docker on CentOS7 が出力する firewalld のエラーを回避
$ systemctl status firewalld.service
とするとちらりとエラーが見えたので，/var/log/firewalld を見てみると次のようなエラーが出ていた．
2016-02-23 23:20:48 ERROR: COMMAND_FAILED: '/sbin/iptables -w2 -t nat -D PREROUTING' failed: iptables: Bad rule (does a matching rule exist in that chain?). 2016-02-23 23:20:48 ERROR: COMMAND_FAILED: '/sbin/iptables -w2 -t nat -D OUTPUT' failed: iptables: Bad rule (does a matching rule exist in that chain?). 2016-02-23 23:20:48 ERROR: COMMAND_FAILED: '/sbin/iptables -w2 -D FORWARD -i docker0 -o docker0 -j DROP' failed: iptables: Bad rule (does a matching rule exist in that chain?). 2016-02-23 23:20:48 ERROR: COMMAND_FAILED: '/sbin/iptables -w2 -t nat -n -L DOCKER' failed: iptables: No chain/target/match by that name. 2016-02-23 23:20:48 ERROR: COMMAND_FAILED: '/sbin/iptables -w2 -t nat -C PREROUTING -m addrtype --dst-type LOCAL -j DOCKER' failed: iptables: No chain/target/match by that name. 2016-02-23 23:20:48 ERROR: COMMAND_FAILED: '/sbin/iptables -w2 -t nat -C OUTPUT -m addrtype --dst-type LOCAL -j DOCKER ! --dst 127.0.0.0/8' failed: iptables: No chain/target/match by that name.
下記ページを参考に，firewalld ではなく iptables を使うように設定した．
