osmc@osmc:~$ sudo apt-get update && sudo apt-get dist-upgrade
Get:1 http://ftp.debian.org/debian stretch-backports InRelease [91.8 kB]Get:3 http://mirrordirector.raspbian.org/raspbian stretch InRelease [15.0 kB]
Ign:4 http://deb.debian.org/debian stretch InRelease
Get:5 http://deb.debian.org/debian-security stretch/updates InRelease [94.3 kB]
Get:6 http://deb.debian.org/debian stretch-updates InRelease [91.0 kB]
Hit:2 http://ftp.fau.de/osmc/osmc/apt stretch InRelease
Get:7 http://deb.debian.org/debian stretch Release [118 kB]
Get:8 http://deb.debian.org/debian stretch Release.gpg [2410 B]
Get:9 http://mirrordirector.raspbian.org/raspbian stretch/main armhf Packages [11.7 MB]
Err:5 http://deb.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 AA8E81B4331F7F50
Err:6 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 NO_PUBKEY 04EE7237B7D453EC
Err:1 http://ftp.debian.org/debian stretch-backports InRelease
  The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 7638D0442B90D010 NO_PUBKEY 04EE7237B7D453EC
Ign:8 http://deb.debian.org/debian stretch Release.gpg
Reading package lists... Done
W: GPG error: http://deb.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 AA8E81B4331F7F50
E: The repository 'http://deb.debian.org/debian-security stretch/updates InRelease' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
W: 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 NO_PUBKEY 04EE7237B7D453EC
E: The repository 'http://deb.debian.org/debian stretch-updates InRelease' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
W: GPG error: http://ftp.debian.org/debian stretch-backports InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 7638D0442B90D010 NO_PUBKEY 04EE7237B7D453EC
E: The repository 'http://ftp.debian.org/debian stretch-backports InRelease' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
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 7638D0442B90D010 NO_PUBKEY 04EE7237B7D453EC NO_PUBKEY EF0F382A1A7B6500
E: The repository 'http://deb.debian.org/debian stretch Release' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
osmc@osmc:~$