The way I do it is very easy. Use knx-hdinstall. Then copy what you want to the other partitions. All you have to do then is a quick edit to the text file /etc/fstab. For example add a line like:

/dev/hda5 /home defaults 0 0

After rebooting this will make partition 5 be the /home directory. By the way I am not sure that it is exactly right because I am not on a Linux box right now; but it is really easy to figure out once you take a look at fstab.