linux安装教程参考，https://blog.51cto.com/cloudcs/5245337
yum源配置

本地yum源配置：
8版本配置：将光盘iso挂载到某个目录，/dev/cdrom是/dev/sr0软链接，# mount /dev/cdrom /mnt，# ls /mnt
AppStream  BaseOS  EFI  images  isolinux  media.repo  TRANS.TBL
# cd /etc/yum.repos.d/  全部备份后清空再新建 # vim test.repo
[os]
name = os
baseurl = file:///mnt/BaseOS
gpgcheck = 0

[app]
name = app
baseurl = file:///mnt/AppStream
gpgcheck = 0

清缓存 yum clean all，yum repolist all
7版本配置：将光盘iso挂载到某个目录，# mount /dev/cdrom /mnt，# ls /mnt  有repodata和Packages等目录
# cd /etc/yum.repos.d/  全部备份后清空再新建 # vim test.repo
[os]
name = os
baseurl = file:///mnt
gpgcheck = 0

在线yum源配置（要能连外网，找到vault过期源）
8版本，# cat abc.repo 
[BaseOS]
name = BaseOS
baseurl = https://repo.huaweicloud.com/centos-vault/8.2.2004/BaseOS/x86_64/os/
gpgcheck = 0

[AppStream]
name = AppStream
baseurl = https://mirrors.aliyun.com/centos-vault/8.2.2004/AppStream/x86_64/os/
gpgcheck = 0

7版本，# cat abc.repo 
[os]
name = os
baseurl = http://mirrors.aliyun.com/centos-vault/7.6.1810/os/x86_64
gpgcheck = 0