Ubuntu uses a security mechanism called to ensure that packages haven't been tampered with. If the digital signature (the .gpg key) for a repository is missing or doesn't match, APT blocks the update to prevent potential security risks. Common causes on Ubuntu 22.04 (Jammy Jellyfish) include:
The repository configuration might be looking for a key file that doesn't exist or is in the wrong directory.
Use curl to fetch the key and gpg --dearmor to save it in the recommended keyring location. Ubuntu uses a security mechanism called to ensure
sudo rm /etc/apt/sources.list.d/docker.list sudo rm /etc/apt/keyrings/docker.gpg Use code with caution.
The error message the repository 'https://download.docker.com/linux/ubuntu jammy inrelease' is not signed occurs when Ubuntu’s package manager () cannot verify the authenticity of the Docker repository. This usually stems from a missing or outdated GPG key, incorrect file permissions, or legacy repository configurations from older Ubuntu versions. Why Is the Repository "Not Signed"? Use curl to fetch the key and gpg
The key file might exist but isn't readable by the APT system. How to Fix the "Not Signed" Error
To resolve this, you must cleanly remove the old configuration and re-import the official Docker GPG key using modern security standards. This usually stems from a missing or outdated
Older methods used apt-key , which is now deprecated in favor of individual keyrings in /etc/apt/keyrings/ .