How ubuntu makes initrd.gz?

Hello,
  I'm trying to generate a new initrd. It should be the same as the
initrd of ubuntu but with an extra udeb.

  I've looked at the scripts of cdimage [1], but they don't touch the
initrd.

  In d-i, it was a makefile [2] to do that but i don't know how ubuntu
do this work. Any help will be welcome.

[1]
http://people.ubuntu.com/~cjwatson/archives/[EMAIL PROTECTED]/cdimage/
[2]  http://svn.debian.org/wsvn/d-i/trunk/installer/build/?rev=0&sc=0
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Carlos Parra Camargo
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