The iMac and possibly some other machines allow for netbooting the OS from another machine. This opens a number of possibilities for diskless clients and other fun things, but it can also be used to kick-off an install without burning a CD.

To do this you'll need to setup a dhcpd daemon or bootp daemon on your server, as well as tftpd.

tftpd daemon:

/etc/inetd.conf should have the following line enabled:

tftp    dgram   udp     wait    root    /usr/sbin/tcpd  in.tftpd

/etc/hosts.allow should be opened up for tftp on your local network:

in.tftpd:  192.168.192.

(This is my local network IP block - yours may vary)
If you have to change these, be sure to stop/start inetd:

/etc/rc.d/init.d/inet restart

The default directory is /tftpboot. As a minimum you'll need a Linux kernel, yaboot, yaboot.conf, and some sort of a ramdisk image (I'm showing a rescue image below):

bash-2.03$ ls -l /tftpboot/

-rw-r--r--   1 root     root      1243868 May 22 17:16 rescue.gz
-rw-r--r--   1 root     root      2455573 May 22 17:16 vmlinux
-rw-r--r--   1 root     root        58556 May 22 17:16 yaboot
-rw-r--r--   1 root     root         1396 May 22 17:20 yaboot.conf

dhcpd daemon:

For the dhcpd setup, you'll need the MAC address of your machine. In MacOS you can find this by going into the TCP/IP setup. If you're already running Linux on the machine try:

[stew@powerbook linux]$ dmesg | grep eth0
eth0: BMAC+ at 00:50:e4:b9:07:70

The series of hex numbers seperated by colons is the MAC address of the ethernet adapater. Now you need to setup /etc/dhcpd.conf:

default-lease-time            21600;
max-lease-time                21600;

option subnet-mask            255.255.255.0;
option broadcast-address      192.168.192.255;
option routers                192.168.192.1;
option domain-name-servers    192.168.192.1;
option domain-name            "ays.net";

shared-network WORKSTATIONS {
    subnet 192.168.192.0 netmask 255.255.255.0 {
    }
}

group   {
    use-host-decl-names       on;
 
    host imac {
        hardware ethernet     00:05:02:6B:45:29;
        fixed-address         192.168.192.5;
        filename              "/tftpboot/yaboot";
    }
}

Then start or restart dhcpd:

/etc/rc.d/init.d/dhcpd start

If the server starts up normally, you should see something like this in /var/log.messages:

May 22 17:19:06 moe dhcpd: Copyright 1995, 1996, 1997, 1998 The Internet Software Consortium.
May 22 17:19:06 moe dhcpd: All rights reserved.
May 22 17:19:06 moe dhcpd: Listening on Socket/eth0/WORKSTATIONS
May 22 17:19:06 moe dhcpd: Sending on   Socket/eth0/WORKSTATIONS
May 22 17:19:06 moe dhcpd: dhcpd startup succeeded

That should be it. Instead of holding down the "C" key on the Apple machine, use the "N" key and you should see the yaboot boot prompt.

I'm running an Iopener here as a diskless client, and you could apply the same techniques to the iMac. I know a guy here in Cleveland running a whole lab of iMacs, where he's netbooting them all (MacOS). This is great as an admin, as you don't have to worry about the users borking up the configuration. Just reboot and you're back to a clean setup.

You might want to checkout the for some more ideas of what you can do, now that you've got the iMac netbooting.