yum源与更新系统

[1] 首先备份/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源配置文件所在文件夹

[root@localhost yum.repos.d]# cd /etc/yum.repos.d/

[3] 下载163的yum源配置文件，放入/etc/yum.repos.d/(操作前请做好相应备份)

[root@localhost yum.repos.d]# wget http://mirrors.163.com/.help/CentOS7-Base-163.repo

[4] 运行以下命令生成缓存：

yum makecache

yum clean all