【yum源更新】使用yum安装软件报错Could not resolve...报错Errors during downloading metadata for repository ‘Ap

使用yum安装软件报错
Could not resolve host: mirrorlist.centos.org； 未知的错误
报错Errors during downloading metadata for repository ‘AppStream‘:

一、问题描述：yum安装应用失败

>>   以安装svn失败为例报错信息如下
[root@ecm-test ~]# yum install subversion
CentOS-8 - AppStream                                                                                                            0.0  B/s |   0  B     00:40    
Errors during downloading metadata for repository 'AppStream':
  - Curl error (6): Couldn't resolve host name for http://mirrors.tuna.tsinghua.edu.cn/centos/8-stream/AppStream/x86_64/os/repodata/repomd.xml [Could not resolve host: mirrors.tuna.tsinghua.edu.cn]
Error: Failed to download metadata for repo 'AppStream': Cannot download repomd.xml: Cannot download rep
odata/repomd.xml: All mirrors were tried

>> 以安装rzsz为例报错信息如下
[root@localhost ~]# yum install -y lrzsz
已加载插件：fastestmirror
Loading mirror speeds from cached hostfile
Could not retrieve mirrorlist http://mirrorlist.centos.org/?release=7&arch=x86_64&repo=os&infra=stock error was
14: curl#6 - "Could not resolve host: mirrorlist.centos.org; 未知的错误"
 One of the configured repositories failed (未知),
 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=<repoid> ...
     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 <repoid>
        or
            subscription-manager repos --disable=<repoid>
     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=<repoid>.skip_if_unavailable=true
Cannot find a valid baseurl for repo: base/7/x86_64

二、原因分析：

起因：CentOS 团队于2021年12月31日停止对 CentOS8 更新和维护，并从官方镜像中移除CentOS 8的所有包，导致在使用yum源安装或更新会报上述失败错误。
结论：yum源配置问题或旧的yum源失效导致yum安装多种软件报错。

三、解决办法

1、进入仓库源文件夹下

cd /etc/yum.repos.d/

2、修改镜像配置内容

sed -i 's/mirrorlist/#mirrorlist/g' /etc/yum.repos.d/CentOS-*

sed -i 's|#baseurl=http://mirror.centos.org|baseurl=http://vault.centos.org|g' /etc/yum.repos.d/CentOS-*

3、清空原有缓存，并重新生成

yum clean all && yum makecache

4、更新软件包

yum update -y

结束！

解决方案（参考）：

参考阿里镜像源，找对应centos8\7\6进行修改镜像源

https://developer.aliyun.com/mirror/centos