Fixing "no public key" errors in DNF

Fixing "No Public Key" Errors in DNF and Other Linux Package Managers

One common hurdle Linux users might face when updating packages or installing new software using package managers like DNF, APT, and Zypper is the "no public key" error. This error typically occurs when the package manager cannot verify the authenticity of the packages due to missing or outdated GPG (GNU Privacy Guard) keys. This post will guide you through resolving these errors across various package managers.

Understanding "No Public Key" Errors

These errors happen when the package manager attempts to verify the digital signature of the package using a GPG key that is not available on your system. Each repository configures its own GPG key to ensure that the packages are secure and not tampered with.

Fixing "No Public Key" Errors in DNF (Fedora, CentOS, RHEL)

DNF, or Dandified YUM, is the package manager used in Fedora, CentOS, and RHEL. If you encounter a "no public key" error like NOKEY GPG, here's how to resolve it:

Find the Key ID: First, note the key ID from the error message.
Import the Key: You can import the missing key using the following command:
```
sudo dnf rpm --import /etc/pki/rpm-gpg/RPM-GPG-KEY-[distro]
```
Replace [distro] with your Linux distribution identifier.
Verify the Key: Ensure the key has been successfully imported:
```
gpg --list-keys
```
Retry the Update/Installation: Run your DNF command again. It should now work without the key error.

For Debian and Ubuntu Users (APT)

APT (Advanced Package Tool) is another popular package management utility, used primarily by Debian and Ubuntu. Here’s how to address the "no public key" error:

Identify the Key: Look for the key in the error message.
Add the Key: Use the apt-key command to import the GPG key:
```
sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys [key]
```
Replace [key] with the actual key ID displayed in the error message.
Update APT: Refresh your repository list:
```
sudo apt update
```
Retry: Try installing or updating the package again.

Resolving Issues in Zypper (openSUSE, SUSE)

Zypper is the command line interface of the ZYpp package manager, used by openSUSE and SUSE. Here’s how to fix the "no public key" error:

Find the Missing Key: The error message will include the key ID.
Import the Key: You can import the key directly as follows:
```
sudo zypper --gpg-auto-import-keys refresh
```
Re-attempt Your Command: With the keys updated, your Zypper command should now proceed without issues.

General Tips

Check Your Internet Connection: Sometimes, importing GPG keys can fail due to network issues.
Update Your System: Ensure your entire system is up to date. Sometimes, the necessary keys are included in recent updates.
Secure Your Keys: Only import keys from trusted sources to avoid security risks.

Conclusion

Dealing with "no public key" errors can seem daunting, but with the right commands and a bit of patience, you can resolve these issues and get back to managing your Linux packages. Always keep your system updated and ensure that keys are added from reliable sources to keep your system secure.

Remember, each package manager and Linux distribution might have slightly different commands or methods, and understanding these nuances can help you navigate the complexities of Linux package management more effectively.