Debconf
From DWIKI
The actual config data
/var/cache/debconf/config.dat
The location of relevant files per package
/var/lib/dpkg/info
Finding packages that should work for dpkg-reconfigure:
find /var/lib/dpkg/info -name \*.postinst | xargs grep -l debconf| sed 's/^.*\/\(.*\)/\1/g;s/.postinst//g'
FAQ
delete values from database
When testing your config file you will find that after 1 try it no longer shows dialog, fix this by setting priority to critical and clean database. It does not seem possible to directly edit config.dat, but:
echo PURGE | debconf-communicate <packagename>