Upgrade Ubuntu from Edgy to Feisty

http://www.ubuntugeek.com/upgrade-ubuntu-610-edgy-eft-to-ubuntu-704-feisty-fawn-2.html
Method 2 – Using apt-get
Edit your /etc/apt/sources.list as root. Change every occurrence of edgy to feisty.
Use any prefered editor. If you have a CD-ROM line in your file, then remove it.
sudo vi /etc/apt/sources.list
or
use the following Simple command
sudo sed -e ’s/\edgy/ feisty/g’ -i /etc/apt/sources.list
Now you need to update the source list using the following command
sudo apt-get [...]