Nginx - Custom configuration files location - nginx

Question

I use Nginx with many domains. Some of these domains have custom configurations. I'm including these files inside the server blocks in the Nginx configurations.
For example:
server {
... some configurations things here...
include /var/somewhere/custom.conf;
etc.. etc..
}
The configuration files of Nginx are inside: /etc/nginx
To try and keep everything in one place and not have my custom configuration files all over the place I would like to place my custom configuration files inside /etc/nginx/some_directory
Can I create a sub directory inside /etc/nginx without it causing any issues with Nginx itself? I want to create /etc/nginx/some_directory/ and place my many custom configuration files inside it and include them.
I'm specifically asking this question because I don't want to break something on my production server.

Answer 1

If nginx doesn't know about a directory, it'll not touch it. You can verify that by greping against such pattern in nginx's codebase.
However, messing with a foreign folder structure might cause problems with permissions and ownership of the files, therefore either just use a pre-defined folders nginx prepared for you (/etc/nginx/sites-enabled and /etc/nginx/sites-available) which you can use with symlinks such as nginx itself does
# ls /etc/nginx/sites-enabled
default -> /etc/nginx/sites-available/default
# ls /etc/nginx/sites-available
default
otherwise you're getting into a situation what C/C++ programmers call an undefined behavior and there's no guarantee that what works now will work in the future / nginx doesn't change as well as the distro maintainers might mess with the folder structure and permissions for the packages in distro package manager.
Example:
Nginx might verify the full /etc/nginx tree's permissions and owners - if your folders/files don't match it might cause a warning or crash even. If it's installed by a package manager, it might cause issues when removing the package itself e.g. if the package manager attempts to remove only a known list of folders + afterwards the parent i.e. /etc/nginx by rmdir or similar. Situations you don't really want to get into and debug when you can use allowed folders or symlinks or your own folders that are not bound to an application or behavior except the one you define.