YDL 4.0 network boot on Xserve G5

[norman@cs.toronto.edu (Norman Wilson)]

I'm trying to install Yellow Dog Linux 4.0 on an Apple Xserve G5.
For strategic reasons I'd rather boot and install over the network,
but I'm having trouble getting yaboot to do what I want.

I'm using the yaboot supplied in the Yellow Dog distribution; it
appears to be version 1.3.10.

First problem: it can't read a configuration file.  Starting from
the Open Firmware prompt:

  0 > boot enet:0,yaboot 
  CLIENT: 000d939bc29c 192.168.70.141
  SERVER: 000c6e6e66bb 192.168.70.124 
  Transfer FILE: yaboot /
  TFTP-actual=2397c TFTP-adler32=7b502b4c load-size=2397c adler32=7b502b4c 

  Loading ELF


  method 'load' failed fffffefc
  Error, can't read config file
  Welcome to yaboot version 1.3.10
  Enter "help" to get some basic usage information
  boot:

I can see from network traces that it doesn't even try to fetch
yaboot.conf from the TFTP server.  Can anyone tell me why not,
and how to straighten it out?

Second problem, which may make the first irrelevant: I tried loading
the kernel directly from the network.  Yaboot finds it and tells
the firmware to read it, but then all falls down:

  boot: enet:0,vmlinux-2.6.8-1.ydl.7g5
  Please wait, loading kernel...
  CLIENT: 000d939bc29c 192.168.70.24
  SERVER: 000c6e6e66bb 192.168.70.124 
  Transfer FILE: vmlinux-2.6.8-1.ydl.7g5 method 'load' failed 00000300

  Can't read Elf e_ident/e_type/e_machine info
  boot: 

Network traces show the kernel file being loaded correctly, though I
haven't counted packets to make sure.  I have fetched each of the
files through the tftp command on another system, so I am sure the
server is serving up the right stuff.

A bit of Googling turns up a note suggesting that yaboot version 1
cannot handle a TFTP image larger than 4MB.  If so, that's the second
problem: the kernel I'm trying to load is 4621928 bytes.

Suggestions?  Might a newer yaboot help, or is all of this stuff that
won't get better until version 2?

Norman Wilson
Systems research lab, Department of Computer Science
University of Toronto