Howto:
  1. Install Debian Etch, or Lenny!

  2. Add
    deb http://www.atlantech.com/~john/openssi-etch ./
        
    to your sources.list

  3. Add
    Package: *
    Pin: origin www.atlantech.com
    Pin-Priority: 1000
        
    to your /etc/apt/preferences

  4. Create a file /etc/apt/apt-conf.d/90allow-unauthenticated containing:
    APT::Get::AllowUnauthenticated "true";
        
  5. apt-get update

  6. apt-get install initrd-tools

  7. If you're using Debian Lenny then:
    apt-get remove nfs-common
        
    You can add it back again later if you want it.

  8. Add the module for your cluster-interconnect nic to /etc/mkinitrd/modules

  9. As we're going to remove the running kernel we must modprobe all modules needed to build the initrd or we won't be able to make a bootable system (don't forget this or you'll be stuck with an unbootable system):
    modprobe loop
    modprobe ext2
        

  10. apt-get dist-upgrade

    At this point you will be warned that the running kernel will be removed.  This is because of a necessary downgrade of udev.  Allow it to happen.

    :-(  Warning - your system is unbootable starting from this point.

  11. apt-get install openssi

    configure the node number, cluster interconnect,2 clustername, root failover as usual.

  12. apt-get install syslinux if it's not already installed (temporary step due to an error on my part).

  13. :-)       Your system should now be rebootable.  Reboot it.

  14. The current version of dhcpd has an irritating "bug" - it no longer has a default for the "next-server" option (i.e. the address of the tftp server).  You'll have to add the option:
    next-server xxx.xxx.xxx.xxx;
        
    (where xxx.xxx.xxx.xxx is the cluster interconnect address for the initnode) to the file /etc/dhcp3/dhcpd.proto

  15. run:
    mkdhcpd.conf
  16. run:
    invoke-rc.d dhcp3-server restart
        
  17. Now you can try booting a secondary node with etherboot or PXE, then ssi-addnode as usual
Still many rough edges, and the kernel is not up-to-date with Roger's latest work, put it works somewhat.

All the sources are available for "apt-get source" at the same location as the binaries.