> W: 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 > CBF8D6FD518E17E1 NO_PUBKEY EF0F382A1A7B6500 > W: The repository 'http://deb.debian.org/debian stretch Release' 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. > E: Failed to fetch > http://deb.debian.org/debian/dists/stretch/updates/main/source/Sources 404 > Not Found [IP: 52.85.41.44 80] > E: Some index files failed to download. They have been ignored, or old ones > used instead. > >
Read this: https://unix.stackexchange.com/questions/75807/no-public-key-available-on-apt-get-update
