Centos 修改源

# 查看源 
cat /etc/yum.repos.d/CentOS-Base.repo 

# 备份 
cd /etc/yum.repos.d/ 
sudo mv CentOS-Base.repo CentOS-Base.repo.bak 

# 下载阿里源 
sudo curl -o /etc/yum.repos.d/CentOS-Base.repo https://mirrors.aliyun.com/repo/Centos-7.repo

# 清理缓存 
sudo yum clean all 
# 生成新的缓存 
sudo yum makecache