no-ip provides free hostname for their ddns clients. For example, you can get a xxx.ddns.net domain name in their website.

Then you may want to setup a ddns client for this hostname. Otherwise no-ip will disable your domain name due to inactivity.

For example, I have a VPS whose system is Debian 12. So I installed no-ip's official ddns client 'noip-duc' on this VPS.

 # Download and install the linux DUC in terminal.
 $ wget --content-disposition https://www.noip.com/download/linux/latest
 $ tar zxf noip-duc_3.3.0.tar.gz
 $ sudo apt install ./noip-duc_3.3.0_amd64.deb
   
 # To login and send updates using DDNS Keys enter the following:
 $ noip-duc -g all.ddnskey.com --username <DDNS Key Username> --password <DDNS Key Password>
 

You can get <DDNS Key Username> and <DDNS Key Password> on their website as well.

The command noip-duc run at front-end. If you want to run it as a system service, then take the following steps.

 $ sudo mkdir -p /etc/noip-duc
 $ sudo vi /etc/noip-duc/noip-duc.env
   DDNS_USER="your_ddns_username"
   DDNS_PASS="your_ddns_password"
   
 $ sudo vi /etc/systemd/system/noip-duc.service
   [Unit]
   Description=No-IP Dynamic DNS Update Client
   After=network.target
   
   [Service]
   Type=simple
   ExecStart=/usr/bin/noip-duc -g all.ddnskey.com --username ${DDNS_USER} --password ${DDNS_PASS}
   EnvironmentFile=/etc/noip-duc/noip-duc.env
   Restart=on-failure
   RestartSec=30s
   User=your_user
   Group=your_user
   
   [Install]
   WantedBy=multi-user.target
 

Enable it as systemd service.

 $ sudo systemctl daemon-reload
 $ sudo systemctl enable noip-duc.service
 $ sudo systemctl start noip-duc.service
 $ sudo systemctl status noip-duc.service
 

Run the command to check logs.

 $ journalctl -u noip-duc.service -f
 

As long as you keep noip-duc running on the system, you can keep the domain name for free.