You use a TFTP server (rather than FTP server) coupled with a DHCP server to drive the serverside of the PXE boot process. The DHCP is required by PXE, but it *SHOULD* be possible to specify an IP address (and "nodhcp") in the APPEND line of the pxelinux.cfg/default file, though it doesn't work for me. You then use a Network File System (NFS) server to mount the image over the network so that it can be read by the client.

While FTP is capable of GETting designated parts of files by resuming then closing, there is no "FTPFS" for Linux - and even if someone wrote one now, it would need to be integrated into the Knoppix startup. It would probably also be a rather messy setup with many corners cut for general filesystem compatibility.

You *could* TFTP the entire Knoppix image to the client at PXE time, but that would take ages and you'd need about 800Mb RAM to make it useable. As I understand it, NFS allows the client to access bits of the file instead of having to load the whole thing in first. That's why the CDROM keeps spinning while you're using Knoppix - it keeps going back for more.

IF you only have 1 client machine, you can set up your DHCP to give out IPs with a range of 1, e.g. from 192.168.0.65 to 192.168.0.65. Then your client would always get the same address. What I have found, using the Tftp32d by Ph. Jounin, is that if I'm using only one client it always gets the first IP address anyway, which is 192.168.0.128.