将Centos的yum源更换为国内的阿里云源,yum失败dns处理

https://yq.aliyun.com/articles/33286 (将Centos的yum源更换为国内的阿里云源)

http://blog.csdn.net/inslow/article/details/54177191

        阿里云是最近新出的一个镜像源。得益于阿里云的高速发展，这么大的需求，肯定会推出自己的镜像源。
阿里云Linux安装镜像源地址：http://mirrors.aliyun.com/

[root@localhost home]# yum repolist

Loaded plugins: fastestmirror

Loading mirror speeds from cached hostfile

 * base: mirrors.aliyun.com

 * extras: mirrors.aliyun.com

 * updates: mirrors.aliyun.com

可以查看本机的yum源是哪里的？

CentOS系统更换软件安装源
第一步：备份你的原镜像文件，以免出错后可以恢复。

mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.backup

第二步：下载新的CentOS-Base.repo 到/etc/yum.repos.d/

CentOS 6
wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-6.repo

CentOS 7

wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo

更改CentOS-Media.repo使其为不生效：

enabled=0

第三步：运行yum makecache生成缓存

yum clean all
yum makecache

 ==========================================

[root@node1 data]# wget https://s3-us-west-2.amazonaws.com/grafana-releases/release/grafana-4.5.1-1.x86_64.rpm

--2017-09-22 13:00:12--  https://s3-us-west-2.amazonaws.com/grafana-releases/release/grafana-4.5.1-1.x86_64.rpm

Resolving s3-us-west-2.amazonaws.com (s3-us-west-2.amazonaws.com)... failed: Name or service not known.

wget: unable to resolve host address ‘s3-us-west-2.amazonaws.com’

      下载yum镜像的时候出现wget失灵的情况，