1.挂载iso

mount -o loop /opt/CentOS-7-x86_64-Everything-1810.iso /mnt/cdrom

2.备份原repo文件

cd /etc/yum.repos.d/
mkdir bak
mv *.repo /etc/yum.repos.d/bak

3.创建repo文件

[base]
name=CentOS
baseurl=file:///mnt/cdrom
enabled=1
gpgcheck=0
gpgkey=file:///mnt/cdrom/rpm-gpg/RPM-GPG-KEY-CentOS-7

4.清理yum缓存

yum clean all