W: GPG error: http://debian.linux-systeme.com sid Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY F35E97D46941C9D8
W: GPG error: http://www.steve.org.uk sarge Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY F3E8C641DC2698A1
W: GPG error: http://puga.vdu.lt sarge Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 00CB25206E825E4E
W: GPG error: http://puga.vdu.lt sid Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 00CB25206E825E4E

gpg --keyserver subkeys.pgp.net --recv-keys F35E97D46941C9D8
gpg --keyserver subkeys.pgp.net --recv-keys F3E8C641DC2698A1
gpg --keyserver subkeys.pgp.net --recv-keys 00CB25206E825E4E

apt-get install debian-keyring gpgkeys
apt-key add /usr/share/keyrings/debian-role-keys.gpg

gpg --armor --export 00CB25206E825E4E | apt-key add -
gpg --armor --export F35E97D46941C9D8 | apt-key add -
gpg --armor --export F3E8C641DC2698A1 | apt-key add -

apt-get update