How to solve REMOTE HOST IDENTIFICATION HAS CHANGED.

This tutorial provides step-by-step instructions for installing Nginx on a Ubuntu 22.04 system, guiding users through the process of setting up the popular web server software on their Ubuntu-based environment.

Step 1

Update apt

sudo apt update
sudo apt install nginx

Step 2

Adjusting the firewall

systemctl status nginx

service nginx status

Output
● nginx.service - A high performance web server and a reverse proxy server
     Loaded: loaded (/lib/systemd/system/nginx.service; enabled; vendor preset: enabled)
     Active: active (running) since Sun 2024-04-07 21:18:17 UTC; 4min 27s ago
       Docs: man:nginx(8)
    Process: 1829 ExecStartPre=/usr/sbin/nginx -t -q -g daemon on; master_process on; (code=exited, status=0/SUCCESS)
    Process: 1830 ExecStart=/usr/sbin/nginx -g daemon on; master_process on; (code=exited, status=0/SUCCESS)
   Main PID: 1934 (nginx)
      Tasks: 3 (limit: 2323)
     Memory: 5.4M
        CPU: 32ms
     CGroup: /system.slice/nginx.service
             ├─1934 "nginx: master process /usr/sbin/nginx -g daemon on; master_process on;"
             ├─1937 "nginx: worker process" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" ""
             └─1938 "nginx: worker process" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" ""

Check your IP to make sure Nginx is running

curl -4 icanhazip.com

To stop nginx:

sudo systemctl stop nginx

To start the web server when it is stopped, type:

sudo systemctl start nginx To stop and then start the service again, type:

sudo systemctl restart nginx If you are only making configuration changes, Nginx can often reload without dropping connections. To do this, type:

sudo systemctl reload nginx By default, Nginx is configured to start automatically when the server boots. If this is not what you want, you can disable this behavior by typing:

sudo systemctl disable nginx To re-enable the service to start up at boot, you can type:

sudo systemctl enable nginx

https://www.digitalocean.com/community/tutorials/how-to-install-nginx-on-ubuntu-22-04