因为测试需要，安装了CentOS 6.4,进行更新时yum提示不可用。
按照阿里云开源镜像(https://developer.aliyun.com/mirror/centos)的说明：
wget -O /etc/yum.repos.d/CentOS-Base.repo https://mirrors.aliyun.com/repo/Centos-6.repo
配置完成后，运行yum makecache时报错，提示repomd.xml找不到，错误码404.拷贝对应的地址到浏览器确实404打不开。
除了readme，什么也没有了,readme文件内容如下：
This directory (and version of CentOS) is deprecated. For normal users, you should use /6/ and not /6.4/ in your path. Please see this FAQ concerning the CentOS release scheme: https://wiki.centos.org/FAQ/General If you know what you are doing, and absolutely want to remain at the 6.4 level, go to http://vault.centos.org/ for packages. Please keep in mind that 6.0, 6.1, 6.2, 6.3 and 6.4 no longer gets any updates, nor any security fix's.
后来查阅资料(https://wiki.centos.org/FAQ/General)，是停止维护了
CentoS 6 停止维护更新日期2020年11月30日
CentOS 7 停止维护更新日期2024年6月30日
CentOS 8 停止维护更新日期2021年12月31日
还有一个阿里云源(centos-vault)可以使用，整理内容如下，直接复制可用。
# CentOS-Base.repo # # The mirror system uses the connecting IP address of the client and the # update status of each mirror to pick mirrors that are updated to and # geographically close to the client. You should use this for CentOS updates # unless you are manually picking other mirrors. # # If the mirrorlist= does not work for you, as a fall back you can try the # remarked out baseurl= line instead. # # [base] name=CentOS-6.4 - Base baseurl=http://mirrors.aliyun.com/centos-vault/6.4/os/x86_64/ gpgcheck=1 gpgkey=http://mirrors.aliyun.com/centos-vault/RPM-GPG-KEY-CentOS-6 [updates] name=CentOS-6.4 - Updates baseurl=http://mirrors.aliyun.com/centos-vault/6.4/updates/x86_64/ gpgcheck=1 gpgkey=http://mirrors.aliyun.com/centos-vault/RPM-GPG-KEY-CentOS-6 [extras] name=CentOS-6.4 - Extras baseurl=http://mirrors.aliyun.com/centos-vault/6.4/extras/x86_64/ gpgcheck=1 gpgkey=http://mirrors.aliyun.com/centos-vault/RPM-GPG-KEY-CentOS-6 [centosplus] name=CentOS-6.4 - Plus baseurl=http://mirrors.aliyun.com/centos-vault/6.4/centosplus/x86_64/ gpgcheck=1 enabled=0 gpgkey=http://mirrors.aliyun.com/centos-vault/RPM-GPG-KEY-CentOS-6 [contrib] name=CentOS-6.4 - Contrib baseurl=http://mirrors.aliyun.com/centos-vault/6.4/contrib/x86_64/ gpgcheck=1 enabled=0 gpgkey=http://mirrors.aliyun.com/centos-vault/RPM-GPG-KEY-CentOS-6
OK，问题解决~
