how to create initrd for pxe kickstart boot

[Farkas Levente]

hi,
i need to create a new inird which include r1000 ethernet driver for oxe
boot. i read everywhere that i've to:
---------------------
mv initrd.imginitrd.img.gz
gunzip initrd.img.gz
mkdir init
mount -o loop initrd.img init
----------------------
but these last step always gives me:
mount: you must specify the filesystem type
and i can't find any kind of fs type which would be good.
although with
gunzip initrd.img | cpio -i --make-directories
seems to working, but even if i don't modify it and
find . -print | cpio -o -c |gzip -9 >initrd.img.new
the result is different form the original one.
so what is the proper procedure to recreate the initrd file?
thank you for your help in advance.

-- 
  Levente                               "Si vis pacem para bellum!"