD is burned with an iso disk image. How do I either (a) reference the disk image in the CD boot command (e.g., boot cd:,\install\yaboot doesn't work) or (b) burn a non-iso CD?
Right now I'm working with the 10.04 Desktop distro.