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。

修改yum为网易源

1、首先备份系统自带yum源配置文件/etc/yum.repos.d/CentOS-Base.repo

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

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

wget http://mirrors.163.com/.help/CentOS7-Base-163.repo

CentOS6

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

CentOS5

wget http://mirrors.163.com/.help/CentOS5-Base-163.repo

4、运行yum makecache生成缓存

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

修改yum为阿里源

1、首先备份系统自带yum源配置文件/etc/yum.repos.d/CentOS-Base.repo

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

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

CentOS6

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

CentOS5

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

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