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

[Ralf Mardorf]

On Sun, 13 Dec 2020 16:44:56 +0000, Colin Law wrote:
>On Sun, 13 Dec 2020 at 16:30, Ralf Mardorf via ubuntu-users
><ubuntu-users at lists.ubuntu.com> wrote:
>>
>> 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.  
>
>You would still have exactly the same problem as a vendor would have
>to modify the main config file, which would override your amendments.
>Plus you would have the original problem when the package supplier
>modifies that file that it would overwrite your version.

Here I disagree. There's an issue for configs with or without the
drop-in approach.

By an upgrade Arch Linux does install a new config with the suffix
".pacnew".

Either as

/etc/foo.conf.pacnew

or as

/etc/foo.d/bar.conf.pacnew

I'm quite sure that usually /etc/foo.conf.pacnew is ignored, since
usually /etc/foo.conf.bak etc. is ignored (too) and instead
/etc/foo.conf is used, but I wonder, if /etc/foo.d/bar.conf.pacnew does
override /etc/foo.d/bar.conf, since those drop-in files are seemingly
allowed to use what ever name and suffixes they like.

Btw. I never checked if on Arch Linux /etc/pacman.d/mirrorlist is
overridden by /etc/pacman.d/mirrorlist.pacnew, but I'm sure that
/etc/X11/xorg.conf is used instead of "xorg.conf.crt",
"xorg.conf.dual.1", "xorg.conf.multi.1" or "xorg.conf.multi.only60hz",
by Arch Linux as well as Ubuntu, when not inside of a drop-in
directory.

ASAP I'll test on Arch Linux and Ubuntu, if a drop-in file foo.conf.bak
does override a drop-in file foo.conf.