The add-apt-repository script adds an apt repository to /etc/apt/sources.list or a file in the /etc/apt/sources.list.d/ directory in the case of PPAs. You can manually add external repos to your sources list too. Removing packages is very simple, but what about removing such apt repositories? Actually, that’s pretty simple too. There are multiple ways to go about this, from using the same add-apt-repository script, to manually deleting the files and entries. Remove Repo from Software & Updates If you’re new to Ubuntu, you may prefer performing tasks graphically. To remove apt repositories specifically, search and open Software & Updates. In the Other Software tab, select the repo and press Remove. It’s that easy. Do keep in mind that this only removes the repositories. You must uninstall the packages separately. Using add-apt-repository The add-apt-repository script supports the remove flag for removing the specified repositories. You can use this method to easily remove PPAs. sudo add-apt-repository --remove ppa:PPA-Name/ppa Simply replace PPA-Name with the actual name like so sudo add-apt-repository --remove ppa:mozillateam/ppa Remove Repo Source Manually If you manually created a sources entry or file to add a repo, you’ll also need to manually delete them. To remove entries from the sources list, open it with a text editor. sudo nano /etc/apt/sources.list Comment out or remove the repos you no longer need, save the changes, and exit the editor. Similarly, to remove PPAs and manually added repos, list the contents of the sources.list.d directory. ls /etc/apt/sources.list.d Now, delete the appropriate .list or .sources file to remove the repository. sudo rm /etc/apt/sources.list.d/google-chrome.list Deleting GPG Keys External apt repositories are usually signed with GPG keys to verify that the packages can be trusted. These keys are stored in the /etc/apt/trusted.gpg.d/ directory. After removing the repos, you need to remove the keys separately. If you added the keys with apt-key, you can use the same utility to remove the keys as well. First, list the trusted keys and note the key ID of the relevant repo. sudo apt-key list Then, enter the last 8 characters of the key to delete it like so sudo apt-key del D38B4796 Alternatively, if you added the GPG keys manually, you should delete them manually as well like so sudo rm /etc/apt/trusted.gpg.d/google-chrome.gpg