DNS/unbound/unbound.confについて、ここに記述してください。

/harden-referral-path

# Unbound configuration file for Debian.
#
# See the unbound.conf(5) man page.
#
# See /usr/share/doc/unbound/examples/unbound.conf for a commented
# reference config file.
#
# The following line includes additional configuration files from the
# /etc/unbound/unbound.conf.d directory.
## include: "/etc/unbound/unbound.conf.d/*.conf"

server:
        directory: "/etc/unbound"
        username: unbound
#       chroot: "/etc/unbound"
        logfile: "/etc/unbound/unbound.log"
        verbosity: 2
        interface: 127.0.0.2
        harden-referral-path: yes
        minimal-responses: yes
        max-udp-size: 512
        edns-buffer-size: 512
        do-ip4: yes
        do-ip6: no
        do-udp: yes
        do-tcp: yes
        cache-min-ttl: 120
        cache-max-ttl: 86400
        qname-minimisation: yes
        use-caps-for-id: yes
        target-fetch-policy: "0 0 0 0 0 0"
#        tcp-upstream: yes
        logfile: "/etc/unbound/unbound.log"

unbound-checkconf ではエラーなし。

DLVも含め他のドメインの検証も無効にします。unbound.confファイルの記述は次のようになります:

server:
        module-config: "iterator"