The main issue is to use configuration files residing somewhere in the filesystem. This looks like a global variable in a codebase (something we generally try to avoid).
Instead, the configuration file should be explicitly provided as a command line argument. Systemd sandboxing can also be useful to ensure the program only uses the expected set of files.
For instance, on my NixOS machine, the Nginx configuration is not in `/etc/nginx` but explicitly provided and can then be known with ps:
$ ps aux | grep nginx
nginx: master process /nix/store/9iiqv6c3q8zlsqfp75vd2r7f1grwbxh7-nginx-1.24.0/bin/nginx -c /nix/store/9ffljwl3nlw4rkzbyhhirycb9hjv89lr-nginx.conf
For instance, on my NixOS machine, the Nginx configuration is not in `/etc/nginx` but explicitly provided and can then be known with ps:
$ ps aux | grep nginx
nginx: master process /nix/store/9iiqv6c3q8zlsqfp75vd2r7f1grwbxh7-nginx-1.24.0/bin/nginx -c /nix/store/9ffljwl3nlw4rkzbyhhirycb9hjv89lr-nginx.conf