/var/named/chroot/var/named: デバイスが使用中です。

指定されたサービスを再起動すると、次のエラーが発生します。

./etc/init.d/named restart

Stopping named:                                            [  OK  ]
Starting named: 
Error in named configuration:
zone enum4red.com/IN: has 0 SOA records
zone enum4red.com/IN: has no NS records
zone enum4red.com/IN: not loaded due to errors.
_default/enum4red.com/IN: bad zone
zone localhost.localdomain/IN: loaded serial 0
zone localhost/IN: loaded serial 0
zone 1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa/IN: loaded serial 0
zone 1.0.0.127.in-addr.arpa/IN: loaded serial 0
zone 0.in-addr.arpa/IN: loaded serial 0
                                                           [FAILED]
umount: /var/named/chroot/var/named: device is busy.
        (In some cases useful info about processes that use
         the device is found by lsof(8) or fuser(1))

ログは次のとおりです

Oct  7 04:35:46 localhost named: zone enum4red.com/IN: has 0 SOA records
Oct  7 04:35:46 localhost named: zone enum4red.com/IN: has no NS records
Oct  7 04:35:46 localhost named: zone enum4red.com/IN: not loaded due to errors.
Oct  7 04:35:46 localhost named: _default/enum4red.com/IN: bad zone
Oct  7 04:35:46 localhost named: zone localhost.localdomain/IN: loaded serial 0
Oct  7 04:35:46 localhost named: zone localhost/IN: loaded serial 0
Oct  7 04:35:46 localhost named: zone 1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa/IN: loaded serial 0
Oct  7 04:35:46 localhost named: zone 1.0.0.127.in-addr.arpa/IN: loaded serial 0
Oct  7 04:35:46 localhost named: zone 0.in-addr.arpa/IN: loaded serial 0

何が問題なのかご存知ですか？