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