CentOS使用yum安装包报错No more mirrors to try解决方法

报错如下

Loaded plugins: fastestmirror, update-motd
Loading mirror speeds from cached hostfile
http://mirrors.163.com/centos/7-7.1908.0.el7.centos/os/x86_64/repodata/repomd.xml: [Errno 14] HTTP Error 404 - Not Found
Trying other mirror.
To address this issue please refer to the below wiki article 

https://wiki.centos.org/yum-errors

If above article doesn't help to resolve this issue please use https://bugs.centos.org/.



 One of the configured repositories failed (CentOS-7-7.1908.0.el7.centos - Base - 163.com),
 and yum doesn't have enough cached data to continue. At this point the only
 safe thing yum can do is fail. There are a few ways to work "fix" this:

     1. Contact the upstream for the repository and get them to fix the problem.

     2. Reconfigure the baseurl/etc. for the repository, to point to a working
        upstream. This is most often useful if you are using a newer
        distribution release than is supported by the repository (and the
        packages for the previous distribution release still work).

     3. Run the command with the repository temporarily disabled
            yum --disablerepo=base ...

     4. Disable the repository permanently, so yum won't use it by default. Yum
        will then just ignore the repository until you permanently enable it
        again or use --enablerepo for temporary usage:

            yum-config-manager --disable base
        or
            subscription-manager repos --disable=base

     5. Configure the failing repository to be skipped, if it is unavailable.
        Note that yum will try to contact the repo. when it runs most commands,
        so will have to try and fail each time (and thus. yum will be be much
        slower). If it is a very temporary problem though, this is often a nice
        compromise:

            yum-config-manager --save --setopt=base.skip_if_unavailable=true

failure: repodata/repomd.xml from base: [Errno 256] No more mirrors to try.
http://mirrors.163.com/centos/7-7.1908.0.el7.centos/os/x86_64/repodata/repomd.xml: [Errno 14] HTTP Error 404 - Not Found

原因分析，源地址错误
处理方法

#进入源文件配置目录
cd /etc/yum.repos.d
#下载源
wget -O CentOS-Base.repo http://mirrors.163.com/.help/CentOS7-Base-163.repo

修改

注意：把变量releasevr修改成对应的版本号，不同版本号可能不同

 sed 's#$releasever#7.9.2009#g' CentOS-Base.repo -i

不修改自动获取的如下

可以复制该地址尝试能否使用浏览器打开