Make sure that you have the packages "ubuntu-minimal" and "ubuntu-standard" installed, regardless of whether you're using Ubuntu, Kubuntu, Xubuntu or Edubuntu:
sudo apt-get install ubuntu-minimal ubuntu-standard
The appropriate desktop package for your version of Ubuntu must also be installed. They are "ubuntu-desktop" for Ubuntu, "kubuntu-desktop" for Kubuntu, "xubuntu-desktop" for Xubuntu, and "edubuntu-desktop" for Edubuntu:
sudo apt-get install ubuntu-desktop
sudo apt-get install kubuntu-desktop
sudo apt-get install xubuntu-desktop
sudo apt-get install edubuntu-desktop
Edit your /etc/apt/sources.list as root. Change every occurrence of edgy to feisty. It is also recommended that you remove or disable any extra repository that may have been added besides the Ubuntu repositories.
Long route: Use your preferred editor. If you have a CD-ROM line in your file, then remove it.
gksudo gedit /etc/apt/sources.list
kdesu kate /etc/apt/sources.list
gksudo mousepad /etc/apt/sources.list
In any terminal program.
sudo nano /etc/apt/sources.list
sudo vi /etc/apt/sources.list
sudo sed -e 's/\sedgy/ gusty/g' -i /etc/apt/sources.list
NOTE: This might not remove old CD-ROM lines. Manual inspection is suggested after running this command. (see Long Route)
If you have the alternate install CD, you can save bandwidth by loading the CD into your CD-ROM drive and using:
sudo apt-cdrom add
Perform the upgrade:
sudo apt-get update && sudo apt-get dist-upgrade && sudo apt-get dist-upgrade
OR, You can also use Aptitude:
sudo aptitude update && sudo aptitude dist-upgrade && sudo aptitude dist-upgrade
NOTE: The first run of dist-upgrade will upgrade everything except for upstart. After this a second dist-upgrade will finish the upgrade.
Just to be totally sure that everything is installed properly, run these commands:
sudo apt-get update && sudo apt-get dist-upgrade
sudo apt-get -f install
sudo dpkg --configure -a
Running dist-upgrade again is done to ensure that no packages are left to install or upgrade. In some cases, certain packages fail to install even after running dist-upgrade the second time.
Reboot in order to effect all changes. (kernel upgrades, upstart, etc...)