Here’s how to only allow authenticated users to view your websites - great way to boot freeloaders and guarantee your system’s (or your vps’) resources for yourself.

The guide is meant for debian but can be easily adapted to suit your needs. I assume you have followed Luke Smith’s tutorial and have NGINX running with certbot for certificates.

Create a username and password for authentication (or more than 1 user)

First:

sudo apt install apache2

Apache2 is only needed to create its files in /etc/ otherwsie apache2-utils commands below will fail. My configuration uses NGINX so I’ll delete apache2.

Second:

sudo apt install apache2-utils

Third:

sudo apt remove apache2

Create a username you wish to authenticate with the following comnmand:

sudo htpasswd -c /etc/apache2/.htpasswd admin1

You will be prompted to provide a password, feel free to generate a secure 32+ character one and save it in your password manager of choice.

If you wish to create multiple other users simply remove -c from the command and change the name.

sudo htpasswd /etc/apache2/.htpasswd admin2

Then provide a new password (the same password can also work but it’s more secure that way).

Add the htpasswd file to NGINX

Navigate to the NGINX configuration file you wish to protect:

nano /etc/nginx/sites-available/<yourFileHere>

Add the following in the same server block and on the same level as listen [::]:443 ssl;:

auth_basic           "Administrator’s Area";
auth_basic_user_file /etc/apache2/.htpasswd;

Further reading here.