sudo apt update Ign:1 http://deb.debian.org/debian stretch InRelease Hit:2 http://security.debian.org/debian-security stretch/updates InRelease Get:3 http://deb.debian.org/debian stretch-updates InRelease [90.3 kB] Err:2 http://security.debian.org/debian-security stretch/updates InRelease The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 9D6D8F6BC857C906 NO_PUBKEY 8B48AD6246925553 Err:3 http://deb.debian.org/debian stretch-updates InRelease The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 7638D0442B90D010 Hit:4 http://deb.debian.org/debian stretch Release Err:5 http://deb.debian.org/debian stretch Release.gpg The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 8B48AD6246925553 NO_PUBKEY 7638D0442B90D010 NO_PUBKEY EF0F382A1A7B6500 Fetched 90.3 kB in 1s (78.1 kB/s) Reading package lists... Done Building dependency tree Reading state information... Done All packages are up to date. 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.debian.org/debian-security stretch/updates InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 9D6D8F6BC857C906 NO_PUBKEY 8B48AD6246925553 W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://deb.debian.org/debian stretch-updates InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 7638D0442B90D010 W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://deb.debian.org/debian stretch Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 8B48AD6246925553 NO_PUBKEY 7638D0442B90D010 NO_PUBKEY EF0F382A1A7B6500 W: Failed to fetch http://security.debian.org/debian-security/dists/stretch/updates/InRelease The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 9D6D8F6BC857C906 NO_PUBKEY 8B48AD6246925553 W: Failed to fetch http://deb.debian.org/debian/dists/stretch-updates/InRelease The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 7638D0442B90D010 W: Failed to fetch http://deb.debian.org/debian/dists/stretch/Release.gpg The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 8B48AD6246925553 NO_PUBKEY 7638D0442B90D010 NO_PUBKEY EF0F382A1A7B6500 W: Some index files failed to download. They have been ignored, or old ones used instead.
