user@machine:~ $ sudo apt-get update
Stary:3 http://archive.raspbian.org/raspbian jessie InRelease
Pobieranie:4 http://ftp.debian.org/debian stretch-backports InRelease [91,8 kB]
Ign:4 http://ftp.debian.org/debian stretch-backports InRelease
Pobieranie:5 http://ftp.debian.org/debian stretch-backports/main armhf Packages [590 kB]
Pobieranie:6 http://ftp.debian.org/debian stretch-backports/main Translation-en [460 kB]
Pobrano 1141 kB w 3s (288 kB/s)
Czytanie list pakietów... Gotowe
W: Błąd GPG: http://ftp.debian.org/debian stretch-backports InRelease: Następujące podpisy nie mogły zostać zweryfikowane z powodu braku klucza publicznego: NO_PUBKEY 7638D0442B90D010 NO_PUBKEY 04EE7237B7D453EC
W: The repository 'http://ftp.debian.org/debian stretch-backports 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.
root@machine:~# gpg --keyserver pgp.mit.edu --recv-keys 7638D0442B90D010 04EE7237B7D453EC
gpg: keybox '/root/.gnupg/pubring.kbx' created
gpg: failed to start the dirmngr '/usr/bin/dirmngr': Nie ma takiego pliku ani katalogu
gpg: connecting dirmngr at '/root/.gnupg/S.dirmngr' failed: Nie ma takiego pliku ani katalogu
gpg: keyserver receive failed: Brak dirmngr
root@machine:~# rm .gnupg/pubring.kbx
root@machine:~# apt-get install dirmngr
root@machine:~# gpg --keyserver pgp.mit.edu --recv-keys 7638D0442B90D010 04EE7237B7D453EC
gpg: keybox '/root/.gnupg/pubring.kbx' created
gpg: key E0B11894F66AEC98: 12 signatures not checked due to missing keys
gpg: /root/.gnupg/trustdb.gpg: trustdb created
gpg: key E0B11894F66AEC98: public key "Debian Archive Automatic Signing Key (9/stretch)
gpg: key 7638D0442B90D010: 13 signatures not checked due to missing keys
gpg: key 7638D0442B90D010: public key "Debian Archive Automatic Signing Key (8/jessie)
gpg: no ultimately trusted keys found
gpg: Total number processed: 2
gpg: imported: 2
root@machine:~# gpg --armor --export 7638D0442B90D010 | apt-key add -
OK
root@machine:~# gpg --armor --export 04EE7237B7D453EC | apt-key add -
OK
root@machine:~# exit
user@machine:~ $ sudo apt-get update
Pobieranie:1 http://ftp.debian.org/debian stretch-backports InRelease [91,8 kB]
Stary:2 http://raspbian.raspberrypi.org/raspbian stretch InRelease
Stary:3 http://archive.raspbian.org/raspbian jessie InRelease
Stary:4 http://archive.raspberrypi.org/debian stretch InRelease
Pobrano 91,8 kB w 2s (35,2 kB/s)
Czytanie list pakietów... Gotowe