cd /etc/yum.repos.d && rm -rf CentOS-Base.repo && vi CentOS-Base.repo
[base]
name=CentOS-7.9.2009 - Base - tsinghua.com
#mirrorlist=
baseurl=https://mirrors.tuna.tsinghua.edu.cn/centos-vault/7.9.2009/os/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
#released updates
[updates]
name=CentOS-7.9.2009 - Updates - tsinghua.com
#mirrorlist=
baseurl=https://mirrors.tuna.tsinghua.edu.cn/centos-vault/7.9.2009/updates/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
#additional packages that may be useful
[extras]
name=CentOS-7.9.2009 - Extras - tsinghua.com
#mirrorlist=
baseurl=https://mirrors.tuna.tsinghua.edu.cn/centos-vault/7.9.2009/extras/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
#additional packages that extend functionality of existing packages
[centosplus]
name=CentOS-7.9.2009 - Plus - tsinghua.com
baseurl=https://mirrors.tuna.tsinghua.edu.cn/centos-vault/7.9.2009/centosplus/$basearch/
gpgcheck=1
enabled=0
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
清理缓存文件和重新生成yum源缓存：
yum clean all && yum makecache
