1.linux操作环境：使用的是阿里云ECS;
2.背景：在进行Nginx依赖环境安装的时候，对应提示镜像地址404；
[root@47.94.xxx.xxx/10.xx.xx.216 nginx-1.20.1]# yum -y install gcc zlib zlib-devel pcre-devel openssl openssl-devel
Loaded plugins: fastestmirror
Setting up Install Process
Loading mirror speeds from cached hostfile
http://mirrors.aliyuncs.com/centos/6/os/x86_64/repodata/repomd.xml: [Errno 14] PYCURL ERROR 22 - "The requested URL returned error: 404 Not Found"
Trying other mirror.
To address this issue please refer to the below knowledge base article
https://access.redhat.com/articles/1320623
If above article doesn't help to resolve this issue please open a ticket with Red Hat Support.
Error: Cannot retrieve repository metadata (repomd.xml) for repository: base. Please verify its path and try again
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3.解决
阿里云ESC云主机centos系统yum更新时，会遇到类似如下404等错误：
http://mirrors.aliyun.com/centos/6/os/x86_64/repodata/repomd.xml: [Errno 14] PYCURL ERROR 22 - "The requested URL returned error: 404 Not Found" Trying other mirror.
http://mirrors.aliyuncs.com/centos/6/os/x86_64/repodata/repomd.xml: [Errno 14] PYCURL ERROR 7 - "couldn't connect to host" Trying other mirror.
Error: Cannot retrieve repository metadata (repomd.xml) for repository: base. Please verify its path and try again
经过研究发现阿里云的yum源好多都不完善，才会出现以上错误导致yum源无法更新，解决方法只需要按照以下步骤修改文件就可以解决阿里云centos系统yum源错误，如果懂命令就登陆ssh使用命令修改，如果是新手可以使用winscp登陆后下载/etc/yum.repos.d/目录下的CentOS-Base.repo、epel.repo文件进行修改。
把CentOS-Base.repo文件中的以下网址
http://mirrors.aliyun.com/centos/
http://mirrors.aliyuncs.com/centos/
http://mirrors.cloud.aliyuncs.com/centos/
修改成
http://mirrors.aliyun.com/centos-vault/centos/
把epel.repo文件中的
enabled=1修改enabled=0
4.清除并更新yum缓存
yum clean all && yum makecache # 清除和缓存
