在安装一些第三方 bash 脚本（到容器中）后，我在私有 docker 网络上的 DNS 系统遇到了问题。
条目：我的主机系统是 CentOS 7.6，docker 版本 - 18.09.6，build 481bc77156。我用来运行容器的基本镜像是https://hub.docker.com/_/centos/ （还应用了一些额外的 Dockerfile 指令来启用 systemd：
FROM centos:7
ENV container docker
RUN (cd /lib/systemd/system/sysinit.target.wants/; for i in *; do [ $i == \
systemd-tmpfiles-setup.service ] || rm -f $i; done); \
rm -f /lib/systemd/system/multi-user.target.wants/*;\
rm -f /etc/systemd/system/*.wants/*;\
rm -f /lib/systemd/system/local-fs.target.wants/*; \
rm -f /lib/systemd/system/sockets.target.wants/*udev*; \
rm -f /lib/systemd/system/sockets.target.wants/*initctl*; \
rm -f /lib/systemd/system/basic.target.wants/*;\
rm -f /lib/systemd/system/anaconda.target.wants/*;
VOLUME [ "/sys/fs/cgroup" ]
CMD ["/usr/sbin/init"]
）
容器使用这样的参数运行：
docker run -dit --name="mycontainer" --restart always --privileged --net mynetwork -p 22004:22 --expose 80 --expose 443 local/centos-systemd:my_tag
之后，dns 就可以正常工作了（在容器级别）：
[root@3e9a75147f38 /]# ping google.com
PING google.com (108.177.14.101) 56(84) bytes of data.
64 bytes from lt-in-f101.1e100.net (108.177.14.101): icmp_seq=1 ttl=47 time=4.71 ms
64 bytes from lt-in-f101.1e100.net (108.177.14.101): icmp_seq=2 ttl=47 time=5.12 ms
64 bytes from lt-in-f101.1e100.net (108.177.14.101): icmp_seq=3 ttl=47 time=5.10 ms
64 bytes from lt-in-f101.1e100.net (108.177.14.101): icmp_seq=4 ttl=47 time=5.21 ms
但是，一旦我通过第三方 bash 脚本安装了一些额外的 Web 环境，域解析到容器就会失败：
[root@docker /]# ping google.com
ping: google.com: Name or service not known
在文件 /etc/resolv.conf 中没有任何变化：
[root@docker /]# cat /etc/resolv.conf
nameserver 127.0.0.11
options ndots:0
通过 ip 地址 ping 可以正常工作：
PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.
64 bytes from 8.8.8.8: icmp_seq=1 ttl=46 time=4.59 ms
64 bytes from 8.8.8.8: icmp_seq=2 ttl=46 time=4.66 ms
64 bytes from 8.8.8.8: icmp_seq=3 ttl=46 time=4.62 ms
一些附加数据：
# docker inspect network mynetwork
<...>
"IPAM": {
"Driver": "default",
"Options": {},
"Config": [
{
"Subnet": "172.18.0.0/16",
"Gateway": "172.18.0.1"
}
]
},
"Internal": false,
"Attachable": false,
"Ingress": false,
"ConfigFrom": {
"Network": ""
},
"ConfigOnly": false,
"Containers": {
<...>
在安装 bash 脚本之前：
[root@3e9a75147f38 /]# traceroute google.com
traceroute to google.com (173.194.73.100), 30 hops max, 60 byte packets
1 gateway (172.18.0.1) 0.038 ms 0.021 ms 0.020 ms
2 10.112.119.1 (10.112.119.1) 0.451 ms 0.572 ms 0.660 ms
3 121.spb.net.selectel.ru (188.93.17.121) 1.069 ms 1.033 ms 1.018 ms
4 62.spb.net.selectel.ru (188.93.17.62) 1.308 ms 1.286 ms 1.127 ms
5 188.93.16.145 (188.93.16.145) 6.547 ms 6.527 ms 6.543 ms
6 74.125.244.181 (74.125.244.181) 1.342 ms 74.125.244.133 (74.125.244.133) 1.217 ms 74.125.244.180 (74.125.244.180) 1.173 ms
7 216.239.42.53 (216.239.42.53) 5.326 ms 5.940 ms 216.239.42.85 (216.239.42.85) 4.915 ms
8 209.85.249.173 (209.85.249.173) 5.050 ms 5.021 ms 4.799 ms
9 64.233.175.175 (64.233.175.175) 4.784 ms 72.14.236.115 (72.14.236.115) 4.941 ms 4.754 ms
[root@3e9a75147f38 /]# dig google.com
; <<>> DiG 9.9.4-RedHat-9.9.4-74.el7_6.1 <<>> google.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 1288
;; flags: qr rd ra; QUERY: 1, ANSWER: 6, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;google.com. IN A
;; ANSWER SECTION:
google.com. 197 IN A 173.194.73.100
google.com. 197 IN A 173.194.73.139
google.com. 197 IN A 173.194.73.138
google.com. 197 IN A 173.194.73.102
google.com. 197 IN A 173.194.73.113
google.com. 197 IN A 173.194.73.101
;; Query time: 2 msec
;; SERVER: 127.0.0.11#53(127.0.0.11)
;; WHEN: Tue Jun 11 02:49:37 UTC 2019
;; MSG SIZE rcvd: 135
安装 bash 脚本后：
[root@docker /]# traceroute google.com
google.com: Name or service not known
Cannot handle "host" cmdline arg `google.com' on position 1 (argc 1)
[root@docker /]# dig google.com
; <<>> DiG 9.9.4-RedHat-9.9.4-74.el7_6.1 <<>> google.com
;; global options: +cmd
;; connection timed out; no servers could be reached
放置在此专用网络中的其他容器可以正确使用 DNS，直到未安装此 bash 脚本。此脚本安装了大量数据和服务（带有 nginx、httpd、mysql、nodejs 等的 Web 环境），我无法对其进行调试并找出破坏 DNS 的具体时刻。
关于如何修复此 DNS 问题，有什么想法吗？