edit and rebuild the initrd

[Hadders]

Hi all,
  Well, I'm close to fixing this problem (i think)

I've unpacked the 2.6.18-1 initrd and had a look at the "init" file. 
Then I compared this with the 2.6.15-1 (base) kernel init file in its initrd

There's a difference!
Namely after the base init does its mkblkdevs (make bulk devices?) there 
are the following lines

rmparts sdb
rmparts sda
dm create isw_cdgbeijgjh_iaa 0 1250275846 striped 2 256 8:0 8:16 0
dm partadd isw_cdgbeijgjh_iaa

Okay. I think this is the dm commands to access the container? If so, 
then all I need to do is put these commands into my new kernel initrd 
and *bham* I'm cooking with gas?!
I've fixed all the device mapper errors by upgrading dmraid....

So my question is: do I simply copy and paste these into the new "init" 
file at much the same place and then repack the new initrd for 2.6.18-1.
How do I repack/recreate the initrd (mixed results on google)?

Thanks. Hadders