Customized scripts in Debian Installer

[aaraujo@cenditel.gob.ve]

Dear friends of debian-boot,
I am reading Debian installer documentation in order to know how to execute
customized scripts during Debian installation process. I found that it is
possible to build an udeb package and include it in Debian installer using
udeb_include file in my customized Debian GNU/Linux 5.0 CD.

I also read that it is possible to execute scripts if udeb package place
them in /usr/lib/finish-install.d directory (with an appropiate name).

Well, my script runs some commands but one of them needs an user input,
like a password from the user, for example:

cryptsetup -y create private /dev/sda5

This command ask the user for a password, so I would like to know
whether Debian installer is going to permit the user entering
the password (prompt) or I have to to do something.

Another questions is:
which is the best practice to run customized scripts:
putting commands in postinst file or a file inside
/usr/lib/finish-install.d directory?

Could anyone please help me?

Best regards

Antonio Araujo