Among the improvements and new features:
When you open the Source Editor, Ubuntu Tweak will show you the main sources.list in the window.
And you can select the drop down menu to view or edit the other list files. They are stored in /etc/apt/sources.list.d/.
After you click the “refresh” to update and the operation finish, a convenient dialog will display.
With this dialog, you will know what new applications can be installed and what updates can be applied.
-Add/Remove can install Themes
-Improved PolicyKit mechanism
How to install / upgrade Ubuntu Tweak
Open a terminal and paste the following commands:
sudo sh -c 'echo "deb http://ppa.launchpad.net/tualatrix/ppa/ubuntu jaunty main" >> /etc/apt/sources.list'
(Replace jaunty with your Ubuntu version, if different)
sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 0624A220
And then install Ubuntu Tweak:
sudo apt-get update && sudo apt-get install ubuntu-tweak
Or if you are upgrading from an older version:
sudo apt-get update && sudo apt-get upgrade
2. Downloading Ubuntu Tweak .deb Files
You can simply download the .DEB file for your Ubuntu version from HERE if you don't wish to add the Ubuntu Tweak PPA repository.