How to preconfigure debconf values?

[Josef Wolf <jw@raven.inka.de>]

Hello.

I hope I am in the correct mailing list here.  If I'm not, please somebody
point me to the correct one.

I am trying to create an live-CD via debootstrap.  Here is what I have done
so far:

  # Download packages to temp directory, so we don't need to download them
  # again if we want to start over from scratch again
  #
  debootstrap --arch i386 \
              --download-only \
              --include=syslinux,perl,debootstrap,grub,ppp \
              etch etch/pkgs

  # Create base structure
  #
  rm -rf etch/target
  cp -a etch/pkgs etch/target
  sudo debootstrap --arch i386 \
                   --include=syslinux,perl,debootstrap,grub,ppp \
                   etch etch/target

  # Now copy/modify some templates to get the basics configured.
  #
  sudo cp templates/etc/network/interfaces etch/target/etc/network/interfaces
  sudo cp templates/etc/hosts              etch/target/etc/hosts
  sudo cp templates/etc/apt/sources.list   etch/target/etc/apt/sources.list
  sudo cp templates/etc/resolv.conf        etch/target/etc/resolv.conf
  sudo cp templates/etc/hostname           etch/target/etc/hostname
  sudo cp templates/etc/fstab              etch/target/etc/fstab
  sudo chroot etch/target \
      perl -i -pe \
      's/__FLAVOR__/etch/g;s/__HOSTNAME__/box/g;s/__DOMAIN__/asd.de/g' \
      /etc/network/interfaces \
      /etc/hosts \
      /etc/apt/sources.list \
      /etc/resolv.conf \
      /etc/hostname \
      /etc/fstab

  # Upgrade the distribution.
  #
  sudo chroot etch/target apt-get update
  sudo chroot etch/target apt-get dist-upgrade -y

That was almost straight-forward so far.  But now I'm somewhat stuck.
I'd like to preconfigure debconf.  Something like

  debconf-preconfigure time/zone Europe/Berlin
  apt-get install tzdata

But I just can't figure out from debconf documentation how to do that.
The closest I could find is dpkg-preconfigure.  But this requires to
download the packages before letting them to be preconfigured.  I'd
rather have something like the d-i preseed mechanism.

Any hints?