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
内容扩展
Docker容器内不能联网的6种解决方案
1.使用–net:host选项
2.使用–dns选项
3.改dns server
4.不用dnsmasq
5.重建docker0网络
6.直接在docker内修改/etc/hosts
