if you want to test your partman receipts. here is a tiny guide on how you can get presseded automatic partitioing to work

put the following as a textfile called myseed on a floppydisk

d-i     partman-auto/disk               string /dev/discs/disc0/disc
d-i     partman-auto/expert_recipe_file string /lib/partman/recipes-debian-edu/12-boot-root
d-i     partman/confirm_write_new_label boolean true
d-i     partman/choose_partition        select Finish partitioning and write changes to disk
d-i     partman/confirm                 boolean true

note: all lines start with d-i, and are rather long.

on the cd boot prompt type

install preseed/file=/cdrom/myseed

the installer will now run and automaticaly configure according to your recipe file /lib/partman/recipes-debian-edu/12-boot-root

while writing your recipe you might want to put it on the floppy too and use

d-i     partman-auto/expert_recipe_file string /floppy/myrecipe

this saves you from waiting on a new etch test for testing your recipe.

Source: Ronny Aasen on debian-edu Mailingliste