How To Delete A APT Repository And GPG Key In Ubuntu?

Reference: https://ostechnix.com/how-to-delete-a-repository-and-gpg-key-in-ubuntu/

Delete a repository in Ubuntu

Whenever you add a repository using "add-apt-repository" command, it will be stored in /etc/apt/sources.list file.

To delete a software repository from Ubuntu and its derivatives, just open the /etc/apt/sources.list file and look for the repository entry and delete it.

$ sudo nano /etc/apt/sources.list

As you can see in the below screenshot, I have added Oracle Virtualbox repository in my Ubuntu system.

The contents of /etc/apt/sources.list file

To delete this repository, simply remove the entry. Save and close the file.

If you have added PPA repositories, look into /etc/apt/sources.list.d/ directory and delete the respective entry.

Alternatively, you can delete the repository using "add-apt-repository" command. For example, I am deleting the Systemback repository like below.

$ sudo add-apt-repository -r ppa:nemh/systemback

Finally, update the software sources list using command:

$ sudo apt update

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Delete repository keys in Ubuntu

We use "apt-key" command to add the repository keys. First, let us list the added keys using command:

$ sudo apt-key list

This command will list all added repository keys.

/etc/apt/trusted.gpg -------------------- pub rsa1024 2010-10-31 [SC] 3820 03C2 C8B7 B4AB 813E 915B 14E4 9429 73C6 2A1B uid [ unknown] Launchpad PPA for Kendek pub rsa4096 2016-04-22 [SC] B9F8 D658 297A F3EF C18D 5CDF A2F6 83C5 2980 AECF uid [ unknown] Oracle Corporation (VirtualBox archive signing key) <info@virtualbox.org> sub rsa4096 2016-04-22 [E] /etc/apt/trusted.gpg.d/ubuntu-keyring-2012-archive.gpg ------------------------------------------------------ pub rsa4096 2012-05-11 [SC] 790B C727 7767 219C 42C8 6F93 3B4F E6AC C0B2 1F32 uid [ unknown] Ubuntu Archive Automatic Signing Key (2012) <ftpmaster@ubuntu.com> /etc/apt/trusted.gpg.d/ubuntu-keyring-2012-cdimage.gpg ------------------------------------------------------ pub rsa4096 2012-05-11 [SC] 8439 38DF 228D 22F7 B374 2BC0 D94A A3F0 EFE2 1092 uid [ unknown] Ubuntu CD Image Automatic Signing Key (2012) <cdimage@ubuntu.com> /etc/apt/trusted.gpg.d/ubuntu-keyring-2018-archive.gpg ------------------------------------------------------ pub rsa4096 2018-09-17 [SC] F6EC B376 2474 EDA9 D21B 7022 8719 20D1 991B C93C uid [ unknown] Ubuntu Archive Automatic Signing Key (2018) <ftpmaster@ubuntu.com>

As you can see in the above output, the long (40 characters) hex value is the repository key. If you want APT package manager to stop trusting the key, simply delete it using command:

$ sudo apt-key del "3820 03C2 C8B7 B4AB 813E 915B 14E4 9429 73C6 2A1B"

Or, specify the last 8 characters only:

$ sudo apt-key del 73C62A1B

Done! The repository key has been deleted. Run the following command to update the repository lists:

$ sudo apt update