The Ubuntu Sources List Generator is one great tool that you can use to generate source list for your Ubuntu.
Go to the Ubuntu Sources List Generator site.
Select the Country where you want to download the repository from.
Select your Ubuntu release.
Scroll down the list and select the components that you want in your repository. The standard ones are “Main”, “Restricted”, “Universe”, “Multiverse”, “Security” and “Updates”. You can also include “Partner” and “Extra” to include additional software that are not provided by Ubuntu.
In addition to the main sources, the Generator also include popular PPAs like Cairo Composite Manager, Cortina Wallpaper changer, GIMP, Google Chrome, Virtualbox, Steam, Spotify etc. that you can include in your sources list. Simply check the box beside the PPA.
Lastly, scroll all the way down to the bottom and press the “Generate List” button.
On the next page, you should see three big boxes. The first box at the top contains the sources list that you have selected and you will need to copy/paste them into your sources.list file. In your terminal, Paste the sources lists into the document (for a new slate, you might want to erase all the existing sources listed in the file before pasting the new sources list in). Save and exit.
If you have added third party software’s PPA, it will show you the PPA key that you need to add to your system. Run the commands in your terminal, line by line.
The third box is the alternate layout for Synaptic, which you can ignore most of the time. To complete the process, you need to update and upgrade your system: That’s it.