On 02/24/2018 09:42 PM, Paul Hoffman wrote:
> For example, when using the instructions you gave, I get.
>
> W: GPG error:
> http://download.opensuse.org/repositories/home:/CZ-NIC:/knot-resolver-latest/xUbuntu_16.04 
> Release: The following signatures couldn't be verified because the
> public key is not available: NO_PUBKEY 74062DB36A1F4009

There are multiple ways you can use.  In case you want this one, at the
end of the page there's information how to add the keys.  (I haven't
tested this, but the key seems fine, as judged by my gpg.)

wget -nv https://download.opensuse.org/repositories/home:CZ-NIC:knot-resolver-latest/xUbuntu_16.04/Release.key -O Release.key
sudo apt-key add - < Release.key
sudo apt-get update

--Vladimir