centos9 配置yum源（清华源）

sudo cp -r /etc/yum.repos.d /etc/yum.repos.d.backup

备份yum源

sudo vim /etc/yum.repos.d/CentOS-Base.repo

编辑yum源仓库

[baseos]  
name=CentOS Stream $releasever - BaseOS  
baseurl=https://mirrors.tuna.tsinghua.edu.cn/centos-stream/9-stream/BaseOS/$basearch/os/  
gpgcheck=1  
enabled=1  
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-centosofficial  
  
[appstream]  
name=CentOS Stream $releasever - AppStream  
baseurl=https://mirrors.tuna.tsinghua.edu.cn/centos-stream/9-stream/AppStream/$basearch/os/  
gpgcheck=1  
enabled=1  
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-centosofficial

将此代码，插入打开的文件中，将之前文件清空，插入即可。

yum clean all

yum makecache

清理文件，建立缓存。