yum源更新

[centos8] wget -O /etc/yum.repos.d/CentOS-Base.repo https://mirrors.aliyun.com/repo/Centos-vault-8.5.2111.repo centos系统源地址：https://developer.aliyun.com/mirror/centos?spm=a2c6h.13651102.0.0.41a81b11t9nn0q

_yum_update(){
mkdir /back && cp -r /etc/yum.repos.d/* /back/
rm -rf /etc/yum.repos.d/*
wget -O /etc/yum.repos.d/CentOS-Base.repo https://mirrors.aliyun.com/repo/Centos-vault-8.5.2111.repo
yum clean all
yum makecache
}
_yum_update