While I upgrading my gentoo box, the BIND had been recomplied. After I re-steup my configurations there exists an error on the log.
max open files (1024) is smaller than max sockets (4096)
This is a bug introduced from kernel and I found a solution from Bombcar Heavy Blog.
# cd /etc/security/limits.d
# vim named.conf
And fillout the settings:
named soft nofile 4096
Then modify the named.conf settings:
# vim /etc/bind/named.conf
In the Options section, filling it:
Finally, restart the named and the error disappear. 😀