This error occurs when apt cannot find a Release file in a repository, typically because the repository isn't available for your Ubuntu version or the URL is incorrect. The Release file contains essential metadata that apt needs to verify and list available packages.
When you run apt-get update, apt contacts each repository in your sources list to fetch package information. Each repository must provide a Release file—a special file containing metadata like the supported Ubuntu codenames, cryptographic signatures, and package listings. Without this file, apt cannot verify the repository's authenticity or determine which packages are available. This error indicates that either the repository doesn't support your Ubuntu version, the URL is wrong, or the repository no longer exists.
Run the following command to see your Ubuntu version and codename (like focal, jammy, etc.):
lsb_release -aNote the codename—you'll need this to verify if the repository supports your version.
Run apt-get update and look at the error message carefully:
sudo apt-get updateThe error will show the exact repository URL causing the problem. Write down the URL—you'll need it in the next step.
Copy the repository URL (or the PPA name) and search for it online. For PPAs, visit https://launchpad.net/~ppa-owner/+archive/ubuntu/ppa-name to see which Ubuntu versions are supported. Check whether your codename (from step 1) is in the supported list.
If the repository doesn't support your Ubuntu version, remove it using:
sudo add-apt-repository --remove ppa:ppa-owner/ppa-nameOr, if it's a custom repository in your sources list:
sudo nano /etc/apt/sources.list.d/problematic-repo.listDelete the line or comment it out (add # at the start), save (Ctrl+O, Enter, Ctrl+X), then run:
sudo apt-get updateOnce the repository is removed, run apt-get update again to confirm the error is gone:
sudo apt-get updateIf successful, you'll see no errors for the removed repository.
If you still need the software from that repository, try:
- Search for an updated PPA that supports your Ubuntu version
- Check the project's official website for installation instructions
- Use Snap packages: snap search package-name and snap install package-name
- Use Flatpak: A cross-distribution alternative to PPAs
- Download .deb files directly from the project's GitHub or official repository
Different Ubuntu releases have different codenames (20.04=focal, 22.04=jammy, 24.04=noble). A PPA compiled for focal won't work on jammy without recompilation. Some repositories provide separate branches per codename in their structure (e.g., launchpad.net shows build history by series). If you encounter this frequently, use 'Ubuntu Pro' repositories or stick to officially maintained PPAs from well-known projects. For servers, consider using the official Ubuntu repositories or checking DistroWatch for alternatives compatible with your specific version.
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