Create and install SSL for your site using Let's encrypt and Nginx on server Ubuntu 20.04

Create a certificate

SSH into the server

SSH into the server running your HTTP website as a user with sudo privileges.

Enable the universe repository

You'll need to make sure the Ubuntu universe repository is in your list of repositories. To do so, run the following commands on the command line on the machine:

sudo apt-get update
sudo apt-get install software-properties-common
sudo add-apt-repository universe
sudo apt-get update

Install Certbot

sudo apt-get install certbot python3-certbot-nginx

Create a certificate

sudo certbot certonly --nginx

Install your SSL certificate to Nginx

You need to redirect all HTTP requests to HTTPS requests.

server {
    listen [::]:80;
    listen 80;

    server_name yoursite.com www.yoursite.com;
    # redirect http to https www
    return 301 https://www.yoursite.com$request_uri;
}

server {
    listen [::]:443 ssl http2;
    listen 443 ssl http2;

    server_name yoursite.com;

    ssl_certificate /etc/letsencrypt/live/yoursite.com/fullchain.pem;
    ssl_certificate_key /etc/letsencrypt/live/yoursite.com/privkey.pem;

    root [your-site-root-path];

    # redirect https non-www to https www
    return 301 https://www.yoursite.com$request_uri;
}

server {
    listen [::]:443 ssl http2;
    listen 443 ssl http2;

    server_name www.yoursite.com;
    root [your-site-root-path];

    ssl_certificate /etc/letsencrypt/live/yoursite.com/fullchain.pem;
    ssl_certificate_key /etc/letsencrypt/live/yoursite.com/privkey.pem;

    ## Nginx config for serving your application
	## ...
}

Renew your certificates

Edit the crontab file:

sudo vim /etc/crontab

Add this cron job to renew your certificates automatically:

0 0,12 * * * certbot renew >/dev/null 2>&1

Tada!