centos 7 yum 报错 Could not retrieve mirrorlist http://mirrorlist.centos.org?arch=x86_64&release=7&repo=sclo-rh error was 14: curl#6 - "Could not resolve host: mirrorlist.centos.org; 未知的错误"

## 问题原因
出现这个错误是因为使用的 CentOS 7 仓库已经被归档，当前的镜像地址无法找到所需的文件。CentOS 7 的官方支持已经结束，部分仓库已被移至归档库。这导致了你的 yum 命令无法找到所需的元数据文件。CentOS 7 的官方仓库在 2024 年 6 月 30 日之后已经停止维护。因此，使用最新的 CentOS 7 官方仓库可能会遇到问题。
## 解决方法
修改/etc/yum.repos.d目录下 CentOS-Base.repo
```bash
cd /etc/yum.repos.d && cp CentOS-Base.repo CentOS-Base.repo.bak && vi CentOS-Base.repo
```
修改文件为
```bash
# 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-$releasever - Base
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=os&infra=$infra
#baseurl=http://mirror.centos.org/centos/$releasever/os/$basearch/
#baseurl=http://vault.centos.org/7.9.2009/x86_64/os/
baseurl=http://vault.centos.org/7.9.2009/os/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
 
#released updates 
[updates]
name=CentOS-$releasever - Updates
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=updates&infra=$infra
#baseurl=http://mirror.centos.org/centos/$releasever/updates/$basearch/
#baseurl=http://vault.centos.org/7.9.2009/x86_64/os/
baseurl=http://vault.centos.org/7.9.2009/updates/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
 
#additional packages that may be useful
[extras]
name=CentOS-$releasever - Extras
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=extras&infra=$infra
#$baseurl=http://mirror.centos.org/centos/$releasever/extras/$basearch/
#baseurl=http://vault.centos.org/7.9.2009/x86_64/os/
baseurl=http://vault.centos.org/7.9.2009/extras/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
 
#additional packages that extend functionality of existing packages
[centosplus]
name=CentOS-$releasever - Plus
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=centosplus&infra=$infra
#baseurl=http://mirror.centos.org/centos/$releasever/centosplus/$basearch/
#baseurl=http://vault.centos.org/7.9.2009/x86_64/os/
baseurl=http://vault.centos.org/7.9.2009/centosplus/$basearch/
gpgcheck=1
enabled=0
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7

[centos-sclo-rh]
name=CentOS-7 - SCLo rh
baseurl=http://vault.centos.org/centos/7/sclo/$basearch/rh/
gpgcheck=1
enabled=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-SIG-SCLo
 
[centos-sclo-sclo]
name=CentOS-7 - SCLo sclo
baseurl=http://vault.centos.org/centos/7/sclo/$basearch/sclo/
gpgcheck=1
enabled=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-SIG-SCLo
```
保存后执行
```bash
sudo yum clean all && sudo yum makecache
```