i want my ubuntu server free domin. there are free domain service providers , but dyndns is not free now.( 2014/09/10) freedns.afraid.org is free at this mounent. 1. join http://freedns.afraid.org 2. add subdomains. mysubdomain.mooo.com 3.install ddclient sudo apt-get install ddclient 4.edit /usr/sbin/ddclient sha1 to sha 5.edit /etc/ddclient.conf # Configuration file for ddclient generated by debconf # # /etc/ddclient.conf syslog=yes daemon=5m timeout=10 ssl=yes protocol=freedns use=if, if=eth0 server=freedns.afraid.org login= loginid password=' loginpw ' mysubdomain01.mooo.com mysubdomain02.mooo.com 6.restart ddclient sudo service ddclient restart 7. see log sudo tail -f /var/log/syslog ref - http://askubuntu.com/questions/211173/how-can-i-get-ddclient-to-work-with-freedns