anchor.diff:            The set of system-wide known SSH hosts.
           '';
           example = [
  -          { 
  +          {
               hostNames = [ "myhost" "myhost.mydomain.com" "10.10.1.4" ];
               publicKeyFile = ./pubkeys/myhost_ssh_host_dsa_key.pub;
             }
  -          { 
  +          {
               hostNames = [ "myhost2" ];
               publicKeyFile = ./pubkeys/myhost2_ssh_host_dsa_key.pub;
             }
  
positive.code:     usersWithKeys = attrValues (flip filterAttrs config.users.extraUsers (n: u:
        length u.openssh.authorizedKeys.keys != 0 || length u.openssh.authorizedKeys.keyFiles != 0
      ));
    }; map mkAuthKeyFile usersWithKeys;
  
  in
  
  
negative.code:     };
    };
  
    authKeysFiles = let
      mkAuthKeyFile = u: {
        target = "ssh/authorized_keys.d/${u.name}";
        mode = "0444";
  