Centos7更新yum源

查看当前的 yum 源

yum repolist

对CentOS-Base.repo进行备份

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

使用阿里云源替换本地源

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

清除yum缓存并更新

yum clean all
yum makecache

安装epel源

yum list | grep epel-release 
yum install -y epel-release

使用阿里开源镜像提供的epel源

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

再次清除系统yum缓存，并重新生成新的yum缓存

yum clean all
yum makecache

查看新 yum 源

yum repolist enabled
yum repolist all

tips

如果在yum makecache的过程中一直报：
Another app is currently holding the yum lock; waiting for it to exit...
不必慌张，输入以下命令即可

rm -f /var/run/yum.pid