How to check what files have been customised in /etc?

[Ralf Mardorf]

On Sun, 13 Dec 2020 17:16:56 +0100, Ralf Mardorf wrote:
>Usually we nowadays tend to name drop-in files starting with a high
>number, to most widely ensure that it's the last used file for
>configuration. Instead of "foo.conf" it becomes "99-foo.conf". This
>isn't absolutely secure, IOW after each upgrade we need to check all
>our drop-in directories against files, that enforce settings that
>render our installs useless for our field of application.

This assumes that other files are named "01-foo.conf" etc. and no file
"foo.conf", let alone "goo.conf" does exist.

This issue wouldn't exist, if all settings would be provided by one file
and no drop-in file would be allowed to override settings.