yum源配置

1)

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

2)

wget -O /etc/yum.repos.d/CentOS-base.repo http://mirrors.aliyun.com/repo/Centos-7.repo
或者
curl -o /etc/yum.repos.d/CentOS-base.repo http://mirrors.aliyun.com/repo/Centos-7.repo
3)

yum clean all 

yum makecache

yum update -y

所有的yum源

yum repolist all

可用的yum源

yum repolist enabled