Even I was getting this error "W: GPG error: http://nginx.org lucid Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY ABF5BD827BD9BF62", so I started searching and landed here. And Yes, that mail thread reply really worked for me. $ wget http://nginx.org/packages/keys/nginx_signing.key $ cat nginx_signing.key | sudo apt-keyby nishalspace - Nginx Mailing List - English