有时候CentOS默认的yum源不一定是国内镜像，导致yum在线安装及更新速度不是很理想。这时候需要将yum源设置为国内镜像站点。国内主要开源的开源镜像站点应该是网易和阿里云了。
网易官方源：http://mirrors.163.com/
阿里官方源：https://opsx.alibaba.com/mirror?lang=zh-CN
一、修改CentOS默认yum源为mirrors.163.com
1、首先备份系统自带yum源配置文件/etc/yum.repos.d/CentOS-Base.repo
[root@localhost ~]# mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.backup
2、进入yum源配置文件所在的文件夹
[root@localhost ~]# cd /etc/yum.repos.d/
3、下载163的yum源配置文件到上面那个文件夹内
CentOS7
[root@localhost yum.repos.d]# wget http://mirrors.163.com/.help/CentOS7-Base-163.repo
CentOS6
[root@localhost yum.repos.d]# wget http://mirrors.163.com/.help/CentOS6-Base-163.repo
CentOS5
[root@localhost yum.repos.d]# wget http://mirrors.163.com/.help/CentOS5-Base-163.repo
4、运行yum makecache生成缓存
[root@localhost yum.repos.d]# yum makecache
5、这时候再更新系统就会看到以下mirrors.163.com信息
[root@localhost yum.repos.d]# yum -y update
已加载插件：fastestmirror, refresh-packagekit, security
设置更新进程Loading mirror speeds from cached hostfile
* base: mirrors.163.com
* extras: mirrors.163.com
* updates: mirrors.163.com
二、修改CentOS默认yum源为mirrors.aliyun.com
1、首先备份系统自带yum源配置文件/etc/yum.repos.d/CentOS-Base.repo
[root@localhost ~]# mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.backup
2、下载ailiyun的yum源配置文件到/etc/yum.repos.d/
CentOS7
[root@localhost ~]# wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo
CentOS6
[root@localhost ~]# wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-6.repo
CentOS5
[root@localhost ~]# wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-5.repo
3、运行yum makecache生成缓存
[root@localhost ~]# yum makecache
4、这时候再更新系统就会看到以下mirrors.aliyun.com信息
[root@localhost ~]# yum -y update
已加载插件：fastestmirror, refresh-packagekit, security
设置更新进程Loading mirror speeds from cached hostfile
* base: mirrors.aliyun.com
* extras: mirrors.aliyun.com
* updates: mirrors.aliyun.com
相关链接
官方主页: http://www.centos.org/
邮件列表: http://www.centos.org/modules/tinycontent/index.php?id=16
论坛: http://www.centos.org/modules/newbb/
文档: http://www.centos.org/docs/
Wiki: http://wiki.centos.org/