Cleanup of unused, left-over old configuration files

aptitude search '~c'

In aptitude: filter ~c

Cleanup of transitional packages

deborphan

Find manually installed packages

Filter: !~M~i

Find non-maintained files

cruft

Find modified configuration files

https://serverfault.com/questions/90400/how-to-check-for-modified-config-files-on-a-debian-system#90401

dpkg-query -W -f='${Conffiles}\n' '*' | awk 'OFS=" "{print $2,$1}' | LANG=C md5sum -c 2>/dev/null | awk -F': ' '$2 !~ /OK$/{print $1}' | sort | less

debsums -ce