https://github.com/troglobit/inadyn
Inadyn is a small and simple Dynamic DNS, DDNS, client with HTTPS support. Commonly available in many GNU/Linux distributions, used in off the shelf routers and Internet gateways to automate the task of keeping your Internet name in sync with your public¹ IP address. It can also be used in installations with redundant (backup) connections to the Internet.
Most people are unaware they share a pool of Internet addresses with other users of the same Internet Service Provider (ISP). Protocols like DHCP, PPPoE, or PPPoA are used to give you an address and a way to connect to the Internet, but usually not a way for others to connect to you. If you want to run an Internet server on such a connection you risk losing your IP address every time you reconnect, or as in the case of DHCP even when the lease is renegotiated.
By using a DDNS client like inadyn you can register an Internet name with a DDNS provider, like FreeDNS. The DDNS client updates your DNS record periodically and/or on demand when your IP address changes. Inadyn can maintain multiple host records with the same IP address, use a combination of a script, the address from an Internet-facing interface, or default to using the IP address change detector of the DDNS provider.
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¹ Public IP address is the default, private addresses can also be used.