How to release and renew a DHCP IP address in Ubuntu 10.04 (Lucid)/9.10 (Karmic)/9.04(Jaunty)

We have already discussed how to setup DHCP server in Ubuntu .This tutorial will explain how to release and renew a DHCP IP address in Ubuntu 10.04 (Lucid)/9.10 (Karmic)/9.04(Jaunty)