docker容器ping不通外网

背景

今天在docker搭建redis环境的时候，发现yum拉取不到资源，上不到网，报了如下错误

http://mirrors.aliyun.com/centos/6.10/extras/x86_64/Packages/epel-release-6-8.noarch.rpm: [Errno 14] PYCURL ERROR 6 - "Couldn't resolve host 'mirrors.aliyun.com'"
Trying other mirror.
http://mirrors.neusoft.edu.cn/centos/6.10/extras/x86_64/Packages/epel-release-6-8.noarch.rpm: [Errno 14] PYCURL ERROR 6 - "Couldn't resolve host 'mirrors.neusoft.edu.cn'"
Trying other mirror.
http://mirrors.nwsuaf.edu.cn/centos/6.10/extras/x86_64/Packages/epel-release-6-8.noarch.rpm: [Errno 14] PYCURL ERROR 6 - "Couldn't resolve host 'mirrors.nwsuaf.edu.cn'"
Trying other mirror.
http://mirrors.shu.edu.cn/centos/6.10/extras/x86_64/Packages/epel-release-6-8.noarch.rpm: [Errno 14] PYCURL ERROR 6 - "Couldn't resolve host 'mirrors.shu.edu.cn'"
Trying other mirror.
http://mirrors.sohu.com/centos/6.10/extras/x86_64/Packages/epel-release-6-8.noarch.rpm: [Errno 14] PYCURL ERROR 6 - "Couldn't resolve host 'mirrors.sohu.com'"
Trying other mirror.
http://mirrors.tuna.tsinghua.edu.cn/centos/6.10/extras/x86_64/Packages/epel-release-6-8.noarch.rpm: [Errno 14] PYCURL ERROR 6 - "Couldn't resolve host 'mirrors.tuna.tsinghua.edu.cn'"
Trying other mirror.
http://mirrors.zju.edu.cn/centos/6.10/extras/x86_64/Packages/epel-release-6-8.noarch.rpm: [Errno 14] PYCURL ERROR 6 - "Couldn't resolve host 'mirrors.zju.edu.cn'"
Trying other mirror.

测试wget

wget http://mirrors.163.com/.help/CentOS6-Base-163.repo

结果报错

unknown host mirrors.163.com

测试ping

在容器内部
ping www.baidu.com

结果还是失败

ping: unknown host www.baidu.com

多开一个终端，进入主机（不是进入容器），进行ping命令测试发现是OK的，基本可以确定是docker的问题了，而不是网络问题

解决方法

停止所有容器，重启docker

service docker restart

all done