我这台虚拟机新安装的，所以打算更换阿里云的cd /etc/yum.repos.d目录如下
之后我们在这个目录下面执行命令如下
mv CentOS-Base.repo CentOS-Base.repo.bak（把原来的repo源备份一下）
wget -O CentOS-Base.repo https://mirrors.aliyun.com/repo/Centos-7.repo?spm=a2c6h.25603864.0.0.1d2f59699F3hjk
wget -O /etc/yum.repos.d/epel.repo https://mirrors.aliyun.com/repo/epel-7.repo
之后在执行命令生成缓存
yum clean all
yum makecache
[dh url="https://mirrors.aliyun.com/repo/" icon="" des=""]阿里云repo[/dh][dh url="https://developer.aliyun.com/mirror/epel?spm=a2c6h.13651102.0.0.553e1b115XqCjb" icon="" des=""]阿里云epel[/dh]