I want to change my software sources because I don't want to update my Ubuntu from other software sources. I tried to change it from Unity dock: I typed software source
and a icon appeared but when I clicked nothing happened.
And then I tried it from Update manager: I clicked on edit->source
but nothing happened.
I am still able to download and install updates as well as software from Ubuntu Software Center
/etc/apt/sources.list
. Make sure you make a backup copy of the file before you edit it so that you can go back to it if the need arises./etc/apt/sources.list