Ubuntu Linux Renew DHCP

How do I renew a dhcp assigned IP address under Ubuntu Linux desktop or Laptop systems?

You need to use "Dynamic Host Configuration Protocol" client called dhclient to renew IP address under Ubuntu Linux. Open the terminal and type the following command to release current address:
$ sudo dhclient -r
You can also ask for new IP address (e.g., for wlan0 get new IP address), enter:
$ sudo dhclient wlan0
OR
$ sudo dhclient eth0
Another option, enter:
$ sudo dhclient -r && sudo dhclient