Ubuntu/Linux configuration file usage convention

Question

I have been using Ubuntu Linux occasionally for some time. I know the /etc folder is for configuration files. But I have always found 2 things difficult:

1. Find the correct configuration file to modify for a specific scenario.
2. Map the configuration GUI to the backend configuration file in the /etc folder so I can script it next time.

So, my quetsions are:

1. Once I install a new pacakge, how can I find all its configuration files?
2. What's the usage convention of the numerous configuration files in /etc folder? Is there some catagorization schema such as folder for network configuration, folder for user management configuration, etc.?
3. Is it possible for some configuration files live outside the /etc folder?

Thanks and pardon me if this is a naive question.

Answer 1

Once I install a new pacakge, how can I find all its configuration files?

Run dpkg -L package-name and see which files the package contains in /etc (which should all be configuration files). Look in the package documentation and manpages for any other configuration files it may use.

What's the usage convention of the numerous configuration files in /etc folder? Is there some catagorization schema such as folder for network configuration, folder for user management configuration, etc.?

Usually, /etc/<program-name>.conf or /etc/<program-name>.d. It could be anything (for example, /etc/NetworkManager, /etc/wgetrc).

Is it possible for some configuration files live outside the /etc folder?

Certainly. Though convention is for configuration to be in /etc, configuration that is not supposed to be edited by users/administrators can be elsewhere. For example, /lib/systemd/system contains all the systemd units from packages (whereas Upstart jobs would be in /etc/init).