How to Resolve Docker Installation Issues on Ubuntu


While assisting with the setup of CasaOS—a streamlined, home cloud operating system designed with privacy in mind—on Ubuntu Jammy, we stumbled upon a snag during the Docker installation process. The hiccup was rooted in an incorrect Docker repository URL that pointed to Debian rather than Ubuntu, leading to the following error:

E: The repository ' jammy Release' does not have a Release file.

The crux of the issue was that although we were configuring Docker on Ubuntu Jammy, the docker.list file referenced the Debian repository. Here’s how we addressed and resolved the problem.

Resolving the Repository URL Error

The first step to correcting the Docker installation error involves modifying the repository URL from Debian to Ubuntu within the Docker list file.

  1. Open the Docker list file for editing:
sudo nano /etc/apt/sources.list.d/docker.list
  1. Modify the repository URL by replacing debian with ubuntu, ensuring it accurately points to the Ubuntu repository:
deb [arch=amd64 signed-by=/usr/share/keyrings/docker.asc] jammy stable

Updating and Installing Docker

With the repository URL corrected, proceed to update your package index and prepare for Docker installation:

sudo apt update

Fixing the Missing GPG Key Error

Encountering a missing GPG key error indicates your system is missing the necessary credentials to verify Docker’s packages, which is critical for a secure installation. Here’s how to rectify this:

  1. Retrieve and add the missing Docker GPG key to your system’s trusted keys:
curl -fsSL | sudo gpg --dearmor -o /usr/share/keyrings/docker-archive-keyring.gpg
  1. Update the Docker list file once more, ensuring it uses the signed-by option with the newly added GPG key:
sudo nano /etc/apt/sources.list.d/docker.list

Modify the entry to:

deb [arch=amd64 signed-by=/usr/share/keyrings/docker-archive-keyring.gpg] jammy stable

Update APT and Proceed with Docker Installation

Following the addition of the GPG key, update your APT package index to reflect these changes:

sudo apt update

Simplifying Docker Installation

To streamline the Docker installation process, I’ve created a script that automates these steps. This can be particularly useful for those setting up multiple systems or preferring a more straightforward approach:


After addressing the repository URL and missing GPG key issues, Docker installation on Ubuntu Jammy proceeded without a hitch, paving the way for a successful CasaOS setup. This experience underscores the importance of attention to detail in software configuration and the effectiveness of community-shared solutions for overcoming common technical challenges.