1，输入命令查看系统的版本号 cat /etc/centos-release

2，打开 https://vault.centos.org/ 查看需要的系统版本URL路径

3，修改文件/etc/yum.repos.d/CentOS-Base.repo为以下内容

[centos-office]
name=centos-office
failovermethod=priority
baseurl=https://vault.centos.org/6.10/os/x86_64/
gpgcheck=1
gpgkey=https://vault.centos.org/6.10/os/x86_64/RPM-GPG-KEY-CentOS-6

4，修改完成后执行
yum clean all
rm -rf  /var/cache/yum/
yum makecache