Генерируем ключи:
    dnssec-keygen -a HMAC-MD5 -b 512 -n USER foo22.bar44.com.

Настройки сервера:

/etc/named.conf:
    include "keys.conf";
    ......
    zone  "bar44.com" {
        type master;
        file  "bar44.com.zone";
        update-policy {
	   grant laptop.bar44.com. name laptop.bar44.com. A TXT;
               grant foo22.bar44.com. subdomain bar44.com. ANY;
        };
        # или   
        #allow-update {
        #     key foo22.bar44.com.
        #};
    };

/etc/namedb/keys.conf:
    key foo22.bar44.com. {
	algorithm HMAC-MD5;
	secret "секретный ключ";

    };

Для обновления зоны:
    nsupdate -k Kfoo22.bar44.com.+157+12505.private -v cmd_file.txt

Пример cmd_file.txt:
    server ns.bar44.com
    zone bar44.com
    update delete somehost.bar44.com. A
    update add somehost.bar44.com. 86400 A 10.10.10.1
    show
    send