On Wed, 2020-05-20 at 09:52:51 +0200, Mick Bert wrote: > I am trying to update debian in my iBook G4 since a very long time, but the > "apt update" command fails due to mising public key for signature checking. Extract the key ID from the error message, fetch the key (using gpg --recv-keys), then add it to the keyring known to APT (apt-key add) ... HTH, Steffen