INADYN is a dynamic DNS client. That is, it maintains the IP address of a host name. It periodically checks whether the IP address stored by the DNS server is the real current address of the machine that is running INADYN.
The project website and documentation is available here:
Once installed, you will need to modify the inadyn-start.sh file to enter your userid, password, domain alias, etc. The default setup uses dyndns.org. If you use a different provider, please see the documentation at the project site.