Prerequisites

You have domain name pointing to your server public IP.

Installation process

sudo apt update
sudo apt install nginx
sudo systemctl enable nginx
sudo apt install certbot
sudo openssl dhparam -out /etc/ssl/certs/dhparam.pem 2048
sudo mkdir -p /var/lib/letsencrypt/.well-known
sudo chgrp www-data /var/lib/letsencrypt
sudo chmod g+s /var/lib/letsencrypt
sudo vim /etc/nginx/snippets/letsencrypt.conf

location ^~ /.well-known/acme-challenge/ {
  allow all;
  root /var/lib/letsencrypt/;
  default_type "text/plain";
  try_files $uri =404;
}

sudo vim /etc/nginx/snippets/ssl.conf

ssl_dhparam /etc/ssl/certs/dhparam.pem;

ssl_session_timeout 1d;
ssl_session_cache shared:SSL:50m;
ssl_session_tickets off;

ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
ssl_ciphers 'ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:DHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA256:ECDHE-ECDSA-AES128-SHA:ECDHE-RSA-AES256-SHA384:ECDHE-RSA-AES128-SHA:ECDHE-ECDSA-AES256-SHA384:ECDHE-ECDSA-AES256-SHA:ECDHE-RSA-AES256-SHA:DHE-RSA-AES128-SHA256:DHE-RSA-AES128-SHA:DHE-RSA-AES256-SHA256:DHE-RSA-AES256-SHA:ECDHE-ECDSA-DES-CBC3-SHA:ECDHE-RSA-DES-CBC3-SHA:EDH-RSA-DES-CBC3-SHA:AES128-GCM-SHA256:AES256-GCM-SHA384:AES128-SHA256:AES256-SHA256:AES128-SHA:AES256-SHA:DES-CBC3-SHA:!DSS';
ssl_prefer_server_ciphers on;

ssl_stapling on;
ssl_stapling_verify on;
resolver 8.8.8.8 8.8.4.4 valid=300s;
resolver_timeout 30s;

add_header Strict-Transport-Security "max-age=15768000; includeSubdomains; preload";
add_header X-Frame-Options SAMEORIGIN;
add_header X-Content-Type-Options nosniff;

sudo vim /etc/nginx/sites-available/dev.cmsnesia.com.conf

server {
  listen 80;
  listen [::]:80;
  server_name dev.cmsnesia.com;
  
  root /var/www/html
  
  include snippets/letsencrypt.conf;
}

sudo ln -s /etc/nginx/sites-available/dev.cmsnesia.com.conf /etc/nginx/sites-enabled/
sudo systemctl restart nginx
sudo certbot certonly --agree-tos --email [email protected] --webroot -w /var/lib/letsencrypt/ -d dev.cmsnesia.com
sudo vim /etc/nginx/sites-available/dev.cmsnesia.com.conf

server {
    listen 80;
    listen [::]:80;
    server_name dev.cmsnesia.com;
  
    root /var/www/html
    include snippets/letsencrypt.conf;
    return 301 https://dev.cmsnesia.com$request_uri; # redirect http to https
}

server {
    listen 443 ssl http2;
    server_name dev.cmsnesia.com;

    ssl_certificate /etc/letsencrypt/live/dev.cmsnesia.com/fullchain.pem;
    ssl_certificate_key /etc/letsencrypt/live/dev.cmsnesia.com/privkey.pem;
    ssl_trusted_certificate /etc/letsencrypt/live/dev.cmsnesia.com/chain.pem;
    include snippets/ssl.conf;
    include snippets/letsencrypt.conf;
}

sudo vim /etc/cron.d/certbot

0 */12 * * * root test -x /usr/bin/certbot -a \! -d /run/systemd/system && perl -e 'sleep int(rand(3600))' && certbot -q renew --renew-hook "systemctl reload nginx"

sudo certbot renew --dry-run