CentOS7 更新yum源

对CentOS-Base.repo进行备份

cd /etc/yum.repos.d
cp CentOS-Base.repo CentOS-Base.repo.bak

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 makecache
yum -y update

tips

若是在yum makecache的过程当中一直报：
Another app is currently holding the yum lock; waiting for it to exit...
没必要慌张，输入如下命令便可

rm -f /var/run/yum.pid