Why does my Xserve simply eject Linux install CDs instead of reading / booting from them?

I have an Xserve G4, dual 1.33 GHz processors, 2 GB of RAM, 1 CD-ROM drive, 2 internal Hard Drives (read: Nowhere really to back them up to). I also have 1 EXTERNAL Hard Drive, Firewire, but just like the internal drives, I can't reformat with any sort of ease, too much data. Now for the problem: I am trying to install Linux, specifically Gentoo or ArchLinux, for a multitude of reasons spanning from: wanting to get away from dependancy on Mac OS, to not liking the performance of old versions of Mac OS X in a modern (internet) age. I have Live CDs for Ubuntu 8, and the latest Gentoo Minimal Install PPC disk. I can not, however, get the computer to accept the CDs. About 20 seconds after inserting the CD to the body of the Xserve, it comes right back out. These are 700 MB CDs, with 680 MB and 140 MB of data on them, respectively. The burns had no errors, I have the console reports handy if they are requested. Possible solutions/diagnoses I have come up with, but can't act on without advice on how to:

• The CD drive is defective? (How do I test this?)
• Boot to one of my 2 spare (10 GB each) hard drive partitions on my HFS drive, no success on that front so far.
• Would using an external CD Drive work for boot-from-CD? I have one that connects using FireWire

Oh, just a note, my goal is to use mac-fdisk once I get within a Linux environment to see about resizing my hard drive, or I'll just backup the main drive's non-standard data to the external, and restore using the disk-image of 10.4 Server I have. Would mac-fdisk actually be able to resize, or is that just parted? Any help would be greatly appreciated. Thank you!