finding obsolete conffiles

when updating from lenny to squeeze, one will face two major upgrades of the system:

for people not wanting to convert yet as not everything is supported yet, this can be postponed if desired.

a new, faster system for booting (it looks even faster than upstart to me). its upgrade might fail for some packages on the system not being --purged but just --removed.

getting a list of obsolete conffiles is as simple as

dpkg-query -W -f='${Conffiles}\n' | grep obsolete

if you're absolutely sure you dont need any of the old stuff (possibly including your own customisations) you might also do

dpkg --purge $(dpkg -l|awk '/^rc/ {print $2}')

which will simply purge all removed but not purged packages.