Scaricamento di:1 http://archive.ubuntu.com/ubuntu xenial InRelease [247 kB]
Scaricamento di:2 http://security.ubuntu.com/ubuntu xenial-security InRelease [102 kB]
Scaricamento di:3 http://archive.ubuntu.com/ubuntu xenial-security InRelease [102 kB]
Err:2 http://security.ubuntu.com/ubuntu xenial-security InRelease
  È stata trovata almeno una firma non valida.
Ign:1 http://archive.ubuntu.com/ubuntu xenial InRelease      
Ign:3 http://archive.ubuntu.com/ubuntu xenial-security InRelease
Recuperati 451 kB in 1s (234 kB/s)
Lettura elenco dei pacchetti... Fatto
W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://security.ubuntu.com/ubuntu xenial-security InRelease: È stata trovata almeno una firma non valida.
W: Errore GPG: http://archive.ubuntu.com/ubuntu xenial InRelease: È stata trovata almeno una firma non valida.
W: The repository 'http://archive.ubuntu.com/ubuntu xenial InRelease' is not signed.
N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.
W: Errore GPG: http://archive.ubuntu.com/ubuntu xenial-security InRelease: È stata trovata almeno una firma non valida.
W: The repository 'http://archive.ubuntu.com/ubuntu xenial-security InRelease' is not signed.
N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.
W: Impossibile recuperare http://security.ubuntu.com/ubuntu/dists/xenial-security/InRelease  È stata trovata almeno una firma non valida.
W: Impossibile scaricare alcuni file di indice: saranno ignorati o verranno usati quelli vecchi.