Fixing NO_PUBKEY GPG Errors on Ubuntu – The Cleanest Way

While updating my Ubuntu server, I encountered this annoying error:

bash
NO_PUBKEY [KEY_ID]
The following signatures couldn't be verified...

After trying a few things, I found a clean and reliable fix that worked without breaking the apt system.

👉 I’ve documented the full step-by-step solution with copy-paste commands, explained clearly in this blog:

🔗 [[Fixing Ubuntu Apt GPG Errors (NO_PUBKEY)](https://cicdtrail.com/ubuntu-apt-update-gpg-error/)]